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

Transcription

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

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

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4 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

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

6 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.

7 Balancing Basics Simplified building schematic Each leg has 5 of resistance The lowest terminal has 20 of resistance, the furthest has 50 5 Terminal 50 13gpm 1 Terminal gpm 13gpm 7gpm Different resistances cause differing flows By adding manual balancing valves, we can equal out all the resistances and therefore all the flows Terminal gpm 13gpm 3 Terminal gpm 10gpm 13gpm

8 Why Balance?

9 Manual Balancing Valves

10 Q = Cv P

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12 Manual Balancing Valves Calibrated Orifice vs. fixed orifice (Venturi) Ball, Globe, Butterfly Accuracy Precision Typically Balancing AND Shut Off

13 Manual Balancing Process Lifts, Ladders, Drop Ceilings, Furniture

14 Proportional Balancing Set valves to the correct ratio, they will all be in the same % of overflow or underflow 2gpm 2gpm 2gpm 2gpm 2gpm 2gpm 2gpm 2gpm 2gpm Balance each section within itself 2gpm 2gpm 2gpm Use partner valve to balance sections together 8gpm 8gpm 8gpm

15 Splitting into Hydronic Modules

16 Balancing a Module

17 Hydraulic Interactivity

18 Balancing a Module

19 Balancing a Module

20 Balancing a Module

21 Order for Balancing Modules

22 Full Pump Heat, Valves Wide Open

23 Proportional Branches

24 Balance All Partner Valves

25 Optimize Pump Head

26 Manual Balancing Reality Infinite Solutions

27 Automatic Flow Controllers

28 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 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

29 Automatic Flow Controllers

30 Automatic Flow Controllers Q = Cv P 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

31 Partial Load Conditions

32 % of cooling season below this load % of heating season below this load 58% Differential pressure variations Heating 2 P q Power 120% 100% Dp piping 100% 80% Dallas Thermal plant load [%] 50 % load Thermal plant load [%] 80% 60% 40% 20% 0% 0% 50% 100% 150% 200% Flow At constant supply water temperature 4% press. drop 20 % flow 60% 40% 20% 0% 0% 20% 40% 60% 80% 100% Flow 68% April 2010 Cooling Pressure drops are reduced to 4% of their design value. 32

33 Control loop Set value U Disturbances Sensor k1 x x = U - x Controller k2 Actuator Valve Terminal Power Room Signal Lift Flow output k3 k4 k volts 0-100% 0-100% 0-100% x x = controlled value Power output % Heat output in % Flow in% Flow in % Flow in % Lift h in % Lift h in % = Power output % Heat output in % Terminal unit characteristic April 2010 Control valve characteristic 33

34 50 50 Terminal 10gpm 3gpm Terminal 40 10gpm 13gpm 7gpm 2 10gpm 10gpm 13gpm 15gpm Manual Balancing Terminals are set to 10gpm with static When As other one terminals control valve try to closes modulate, down, valves. As more When portions all control of the building valves are the overflow other situation terminals intensifies, overflow, wasting open, close, system the situation is comfortable gets worse & energy increasing energy costs efficient Terminal 10gpm 13gpm Terminal 17gpm 10gpm 13gpm 4 10gpm 13gpm 11gpm 8gpm 10gpm 13gpm 15gpm 17gpm All circuits are interactive dp sensor placement is critical

35 Overflow = Low ΔT gpm 15gpm 20gpm Design: 10GPM, 40 ΔT

36 Heat Overflow Effects on Coils Coils are designed to flow a certain amount Over 100% flow, the efficiency of the coil reduces 120% 150% flow = 110% heat 250% flow = 120% heat 100% 80% 60% 40% 20% 0% 0% 20% 40% 60% 80% 100% 120% 140% 160% 180% 200% Flow 220% 240%

37 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. Q = Cv P

38 Control Valve Authority with an Automatic Balancing Valve Required Flow 7.5gpm 2.5gpm 10gpm Actual Flow 10gpm 5gpm

39 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

40 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?

41 Best of Both Options? Pressure Independent, Balancing Control Valves 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! Q = Cv P

42 Control loop Set value U Disturbances Sensor k1 x x = U - x Controller k2 Actuator Valve Terminal Power Room Signal Lift Flow output k3 k4 k volts 0-100% 0-100% 0-100% x x = controlled value Power output % Heat output in % Flow in% Flow in % Flow in % Lift h in % Lift h in % = Power output % Heat output in % Terminal unit characteristic April 2010 Control valve characteristic 42

43 Autoflow vs. PICV Always be able to verify flow!

44 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

45 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!

46 Questions?