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DDC Controls Package ManualVHC-36, -42 and -50
Operation Instructions Manual
Model: VHC-36, VHC-42, VHC-50
©2009 Venmar CES Inc.
VCES-DDC-IOM-1C 2
Table of Contents
Overview...............................................................................................................................................................................3Features.and.Benefits..........................................................................................................................................................3
Terminal.Strip.................................................................................................................................................................3Control.Details......................................................................................................................................................................4
Stand.Alone.Operation..................................................................................................................................................4Network.Operation........................................................................................................................................................4
Ventilation.Control.Scheduling.Modes...............................................................................................................................4Temperature.Control.Configuration...................................................................................................................................5Setpoint.Adjustment............................................................................................................................................................6VHC.Sequence.of.Operation................................................................................................................................................7DDC.Interface.....................................................................................................................................................................11Appendix.A:.Control.Wiring.Connections.Example.........................................................................................................13Appendix.B:.DDC.Points.Reference.Guide........................................................................................................................16Appendix.C:.Standard.Network.Practice..........................................................................................................................19Appendix.D:.DDC.Troubleshooting.Guide........................................................................................................................21
Manufacturer reserves the right to discontinue or change specifications or designs without notice or obligation.
©Venmar CES Inc. 2012. All rights reserved throughout the world.
Illustrations cover the general appearance of Venmar CES products at the time of publication and Venmar CES reserves the right to make changes in design and construction at any time without notice.
™® The following are trademarks or registered trademarks of their respective companies: Variable Refrigerant Control from Venmar CES.
CES Group, LLC d/b/a Venmar CES furnishes equipment pursuant to its then-current Terms and Conditions of Sale and Lim-ited Warranty, copies of which can be found under the Terms & Conditions of Sale and Warranty link at www.ces-group.com. Extended warranties, if any, shall be as offered and acknowledged in writing by Venmar CES.
VCES-DDC-IOM-1C 3
The DDC control package is programmed for a range of temperature control and scheduling modes which are field selectable. The control package enables the VHC to control discharge air temperature, room/return air tem-perature or discharge in conjunction with room air tem-perature based on sensor readings. It can also be used to control the amount of air being recirculated back into the building.
This manual provides instructions and information on configuring and adjusting the control for a specific stand alone or networking application.
• No extra controls needed to accommodate discharge air temperature control.
• A room thermostat may be used to control room heating and cooling.
• A room humidistat may be used to control room humidity.
• Native BACnet firmware with MS/TP RS485 protocol.• Can be optionally interfaced with many different
protocols with the use of a terminal server, like Lon-works, Modbus, Metasys, etc.
A low voltage Field Wiring (FW) interface terminal strip is provided for shipped loose or field supplied controls, sensor or interlock connections to fully integrate the unit. Interconnections to a BMS are minimal. Refer to Appendix
G and H in the VHC-36, 42 and 50 Installation, Opera-tion and Maintenance Instructions Manual, for example of start-up connections, plus input and output connections available.
Overview
Features and Benefits
Terminal.Strip
Net 1 BacNet terminals
DDC inputs
DDC outputs
Net 2 LinkNet terminals
Net 1 jumper setting
BacNet address jumpers
Figure 1: DDC layout
VCES-DDC-IOM-1C 4
The DDC control package includes a four-button user in-terface called the BacStat II. This device can be mounted anywhere and when room air tempering is needed, can be configured as a room thermostat. A wide range of config-uration options are included and can be accessed through the BacStat (see Figure 2).
For stand alone operation an external dry contact (ex: re-mote time clock, CO2 sensor or manual selector switch, etc.) for scheduling mode must be provided by others or is available as an accessory item. This is the only connection required to start single-speed units.
The Delta DDC is a native BACnet device that can com-municate over an RS-485 network running between 9,600 and 76,800 baud. Delta products are tested for interoper-ability between multiple vendors at the BACnet Testing Laboratory (BTL). The use of a BTL listed front end will greatly simplify network installation and allow problemfree communication.
When connected to the network, all scheduling can be taken over by the front end control system (provided by others). Additional access is provided to dozens of control variables which give the Building Management System as much control as needed (with the exception of critical functions, such as the defrost strategy and other fail safes).
Occupied Ventilation (Ov)Jumper across FW 304–305. This is the main mode that will enable the unit to run in 100% fresh air mode. Free cooling and defrost will initiate based on the setpoint.
Unoccupied (Un)No jumpers on any of the terminals 304, 305, 306, 307 or 308. The unit will turn off.
Unoccupied Recirculation (Ur) (Optional)Jumper across FW 305–306. The unit will turn off un-less there is a call for heating/cooling or dehumidification across the heating/cooling or dehumidification contacts. This call must come from an optional thermostat or hu-midistat. The unit will run in recirc mode upon a call.
Occupied Recirculation (Or) (Optional)Jumper across FW 306–307. The unit will run and recirc a percentage of air. The outside and exhaust air dampers may be adjusted to open a certain percentage, thus reduc-ing the amount of fresh air and increasing the amount or recirc air.
Adjust the following parameters:
#143 – Outside Air Damper Minimum Setpoint• Limits: 0–100%• Factory set: 100%• BACnet variable: AV150• Function: The outside air damper minimum setpoint
is set in conjunction with the exhaust air damper minimum setpoint to allow for the required recircula-tion air.
#144 – Exhaust Air Damper Minimum Setpoint• Limits: 0–100%• Factory set: 100%• BACnet variable: AV151• Function: The exhaust air damper minimum setpoint
is set in conjunction with the outside air damper minimum setpoint to allow for the required recircula-tion air.
Building Management System SchedulingAlternatively the software point MV12 can be used to schedule the unit as described above. If this method is
Control DetailsStand.Alone.Operation
Network.Operation
Ventilation Control Scheduling Modes
Figure 2: BacStat II
VCES-DDC-IOM-1C 5
being used then you must not provide any jumpers to ter-minals 304, 305, 306, 307 or 308.
The remote unit control multi-state variable is used to en-able the unit through a Bacnet interface. Set MV12 to:
• 2 for unoccupied mode.• 4 for occupied recirculation mode (optional).• 6 for unoccupied recirculation mode (optional).• 10 for ventilation mode.
The VHC unit can be configured to control building tem-perature a variety of ways. Adjust #153 – Zone Configura-tion to change temperature control to discharge air, room air or return air control. Default settings from factory allow the unit to be controlled by discharge air temperature.
Adjust the following setpoint:
#153 – Zone Configuration• Limits: NO, RM, RET• Factory set: NO• BACnet variable: MV11 function – Zone configura-
tion allows the unit to be used for zone heating and cooling. – NO: No zone control (discharge only) – RM: Room air zone control (BacStat II) – RET: Return air zone control (RA temp sensor)
Discharge Air Temperature Control (MV11 = NO)This type of control is used when the VHC is required to maintain a discharge temperature only. The BacStat will not provide room control in this mode. An optional ther-mostat may be used to provide additional heating or cool-ing when connected to the heating override or cooling override terminals on the FW terminal strip (see Override Contact Control (Optional)).
Adjust the following setpoints:
#107 – Cooling Setpoint• Limits: 50–80°F [10–27°C]• Factory set: 60°F• BACnet variable: AV10 function – The cooling set-
point is the temperature that the reheat will heat the supply air up to (summer mode only).
#115 – Coil Leaving Setpoint• Limits: 40–65°F [4–18°C]• Factory set: 55°F• BACnet variable: AV143 function – The coil leav-
ing setpoint is the temperature that the cooling coil will cool the coil leaving air temperature down to during discharge air temperature control (summer mode only).
#111 – Heating Setpoint• Limits: 50–105°F [10–40°C]
• Factory set: 80°F• BACnet variable: AV20• Function: The heating setpoint is the temperature
that the post heat will heat the supply air up to dur-ing discharge air temperature control (winter mode only).
Room Air Temperature Control (MV11 = RM)The BacStat must be mounted in the room for this type of control.
This type of control is used when you want to maintain a room temperature. The VHC will heat/cool based on the BacStat temperature. An optional thermostat can be used to provide additional heating or cooling when connected to the heating override or cooling override terminals on the FW terminal strip (see Override Contact Control (Op-tional)).
Adjust the following setpoints:
#147 – Summer Zone Setpoint• Limits: 60–80°F [15–25°C]• Factory set: 70°F• BACnet variable: AV84 function – The summer zone
setpoint is the room or return air setpoint for sum-mer mode.
#150 – Winter Zone Setpoint• Limits: 60–80°F [15–25°C]• Factory set: 70°F• BACnet variable: AV87• Function: The winter zone setpoint is the room or re-
turn air setpoint for winter mode.
Return Air Temperature Control (MV11 = RET)This type of control is used when you want to maintain a return temperature. This application is typical for VHC units providing air to several rooms. The VHC will heat/cool based on the return air temperature. An optional thermostat can be used to provide additional heating or cooling when connected to the heating override or cooling override terminals on the FW terminal strip (see Override Contact Control (Optional)).
Temperature Control Configuration
VCES-DDC-IOM-1C 6
Adjust the following setpoints:
#147 – Summer Zone Setpoint• Limits: 60–80°F [15–25°C]• Factory set: 70°F• BACnet variable: AV84• Function: The summer zone setpoint is the room or
return air setpoint for summer mode.#150 – Winter Zone Setpoint• Limits: 60–80°F [15–25°C]• Factory set: 70°F• BACnet variable: AV87• Function: The winter zone setpoint is the room or re-
turn air setpoint for winter mode.
Override Contact Control (Optional)Alternatively the unit may be controlled by its heating, cooling, dehumidification contacts. The heating contact is only provided on units with heating options and the cool-ing/dehumidification contact is only provided on units with cooling options. An optional room thermostat (or contact closure) may be used to provide a dry contact closure across terminals FW 314–315 for cooling, or FW 318–319 for heating.
These override contacts can be used in any of the three temperature control modes listed above. When the unit
is running normally, it will run based on its corresponding setpoints. When an override contact is made, the unit will change its setpoints as follows:
#118 – Coil Override Leaving Setpoint• Limits: 40–65°F [4–18°C]• Factory set: 50°F• BACnet variable: AV146• Function: The coil override leaving setpoint is the
temperature that the cooling coil will cool the coil leaving air temperature down to during room air temperature/humidity control (summer mode only).
#121 – Heating Override Setpoint• Limits: 50–105°F [10–40°C]• Factory set: 90°F• BACnet variable: AV140• Function: The heating override setpoint is the tem-
perature that the post heat will heat the supply air up to during room air temperature control (winter mode only).
An optional humidistat may be used to provide a dry contact closure across terminals FW 316–317 for dehumidification.
In order to give more flexibility to the user, the setpoints are fully adjustable from the BacStat interface. For a full modulating system (ex. SCR electric heat) you only need to adjust the setpoint value. When using a binary switch (ex. summer/winter changeover) or when staging a device (ex. compressors), a span or differential is needed to separate the ‘On’ and ‘Off’ point to eliminate the fast cycling. In this case, Venmar CES uses the Setpoint-Span-Reset ad-justment method.
• The Setpoint is the value to reach.• The Span is the band width between the ‘On’ and
‘Off’ point.• The Reset is the percentage of the span value under
the setpoint (refer to Figure 3).
Setpoint Adjustment
60°F
40°F
100°F
Summer setpoint (60°F)59°F off
64°F on
Summer modeOn = 64°F
Reset = 20%
OA temp
Summer modeOn = 64°F
Summer modeOff = 59°F
OA
T ºF
Span = 5
Δt (Change in time)
Summer mode
Sum
mer
mode
Winter mode
For this example: Sum_Stp = 60°F Sum_Span = 5 Sum_Reset = 20
To calculate: Summer switch On = Sum_Stp + (Sum_Span * ((100 - Sum_Rst) / 100)) Summer switch Off = Sum_Stp - (Sum_Span * (Sum_Rst / 100))
Figure 3: Setpoint adjustment example
VCES-DDC-IOM-1C 7
Ventilation
On a call for occupied ventilation (occupancy contact closed):
• Wheel starts (not in free cooling).• Recirculation damper closes (if equipped).• Exhaust air damper opens.• Outside air damper opens.• After exhaust air damper opens; exhaust blower starts.• After outside air damper opens; supply blower starts.
Occupied RecirculationOn a call for occupied recirculation (if equipped) (occupied recirculation contacts closed):
• Wheel starts (not in free cooling).• Recirculation damper closes.• After exhaust air damper opens; exhaust blower starts.• After supply air damper opens; supply blower starts.• Return air damper opens.• Outside and exhaust air dampers modulate to the
damper minimum setpoints.
Unoccupied RecirculationOn a call for unoccupied recirculation (if equipped) (unoc-cupied recirculation contacts closed and a call for cooling or heating):
• Wheel stops.• Recirculation damper opens.• Exhaust air damper closes.• Outside air damper closes.• Supply blower starts.
Summer/Winter ChangeoverThe summer setpoint, parameter #104, is the tempera ture setpoint that the outdoor air temperature sensor must reach in order to change from heating to cooling or visa versa. When the outdoor air temperature is above this setpoint, you will be in summer mode and your heating components will be disabled. When the outdoor air tem-perature is below this setpoint, you will be in winter mode and your cooling components will be disabled.
Adjust the following setpoints:
#104 – Summer Setpoint• Limits: 5–80°F [−15–27°C]• Factory set: 60°F• BACnet variable: AV5• Function: The summer setpoint is the temperature for
the unit to changeover between summer and winter modes of operation.
#105 – Summer Span• Limits: 1–8°F [0.5–5°C]• Factory set: 4°F• BACnet variable: AV6• Function: The summer span is the differential above
and below the summer setpoint.#106 – Summer Reset• Limits: 0–100%• Factory set: 50%• BACnet variable: AV7• Function: The summer reset is the shift in the span
below the summer setpoint by X%.
CoolingFree.coolingFree cooling can be disabled by adjusting parameter #130.
Adjust the following setpoint:
#130 – Free Cooling Select• Limits: On/off• Factory set: On• BACnet variable: BV61• Function: This variable enables or disables free cooling.
Dry Bulb Setpoint (On/Off)
If the outside air temperature is above the summer set-point (selectable) and if the outside air temperature is less than the return air temperature and less than the free cooling temperature setpoint range, the wheel stops.
Adjust the following setpoints:
#127 – Dry Bulb Free Cooling Setpoint• Limits: 40–80°F [5–27°C]• Factory set: 65°F• BACnet variable: AV60• Function: The dry bulb free cooling setpoint is the
temperature that the unit will go into free cooling.#128 – Dry Bulb Free Cooling Span• Limits: 4–20°F [2–12°C]• Factory set: 4°F• BACnet variable: AV61• Function: The dry bulb free cooling span is the differ-
ential above and below the free cooling setpoint.#129 – Dry Bulb Free Cooling Reset• Limits: 0–100%• Factory set: 50%• BACnet variable: AV62• Function: The enthalpy free cooling reset is the per-
centage of the span value under the setpoint.Setpoint Enthalpy (On/Off)
If the outside air temperature is above the summer set-point (selectable) and if the outside air enthalpy is in the enthalpy free cooling setpoint range, the wheel stops.
VHC Sequence of Operation
IMPORTANTThe following conditions may not occur in the exact order as listed.
VCES-DDC-IOM-1C 8
Adjust the following setpoints:
#124 – Enthalpy Free Cooling Setpoint• Limits: 10–70 Btu/lbs [23–163 Joules/Gram]• Factory set: 20 Btu/lbs• BACnet variable: AV45• Function: The enthalpy free cooling setpoint is the
measured enthalpy that the unit will go into free cooling.
#125 – Enthalpy Free Cooling Span• Limits: 5–20 Btu/lbs [11–46 Joules/Gram]• Factory set: 5 Btu/lbs• BACnet variable: AV46• Function: The enthalpy free cooling span is the differ-
ential above and below the free cooling setpoint.#126 – Enthalpy Free Cooling Reset• Limits: 0–100%• Factory set: 50%• BACnet variable: AV47• Function: The enthalpy free cooling reset is the per-
centage of the span value under the setpoint.Differential Enthalpy (On/Off)
If the outside air temperature is above the summer set-point (selectable) and if the outside air enthalpy is less than return air enthalpy and in the enthalpy free cooling setpoint range, the wheel stops.
Adjust the following setpoints:
#124 – Enthalpy Free Cooling Setpoint• Limits: 10–70 Btu/lbs [23–163 Joules/Gram]• Factory set: 20 Btu/lbs• BACnet variable: AV45• Function: The enthalpy free cooling setpoint is the
measured enthalpy that the unit will go into free cooling.
#125 – Enthalpy Free Cooling Span• Limits: 5–20 Btu/lbs [11–46 Joules/Gram]• Factory set: 5 Btu/lbs• BACnet variable: AV46• Function: The enthalpy free cooling span is the differ-
ential above and below the free cooling setpoint.#126 – Enthalpy Free Cooling Reset• Limits: 0–100%• Factory set: 50%• BACnet variable: AV47• Function: The enthalpy free cooling reset is the per-
centage of the span value under the setpoint.Variable Free Cooling (Dry Bulb Setpoint Wheel VFD Modulation)
If the outside air temperature is above the summer set-point (selectable) and if the outside air temperature is less than the return air temperature and less than the supply
air temperature setpoint, the wheel modulates to the wheel leaving temperature setpoint.
Dx.Cooling,.WSHP.Cooling,.One.Compressor,.Optional.VRC®.(Discharge.Air.Temperature.Control)If the outside air temperature is above the summer set-point (selectable) and if the coil leaving air temperature rises above the coil leaving air temperature setpoint (se-lectable), the first compressor starts. Modulate compressor to coil leaving air temperature setpoint. Reheat heats up the supply air to the cooling setpoint (if equipped).
Dx.Cooling,.WSHP.Cooling,.Two.Compressors,.Single.Compressor,.Two-stage.(Discharge.Air.Temperature.Control)If the outside air temperature is above the summer set-point (selectable) and if the coil leaving air temperature rises above the coil leaving air setpoint (selectable), the first compressor starts. If more cooling is needed based on the coil leaving air temperature setpoint, after staging delay, the second compressor starts. Reheat heats up the supply air to the cooling setpoint (if equipped).
Dx.Cooling,.WSHP.Cooling,.Two.Compressors,.First.Compressor.VRC.(Discharge.Air.Temperature.Control)If outside air temperature is above summer setpoint (se-lectable), and if coil leaving air temperature rises above coil leaving air setpoint (selectable), first compressor starts and modulates to maintain setpoint. If more cooling is needed based on coil leaving air temperature setpoint, after stag-ing delay, second compressor starts. The first compressor will continue to modulate to maintain coil leaving air tem-perature. Reheat heats up supply air to cooling setpoint (if equipped)
Dx.Cooling,.WSHP.Cooling,.One.Compressor,.Optional.VRC.(Room.Air.Temperature.Control)If the outside air temperature is above the summer set-point (adjustable) and if the (return) room air temperature rises above the summer zone setpoint and the coil leaving air temperature is above the coil leaving setpoint, the first compressor starts. Compressor modulates to coil leaving air temperature setpoint (adjustable). This continues until (return) room air temperature is satisfied.
Dx.Cooling,.WSHP.Cooling,.Two.Compressors.or.Two-stage.Single.Compressor.(Room.Air.Temperature.Control)If the outside air temperature is above the summer set-point (selectable) and if the (return) room air temperature rises above the summer zone setpoint and the coil leaving air is above the coil leaving setpoint, the first compressor starts. If more cooling is needed, based on the coil leav-
VCES-DDC-IOM-1C 9
ing air temperature setpoint, after staging delay, second compressor starts. This process continues until the (return) room air temperature is satisfied.
Dx.Cooling,.WSHP.Cooling,.Two.Compressors,.First.Compressor.VRC®.(Room.Air.Temperature.Control)If outside air temperature is above summer setpoint (se-lectable), and if (return) room air temperature rises above summer zone setpoint and coil leaving air is above coil leaving setpoint, first compressor starts and modulates to maintain setpoint. If more cooling is needed based on coil leaving air temperature setpoint, after staging delay, sec-ond compressor starts. The first compressor will continue to modulate to maintain coil leaving air temperature. Re-heat heats up supply air to cooling setpoint (if equipped).
Dehumidification.(Room.Air.Temperature.Control)If the outside air temperature is above the summer set-point (selectable) and if the return (room) air humidity rises above the return (room) air humidity setpoint, based on optional room humidistat, the first compressor starts. Re-heat heats up the supply air to the cooling setpoint (select-able). If more cooling is needed, based on the coil override leaving air temperature setpoint, after the staging delay, the second compressor starts (if equipped).
This process continues until the return (room) air humidity is satisfied.
Chilled.Water.(Discharge.Air.Temperature.Control)If the outside air temperature is above the summer set-point (selectable), the chilled water valve modulates to maintain the coil leaving air temperature strategy to main-tain the coil leaving air temperature setpoint (selectable). Reheat heats up air to the cooling setpoint (if equipped).
Chilled.Water.(Room.Air.Temperature.Control)If the outside air temperature is above the summer set-point (selectable) and if the room air temperature rises above the room air setpoint, the chilled water valve modu-lates based on a sliding supply air temperature strategy
to maintain the supply air between the summer zone set-point and the minimum supply temperature setpoint.
HeatingGas.or.Electric.SCR.(Discharge.Air.Temperature.Control)If the outside air temperature is below the summer set-point (selectable), the gas module is enabled. Gas burners modulate to maintain the heating setpoint (selectable).
Gas.or.Electric.SCR.(Room.Air.Temperature.Control)If the outside air temperature is below the summer set-point (selectable), the gas module is enabled. If the (re-turn) room air temperature drops below the winter zone setpoint, the gas burners (or electric elements) modulate based on a sliding supply air strategy to maintain the sup-ply air between the winter zone setpoint and the maxi-mum supply air temperature setpoint, until the room air temperature is satisfied.
Gas.or.Electric.Stage.(Discharge.Air.Temperature.Control)If the outside air temperature is below the summer set-point (selectable), the electric post heater is enabled. The heating elements stage to maintain the heating setpoint.
Gas.or.Electric.Stage.(Room.Air.Temperature.Control)If the outside air temperature is below the summer set-point (selectable), the electric post heater is enabled. If the (return) room air temperature drops below the winter zone setpoint, the heating elements modulate based on a sliding supply air strategy to maintain the supply air be-tween the winter zone setpoint and the maximum supply air temperature setpoint, until the room air temperature is satisfied.
Hot.Water.(Discharge.Air.Temperature.Control)If the outside air temperature is below the summer set-point (selectable), the hot water valve modulates to main-tain the heating setpoint (selectable).
Hot.Water.(Room.Air.Temperature.Control)If the outside air temperature is below the summer set-point (selectable), and if the (return) room air temperature drops below the winter zone setpoint, the hot water valve modulates based on a sliding supply air strategy to main-tain the supply air between the winter zone setpoint and the maximum supply temperature setpoint, until the room air temperature is satisfied.
IMPORTANT – COMPRESSOR SAFETYIf either non-freeze switch is made for over two minutes, the last on compressor shuts down for lockout time (selectable, minimum of five minutes). If the non-freeze switch is on for another two minutes, then the first on compressor shuts down for lockout time. If the low pres-sure switch has tripped three times, the compressor will lock off until power is removed from the unit. If on either circuit, the high pressure switch is made, their respective compressor shuts down (manual reset required). There is a minimum of a five minute anti-cycling time before compressors will stage.
VCES-DDC-IOM-1C 10
WSHP.Heating,.One.Compressor,.Optional.VRC®.(Discharge.Air.Temperature.Control)If outside air temperature is below summer setpoint (se-lectable), and if coil leaving air temperature rises above heating setpoint (selectable), first compressor starts. Mod-ulate compressor to heating setpoint. Additional postheat will heat up supply air if heating setpoint cannot be main-tained (if equipped).
WSHP.Heating,.Two.Compressors,.or.Two-stage.Single.Compressor.(Discharge.Air.Temperature.Control)If outside air temperature is below summer setpoint (se-lectable), and if supply air temperature rises above heat-ing setpoint (selectable), first compressor starts. If more heating is needed based on heating setpoint, after staging delay, second compressor starts. Additional postheat will heat up supply air if heating setpoint cannot be main-tained (if equipped).
WSHP.Heating,.Two.Compressors,.First.Compressor.VRC.(Discharge.Air.Temperature.Control)If outside air temperature is below summer setpoint (se-lectable), and if coil leaving air temperature rises above heating setpoint (selectable), first compressor starts and modulates to maintain setpoint. If more cooling is needed based on heating setpoint, after staging delay, second compressor starts. The first compressor will continue to modulate to maintain coil leaving air temperature. Addi-tional postheat will heat up supply air if heating setpoint cannot be maintained (if equipped).
WSHP.Heating,.One.Compressor,.Optional.VRC.(Room.Air.Temperature.Control)If outside air temperature is below summer setpoint (ad-justable), and if (return) room air temperature drops below winter zone setpoint and coil leaving air temperature is below heating setpoint, first compressor starts. Compres-sor modulates to coil leaving air setpoint (adjustable). This continues until (return) room air temperature is satisfied. Additional post heat will heat up supply air if heating set-point cannot be maintained (if equipped).
WSHP.Heating,.Two.Compressors,.or.Two-stage.Single.Compressor.(Room.Air.Temperature.Control)If outside air temperature is below summer setpoint (se-lectable), and if (return) room air temperature rises above winter zone setpoint and coil leaving air is above heating setpoint, first compressor starts. If more cooling needed based on heating setpoint, after staging delay second compressor starts. This continues until (return) room air temperature is satisfied. Additional post heat will heat up supply air if heating setpoint cannot be maintained (if equipped).
WSHP.Heating,.Two.Compressors,.First.Compressor.VRC.(Room.Air.Temperature.Control)If outside air temperature is below summer setpoint (se-lectable), and if (return) room air temperature rises above winter zone setpoint and coil leaving air is above heating setpoint, first compressor starts and modulates to main-tain setpoint. If more cooling is needed based on heating setpoint, after staging delay, second compressor starts. The first compressor will continue to modulate to maintain coil leaving air temperature. Additional post heat will heat up supply air if heating setpoint cannot be maintained (if equipped).
WSHP.Economizer.CoilIf the outside air temperature is above summer setpoint (adjustable) and if the water entering temperature is below the economizer coil setpoint (adjustable) the econo-mizer coil valve will modulate to maintain the coil leaving air temperature. If the economizer coil valve is open 100% for more than two minutes, then the mechanical cooling will be allowed to stage on. The economizer coil valve will remain open while in mechanical cooling until the water entering temperature is above the economizer coil set-point (adjustable).
With both the economizer coil and free cooling options, if the outside air temperature is above summer setpoint and is in the free cooling range, then the economizer coil valve will close and temperature control will follow free cooling. If the outside air temperature rises above the free cooling range and the water entering temperature is below the economizer setpoint (adjustable) then the economizer coil valve will modulate and mechanical cooling will stage on to maintain the coil leaving air temperature as above.
WSHP.Freeze.ProtectionIf the unit has a water leaving temperature sensor and this temperature goes below the water leaving temperature setpoint (adjustable) then the compressor is locked off and the WSHP valve is opened.
WSHP.Head.Pressure.ControlIf the outside air temperature is above the summer set-point (adjustable) and there is the demand for mechani-cal cooling, the head pressure control valve will open to 100%. When the compressor starts, the valve will modu-late to maintain the factory set head pressure setpoint. The valve will be allowed to close to a minimum valve setpoint of 50%. If the compressor has been off for 10 minutes then the valve will close.
If the outside air temperature is below the summer set-point (adjustable) and there is a demand for mechanical heating, the head pressure control valve will open fully and remain open until the compressor has been off for 10 minutes.
VCES-DDC-IOM-1C 11
The BacStat II is the interface to the DDC. It is used to monitor unit operation, provide maintenance/fault feed-back and allow the user to change setpoints. It is con-nected to terminals provided in the control panel area and can either be mounted on the unit (indoor units only), in the control panel area or remotely.
The display shown Figure 4 is the default display when it is idle for several minutes.
The top characters represent the supply air temperature leaving the unit. They also flash, once a second, when one of these conditions occurs:
‘dF’ = Unit is in frost control mode.‘FC’ = Unit is in free cooling mode.‘CF’ = Wheel has failed.‘LP’ = Low pressure alarm has tripped. Requires a manual
reset of DDC power after three failures.‘HP’ = High pressure alarm has tripped. Requires manual
reset of pressure switch.‘LL’ = Coil low limit sensor has tripped (supplied by others).‘LS’ = Low supply air temperature alarm. Requires man-
ual reset of DDC power.‘HS’ = High supply air temperature alarm. Requires man-
ual reset of DDC power.‘OL’ = Supply/exhaust overload has tripped.
Alternatively, it can be an external unit fault (supplied by others).
‘EF’ = Dirty exhaust filters.‘SF’ = Dirty supply filters.‘FS’ = Flow switch alarm or low water leaving tempera-
ture alarm.
DDC Interface
Frost Control (Selectable)Recirculation.DefrostIf the outside air temperature is below the frost control setpoint (selectable), frost control is enabled. Frost control timing varies depending upon strategy selected.
• Outside air damper closes.• Recirculation damper opens.• After delay, exhaust air damper closes and exhaust
blower stops.• Supply blower keeps running.• Wheel stops.
Exhaust.Only.DefrostIf the outside air temperature is below the frost control setpoint (selectable), frost control is enabled. Frost control timing varies depending upon strategy selected.
• Outside air damper closes.• Exhaust air damper is open.• Recirculation damper stays closed (if equipped).• Exhaust blower keeps running.• Supply blower stops.• Wheel keeps running.
Preheat.Frost.PreventionIf the outside air temperature is below the frost control setpoint (selectable), frost control is enabled.
If the preheater is on/off, first stage preheating is enabled. If the outside air temperature drops below the frost con-trol setpoint plus the differential, second stage preheating is enabled. This process continues for the third and fourth stages of preheating.
If the preheater is modulating, the heater elements modu-late to maintain the frost control setpoint (selectable).
Variable.Speed.Defrost.(VSD).Frost.PreventionThe VSD frost control setting is 33°F (selectable). If the exhaust air temperature drops below the VSD control set-point (selectable), the wheel slows down to 30% of the nominal speed. The wheel continues to modulate to main-tain the frost control setpoint.
Non-defrostNo defrost strategy is implemented.
Figure 4: BacStat II
VCES-DDC-IOM-1C 12
The middle characters represent the mode the unit is in:
‘Un’ = Unoccupied.‘Ov’ = Occupied ventilation.‘Or’ = Occupied recirculation.‘Ur’ = Unoccupied recirculation.
The bottom characters represent the supply air cooling/heating setpoint. If the zone configuration is set to dis-charge air control (MV11= NO) and the unit has hot gas reheat, then this will display the cooling setpoint in sum-mer mode and the heating setpoint in the winter mode. If the unit does not have hot gas reheat then it will display the coil leaving setpoint in the summer mode. If the zone configuration is set to room or return air (MV11= RM or RET) then this will display the summer zone setpoint in the summer mode and the winter zone setpoint in the winter mode.
To navigate through the setpoints, use the on and off buttons—on to go up, off to go down. To change the set-points, use the up and down arrow buttons. Push once on the up button to go up, push it again to stop. See Appen-dix B for the entire read and read/write variables.
Supply air temperature/maintenance
Mode
Heating/cooling icon
Supply airsetpoint
Supply fan on icon
Figure 5: Main screen
Item number
Description
Setpoint
Figure 6: Changing setpoints
VCES-DDC-IOM-1C 13
1. Complete wire connections between the unit and the exhaust air damper by matching the correct wire colors on the actuator and end switch with the wire colors on the schematic before installing (ACT4004, if applicable).
2. The supply air temperature sensor (SN3002) is in-cluded loose in the unit and can be found in the con-trol panel. Install the temperature sensor a minimum of 12 feet downstream of the unit. The further the sensor is from the heating/cooling source, the greater the accuracy in readings because more air mixing is allowed. Wire it to IP4 on the DDC (DDC3002). A coil of wire can be found in the supply fan cabinet behind the fan (or in the gas cabinet if applicable). One end of this coil is connected to IP4 on the DDC (DDC3002).
3. Install the BacStat II (DC3036). It is included loose in the unit and can be found in the control panel. De-termine required location and connect to terminals FW 380, 381, 382 and 383 using two twisted pair cables, the first for power connection. The LinkNet Cable needs to be balanced 100 to 120 ohm nomi-nal impedance Twisted Shielded Pair Cable, Nominal capacitance of 16PF/FT or lower (see Appendix C for networking practice).
4. Units will require a dry contact start interlock. See Stand Alone Operation or Network Operation and Ventilation Control Scheduling Modes. Determine required method, mode and terminals and make connection.
Appendix A: Control Wiring Connections Example
VCES-DDC-IOM-1C 14
NO
T A
CTU
AL
SC
HEM
ATI
CR
EFE
REN
CE O
NLY
NO
T A
CTU
AL
REFE
REN
CE
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
Fro
m 1
018
115
VA
CFr
om
102
0N
eutr
alB
KW
BK
FU30
01H
1H
2
PNL
302
PNL
301
GY
Co
ntr
ols
tran
sfo
rmer
XF3
001
100
VA
X1
X2
Occ
. ven
tco
nta
ctb
y o
ther
s
Un
occ
. rec
irc
con
tact
by
oth
ers
R30
0610
KR
3006
A4.
99K
R30
06B
2.49
KR
3006
C1.
24K
FW 304
FW 305
FW 305
FW 306
FW 306
FW 307
FW 307
FW 308
Y
CYO
O GY
BL
BR
Y Y Y Y R Y V Y BR
BR
BL
VY
No
te:
Rem
ove
jum
per
wh
enO
A d
amp
er a
ctu
ato
ren
d s
wit
ch is
inst
alle
d.
No
te:
Rem
ove
jum
per
wh
enEA
dam
per
act
uat
or
end
sw
itch
is in
stal
led
.JP
3038
JP30
38
AC
T400
1A
CT4
004
S4S6
S4S6
OA
dam
per
en
dsw
itch
set
at
90º
EA d
amp
er e
nd
swit
ch s
et a
t 90
ºB
R
PNL
309
PNL
310
PNL
310
PNL
311
R30
1410
KR
3014
A4.
99K
SN30
08 w
hee
l le
avin
g a
ir
tem
per
atu
rese
nso
r
SN30
10
ou
tsid
e ai
r \
tem
per
atu
rese
nso
r
1 2 1 2 1 2 1 2 1 2
SN30
12 s
up
ply
air
tem
per
atu
rese
nso
r (f
ield
in
stal
led
10
du
ct le
ng
ths)
SN30
14 r
etu
rnai
r te
mp
erat
ure
sen
sor
SN30
16 e
xhau
stai
r te
mp
erat
ure
sen
sor
CB
L300
8
CB
L301
0
CB
L301
2
CB
L301
4
CB
L301
6WWWWW B
KSH
LD
BK
BR
SHLD
BK
SHLD
BK
SHLD
BK
SHLD
PNL
311
PNL
311
PNL
311
PNL
313
R30
182.
49K
R30
18A
1.24
K
Fro
m 3
001
24 V
A−
Fro
m 3
000
24 V
A+
Op
tio
n f
ree
coo
ling
(S
or
D)
SN30
19 o
uts
ide
air
hu
mid
ity
sen
sor
SN30
22 r
etu
rnai
r h
um
idit
yse
nso
r
Op
tio
n f
ree
coo
ling
(D
)
CB
L
CB
L SHLD
SHLD
R W BK
R W BK
PNL
301
PNL
301
+ 0 − + 0 −
To 2
033,
301
6, 3
030,
400
0, 5
029
24 V
AC
+
To 3
016,
303
0, 4
000
24 V
AC
−D
DC
3002
24~
GN
D
24~
GN
D
Power
Power out
+ −
+ −
IP1
IP2
GN
D
GN
D
OP1
GN
D
OP2
GN
D
OP3
GN
D
OP4
GN
D
OP5
GN
D
OP6
GN
D
OP7
GN
D
OP8
GN
D
IP3
GN
D
IP4
GN
D
IP5
GN
D
IP6
GN
D
IP7
GN
D
IP8
GN
D
IP9
GN
D
BK
W SHLD
BK
W SHLD
++++
CR
3011
CR
3009
CR
3007
CR
3013
CR
3015
CR
3017C
OM
+C
OM
+C
OM
CO
M
CO
M
CO
M
To 3
036,
401
2, 4
026
DD
C 2
4 V
AC
+
To 3
037,
401
3, 4
027
DD
C 2
4 V
AC
−
To 3
038,
401
4, 4
028
NET
2+
To 3
039,
401
5, 4
029
NET
2−
Sup
ply
blo
wer
on
NO
202
6N
C
Exh
aust
blo
wer
on
NO
202
7N
C
Wh
eel o
nN
O 2
028
NC
No
te 1
No
te 2
No
te 3
OA
dam
per
actu
ato
rN
O 4
002
NC
400
1
EA d
amp
erac
tuat
or
NO
400
5N
C 4
004
Rec
irc
dam
per
actu
ato
rN
O 4
008
NC
400
7
OP7
(G
ND
)
OP7
OP7
SH
LD
OP8
(G
ND
)
OP8
OP8
SH
LD
To 5
023,
503
0
To 5
022,
503
1
To 5
024,
503
2
To 1
013
To 1
014
To 1
014
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
Op
tio
n s
enso
r co
nta
cts
(D, B
)O
pti
on
hea
tin
g (
H, S
) o
r C
oo
ling
(C
)
Sup
ply
filt
ersw
itch
PS3
026
Exh
aust
filt
ersw
itch
PS3
026A
RY
1.6”
RY
1.6”
RB
40º
W/R
W/Y
BK
BR
OO
PNL
361
PNL
362
PNL
362
PNL
363
PNL
363
PNL
364
PNL
364
PNL
365
BL
BL
VV
V
R30
2810
KR
3028
A4.
99K
R30
28B
2.49
KR
3028
C1.
24K
Low
lim
itth
erm
ost
atTA
S302
6O
L100
3
OL1
001
9695
9695
Exh
aust
blo
wer
Sup
ply
blo
wer
DD
C30
02
IP10
GN
D
IP11
GN
D
Fro
m 3
000
24 V
AC
+Fr
om
300
124
VA
C−
SN30
33
Wh
eel
rota
tio
nse
nso
r
1 2B
K
BR
BR
BL
CR
2028
64
Wh
eel e
nab
le
Wh
eel r
ota
tio
nb
oar
d W
RS3
032
24N
O NC
CO
MC
OM
SEN
VEN
ALA
DIS
DEF
+
DEF
−
Op
tio
n s
enso
r co
nta
cts
(W, B
)
No
te 1
: Op
tio
n o
uts
ide
air
dam
per
(A
, B, C
, D)
No
te 2
: Op
tio
n e
xhau
st a
ir d
amp
er (
A, B
, C, D
)N
ote
3: O
pti
on
def
rost
(D
) o
r u
no
ccu
pie
d r
ecir
FW38
0O G
Y
BL
BR
FW38
1
FW38
2
FW38
3
Fro
m 3
002
DD
C 2
4 V
AC
+
Fro
m 3
003
DD
C 2
4 V
AC
−
Fro
m 3
004
NET
2 +
Fro
m 3
005
NET
2 −
PWR
24V
CO
M
NET
+
NET
−
DC
3036
Bac
Stat
II
Des
crip
tio
n:
– O
ne-
spee
d–
VFD
def
rost
– D
DC
– V
eria
ble
sp
eed
fre
e co
olin
g
No
tes:
Su
pp
lied
by
oth
ers
C
on
trac
tor
inst
alle
d
Co
ntr
acto
r w
irin
g
Req
uir
es s
hie
lded
cab
le
Wir
e le
ader
U
nit
ass
emb
ly (
no
t o
n c
on
tro
l pan
el)
O
pti
on
s
This
dra
win
g is
th
e p
rop
erty
of
Ven
mar
CES
. Its
co
nte
nt
is p
rop
riet
ary
and
can
no
t b
e re
veal
ed t
o o
uts
ide
par
ties
wit
ho
ut
the
wri
tten
co
nse
nt
of
Ven
mar
CES
.
1
#4
#1#2
#3
Figure A1: DDC control wiring connection example 1
VCES-DDC-IOM-1C 15
NO
T A
CTU
AL
SC
HEM
ATI
CR
EFE
REN
CE O
NLY
NO
T A
CTU
AL
REFE
REN
CE
#1
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
Des
crip
tio
n:
– O
ne-
spee
d–
VFD
def
rost
– D
DC
– V
eria
ble
sp
eed
fre
e co
olin
g
No
tes:
Su
pp
lied
by
oth
ers
C
on
trac
tor
inst
alle
d
Co
ntr
acto
r w
irin
g
Req
uir
es s
hie
lded
cab
le
Wir
e le
ader
U
nit
ass
emb
ly (
no
t o
n c
on
tro
l pan
el)
O
pti
on
s
This
dra
win
g is
th
e p
rop
erty
of
Ven
mar
CES
. Its
co
nte
nt
is p
rop
riet
ary
and
can
no
t b
e re
veal
ed t
o o
uts
ide
par
ties
wit
ho
ut
the
wri
tten
co
nse
nt
of
Ven
mar
CES
.
Fro
m 3
000
24 V
AC
+Fr
om
300
124
VA
C−
W/R
CR
3013
CR
3015
CO
M
NC
actu
ato
rO
A d
amp
erC
R30
13
CO
M
NC
EA d
amp
erac
tuat
or
CR
3015
CO
M
NO
EA d
amp
erac
tuat
or
CR
3017
CO
M
NC
reci
rc d
amp
erac
tuat
or
CR
3017
CO
M
NO
reci
rc d
amp
erac
tuat
or
CO
M
NO
actu
ato
rO
A d
amp
er
No
te 1
No
te 2
No
te 3
GN
/R
BK
/R
GN
/R
BK
/R
GN
/R
BK
/R
GN
/R
BK
/R
GN
/R
BK
/R
GN
/R
BK
/R
PNL
330
PNL
331
PNL
332
PNL
333
PNL
334
PNL
335
70
(2)
6V
(1)
70
(2)
6V
(1)
70
(2)
6V
(1)
AC
T400
1O
A d
amp
erac
tuat
or
No
. 301
2N
ote
: Pin
s C
W a
nd
CC
W m
ay b
e sw
app
edo
n a
ctu
ato
r fo
rp
rop
er o
per
atio
n.
For
spri
ng
ret
urn
actu
ato
rs o
nly
pin
s(1
) an
d (
2) a
re u
sed
.
AC
T400
4EA
dam
per
actu
ato
rN
o. 3
012
No
te: P
ins
CW
an
dC
CW
may
be
swap
ped
on
act
uat
or
for
pro
per
op
erat
ion
.Fo
r sp
rin
g r
etu
rnac
tuat
ors
on
ly p
ins
(1)
and
(2)
are
use
d.
AC
T400
7R
ecir
c d
amp
erac
tuat
or
No
No
te: P
ins
CW
an
dC
CW
may
be
swap
ped
on
act
uat
or
for
pro
per
op
erat
ion
.Fo
r sp
rin
g r
etu
rnac
tuat
ors
on
ly p
ins
(1)
and
(2)
are
use
d.
Op
tio
n c
oo
ling
(C
, I, S
)
Fro
m 3
002
DD
C 2
4 V
AC
+
Fro
m 3
003
DD
C 2
4 V
AC
−
Fro
m 3
004
NET
2+
Fro
m 3
005
NET
2−
0 GY
BL
BR
Op
tio
n c
oo
ling
(I)
Op
tio
n c
oo
ling
(I–
D)
PNL
336
PNL
337
PNL
336
PNL
337
R V
R V
PS40
17Lo
w p
ress
ure
con
tro
l 1C
ut
in =
52
psi
gC
ut
ou
t =
57
psi
g
PS40
17A
Low
pre
ssu
reco
ntr
ol 2
Cu
t in
= 5
2 p
sig
Cu
t o
ut
= 5
7 p
sig
Co
olin
g o
verr
ide
con
tact
by
oth
ers
FW 315
FW 314
BL
BL
FW 317
FW 316
BR
BR
Deh
um
idif
icat
ion
con
tact
by
oth
ers
SN40
21C
oo
ling
leav
ing
air
tem
per
atu
rese
nso
r
1 2
CB
L402
1W B
KSH
LD
WBK
BR
Y0VY
SHLD
DD
C e
xpan
der
DD
C40
12
~24
GN
D
GN
D
GN
D
GN
D
GN
D
IP1
IP2
IP3
IP4
++
−
GN
D
GN
D
GN
D
GN
D
OP1
OP2
OP3
OP4
~24
~24
~24
~24
~24
GN
D
GN
D
GN
D
IP1
IP2
+ −
GN
D
GN
D
OP1
OP2
~24
~24
CR
4014
CO
M
+C
OM
+C
OM
No
te 4
Co
olin
gst
age
1N
O 2
006,
403
6N
C
To 4
042
OP2
(24
~)
To 4
03, 4
043
OP2
(G
ND
)
To 4
037,
404
4O
P2
To 5
002,
500
9H
GR
H C
OM
To 5
001,
500
8H
GR
H 0
–10
VD
CC
R40
21
Reh
eat
valv
eN
O 2
010
NC
Op
tio
n c
oo
ling
(I–
D)
/ re
hea
t (N
)
4049
4048
4047
4046
4045
4044
4043
4042
4041
4040
4039
4038
4037
4036
4035
4034
4033
4032
4031
4030
4029
4028
4027
4026
4025
Fro
m 4
015
OP2
(24
~)
Fro
m 4
016
OP2
(G
ND
)
Fro
m 4
017
OP2
0 Y BR
BL
BL
24V
CO
M
0–10
V
CR
4039
Mu
lti-
ple
xin
gre
lay
NC
CO
M NO NC
CO
M NO
FW 402
FW 403
To c
on
den
ser
sect
ion
sta
ge
2
To c
on
den
ser
sect
ion
st
age
1
Op
tio
n c
oo
ling
(S
– 2)
Op
tio
n c
oo
ling
(S
–1, 2
)
CR
4014
CO
M
NO
Co
olin
gst
age
1
V V
FW 400
FW 401
Fro
m 3
002
DD
C 2
4 V
AC
+
Fro
m 3
003
DD
C 2
4 V
AC
−
Fro
m 3
004
NET
2+
Fro
m 3
005
NET
2−
FW 319
FW 318
Hea
tin
g o
verr
ide
con
tact
by
oth
ers
RRBR
BL
BL
BK
W
GY
Y
0
DD
C e
xpan
der
2D
DC
4026
Op
tio
n h
eati
ng
(E,
F, G
, H, I
, S, T
)
CR
4028 Op
tio
n h
eati
ng
(G
, E)
Hea
ten
able
NO
102
9, 1
035,
104
2N
C
To 2
034,
204
0, 4
039
Hea
t C
OM
2
To 2
035,
204
1, 4
040
Hea
t st
aged
To 1
035,
1040
Hea
t C
OM
To 1
034,
1041
Hea
t 0–
10 V
DC
To 1
036,
1042
Hea
t SH
LD
CB
L403
0
WBK
SHLD
Op
tio
n c
oo
ling
(C
)
Op
tio
n h
eati
ng
(H
, I, S
, T)
Fro
m 4
016
OP2
(G
ND
)
Fro
m 4
028
Hea
t C
OM
2
Fro
m 4
029
Hea
t st
aged
Fro
m 4
017
OP2
Y BR
BK
W
FW 371
FW 372
FW 373
FW 3710
− +
To c
hill
edw
ater
valv
eac
tuat
or
To h
ot
wat
erva
lve
actu
ato
r
No
te 1
: O
pti
on
ou
tsid
e ai
r d
amp
er –
A, B
, C, D
No
te 2
: O
pti
on
exh
aust
air
dam
per
– A
, B, C
, DN
ote
3:
Op
tio
n d
efro
st –
D o
r u
no
ccu
pie
d r
ecir
cN
ote
4:
Op
tio
n c
oo
ling
– I
or
S
Power/Net 1
Figure A2: DDC control wiring connection example 2
VCES-DDC-IOM-1C 16
Tabl
e B1
: DD
C P
oint
s Re
fere
nce
Gui
de
Item
#D
escr
ipti
on
Lim
its
Fact
ory
Se
tB
AC
net
V
aria
ble
Fun
ctio
n
1O
t1O
utsi
de a
ir te
mpe
ratu
reN
/AN
/AA
I3Te
mpe
ratu
re r
eadi
ng.
2St
1Su
pply
air
tem
pera
ture
N/A
N/A
AI4
Tem
pera
ture
rea
ding
.3
Rt1
Retu
rn a
ir te
mpe
ratu
reN
/AN
/AA
I5Te
mpe
ratu
re r
eadi
ng.
4Et
1Ex
haus
t ai
r te
mpe
ratu
reN
/AN
/AA
I6Te
mpe
ratu
re r
eadi
ng.
5O
H1
Out
side
air
hum
idity
(o
ptio
nal)
N/A
N/A
AI7
Hum
idity
rea
ding
.
6RH
1Re
turn
air
hum
idity
(o
ptio
nal)
N/A
N/A
AI8
Hum
idity
rea
ding
.
7O
n/of
fSu
pply
blo
wer
ope
ratio
nO
n/of
fN
/ABO
1Su
pply
blo
wer
ope
ratio
n.8
BAC
BacS
tat
room
tem
pera
ture
N/A
N/A
AI1
01Te
mpe
ratu
re r
edin
g.9
Prg
Prog
ram
IDN
/AN
/AA
V10
00Pr
ogra
m ID
.
10D
prD
ampe
r en
d sw
itch
N/A
N/A
M17
UC
(1) –
unc
onne
cted
.N
O (2
) – N
o da
mpe
r en
d sw
itch
mad
e.ED
(6) –
Exh
aust
dam
per
end
switc
h m
ade.
OD
(10)
– O
utsi
de d
ampe
r en
d sw
itch
mad
e.O
D/E
D (1
4) –
Out
side
and
exh
aust
dam
per
end
switc
h m
ade.
101
Stp
Hig
h lim
it se
tpoi
nt10
0°F–
160°
F [3
8°C
–71°
C]
160°
FA
V2
Uni
t sh
uts
dow
n w
hen
supp
ly t
empe
ratu
re r
ises
abo
ve t
his
setp
oint
.
102
Stp
Low
lim
it se
tpoi
nt35
°F–5
0°F
[2°C
–10°
C]
35°F
AV
3U
nit
shut
s do
wn
whe
n su
pply
tem
pera
ture
dro
ps b
elow
thi
s se
tpoi
nt f
or t
he lo
w li
mit
dela
y.
103
Stp
Low
lim
it de
lay
0–15
min
utes
5 m
inut
esA
V4
Use
d in
con
junc
tion
with
the
low
lim
it se
tpoi
nt. A
tim
e de
lay
befo
re t
he u
nit
will
shu
t do
wn
if th
e su
pply
air
drop
s be
low
the
low
lim
it se
tpoi
nt.
104
Stp
Sum
mer
set
poin
t5°
F–80
°F
[−15
°C–2
7°C
]60
°FA
V5
The
sum
mer
set
poin
t is
the
tem
pera
ture
for
the
uni
t to
cha
nge
over
bet
wee
n su
mm
er
and
win
ter
mod
es o
f op
erat
ion.
105
Stp
Sum
mer
spa
n1°
F–8°
F
[0.5
°C–5
°C]
4°F
AV
6Th
e su
mm
er s
pan
is t
he d
iffer
entia
l abo
ve a
nd b
elow
the
sum
mer
set
poin
t.
106
Stp
Sum
mer
res
et0–
100%
50%
AV
7Th
e su
mm
er r
eset
is t
he s
hift
in t
he s
pan
belo
w t
he s
umm
er s
etpo
int
by X
%.
107
Stp
Coo
ling
setp
oint
50°F
–80°
C
[10°
C–2
7°C
]60
°FA
V10
The
cool
ing
setp
oint
is t
he t
empe
ratu
re t
hat
the
rehe
at w
ill h
eat
the
supp
ly a
ir up
to
(sum
mer
mod
e on
ly).
108
Stp
Coo
ling
span
4°F–
12°F
[2
°C–7
°C]
4°F
AV
11Th
e co
olin
g sp
an is
the
diff
eren
tial a
bove
and
bel
ow t
he c
oolin
g se
tpoi
nt.
109
Stp
Coo
ling
rese
t0–
75%
50%
AV
12Th
e co
olin
g re
set
is t
he s
hift
in t
he s
pan
belo
w t
he c
oolin
g se
tpoi
nt b
y X
%.
110
Stp
Coo
l off
min
imum
5–30
min
utes
10 m
inut
esA
V13
Aft
er a
low
pre
ssur
e co
nditi
on p
ersi
sts
and
shut
s th
e co
mpr
esso
r do
wn,
thi
s is
the
am
ount
of
timeb
efor
e th
e D
DC
will
try
to
rest
art
the
com
pres
sor.
111
Stp
Hea
ting
setp
oint
50°F
–105
°F
[10°
C–4
0°C
]80
°FA
V20
The
heat
ing
setp
oint
is t
he t
empe
ratu
re t
hat
the
post
hea
t w
ill h
eat
the
supp
ly a
ir up
to
durin
g di
scha
rge
air
tem
pera
ture
con
trol
(win
ter
mod
e on
ly).
112
Stp
Hea
ting
span
4°F–
20°F
[2
°C–1
2°C
]4°
FA
V21
The
heat
ing
span
is t
he d
iffer
entia
l abo
ve a
nd b
elow
the
hea
ting
setp
oint
.
113
Stp
Hea
ting
rese
t0–
75%
50%
AV
22Th
e he
atin
g re
set
is t
he s
hift
in t
he s
pan
belo
w t
he h
eatin
g se
tpoi
nt b
y X
%.
114
Stp
Hea
t of
f m
inim
um1–
30 m
inut
es4
min
utes
AV
23A
fter
the
hea
ter
has
turn
ed o
ff, t
his
is t
he m
inim
um t
ime
that
the
DD
C w
ill w
ait
befo
re
turn
ing
it ba
ck o
n.
115
Stp
Coi
l lea
ving
set
poin
t40
–80°
F [4
–27°
C]
55°F
AV
143
The
coil
leav
ing
setp
oint
is t
he t
empe
ratu
re t
hat
the
cool
ing
coil
will
coo
l the
coi
l lea
ving
ai
r te
mpe
ratu
re d
own
to d
urin
g di
scha
rge
air
tem
pera
ture
con
trol
(sum
mer
mod
e on
ly).
116
Stp
Coi
l lea
ving
spa
n4°
F–12
°F
[2°C
–7°C
]4°
FA
V14
4Th
e co
il le
avin
g sp
an is
the
diff
eren
tial a
bove
and
bel
ow t
he c
oil l
eavi
ng s
etpo
int.
117
Stp
Coi
l lea
ving
res
et0–
75%
50%
AV
145
The
coil
leav
ing
rese
t is
the
shi
ft in
the
spa
n be
low
the
coi
l lea
ving
set
poin
t by
X%
.
Appendix B: DDC Points Reference Guide
VCES-DDC-IOM-1C 17
Tabl
e B1
: DD
C P
oint
s Re
fere
nce
Gui
de
Item
#D
escr
ipti
on
Lim
its
Fact
ory
Se
tB
AC
net
V
aria
ble
Fun
ctio
n
118
Stp
Coi
l ove
rrid
e le
avin
g se
tpoi
nt40
°F–6
5°F
[4°C
–18°
C]
50°F
AV
146
The
coil
over
ride
leav
ing
setp
oint
is t
he t
empe
ratu
re t
hat
the
cool
ing
coil
will
coo
l the
coi
l le
avin
g ai
rtem
pera
ture
dow
n to
dur
ing
room
air
tem
pera
ture
/hum
idity
con
trol
(sum
mer
m
ode
only
).
119
Stp
Coi
l ove
rrid
e le
avin
g sp
an4–
12°F
[2–7
°C]
4°F
AV
147
The
coil
over
ride
leav
ing
span
is t
he d
iffer
entia
ls a
bove
and
bel
ow t
he c
oil o
verr
ide
leav
-in
g se
tpoi
nt.
120
Stp
Coi
l ove
rrid
e le
avin
g re
set
0–75
%50
%A
V14
8Th
e co
il ov
errid
e le
avin
g re
set
is t
he s
hift
in t
he s
pan
belo
w t
he c
oil o
verr
ide
leav
ing
setp
oint
by
X%
.
121
Stp
Hea
ting
over
ride
setp
oint
50°F
–105
°F
[10°
C–4
0°C
]90
°FA
V14
0Th
e he
atin
g ov
errid
e se
tpoi
nt is
the
tem
pera
ture
tha
t th
e po
st h
eat
will
hea
t th
e su
pply
air
up t
o du
ring
room
air
tem
pera
ture
con
trol
(win
ter
mod
e on
ly).
122
Stp
Hea
ting
over
ride
span
4°F–
20°F
[2
°C–1
2°C
]4°
FA
V14
1Th
e he
atin
g ov
errid
e sp
an is
the
diff
eren
tial a
bove
and
bel
ow t
he h
eatin
g ov
errid
e se
tpoi
nt.
123
Stp
Hea
ting
over
ride
rese
t0–
75%
50%
AV
142
The
heat
ing
over
ride
rese
t is
the
shift
in th
e sp
an b
elow
the
heat
ing
over
ride
setp
oint
by
X%
.
124
Stp
Enth
alpy
fre
e co
olin
g se
tpoi
nt
10–7
0 Bt
u/lb
s [2
3–16
3 Jo
ules
/gr
am]
20 B
tu/lb
sA
V45
The
enth
alpy
fre
e co
olin
g se
tpoi
nt is
the
mea
sure
d en
thal
py t
hat
the
unit
will
go
into
fre
e co
olin
g. S
ite e
leva
tion
(AV
153)
may
nee
d to
be
upda
ted
125
Stp
Enth
alpy
fre
e co
olin
g sp
an5–
20 B
tu/lb
s5
Btu/
lbs
AV
46Th
e en
thal
py f
ree
cool
ing
span
is t
he d
iffer
entia
l abo
ve a
nd b
elow
the
ent
halp
y se
tpoi
nt.
126
Stp
Enth
alpy
fre
e co
olin
g re
set
0–10
0%50
%A
V47
The
enth
alpy
fre
e co
olin
g re
set
is t
he s
hift
in t
he s
pan
belo
w t
he e
ntha
lpy
free
coo
ling
setp
oint
by
X%
.
127
Stp
Dy
bulb
fre
e co
olin
g se
tpoi
nt40
°F–8
0°F
[5°C
–27°
C]
65°F
AV
60Th
e dr
y bu
lb f
ree
cool
ing
setp
oint
is t
he t
empe
ratu
re t
hat
the
unit
will
go
into
fre
e co
ol-
ing.
Use
d w
ith V
SD f
ree
cool
ing
optio
n
128
Stp
Dry
bul
b fr
ee c
oolin
g sp
an4°
F–20
°F
[2°C
–12°
C]
4°F
AV
61Th
e dr
y bu
lb f
ree
cool
ing
span
is t
he d
iffer
entia
l abo
ve a
nd b
elow
the
fre
e co
olin
g se
t-po
int.
Use
d w
ith V
SD f
ree
cool
ing
optio
n.
129
Stp
Dry
bul
b fr
ee c
oolin
g re
set
0–10
0%50
%A
V62
The
enth
alpy
fre
e co
olin
g re
set
is t
he s
hift
in t
he s
pan
belo
w t
he d
ry b
ulb
free
coo
ling
setp
oint
by
X%
. Use
d w
ith V
SD f
ree
cool
ing
optio
n.13
0St
pFr
ee c
oolin
g se
lect
On/
off
On
BV61
This
var
iabl
e en
able
s or
dis
able
s fr
ee c
oolin
g.
131
Stp
Def
rost
set
poin
t−
5°F–
50°F
[−
20°C
–10°
C]
5°F
AV
65Th
e de
fros
t se
tpoi
nt is
the
tem
pera
ture
whe
re t
he u
nit
will
go
into
def
rost
mod
e.
(Def
aults
to
33°F
for
VFD
def
rost
).
132
Stp
Def
rost
spa
n2°
F–10
°F
[1°C
–5°C
]2°
FA
V66
The
defr
ost
span
is t
he d
iffer
entia
l abo
ve a
nd b
elow
the
def
rost
set
poin
t.
133
Stp
Def
rost
res
et0–
100%
50%
AV
67Th
e de
fros
t re
set
is t
he s
hift
in t
he s
pan
belo
w t
he d
efro
st s
etpo
int
by X
%.
134
Stp
Elec
tric
reh
eat
switc
hO
n/of
fO
ffBV
35Th
is v
aria
ble
enab
les
or d
isab
les
elec
tric
reh
eat.
Ena
ble
this
poi
nt o
nly
if yo
u do
not
hav
e H
RG a
nd y
ou w
ish
to u
se y
our
elec
tric
pos
t he
at.
135
Stp
Fact
ory
set,
do
no
t ch
ang
e13
6St
pFa
ctor
y se
t, d
o n
ot
chan
ge
137
Stp
Fact
ory
set,
do
no
t ch
ang
e13
8St
pFa
ctor
y se
t, d
o n
ot
chan
ge
139
Stp
Fact
ory
set,
do
no
t ch
ang
e14
0St
pFa
ctor
y se
t, d
o n
ot
chan
ge
141
Stp
Fact
ory
set,
do
no
t ch
ang
e14
2St
pFa
ctor
y se
t, d
o n
ot
chan
ge
143
Stp
Out
side
air
dam
per
min
imum
0–10
0%10
0%A
V15
0Th
e ou
tsid
e ai
r da
mpe
r m
inim
um s
etpo
int
is s
et in
con
junc
tion
with
the
exh
aust
air
set-
poin
t da
mpe
r m
inim
um s
etpo
int
to a
llow
for
the
req
uire
d re
circ
ulat
ion
air.
144
Stp
Exha
ust
air
dam
per
min
imum
0–10
0%10
0%A
V15
1Th
e ex
haus
t ai
r da
mpe
r m
inim
um s
etpo
int
is s
et in
con
junc
tion
with
the
out
side
air
set-
poin
t da
mpe
r m
inim
um s
etpo
int
to a
llow
for
the
req
uire
d re
circ
ulat
ion
air.
VCES-DDC-IOM-1C 18
Tabl
e B1
: DD
C P
oint
s Re
fere
nce
Gui
de
Item
#D
escr
ipti
on
Lim
its
Fact
ory
Se
tB
AC
net
V
aria
ble
Fun
ctio
n
145
Stp
Burn
er m
inim
um o
utpu
t0–
50%
0%A
V15
2U
sed
to s
et t
he m
inim
um m
odul
ated
out
put
to t
he b
urne
r to
avo
id c
yclin
g. If
Teg
a bu
rner
is
use
d, it
mus
t be
set
to
12%
.14
6St
pSi
te e
leva
tion
0–10
0 (x
100)
ft
10 (x
100)
ftA
V15
3U
sed
for
enth
alpy
cal
cula
tions
.
147
Stp
Sum
mer
zon
e se
tpoi
nt60
°F–8
0°F
[15°
C–2
5°C
]70
°FA
V84
The
sum
mer
zon
e se
tpoi
nt is
the
roo
m o
r re
turn
air
setp
oint
for
sum
mer
mod
e.
148
Stp
Sum
mer
zon
e sp
an1°
F–8°
F
[0.5
°C–5
°C]
2°F
AV
85Th
e su
mm
er z
one
span
is t
he d
iffer
entia
l abo
ve a
nd b
elow
sum
mer
zon
e se
tpoi
nt.
149
Stp
Sum
mer
zon
e re
set
0–10
0%50
%A
V86
The
sum
mer
zon
e re
set
is t
he s
hift
in t
he s
pan
belo
w t
he s
umm
er z
one
setp
oint
by
X%
.
150
Stp
Win
ter
zone
set
poin
t60
°F–8
0°F
[15°
C–2
5°C
]70
°FA
V87
The
win
ter
zone
set
poin
t is
the
roo
m o
r re
turn
air
setp
oint
for
win
ter
mod
e.
151
Stp
Win
ter
zone
spa
n1°
F–8°
F
[0.5
°C–5
°C]
2°F
AV
88Th
e w
inte
r zo
ne s
pan
is t
he d
iffer
entia
l abo
ve a
nd b
elow
win
ter
zone
set
poin
t.
152
Stp
Win
ter
zone
res
et0–
100%
50%
AV
89Th
e w
inte
r zo
ne r
eset
is t
he s
hift
in t
he s
pan
belo
w t
he w
inte
r zo
ne s
etpo
int
by X
%.
153
Stp
Zone
con
figur
atio
nN
O –
RET
– R
MN
OM
V11
The
zone
con
figur
atio
n al
low
s th
e un
it to
be
used
for
zon
e co
olin
g/he
atin
g.
NO
= N
o zo
ne c
ontr
ol
RET
= R
etur
n ai
r zo
ne c
ontr
ol (r
etur
n ai
r te
mpe
ratu
re s
enso
r)
RM =
Roo
m a
ir zo
ne c
ontr
ol (B
acst
at II
tem
pera
ture
sen
sor*
*)
154
Stp
Min
imum
sup
ply
tem
-pe
ratu
reM
in. 4
0°F
[5°C
]50
°FA
V26
Use
d w
ith R
ET o
r RM
zon
e co
nfigu
ratio
n. P
rote
cts
the
room
fro
m t
oo lo
w o
f a
supp
ly a
ir te
mpe
ratu
re.
155
Stp
Max
imum
sup
ply
tem
-pe
ratu
reM
ax. 1
20°F
[4
9°C
]10
0°F
AV
27U
sed
with
RET
or
RM z
one
confi
gura
tion.
Pro
tect
s th
e ro
om f
rom
too
hig
h of
a s
uppl
y ai
r te
mpe
ratu
re.
156
Stp
Fact
ory
set,
do
no
t ch
ang
e15
7St
pFa
ctor
y se
t, d
o n
ot
chan
ge
158
Stp
Fact
ory
set,
do
no
t ch
ang
e15
9St
pFa
ctor
y se
t, d
o n
ot
chan
ge
160
Stp
Fact
ory
set,
do
no
t ch
ang
e16
1St
pFa
ctor
y se
t, d
o n
ot
chan
ge
162
Stp
Fact
ory
set,
do
no
t ch
ang
e16
3St
pFa
ctor
y se
t, d
o n
ot
chan
ge
164
Stp
Com
pres
sor
dela
y10
–300
sec
onds
90 s
econ
dsA
V19
Del
ays
com
pres
sor
to a
llow
the
wat
er v
alve
(s) t
o op
en.
165
Stp
Econ
omiz
er s
elec
tO
n/of
fO
ffBV
141
Enab
les
or d
isab
les
WSH
P Ec
onom
izer
coi
l.
166
Stp
Econ
omiz
er s
etpo
int
40°F
–105
°F
[−20
°C–1
0°C
]65
°FA
V18
0Ec
onom
izer
ent
erin
g w
ater
tem
pera
ture
set
poin
t.
167
Stp
Uno
ccup
ied
reci
rc s
uppl
y fa
n op
tion
On/
off
Off
BV14
5If
Off
and
in U
r m
ode,
sup
ply
fan
only
tur
ns o
n w
ith c
onta
ct o
verr
ide.
If O
n, t
hen
supp
ly
fan
turn
s on
whe
n in
Ur
mod
e.
168
Stp
Wat
er le
avin
g te
mpe
ra-
ture
set
poin
t−
4°F–
50°F
[−
20°C
–10°
C]
35°F
AV
185
Setp
oint
tha
t w
ill t
rip u
nit
on lo
w w
ater
fre
eze
prot
ectio
n (o
ptio
nal).
169
Stp
Fact
ory
set,
do
no
t ch
ang
e17
0St
pFa
ctor
y se
t, d
o n
ot
chan
ge
199
Stp
Con
vers
ion
F to
C°F
–°C
°FBV
99Th
is s
ettin
g is
use
d to
cha
nge
from
Sta
ndar
d to
SI u
nits
.
N/A
N/A
Rem
ote
unit
cont
rol
N/A
MV
12
The
rem
ote
unit
cont
rol m
ulti-
stat
e va
riabl
e is
use
d to
ena
ble
the
unit
thro
ugh
a Ba
cnet
in
ter.
Set
MV
12 t
o (b
ased
on
star
ting
at a
cou
nt o
f on
e):
– 2
for
unoc
cupi
ed m
ode
– 4
for
occu
pied
rec
ircul
atio
n m
ode
(opt
iona
l)–
10 f
or v
entil
atio
n m
ode
– 6
for
unoc
cupi
ed r
ecirc
ulat
ion
mod
e (o
ptio
nal)
Not
e: T
his
varia
ble
can
only
be
mod
ified
thr
ough
a B
MS
VCES-DDC-IOM-1C 19
Unit ControlThe unit can be enabled in ventilation mode by jumpering FW 304 to 305. Alternatively the software point MV12 can be used to schedule the unit. If this method is being used then you must not provide any jumpers to terminals 304, 305, 306, 307 or 308.
The remote unit control multi-state variable is used to en-able the unit through a Bacnet interface.
Set MV12 to:
• 2 for unoccupied mode.• 4 for occupied recirculation mode (optional).• 6 for unoccupied recirculation mode (optional).• 10 for ventilation mode.
BacNet Interface
Interface to the DSC-1180 controller by connecting to the “Net 1” terminal as seen below.
Networking SpecificationsVenmar CES provides equipment with network integration features. The following section outlines basic practices as recognized in the industry. As an HVAC equipment manu-facturer, it is not part of Venmar CES’ mission to provide exhaustive networking design and integration services. In all cases, the advice and services of a networking professional for network design and integration should be employed.
The DDC controllers provided along with Venmar CES equipment will support two types of network connection:
• RS232 (generally used for temporary local access to unit controller – i.e. troubleshooting)
• RS485 – the following specifications pertain to RS485 connection
Most commonly, RS485 is used as the physical layer be-tween panels and unit controllers in HVAC networking
applications. See Table C1 for a summary of specifications concerning the application of RS485 networks.
Cable TypeVenmar CES recommends the use of balanced 22 to 24 AWG twisted pair with a characteristic impedance of 100–120 ohms, capacitance of 17 pF/ft or lower, with a braided shield.
Network ConfigurationRS485 networks use a daisy chain configuration (only one main cable, every device being connected directly along its path).
Figure C2 illustrates two improper network configurations and the proper daisy chain configuration.
Note that there are no troubleshooting methods for these improper types of networks.
The use of an improper network configuration may result in undesirable and unpredictable effects on unit function-alities.
Only the daisy chain configuration is correct for a RS485 network. Figure C3 shows connection in the middle of a daisy chain.
Appendix C: Standard Network Practice
Net 1BacNet terminals
Figure C1: BacNet interface
Star configuration Bus configurationDaisy chainconfiguration
Figure C2: Network configurations – star, bus and daisy chain
Table C1: Summary of Specifications for a RS485 NetworkCategory Specification
Cable type100–120 ohm balanced, twisted shielded pair
Network configuration Daisy chainMaximum distance of chain
4,000 ft [1,200 m]
Maximum stub length 10” [0.25 m]Minimum spacing between devices
12” [0.30 m]
Maximum number of devices
32 devices per daisy chain segment
TerminationTermination use DNT294 network terminator at both ends of a segment
ShieldingConnect shield to DNT294 network terminator
IMPORTANTValues shown are based on starting at a count of one. When using Johnson Controls/Metasys, set the values one lower than shown as they start at zero.
VCES-DDC-IOM-1C 20
Maximum Number of DevicesA maximum of 32 nodes are allowed on a single daisy chain segment. A node is defined as any device (Panel, Zone, Repeater, etc.) connected to the RS485 network. Terminators do not count as a node. Figure C3 shows an example of a system with 5 nodes.
TerminationBoth ends of a daisy chain segment require termination to ensure reliable operation. After the last device on each end of an RS485 network, install a DNT294 Network Ter-minator. The DNT294 (shown in Figure C5 below) provides the correct termination for not only the network, but proper termination of the shield as well.
Shielding and GroundingFigure C6 shows preferred shielding and grounding methods.
Unit AddressingThe BacNet address of a unit is sent out as address 1 from the factory. This address can be adjusted by setting the dip switches located on the DSC-1180 controller. See Figure C7.
− −
−
+
+
+
1 2
RS485port
Figure C3: Proper connection in the middle of a daisy chain
Terminator does notcount as a node Node #2 Node #4
Node #3 Node #5
Node #1
Terminator does notcount as a node
Panel
Legend
Zone/micro/DACcontroller, etc.
Terminator
C
C C
CC
T
T
T
Figure C4: Five node network example
− −
−
+
+
+
1 2
RS485port
RS485 networkterminator
GN
DP1
Network continues...
Shunt
Shield
Rem
ove
sh
un
t ju
mp
er if
sh
ield
is g
rou
nd
edd
irec
tly
at a
ny
oth
er p
oin
t, o
r sh
un
t is
inst
alle
d a
t o
ther
en
d o
f n
etw
ork
.
DNT294 Rev 1.1
Delta © 04/00
Figure C5: DNT294 network terminator
IMPORTANTNote that DNT294 Network Terminators are not provided by Venmar CES.
CAUTIONFailure to follow these recommendations may result in un-desirable and unpredictable effects on unit functionalities. Venmar CES will not take responsibility for issues resulting from improper controls and/or networking practices.
P1
−
+
−
+
−+
RS485port
RS485 networkterminator
GN
D
Shunt
Shield
Rem
ove
sh
un
t ju
mp
er if
sh
ield
is g
rou
nd
edd
irec
tly
at a
ny
oth
er p
oin
t, o
r sh
un
t is
inst
alle
d a
t o
ther
en
d o
f n
etw
ork
.
DNT294 Rev 1.1Delta © 04/00
RS485 networkterminator
GN
DP1
Shunt
Shield
Rem
ove sh
un
t jum
per if sh
ield is g
rou
nd
edd
irectly at any o
ther p
oin
t, or sh
un
t isin
stalled at o
ther en
d o
f netw
ork.
DNT294 Rev 1.1Delta © 04/00
−+
RS485port
−+
RS485port
−+
RS485port
Remove shunt on both ends, allowing shield to go to ground through 180V MOV
Remove shunt on both ends, allowing shield to go to ground through 180V MOVGround shield in
middle of segment
Shield Shield
Solidly groundeach terminal
Figure C6: BacNet address jumpers
BacNetaddressjumpers
Figure C7: BacNet address jumpers
VCES-DDC-IOM-1C 21
All DDC units come with a “BacStat” which can act as a room thermostat where you can change the heating set-point, cooling setpoint, summer setpoint and many more. The BacStat will act as a remote panel and should be looked at first when there is any issue with the unit.
The supply air sensor also functions like a low limit sensor. This is not to be confused with the “LL” alarm indicated above. This sensor has adjustable setpoint limit and time delay accessible through the BacStat points. If the supply air sensor is not connected, it will register as a −59 and the unit will not run after its time delay.
The middle characters represent the mode the unit is in:
Appendix D: DDC Troubleshooting Guide
Table D1: BacStat KeypadKeypad Display
Description
dF
Unit is in frost control mode. (This is a status alarm. It does not indicate that there is a prob-lem with the unit. It simply means that the unit is currently defrosting the wheel. This message will go away after the timed defrost sequence is complete.)
FC Unit is in free cooling mode.CF Wheel has failed.
LPLow pressure alarm has tripped. Requires man-ual reset of DDC power after three failures.
HPHigh pressure alarm has tripped. Requires man-ual reset of pressure switch.
LLCoil low limit sensor has tripped (supplied by others).
LSLow supply air temperature alarm. Requires manual reset of DDC power.
HSHigh supply air temperature alarm. Requires manual reset of DDC power.
OLSupply/exhaust overload has tripped. Alterna-tively, it can be an external unit fault (supplied by others).
EF Dirty exhaust filters.SF Dirty supply filters.
FSFlow switch alarm or low water leaving tem-perature alarm.
Table D2: Unit ModeKeypad Display
Mode
Un Unoccupied
Or Occupied recirculation
Ov Occupied ventilation
Ur Unoccupied recirculation
VCES-DDC-IOM-1C 22
Table D3: DDC Troubleshooting GuideProblem Cause Solution
Unit is not ventilating.
Occupancy contact open.
Check contact closure between field wiring terminals 304 and305 (see wiring schematics in the VHC-36, 42 and 50 IOM forwiring details).Check the BacStat shows ‘OV’ for occupied ventilation.
Blowers are overloaded.
BacStat will flash ‘OL’ in the upper left corner.Check motor overload trip indicator on overload relay (locatedbelow contactor). If it has tripped, press the reset button.Check for proper voltage at output of overload relay (T1, T2, T3)to confirm that the supply and exhaust blower motors are running.
Low limit thermostat tripped.BacStat will show ‘LL’ for low limit. Low limit sensor is suppliedby others.
Supply air sensor not hooked up.
BacStat will show a temperature in the top right corner in therange of −59 to −50. Hook up the sensor that was supplied withthe unit.
Unit is in recirculation/exhaust defrost mode.
BacStat will flash ‘dF’ in the upper left corner. Wait for defrostmode to finish its timed sequence (minimum of six (6) minutes).
Unit is not recirculating (for units with a recirculation damper).
Unoccupied recirculation contact open.
Check contact closure between field wiring terminals 305 and306 (see wiring schematics in the VHC-36, 42 and 50 IOM forwiring details).
Supply blower not running.BacStat will flash ‘OL’ in the upper left corner.Check motor overload trip indicator on overload relay (locatedbelow contactor). If it has tripped, press the reset button.
Unit will not stop ventilating. Occupancy contact closed.Check contact for break between field wiring terminals 304 and305 (see wiring schematics in the VHC-36, 42 and 50 IOM forwiring details).
Air from supply diffusers too cold.
Imbalance of supply and exhaust air.
Check filters and heat exchanger for blockage.BacStat will flash ‘SF’ or ‘EF’ to indicate supply or exhaust filtersare dirty.Check balance of airflows.
Post heat required. Install post heat module.
Wheel failure.BacStat will flash ‘CF’ in the upper left corner if wheel failure isdetected (units with wheel rotation board).
Unit makes an annoying noise.
Blower wheel out of align-ment.
Remove the motor/blower assembly. Adjust the blower assembly.
Enthalpy wheel freezing.
Imbalance of supply and exhaust air.
Check filters and heat exchanger for blockage.
Confirm supply filter needs replacing.
Confirm exhaust filter needs replacing.
Check balance of airflows.
Check for operation of damper actuators.
Defrost mode not function-ing.
Confirm that the unit is in defrost mode. BacStat II will flash ‘dF’in upper left corner. See defrost sequence of operation in theFrost Control section of this document.
Enthalpy wheel not running.
Unit is in free cooling. Confirm that the unit is in free cooling mode.
Unit is in recirculation defrost. BacStat will flash ‘dF’ in upper left corner.
Wheel failure.Units with wheel rotation sensor.BacStat will flash ‘CF’ indicating wheel rotation failure. Checkrelays and verify that motor is getting power.
Drive motor capacitor failure.Check capacitor connections. Check motor operation with a newcapacitor.
Drive pulley.Check for drive belt derailment off of drive pulley or failure.Check for securely fastened pulley on motor shaft.
VCES-DDC-IOM-1C 23
Table D3: DDC Troubleshooting GuideProblem Cause Solution
Exhaust fan will not turn on.
Unit is in recirculation defrost (units equipped with recircu-lation defrost).
BacStat will flash ‘dF’ in upper left corner. Wait for defrost modeto finish its timed sequence.
Unit is in unoccupied recircu-lation(units with recirculationdamper).
BacStat will show ‘UR’. Check if you have a contact closureacross 305 and 306.
Damper end switches are not making.
Check your field wires connected to PNL 310 and 311 for aclosed connection.
Damper will not open. Electrical supply interrupted.
Check wiring on damper actuator.For the outside air damper actuator and recirculation damperactuator (if equipped), measure a 24 VAC across PNL terminals330 and 302.For the exhaust air damper actuator, measure a 24 VAC acrossfactory wired terminals 332 and 302.
Supply fan will not turn on.
Unit is in exhaust defrost (units equipped with exhaust defrost).
BacStat will flash ‘dF’ in upper left corner. Wait for defrost modeto finish its timed sequence.
Damper end switches are not making.
Check field wires connected to PNL 309 and 310 for a closedconnection.
Additional Troubleshooting:
__ Verify DDC jumpers are correct.__ Verify expander board jumpers and address (dip switch settings) are correct.
©2009 Venmar CES Inc.VCES-DDC-IOM-1C (PN 500020459)
February 2014
Venmar CES Inc. has a policy of continuous improvement and reserves the right to change design and specifications without notice.
