Chris Wolak 1

Hydronic BalancingChris Wolak

Chris Wolak 2

Outline

• Introduction

• Static Balancing

• Dynamic Balancing

Chris Wolak 3

Two Reasons for Balancing

• Manual balancing

• On-off Control

• Single Speed Pump

• Pressure Independent balancing

• Modulating Control

• Variable Speed Pump

Chris Wolak 4

Why Balance?• Without balancing, the circuits

closest to the pump would overflow and those further away underflow

Chris Wolak 5

ASHRE 90.1-2010

6.7.2.3.3 Hydronic System Balancing. Hydronic systems shall be proportionally balanced in a manner to first minimize throttling loss; then the pump impeller shall be trimmed or pump speed shall be adjusted to meet design flow conditions

Chris Wolak 6

Terminal 4

Terminal 3

Terminal 2

Terminal 1

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

50’

40’

30’

20’

40’ 7gpm

30’ 13gpm

20’ 17gpm

50’ 3gpm

0’

10’

20’

30’

50’ 10gpm

50’ 10gpm

50’ 10gpm

50’ 10gpm

Simplified Building Schematic

Each leg has 5’ of resistance.

By adding manual balancing valves,

Different resistances cause different flows

we can equal out all the resistances and therefore all the flows

Static Balancing

Chris Wolak 7

Manual Balancing Valves

• Three Functions:

– Throttling

– Flow Measurement

– Shutoff

ASHRAE Handbook 2013 Systems & Equipment, Chapter 47. Valves

Chris Wolak 8

What is Cv?

𝐶𝑣 = 𝐹𝑆𝐺

∆𝑃𝐶𝑣 = 𝐹

1

∆𝑃

11 psi

10 psi

5gpm

Cv?

Chris Wolak 9

2gpm

2gpm

2gpm

2gpm

2gpm

2gpm

2gpm

2gpm

2gpm

2gpm

2gpm

2gpm

Proportional Balancing

• Balance each section within itself

• Use partner valve to balance sections together 8gpm 8gpm 8gpm

Chris Wolak 10

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

50’ 17gpm

Two-Pipe

40’ 13gpm

30’ 7gpm

20’ 3gpm

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

5’

20’

Reverse-Return

50’ 10gpm

50’ 10gpm

50’ 10gpm

50’ 10gpm

Reverse-Return

• Theoretically, reverse-return piping can self balance

• Each terminal has to have the exact same piping

• Hoses, strainers, dirty coils will effect balancing

• No way to verify flows• Adds extra piping

Chris Wolak 12

Two Reasons for Balancing

• Manual balancing

• On-off Control

• Single Speed Pump

• Pressure Independent balancing

• Modulating Control

• Variable Speed Pump

Chris Wolak 13

Terminal 4

Terminal 3

Terminal 2

Terminal 150’

40’

30’

20’

40’ 7gpm

30’ 13gpm

20’ 17gpm

50’ 3gpm

50’ 10gpm

50’ 10gpm

50’ 10gpm

50’ 10gpm

50’ 13gpm

50’ 13gpm

50’ 13gpm

Terminal 1

Terminal 2

Terminal 3

Terminal 4

10gpm

10gpm

10gpm

10gpm

Terminals are set to 10gpm with static valves. When all control valves are open, system is comfortable & efficient

When one control valve closes down, the other terminals overflow, wasting energy

As other terminals try to modulate, overflow situation intensifies, increasing energy costs

As more portions of the building close, the situation gets worse

0gpm

13gpm

13gpm

13gpm8gpm

15gpm

15gpm

0gpm

17gpm

11gpm

Static Balancing

Chris Wolak 14

What is Overflow?

• Buildings are balanced to the full load

• As circuits of a building shut down, others will see excess flow

• Coils will still produce sufficient heat but will use more energy then is needed

Chris Wolak 15

Why Prevent Overflow

• Pump Energy

• Noise / Pipe Erosion

• Boiler / Chiller Efficiency

• Control Valve Authority

• ASHRAE 90.1

Chris Wolak 16

Variable Speed Pumps• Variable flow systems

reduce pumping costs at partial load

• Need to maximize pumping energy savings while keeping a 100% operational cooling/heating system

Constant Speed Pump

Variable Speed Pump

Chris Wolak 18

Overflow Effects on System• Overflow causes water velocity

that is higher than expected per design flow

• Higher water velocity leads to erosion in elbows & heat exchangers

• Control valves work with very short open/close cycles– Limits actuator life

Chris Wolak 19

0%

20%

40%

60%

80%

100%

0% 100%80%60%40%20% 200%180%160%140%120%

120%

220% 240%

Hea

t

Flow

Overflow Effects on Coils

• 250% flow = 120% heat

• Coils are designed to flow a certain amount

• Over 100% flow, the efficiency of the coil reduces

• 150% flow = 110% heat

Chris Wolak 20

Differential Temperature (∆T)

Chris Wolak 21

140°160°170°

180°

10gpm15gpm20gpm

Overflow = Low ΔT

Design:10GPM, 40°ΔT

Chris Wolak 22

ASHRE 90.1-2010

6.4.2.2 Pump Head. Pump differential pressure (head) for the purpose of sizing pumps shall be determined in accordance with generally accepted engineering standards and handbooks acceptable to the adopting authority. The pressure drop through each device and pipe segment in the critical circuit at design conditions shall be calculated

6.5.4.2 Hydronic Variable Flow Systems. HVAC pumping systems having a total pump system power exceeding 10hp that includes control valves designed to modulate or step open and close as a function of load shall be designed for variable fluid flow and shall be capable of reducing pump flow rates to 50% or less of the design flow rate…The control or devices shall be controlled as a function of desired flow or to maintain a minimum required differential pressure. Differential pressure shall be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure

6.7.2.3.3 Hydronic System Balancing. Hydronic systems shall be proportionally balanced in a manner to first minimize throttling loss; then the pump impeller shall be trimmed or pump speed shall be adjusted to meet design flow conditions

Chris Wolak 23

EQM Control Valve

Chris Wolak 24

Pressure Independent Control Valve

Chris Wolak 25

Terminal 4

Terminal 3

Terminal 2

Terminal 150’

40’

30’

20’

40’ 7gpm

30’ 13gpm

20’ 17gpm

50’ 3gpm

50’ 10gpm

50’ 10gpm

50’ 10gpm

50’ 10gpm

50’ 13gpm

50’ 13gpm

50’ 13gpm

Terminal 1

Terminal 2

Terminal 3

Terminal 4

10gpm

10gpm

10gpm

10gpm

Terminals are set to 10gpm with static valves. When all control valves are open, system is comfortable & efficient

When one control valve closes down, the other terminals overflow, wasting energy

As other terminals try to modulate, overflow situation intensifies, increasing energy costs

As more portions of the building close, the situation gets worse

Pressure independent systems maintain a constant flow rate and proper control valve authority

When one control valve closes, desired control is maintained

When other valves modulate, desired flow is achieved through high control valve authority

0gpm

13gpm

13gpm

13gpm8gpm

15gpm

15gpm

0gpm

17gpm

11gpm5gpm

Current Balancing StrategiesLow Control Valve Authority

Differential Pressure ControlHigh Control Valve Authority

Chris Wolak 27

Modulating Control

Time

Ro

om

Tem

p

72°

76°

68°

6:00am

On-off Control

Chris Wolak 28

Control Valve Authority with an ABV

Required Flow Actual Flow

10gpm 10gpm7.5gpm5gpm2.5gpm 5gpm

Chris Wolak 29

Differential Pressure Controller

Chris Wolak 30

P2

(DP Stabilization)

STAD (Flow measuring)

P3

Chris Wolak 31

Dp Controller Placement

Chris Wolak 32

STAP Placement

Chris Wolak 34

140°160°170°

180°

10gpm15gpm20gpm

Low ΔT

Chris Wolak 35

Pressure Independent Options

Dp Controller

Standard Control Valve

Manual Balancing Valve

Pressure Independent Control Valve

Chris Wolak 36

Review Questions

• Which organization requires systems to be proportionally balanced?• What type of balancing is more energy efficient?

• No balancing• Static balancing• Dynamic balancing

• What causes low ΔT?• Why are modulating control valves used?

• Energy efficiency• Better room temperature control• Lower cost

• What does EQM stand for?