Power Transfer Switches- for -

IEEE-IAS - by -

James S. Nasby

Columbia Engineering

C.E. IEEE-IAS 2

Topics to be Covered

Arrangement I (Combo. Unit) Arrangement II (Separately Listed Units) Power Supply Considerations Options

C.E. IEEE-IAS 3

Note: “Alternate Source” may be a “Hot Emergency Bus” as often employed in hospitals.

In these systems, multiple MVA size gen-sets are used along w/ additional upstream Transfer Switches with a path to one or more Utility Connections.

This often results in very high fault currents on the Alternate Source Side.

Also note that two C/Bs will be required in all Arrangement I units per 2010 Edition of NFPA-20.

Two Arrangements

From the 2007 Edition of NFPA-20

C.E. IEEE-IAS 4

Revised to Three

NFPA-20-2013 Fig. A.10.8 1

Revised Arrangement I-A

perLogs #29 & #157

N E

Normal Source See 9.2

Arrangement I-A See 10.8.2.1

Alternate Source See 9.3

See 10.8.3

Note: Need to Renumber "Arrangement I" as "Arrangement I-A"

ATS

CB CB

IS IS

Was "Arrangement I"

See Log #103

Contactor

Listed Combination

Fire Pump Controller

and Transfer Power

Transfer Switch

Motor

C.E. IEEE-IAS 5

Arrangement 1-B

NFPA-20-2013 Fig. A.10.8 2Arrangement I-B

Proposed NewArrangement I-B

per Log #105

Upstream Transfer Switch

Normal Source See 9.2

Alternate Source See 9.3

To other generator

loads

See 9.6.5

Listed Combination Fire Pump Controller

and Power Transfer Switch

See 10.8.2.1 and 10.8.3

EN

N E

See NFPA 70

Article 230

Motor

Gen

"Hot" Emergency Bus

C.E. IEEE-IAS 6

Revised Arrangement II

NFPA-20-2013 Fig. A.10.8 3

Revised Arrangement II

perLogs #29 & #157

Listed Fire Pump Controller

Arrangement II See 10.8.2.2

EN

Normal Source See 9.2

Alternate Source See 9.3

CB

IS*IS*

CB**

ATS

Field Wiring

See 10.8.3 & 9.6.4

Listed Fire PumpPower Transfer

Switch Assembly (Service Entrance Equipment may

Be Separate)

See 10.8.2.2

Single or Separate Enclosure(s)

See 10.8.2.2(4)

See 9.6.5 & NFPA 70 §700.27

* May be Omitted

** May be located at generator if alternate source is a standby

generator.

Motor

C.E. IEEE-IAS 7

Power Supply Systems

Power Supply Weak = Voltage Drop Problems Stiff = Careful Coordination of WIC

Type of System Wye = Typical

Grounded Neutral = Typical Ungrounded = Care & Coordination

Delta = Great Care Needed. Ungrounded Corner Ground 4 Wire High Leg (240 / 120 / 208)

C.E. IEEE-IAS 8

Options (Variations)

Added Ground Lugs (Some Jurisdictions)

Fourth Pole (Neutral) Usually “Overlapping” (Make Before Break) Supplied by Some E.F.P.C. Mfrs.

In Phase Transfer Delays Transfer Until Motor Back EMF Phase Angle

is Close to that of the Intended Source Completely Useless for Pump Motors due to Very

Low Inertia and Large Minimum Load on Motor

C.E. IEEE-IAS 9

Arrangement I (Combo. Unit)

10.8.1 General10.8.2.1 Arrangement I

(Listed Combination Fire Pump Controller and Power Transfer Switch)

10.8.3 Power Transfer Switch Requirements

C.E. IEEE-IAS 10

Arrangement I – Combo. Unit

C.E. IEEE-IAS 11

Short Circuit (WIC)

Coordination

Note: “---” means no Upstream Protection is Required.

E.g.: Self Protecting (Blow Apart) Isolating Switch Provides Suitable Protection of the Internal Transfer Switch.

C.E. IEEE-IAS 12

Arrangement II (Separate Units)

10.8.1 General 10.8.2.2 Arrangement II

(Individually Listed Fire Pump Controller and Power Transfer Switch)

10.8.3 Power Transfer Switch Requirements

C.E. IEEE-IAS 13

Russelectric F.P. Transfer Switch

C.E. IEEE-IAS 14

Arrangement II Requirements:Who Supplies What?

10.8.2.2(2) "An isolating switch, or service disconnect where required, ahead of the normal input terminals of the transfer switch." Ever not required?

10.8.2.2(3) [and 9.2.3.4]: Xfer Switch OCP "shall be selected or set to carry indefinitely the sum of the locked rotor current of the fire pump motor" plus any additional connected loads. E.g.: 600% of motor FLA minimum

10.8.3.4.2: Transfer switch Minimum Sized at only 115% of the motor FLA current - Rarely Enough.

10.8.3.6.4: Phase Reversal Sensing

C.E. IEEE-IAS 15

Arrangement II Requirements:Who Supplies What?

10.8.2.2(4) An isolating switch ahead of the alternate source input terminals of the transfer switch shall meet the following requirements:

(a) The isolating switch shall be lockable in the on position. (b) A placard shall be externally installed on the isolating switch stating

“Fire Pump Isolating Switch,” with letters at least 1 in. (25 mm) in height. (c) A placard shall be placed adjacent to the fire pump controller

stating the location of the isolating switch and the location of the key (if the isolating switch is locked).

(d) The isolating switch shall be supervised to indicate when it is not closed, by one of the following methods:

i. Central station, proprietary, or remote station signal service ii. Local signaling service that will cause the sounding of an

audible signal at a constantly attended point iii. Locking the isolating switch closed

iv. Sealing of isolating switches and approved weekly recorded inspections where isolating switches are located within fenced enclosures or in buildings under the control of the owner

(e) This supervision shall operate an audible and visible signal on the transfer switch and permit monitoring at a remote point where required.

C.E. IEEE-IAS 16

WIC Coordination ExampleTransfer Switch Sizing Example for 100 Hp at 460 Vac

X 115% Thermal X 600% Breaker WIC Coord.

Motor Hp Motor FLAThermal Sizing Upstream Size Switch Size

100 Hp 124 amps 143 amps 150 amp 744 amp 800 amp 400 amp

In this Example, a 150 Amp Xfer Switch meets the 115% criteria; but, it’s Short Circuit (WIC) Rating will be invalid if the upstream device is larger than 250 amps. However, a 250 Amp OCP doesn’t meet the 600% criteria. Hence, a larger Xfer switch is needed. Who does the coordination, and who supplies what?

C.E. IEEE-IAS 17

Are All of These Supplied? 1) The two Position Indicator lights 2) The Engine Start delay timer and the Re-Transfer delay timer, 3) The Engine Start contacts, 4) The Test (Transfer) switch (pushbutton), maybe. 5) The Normal Side Service Disconnect and overcurrent protection fuses or breaker, 6) Otherwise, the required emergency side Isolating Switch which is: 7) Lockable "ON" 8) Having an external "Fire Pump Isolating Switch" placard, 9) A placard next to the controller giving the location of this Isolating Switch10) Supervision of the Isolating Switch by one of the four means given11) Audible and visible alarm to indicate Isolating Switch Open,12) Isolating Switch contacts for remote alarm,13) Means to prevent Higher-than-Normal motor in-rush currents,14) Phase reversal sensing and transfer circuitry.15) Although not required, the Bypass switch may or may not be standard equipment.

C.E. IEEE-IAS 18

Arrangement II Detailed Requirements

Application Guide- for -

Fire Pump Power Transfer Switches- for use with -

Electric Motor Driven Fire Pumps

 By: James S. Nasby, Columbia Engineering,

 This document attempts to outline the salient requirements for the selection coordination and application of fire pump transfer switches upstream of fire pump controllers in order to meet the requirements of NFPA 20 Standard for the Installation of Stationary Pumps for Fire Protection. Power Transfer Switches "Arrangement I" - Combined Transfer Switch & Fire Pump ControllerListed Combination Fire Pump Controller and Power Transfer Switch" units eliminate the majority of the required coordination since it is accomplished by the manufacturers of these combination units. Moreover, this coordination is examined, verified, and documented by both Underwriters Laboratories, Inc. and by Factory Mutual Laboratories. This is the simplest and most verifiable way to meet NFPA 20. Power Transfer Switches "Arrangement II" ‑ Separate Transfer Switch & Fire Pump ControllerThis arrangement consists of a listed Single Power Source (non‑transfer switch) Fire Pump Controller and a listed "Fire Pump Power Transfer Switch". NFPA 20 section 10.1.2.1 makes it clear that a transfer switch used for supplying power to a fire pump must be listed for the service. To wit: “All controllers and transfer switches shall be specifically listed for electric motor‑driven . . .

Note: A full copy is included with the handouts.

C.E. IEEE-IAS 19

Questions ?