Balancing Basics Mike Weisman, ASHRAE Treasurer ASHRAE Golf Outing: - - PowerPoint PPT Presentation

Balancing Basics

Mike Weisman, ASHRAE Treasurer ASHRAE Golf Outing: May 18th, 2018! HEATHERWOODE

Agenda:

• Why balance?
• Manual Balancing Valves
• Manual Balancing Process
• Automatic Flow Controllers
• Partial Load Conditions: Hydraulic Interactivity
• Pressure Independent Control Valves

Two Reasons for Balancing

1. Comfort

• Satisfying Flow Requirements

2. Delta T Realization

• Optimize Coil Performance
• Eliminate Overflow – Partial Load Condition
• More efficient equipment, less required pump heat

Hydronic Heating

Boiler Terminal Terminal Terminal Terminal

140° 180°

HWS HWR Air In Air Out Energy (Heat) is produced at a central location and distributed to various locations via water

Why Balance?

• Without balancing, the circuits closest to the

pump would overflow and those further away underflow

• “I don’t need balancing valves! The control

valves will throttle the flow.”

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’ 13gpm 50’ 13gpm 50’ 13gpm 50’ 13gpm

Simplified building schematic Each leg has 5’ of resistance The lowest terminal has 20’ of resistance, the furthest has 50’ By adding manual balancing valves, Different resistances cause differing flows we can equal out all the resistances and therefore all the flows

Balancing Basics

Why Balance?

Manual Balancing Valves

𝑹 = 𝑫𝒘 × ∆𝑸

• Calibrated Orifice vs. fixed orifice

(Venturi)

• Ball, Globe, Butterfly
• Accuracy
• Precision
• Typically Balancing AND Shut Off

Manual Balancing Valves

Manual Balancing Process

Lifts, Ladders, Drop Ceilings, Furniture…

2gpm 2gpm

2gpm

2gpm 2gpm 2gpm 2gpm 2gpm 2gpm 2gpm 2gpm 2gpm

Proportional Balancing

• Set valves to the correct

ratio, they will all be in the same % of overflow or underflow

• Balance each section

within itself

• Use partner valve to

balance sections together

8gpm 8gpm 8gpm

Splitting into Hydronic Modules

Balancing a Module

Hydraulic Interactivity

Balancing a Module

Balancing a Module

Balancing a Module

Order for Balancing Modules

Full Pump Heat, Valves Wide Open

Proportional Branches

Balance All Partner Valves

Optimize Pump Head

Manual Balancing Reality—Infinite Solutions

Automatic Flow Controllers

Cartridge Design Benefits

• Maintains ±5% accuracy of design flow
• Terminals can be flushed with cartridge in place
• Reduced commissioning time
• Simple selection and identification of flow rate
• Can be fitted adjacent to bend or fitting in pipe

Automatic Flow Controllers

• “Flow Limiter”: A bit of a misnomer.
• Full Flow, Whether you need it or not
• Pressure-Independent Balancing Valve
• Select cartridge based on design flow
• Install It, Check Pressure, Forget About It
• Still NEED Partner Valves!
• Operating Range (Typical): 2-32psi dP

Automatic Flow Controllers

𝑹 = 𝑫𝒘 × ∆𝑸

Automatic Flow Controllers

• Flow is constant within operating dP range
• The Cv of the cartridge adapts to the dP within

the operating range to provide constant design flow

Partial Load Conditions

0% 20% 40% 60% 80% 100% 120% 0% 50% 100% 150% 200%

Differential pressure variations

32

Thermal plant load [%] % of heating season below this load

Dallas

% of cooling season below this load Thermal plant load [%]

Heating Cooling

2

q P  

20 % flow

0% 20% 40% 60% 80% 100% 0% 20% 40% 60% 80% 100%

50 % load 4% press. drop

Power Flow Flow Dp piping

At constant supply water temperature

68% 58%

Pressure drops are reduced to 4% of their design value.

April 2010

Control loop

33

x = U - x 0 - 10 volts 0-100% k2 k3 0-100% 0-100% k4 k5 x Sensor Set value U Terminal Controller x = controlled value Actuator Valve Room Disturbances x Flow Power

• utput

Lift Signal k1

100 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 90 100 80 Flow in % Lift h in % 100 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 90 100 80 100 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 90 100 80 Heat output in %

= +

Heat output in % Flow in % Lift h in %

Terminal unit characteristic Control valve characteristic

Power output % Power output % Flow in%

April 2010

Terminal 4 Terminal 3 Terminal 2 Terminal 1

50’ 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
• pen, system is comfortable &

efficient When one control valve closes down, the other terminals overflow, wasting energy As other terminals try to modulate,

• verflow situation intensifies,

increasing energy costs As more portions of the building close, the situation gets worse 0gpm 13gpm 13gpm 13gpm 8gpm 15gpm 15gpm 0gpm 17gpm 11gpm

Manual Balancing

• All circuits are interactive
• dP sensor placement is critical

140° 160° 170° 180°

10gpm 15gpm 20gpm

Overflow = Low ΔT

Design: 10GPM, 40°ΔT

0% 20% 40% 60% 80% 100% 0% 100% 80% 60% 40% 20% 200% 180% 160% 140% 120% 120% 220% 240%

Heat 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

Autoflow Valve with Modulating Control Valve

• In partial loads, a control valve will start to close (decrease Cv)
• As the control valve modulates, the automatic balancing cartridge will try

to maintain design flow (increase Cv)

• Eventually the control valve will decrease available head pressure enough

to modulate flow

• Also contributes to the same low delta T syndrome.

𝑹 = 𝑫𝒘 × ∆𝑸

Control Valve Authority with an Automatic Balancing Valve

Required Flow Actual Flow 10gpm 10gpm 7.5gpm 5gpm 2.5gpm 5gpm

Manual Valves: Pros and Cons

• PROS
• Performs well with a modulating control valve
• Flexible for changes to the space/water quality
• With proper balancing, can decrease pump head
• CONS
• Labor intensive balancing process/commissioning
• Very dependent on quality of the balancing contractor
• Susceptible to overflow situations

Automatic Valves: Pros and Cons

• PROS
• ONE pass balancing
• ELIMINATES interactivity in the system
• Eliminates overflow situations
• CONS
• “Fighting” with modulating control valves
• Cartridges have tiny openings:
• Higher pressure drop, susceptible to clogging
• Is the correct cartridge installed?

Best of Both Options?

• Pressure Independent, Balancing Control Valves

𝑹 = 𝑫𝒘 × ∆𝑸

• Two valves in one: Balancing Valve, Control Valve with Pressure Regulator
• Pressure drop across the valve seat is fixed
• Very precise modulation!
• Actuator technology can simplify balancing process

Be aware of minimum start pressure! Up to 5 psi for smallest valves!

Control loop

42

x = U - x 0 - 10 volts 0-100% k2 k3 0-100% 0-100% k4 k5 x Sensor Set value U Terminal Controller x = controlled value Actuator Valve Room Disturbances x Flow Power

• utput

Lift Signal k1

100 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 90 100 80 Flow in % Lift h in % 100 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 90 100 80 100 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 90 100 80 Heat output in %

= +

Heat output in % Flow in % Lift h in %

Terminal unit characteristic Control valve characteristic

Power output % Power output % Flow in%

April 2010

Autoflow vs. PICV

Always be able to verify flow!

Applications….

• ON/OFF Control: Chilled beam, fin tubes, WSHP, UH
• Automatic flow controller
• Modulating Control: FCU, VAV, above 1 GPM
• Manual balancing valve
• Systems with lots of diversity in loads, fluctuating dP
• Automatic flow controller, PICV
• Large Flows (AHUs), Precise discharge air temp.
• PICV
• Retrofits, Expansions
• PICV

Final Thoughts…

• Follow the pressure, not the flow
• 1-2 degree change in operating conditions can have a HUGE impact on

system performance!

• One solution doesn’t fit every application!
• The more balancing shutoff valves, the better!

Questions?