Chilled Water System.ppt 3k4e4b
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Chilled Water Piping Systems (VPF Focus)
Agenda – Chilled Water Distribution Systems
Chilled Water Distribution Systems Primary (Constant) / Secondary (Variable – 2W Valves) Low Delta T Primary Only (Variable Flow - 2W Valves)
VPF Design/Control Considerations
Primary (Constant Flow) / Secondary (Variable Flow)
Primary/Secondary System
Secondary Pumps
Typical load with two way valve
Primary Pumps Common Pipe
Primary (Constant Flow) / Secondary (Variable Flow)
2 Way Valves Higher Capital Cost Installed (vs Constant Flow 3W Valve system) Lower CHW Pumping Energy (vs Constant Flow 3W Valve system) Well Understood & Easy to Control
Primary/Secondary System at Design
56.0 °F
44.0 °F
500 ton chillers 1000 GPM Each 56.0-44.0°F
Secondary Pumps 3000 GPM @ 44.0 °F 56.0 °F 44.0 °F
44.0 °F 56.0 °F
Typical Coil 44.0 °F
Primary Pumps
1000 GPM Each
No flow 56.0 °F
3000 GPM @ 56.0 °F
Primary/Secondary System at Part Load
53.0 °F
44.0 °F
75% System Load Secondary Pumps 2250 GPM @ 44.0 °F
53.0 °F 44.0 °F
44.0 °F 53.0 °F
Typical Coil 44.0 °F
Primary Pumps
1000 GPM Each
750 GPM @ 44.0 °F 56.0 °F
3000 GPM @ 53.0 °F
2250 GPM @ 56.0 °F
Primary/Secondary System
50% System Load
OFF
Secondary Pumps 1500 GPM @ 44.0 °F 53.0 °F 44.0 °F
44.0 °F 53.0 °F
Typical Coil 44.0 °F
Primary Pumps
1000 GPM Each
500 GPM @ 44.0 °F 56.0 °F
2000 GPM @ 53.0 °F
1500 GPM @ 56.0 °F
Low Delta T Syndrome
Major Causes of Low Delta T
Dirty Coils
10
Chilled Water Coil
Major Causes of Low Delta T
Dirty Coils Controls Calibration Leaky 2 Way Valves 3 Way Valves at end of Index circuit
12
Primary/Secondary System
Secondary Pumps
Primary Pumps Common Pipe
Primary/Secondary System
Secondary Pumps
Primary Pumps Common Pipe
Major Causes of Low Delta T
Dirty Coils Controls Calibration Leaky 2 Way Valves 3 Way Valves at end of Index circuit Coils piped up backwards
15
Chilled Water Coil
Primary (Constant) / Secondary (Variable)
P Load = Flow X Delta T
S Load = Flow X Delta T
Secondary Pumps
Typical load with 2 way valve Primary Pumps
17
Decoupler /By
Primary (Constant) / Secondary (Variable) Ideal Operation 100% Load = 100% Sec Flow
Secondary Pumps
100% Flow = 3000 gpm
Primary Pumps 100% Flow = 3000 gpm
18
1 2
Decoupler /By 0 gpm
Primary (Constant) / Secondary (Variable) Ideal Operation 67% Load = 67% Sec Flow
Secondary Pumps
67% Flow = 2000 gpm
Primary Pumps 67% Flow = 2000 gpm
19
1 2
Decoupler /By 0 gpm
Primary / Secondary Rule of Flow
Primary flow must always be equal to or greater than Secondary flow.
20
Primary (Constant) / Secondary (Variable) Low Delta T Operation 67% Load = 80% Sec Flow
Secondary Pumps
80% Flow = 2400 gpm (400 gpm over-pumped)
Primary Pumps 100% Flow = 3000 gpm
21
1 0
Decoupler /By 600 gpm
Major Effects of Low Delta T
Higher Secondary Pump Energy Higher CHW Plant Chiller/Auxiliary Energy
Solution to (or reduce effects of) Low Delta T
Address the causes Clean Coils Calibrate controls occasionally Select proper 2W valves (dynamic/close-off ratings) and maintain them no 3W valves in design
find and correct piping installation errors
Over pump chillers at ratio of Design Delta T / Actual Delta T Increase Delta T across chillers with CHW Re-set (down). Use Variable Speed Chillers & sequence to operate from 30 to 70% Load Use VPF Systems (mitigates energy waste in plant) Header pumps & operate more pumps than chillers If dedicated pumping, over-size (design at 80% speed).
23
Primary/Secondary System
Secondary Pumps
P Primary Pumps Common Pipe
Primary Only (Variable Flow)
Primary/Secondary System Secondary Pumps
Typical load with 2 way valve Primary Pumps
Automatic Isolation Valve
Variable Primary System
Primary Pumps
Typical load with 2 way valve By Valve Flow Meter
Primary Only (Variable Flow)
2 Way Valves Lower Capital Cost Installed (vs Primary/Secondary) No secondary pumps/piping/valves/electrical to buy and install No large Common pipe, but smaller By pipe/valve/flow meter/controls
Lower CHW Pumping Energy Smaller Footprint (vs Primary/Secondary) Relatively New & More Complex Controls Reduces Negative Impacts from Low Delta T Chillers are not staged on by flow requirements Chillers can load up and are staged on load
Primary Only (Variable Flow)
Disadvantages Higher (potentially) PSID rated 2-Way valves in system Requires more robust (complex and calibrated) control system Requires coordinated control of chillers, isolation valves, and pumps in sequencing Longer (potentially) Commissioning time Requires greater operator sophistication
Variable-Primary-Flow System
Automatic Isolation Valve
Primary Pumps
By
Flow Meter
Typical load with two way valve
Variable Primary System at Design
Automatic Isolation Valve
500 ton chillers 1000 GPM Each 56.0-44.0°F
56.0 °F 44.0 °F
56.0 °F 44.0 °F
Primary Pumps
3000 GPM @ 44.0 °F Typical load with two way valve
56.0 °F
1000 GPM Each
44.0 °F By Closed
3000 GPM @ 56.0 °F
Variable Primary System – Part Load
75% System Load
Automatic Isolation Valve
56.0 °F 44.0 °F
56.0 °F 44.0 °F
Primary Pumps
2250 GPM @ 44.0 °F
56.0 °F
750 GPM Each
44.0 °F By Closed
2250 GPM @ 56.0 °F
Typical load with two way valve
Variable Primary System – Part Load Chiller off
50% System Load
Automatic Isolation Valve
Pump off 56.0 °F 44.0 °F
Primary Pumps
1500 GPM @ 44.0 °F
56.0 °F
750 GPM Each
44.0 °F By Closed
1500 GPM @ 56.0 °F
Typical load with two way valve
Variable Primary System – Part Load Chiller off
50% System Load Low Δ T
Automatic Isolation Valve
Pump on 52.0 °F 44.0 °F
Primary Pumps
2250 GPM @ 44.0 °F
52.0 °F
750 GPM Each
44.0 °F By Closed
2250 GPM @ 52.0 °F
Typical load with two way valve
Variable Primary System – Min Flow (400 gpm each) Chiller off Automatic Isolation Valve
System flow below chiller minimum flow
Closed
Chiller off
Pumps off
Closed
200 GPM @ 44.0 °F
Primary Pumps 400 GPM (one operating)
50.0 °F 44.0 °F By Open 200 GPM @ 44.0
400 GPM @ 50.0 °F
Flowmeter
200 GPM @ 56.0 °F
Typical load with two way valve
Chiller Design Considerations
Flow rate changes – Staging on additional chillers
Variable Primary System (1 chiller running)
Automatic Isolation Valve
1000 GPM @ 44.0 °F
Primary Pumps
Typical load with two way valve
56.0 °F 44.0 °F
333 GPM Each 1000 GPM
By Closed
1000 GPM @ 56.0 °F
Variable Primary System (Staging on second chiller)
Automatic Isolation Valve
Need to add chiller 1100 GPM @ 45.0 °F
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 1100 GPM
By Closed
1100 GPM @ 57.0 °F
Variable Primary System (Open isolation valve)
Load = F X DT DT = 12 = 57- 45 24 Load = 1/2F X 2DT DT = 24 24 LCHWT = 35!
Automatic Isolation Valve
1100 GPM @ 45.0 °F
550 GPM
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 550 GPM
By Closed
1100 GPM @ 57.0 °F
Variable Primary System (Open isolation valve)
LCHWT approaches 35 Automatic Isolation Valve
LWT Cutout at 4 deg below 44 set-point or 40 Off goes chiller 1
1100 GPM @ 45.0 °F
550 GPM
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 550 GPM
By Closed
1100 GPM @ 57.0 °F
Variable Primary System (Open isolation valve slowly)
Automatic Isolation Valve
Open over 1.5 to 2 min
1100 GPM @ 45.0 °F
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 1100 GPM
By Closed
1100 GPM @ 57.0 °F
VPF Systems Design/Control Considerations Summary Chillers Equal Sized Chillers preferred, but not required Maintain Min flow rates with By control (1.5 fps) Maintain Max flow rates (11.0 to 12.0 fps) Isolation Valves (Modulating or Stroke-able to 1.5 to 2 min) Don’t vary flow too quickly through chillers (VSD Ramp function – typical setting of 10%/min) Chiller Type System Water Volume Chiller Load Active Loads Sequence If Constant Speed – run chiller to max load (Supply Temp rise). Do not run more chillers than needed (water-cooled) If Variable Speed – run chillers between 30% and 70% load (depending on ECWT). Run more chillers than load requires. Add Chiller - CHW Supply Temp or Load (Adjusted* Flow X Delta T) or amps (if CSD) Subtract Chiller - Load (Adjusted* Flow X Delta T) or Amps (if CSD) 42
VPF Systems Design/Control Considerations Summary
Pumps Variable Speed Driven Headered arrangement preferred Sequence with chillers (run more pumps than chillers for over-pumping capability)
on flow (add pump when existing inadequate, subtract when can) optimized algorithm (total kW of more pumps, lower than less pumps) Stay within pump/motor limits (25% to 100% speed) Subtract a Pump at 25 to 30% speed Add a pump back when speed of operating pumps high enough Speed controlled by pressure sensors at end of index circuit
43
VPF Systems Design/Control Considerations Summary
By Valve Maintain a minimum chilled water flow rate through the chillers Differential pressure measurement across each chiller evaporator Flow meter preferred Modulates open to maintain the minimum flow through operating chiller(s). By valve is normally open, but closed unless Min flow breeched Pipe and valve sized for Min flow of operating chillers High Rangeability (100:1 preferred) PSID Ratings for Static, Dynamic, And Close Off = Shut Off Head of Pumps Linear Proportion (Flow to Valve Position) Characteristic preferred Fast Acting Actuator Locate in Plant around chillers/pumps (preferrred) Energy Avoid Network traffic
44
VPF Systems Design/Control Considerations Summary
Load Valves High Rangeability (200:1 preferred) PSID Ratings for Static, Dynamic, And Close Off = Shut Off Head of Pumps Equal Percentage (Flow to Load) Characteristic Slow Acting Actuator
Staging Loads Sequence AHUs On/Off in 10 to 15 min intervals
45
Summary on VPF Design
Chillers
Size equally with same WPDs (best) Respect Min/Max Flows through chillers Set Pump VSD Ramp function to about 10%/min (600 sec 0 to Max Speed) Use Modulating or Strokeable Valves (preferred) on chiller evaps, headered pumping Use 2 Position Valves (1 min stroke) on chiller evaps, dedicated pumping
Pumps
VSD Controllers Headered Pumping Arrangement (preferred) Dedicated Pumping OK (over-size pumps)
2 Way Valves
Select for Static, Dynamic, Close-off ratings (PSID) equal to pump SOH (plus fill pressure) Range-ability 100 to 200:1 If By – fast acting, linear proportion If Coils – slow acting, equal percentage, “On-Off” stagger air units (10-15 min intervals)
Controls
46
Set-point far out in index circuit (lower the value, the better the pump energy) Set Ramp function in VSD Controller (10%/min average) Run 1 more pump than chillers (when headered) Chillers On by common Supply Temp, Load, Amps, Adj Flow (Adj for Low Delta T) Chillers Off by Amps, Load, Adj Flow (Adj for Low Delta T) Over-pump Chillers to combat Low Delta T and get Max Cap out of chillers By controlled by Min flow (preferred) or Min WPD of largest chiller (locate in plant for best energy, but can go anywhere in system)
Chilled Water Piping Systems (VPF Focus)
Questions?
2 Way Valve/Coil Detail
Air
2-Way Control Valve
Service Valve
Return
Supply
Terminal
Balance and Service Valve
Electric Energy Cost Equations
Mass Flow/t X Lift Energy Cost =
Chiller = Energy Cost
Pump = Energy Cost
Fan = Energy Cost
0.7459
X Hours X Cost/Unit Energy
X 33,015 X Efficiency
Mot Eff
Lbs Refrig/hr X Head
0.7459 X Hours X Cost/Unit Energy
X 33,015 X Comp Eff
Mot Eff
GPM X Head
0.7459
X Hours X Cost/Unit Energy
X 3960 X Pump Eff
Mot Eff
CFM X TSP
0.7459 X Hours X Cost/Unit Energy
X 6356 X Fan Eff
Mot Eff
Agenda – Chilled Water Distribution Systems
Chilled Water Distribution Systems Primary (Constant) / Secondary (Variable – 2W Valves) Low Delta T Primary Only (Variable Flow - 2W Valves)
VPF Design/Control Considerations
Primary (Constant Flow) / Secondary (Variable Flow)
Primary/Secondary System
Secondary Pumps
Typical load with two way valve
Primary Pumps Common Pipe
Primary (Constant Flow) / Secondary (Variable Flow)
2 Way Valves Higher Capital Cost Installed (vs Constant Flow 3W Valve system) Lower CHW Pumping Energy (vs Constant Flow 3W Valve system) Well Understood & Easy to Control
Primary/Secondary System at Design
56.0 °F
44.0 °F
500 ton chillers 1000 GPM Each 56.0-44.0°F
Secondary Pumps 3000 GPM @ 44.0 °F 56.0 °F 44.0 °F
44.0 °F 56.0 °F
Typical Coil 44.0 °F
Primary Pumps
1000 GPM Each
No flow 56.0 °F
3000 GPM @ 56.0 °F
Primary/Secondary System at Part Load
53.0 °F
44.0 °F
75% System Load Secondary Pumps 2250 GPM @ 44.0 °F
53.0 °F 44.0 °F
44.0 °F 53.0 °F
Typical Coil 44.0 °F
Primary Pumps
1000 GPM Each
750 GPM @ 44.0 °F 56.0 °F
3000 GPM @ 53.0 °F
2250 GPM @ 56.0 °F
Primary/Secondary System
50% System Load
OFF
Secondary Pumps 1500 GPM @ 44.0 °F 53.0 °F 44.0 °F
44.0 °F 53.0 °F
Typical Coil 44.0 °F
Primary Pumps
1000 GPM Each
500 GPM @ 44.0 °F 56.0 °F
2000 GPM @ 53.0 °F
1500 GPM @ 56.0 °F
Low Delta T Syndrome
Major Causes of Low Delta T
Dirty Coils
10
Chilled Water Coil
Major Causes of Low Delta T
Dirty Coils Controls Calibration Leaky 2 Way Valves 3 Way Valves at end of Index circuit
12
Primary/Secondary System
Secondary Pumps
Primary Pumps Common Pipe
Primary/Secondary System
Secondary Pumps
Primary Pumps Common Pipe
Major Causes of Low Delta T
Dirty Coils Controls Calibration Leaky 2 Way Valves 3 Way Valves at end of Index circuit Coils piped up backwards
15
Chilled Water Coil
Primary (Constant) / Secondary (Variable)
P Load = Flow X Delta T
S Load = Flow X Delta T
Secondary Pumps
Typical load with 2 way valve Primary Pumps
17
Decoupler /By
Primary (Constant) / Secondary (Variable) Ideal Operation 100% Load = 100% Sec Flow
Secondary Pumps
100% Flow = 3000 gpm
Primary Pumps 100% Flow = 3000 gpm
18
1 2
Decoupler /By 0 gpm
Primary (Constant) / Secondary (Variable) Ideal Operation 67% Load = 67% Sec Flow
Secondary Pumps
67% Flow = 2000 gpm
Primary Pumps 67% Flow = 2000 gpm
19
1 2
Decoupler /By 0 gpm
Primary / Secondary Rule of Flow
Primary flow must always be equal to or greater than Secondary flow.
20
Primary (Constant) / Secondary (Variable) Low Delta T Operation 67% Load = 80% Sec Flow
Secondary Pumps
80% Flow = 2400 gpm (400 gpm over-pumped)
Primary Pumps 100% Flow = 3000 gpm
21
1 0
Decoupler /By 600 gpm
Major Effects of Low Delta T
Higher Secondary Pump Energy Higher CHW Plant Chiller/Auxiliary Energy
Solution to (or reduce effects of) Low Delta T
Address the causes Clean Coils Calibrate controls occasionally Select proper 2W valves (dynamic/close-off ratings) and maintain them no 3W valves in design
find and correct piping installation errors
Over pump chillers at ratio of Design Delta T / Actual Delta T Increase Delta T across chillers with CHW Re-set (down). Use Variable Speed Chillers & sequence to operate from 30 to 70% Load Use VPF Systems (mitigates energy waste in plant) Header pumps & operate more pumps than chillers If dedicated pumping, over-size (design at 80% speed).
23
Primary/Secondary System
Secondary Pumps
P Primary Pumps Common Pipe
Primary Only (Variable Flow)
Primary/Secondary System Secondary Pumps
Typical load with 2 way valve Primary Pumps
Automatic Isolation Valve
Variable Primary System
Primary Pumps
Typical load with 2 way valve By Valve Flow Meter
Primary Only (Variable Flow)
2 Way Valves Lower Capital Cost Installed (vs Primary/Secondary) No secondary pumps/piping/valves/electrical to buy and install No large Common pipe, but smaller By pipe/valve/flow meter/controls
Lower CHW Pumping Energy Smaller Footprint (vs Primary/Secondary) Relatively New & More Complex Controls Reduces Negative Impacts from Low Delta T Chillers are not staged on by flow requirements Chillers can load up and are staged on load
Primary Only (Variable Flow)
Disadvantages Higher (potentially) PSID rated 2-Way valves in system Requires more robust (complex and calibrated) control system Requires coordinated control of chillers, isolation valves, and pumps in sequencing Longer (potentially) Commissioning time Requires greater operator sophistication
Variable-Primary-Flow System
Automatic Isolation Valve
Primary Pumps
By
Flow Meter
Typical load with two way valve
Variable Primary System at Design
Automatic Isolation Valve
500 ton chillers 1000 GPM Each 56.0-44.0°F
56.0 °F 44.0 °F
56.0 °F 44.0 °F
Primary Pumps
3000 GPM @ 44.0 °F Typical load with two way valve
56.0 °F
1000 GPM Each
44.0 °F By Closed
3000 GPM @ 56.0 °F
Variable Primary System – Part Load
75% System Load
Automatic Isolation Valve
56.0 °F 44.0 °F
56.0 °F 44.0 °F
Primary Pumps
2250 GPM @ 44.0 °F
56.0 °F
750 GPM Each
44.0 °F By Closed
2250 GPM @ 56.0 °F
Typical load with two way valve
Variable Primary System – Part Load Chiller off
50% System Load
Automatic Isolation Valve
Pump off 56.0 °F 44.0 °F
Primary Pumps
1500 GPM @ 44.0 °F
56.0 °F
750 GPM Each
44.0 °F By Closed
1500 GPM @ 56.0 °F
Typical load with two way valve
Variable Primary System – Part Load Chiller off
50% System Load Low Δ T
Automatic Isolation Valve
Pump on 52.0 °F 44.0 °F
Primary Pumps
2250 GPM @ 44.0 °F
52.0 °F
750 GPM Each
44.0 °F By Closed
2250 GPM @ 52.0 °F
Typical load with two way valve
Variable Primary System – Min Flow (400 gpm each) Chiller off Automatic Isolation Valve
System flow below chiller minimum flow
Closed
Chiller off
Pumps off
Closed
200 GPM @ 44.0 °F
Primary Pumps 400 GPM (one operating)
50.0 °F 44.0 °F By Open 200 GPM @ 44.0
400 GPM @ 50.0 °F
Flowmeter
200 GPM @ 56.0 °F
Typical load with two way valve
Chiller Design Considerations
Flow rate changes – Staging on additional chillers
Variable Primary System (1 chiller running)
Automatic Isolation Valve
1000 GPM @ 44.0 °F
Primary Pumps
Typical load with two way valve
56.0 °F 44.0 °F
333 GPM Each 1000 GPM
By Closed
1000 GPM @ 56.0 °F
Variable Primary System (Staging on second chiller)
Automatic Isolation Valve
Need to add chiller 1100 GPM @ 45.0 °F
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 1100 GPM
By Closed
1100 GPM @ 57.0 °F
Variable Primary System (Open isolation valve)
Load = F X DT DT = 12 = 57- 45 24 Load = 1/2F X 2DT DT = 24 24 LCHWT = 35!
Automatic Isolation Valve
1100 GPM @ 45.0 °F
550 GPM
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 550 GPM
By Closed
1100 GPM @ 57.0 °F
Variable Primary System (Open isolation valve)
LCHWT approaches 35 Automatic Isolation Valve
LWT Cutout at 4 deg below 44 set-point or 40 Off goes chiller 1
1100 GPM @ 45.0 °F
550 GPM
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 550 GPM
By Closed
1100 GPM @ 57.0 °F
Variable Primary System (Open isolation valve slowly)
Automatic Isolation Valve
Open over 1.5 to 2 min
1100 GPM @ 45.0 °F
Primary Pumps
Typical load with two way valve
57.0 °F 45.0 °F
333 GPM Each 1100 GPM
By Closed
1100 GPM @ 57.0 °F
VPF Systems Design/Control Considerations Summary Chillers Equal Sized Chillers preferred, but not required Maintain Min flow rates with By control (1.5 fps) Maintain Max flow rates (11.0 to 12.0 fps) Isolation Valves (Modulating or Stroke-able to 1.5 to 2 min) Don’t vary flow too quickly through chillers (VSD Ramp function – typical setting of 10%/min) Chiller Type System Water Volume Chiller Load Active Loads Sequence If Constant Speed – run chiller to max load (Supply Temp rise). Do not run more chillers than needed (water-cooled) If Variable Speed – run chillers between 30% and 70% load (depending on ECWT). Run more chillers than load requires. Add Chiller - CHW Supply Temp or Load (Adjusted* Flow X Delta T) or amps (if CSD) Subtract Chiller - Load (Adjusted* Flow X Delta T) or Amps (if CSD) 42
VPF Systems Design/Control Considerations Summary
Pumps Variable Speed Driven Headered arrangement preferred Sequence with chillers (run more pumps than chillers for over-pumping capability)
on flow (add pump when existing inadequate, subtract when can) optimized algorithm (total kW of more pumps, lower than less pumps) Stay within pump/motor limits (25% to 100% speed) Subtract a Pump at 25 to 30% speed Add a pump back when speed of operating pumps high enough Speed controlled by pressure sensors at end of index circuit
43
VPF Systems Design/Control Considerations Summary
By Valve Maintain a minimum chilled water flow rate through the chillers Differential pressure measurement across each chiller evaporator Flow meter preferred Modulates open to maintain the minimum flow through operating chiller(s). By valve is normally open, but closed unless Min flow breeched Pipe and valve sized for Min flow of operating chillers High Rangeability (100:1 preferred) PSID Ratings for Static, Dynamic, And Close Off = Shut Off Head of Pumps Linear Proportion (Flow to Valve Position) Characteristic preferred Fast Acting Actuator Locate in Plant around chillers/pumps (preferrred) Energy Avoid Network traffic
44
VPF Systems Design/Control Considerations Summary
Load Valves High Rangeability (200:1 preferred) PSID Ratings for Static, Dynamic, And Close Off = Shut Off Head of Pumps Equal Percentage (Flow to Load) Characteristic Slow Acting Actuator
Staging Loads Sequence AHUs On/Off in 10 to 15 min intervals
45
Summary on VPF Design
Chillers
Size equally with same WPDs (best) Respect Min/Max Flows through chillers Set Pump VSD Ramp function to about 10%/min (600 sec 0 to Max Speed) Use Modulating or Strokeable Valves (preferred) on chiller evaps, headered pumping Use 2 Position Valves (1 min stroke) on chiller evaps, dedicated pumping
Pumps
VSD Controllers Headered Pumping Arrangement (preferred) Dedicated Pumping OK (over-size pumps)
2 Way Valves
Select for Static, Dynamic, Close-off ratings (PSID) equal to pump SOH (plus fill pressure) Range-ability 100 to 200:1 If By – fast acting, linear proportion If Coils – slow acting, equal percentage, “On-Off” stagger air units (10-15 min intervals)
Controls
46
Set-point far out in index circuit (lower the value, the better the pump energy) Set Ramp function in VSD Controller (10%/min average) Run 1 more pump than chillers (when headered) Chillers On by common Supply Temp, Load, Amps, Adj Flow (Adj for Low Delta T) Chillers Off by Amps, Load, Adj Flow (Adj for Low Delta T) Over-pump Chillers to combat Low Delta T and get Max Cap out of chillers By controlled by Min flow (preferred) or Min WPD of largest chiller (locate in plant for best energy, but can go anywhere in system)
Chilled Water Piping Systems (VPF Focus)
Questions?
2 Way Valve/Coil Detail
Air
2-Way Control Valve
Service Valve
Return
Supply
Terminal
Balance and Service Valve
Electric Energy Cost Equations
Mass Flow/t X Lift Energy Cost =
Chiller = Energy Cost
Pump = Energy Cost
Fan = Energy Cost
0.7459
X Hours X Cost/Unit Energy
X 33,015 X Efficiency
Mot Eff
Lbs Refrig/hr X Head
0.7459 X Hours X Cost/Unit Energy
X 33,015 X Comp Eff
Mot Eff
GPM X Head
0.7459
X Hours X Cost/Unit Energy
X 3960 X Pump Eff
Mot Eff
CFM X TSP
0.7459 X Hours X Cost/Unit Energy
X 6356 X Fan Eff
Mot Eff
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