Post on 30-Oct-2014
description
Phone Topics
Applying 19XRV Chillers in Variable Primary Systems
Ron Beliveau
Carrier Commercial Sales
Middletown, CT
Phone Topics
Outline
19XRV chillers in VPF systems.
19XRV Chillers in Variable Primary Systems
1. Review conventional Primary Secondary System.
2. Review Variable Primary Flow System.
3. Review the Benefits of “Max Cap” in both P/S and VPF systems.
4. Review the Benefits of VFD driven chillers in both P/S and VPF systems.
5. Review chiller selection guidelines for VPF applications.
.
WARNING:
55 slides in 45 minutes –
We will be moving very quickly!
Phone Topics
Why VPF?
Why all the interest in VPF?19XRV Chillers in Variable Primary Systems
1. Unlike many items –this isn’t a “sell up” concept – it is actually a lower installed cost.
- VPF Reduces pumping and piping complexities and lowers installation costs.
- Less real estate in mechanical and electrical rooms.
2. Unlike many cost reductions, VPF can offer lower operational costs.
- VPF reduces low T, increasing eff.
- Fewer, but larger pumps have better efficiency.
.
Phone Topics
Primary Secondary Systems.
Primary Secondary Systems use constant speed pumps to supply water to the chillers.
OFF = 0 gpm
ON = 1200 gpm
Phone Topics
Primary Secondary Systems.
The chiller controls to a leaving chilled water set point.
OFF = 0 gpm
ON = 1200 gpm
44 F
Chiller cools 1200 gpm of water to 44F.
How much work is the chiller doing?
Phone Topics
Primary Secondary Systems.
The amount of work the chiller does is related to the return water temperature.
GPM is fixed.
LCHWT is fixed.
Only variable is return temp.
OFF = 0 gpm
ON = 1200 gpm
Tons = GPM x T 24
500 = 1200 x (54-44) / 24
400 = 1200 x (52-44) / 24
300 = 1200 x (50-44) / 24
44 F??
Phone Topics
Chiller (primary) pumps are constant speed (flow).
Secondary pumps are variable speed.
Secondary pump speed (gpm) controlled by DP switch at most hydraulically remote coil.
Primary Secondary Systems.
Phone Topics
If primary gpm equals secondary gpm, there is no flow through the hydraulic decoupler line.
Primary Secondary Systems.
0 gpm 3600 gpm3600 gpm
1200 gpm
1200 gpm
1200 gpm
Phone Topics
If primary gpm is greater than secondary gpm, chilled water flows through the decoupler line, bypassing the coils.
This cold water mixes with the return water, lowering the return temperature to the chillers.
Primary Secondary Systems.
600 gpm 3000 gpm3600 gpm
1200 gpm
1200 gpm
1200 gpm
Phone Topics
If primary gpm is less than secondary gpm, return water flows through decoupler line.
This warm water mixes with the chilled water, raising the entering chilled water temperature to the coils.
If return temp is too high, another chiller / pump set is started.
Primary Secondary Systems.
600 gpm 3000 gpm2400 gpm
0 gpm
1200 gpm
1200 gpm
Phone Topics
Start up.
Coils call for load.
One chiller / pump started and a secondary pump started.
Secondary pump only needs 240 gpm to satisfy coil load.
0 gpm
0 gpm
1200 gpm
240 gpm
0 tons
0 tons
100 tons
960 gpm 240 gpm1200 gpm
46 F 44 F
EX: 100 ton building load
Primary Secondary Systems.
Phone Topics
At 500 tons of building load the secondary pumps require 1200 gpm.
Primary gpm equals secondary gpm and there is no flow through decoupler line.
0 gpm
0 gpm
1200 gpm
1200 gpm
0 tons
0 tons
500 tons
0 gpm 1200 gpm1200 gpm
54 F 44 F
EX: 500 ton building load
Primary Secondary Systems.
Phone Topics
At 550 tons of building load the secondary pumps require 1320 gpm.
For a brief time, primary gpm is less than secondary gpm warm water flows back through decoupler line.
0 gpm
0 gpm
1200 gpm
1320 gpm
0 tons
0 tons
500 tons
120 gpm 1320 gpm1200 gpm
54 F 44 F
EX: 550 ton building load
Primary Secondary Systems.
Phone Topics
To meet coil load, temp sensor turns on chiller and pump set.
Now primary gpm > secondary gpm and chilled water flows through decoupler line bypassing the load.
0 gpm
1200 gpm
1200 gpm
1320 gpm
0 tons
275 tons
275 tons
1080 gpm 1320 gpm2400 gpm
49. 5 F 44 F
EX: 550 ton building load
Primary Secondary Systems.
Phone Topics
When the building reaches 1000 tons, in theory, the chillers are fully utilized and there is no flow through the decoupler line.
0 gpm
0 gpm
1200 gpm
1200 gpm
2400 gpm
2400 gpm
0 tons
500 tons
500 tons
2400 gpm
54 F 44 F
EX: 1000 ton building load
Primary Secondary Systems.
Phone Topics
When building is at full load, there is 1500 tons required by coils and 1500 tons provided by chillers.
System is balanced and there is no flow through decoupler
1200 gpm
1200 gpm
1200 gpm
3600 gpm
500 tons
500 tons
500 tons
0 gpm 3600 gpm3600 gpm
54 F 44 F
EX: 1500 ton building load
Primary Secondary Systems.
Phone Topics
As we unload, the system can shut off the 3rd chiller only if the delta T is at design.
0 gpm
0 gpm
1200 gpm
1200 gpm
2400 gpm
2400 gpm
0 tons
500 tons
500 tons
2400 gpm
54 F 44 F
EX: 1000 ton building load
Primary Secondary Systems.
Phone Topics
If not controlled properly, 1000 ton load could look like this.
3 chillers running at 67% load!
Primary Secondary Systems.
1200 gpm
1200 gpm
1200 gpm
1200 gpm
2400 gpm
2400 gpm
334 tons
333 tons
333 tons
3600 gpm
50.7 F 44 F
EX: 1000 ton building load
Phone Topics
1029 gpm
1200 gpm
1200 gpm
1200 gpm
2571 gpm
2571 gpm3600 gpm
49 F 44 F
EX: 750 ton building load with Low Delta T syndromePrimary
Secondary Systems.
T across dirty coil = 7
Load is 750 Tons, GPM=?
44 F51 F
TONS = GPM x DT / 24
TONS = 1200 X 7 / 24
TONS = 350 ???
TONS = GPM x DT / 24
TONS = 1200 X 5 / 24
TONS = 250
Tons = GPM x T 24
GPM = Tons x 24 TIn perfect world (2)
chillers operate @ 375 tons each.
2@ .479 IKW/Ton
With low delta T (3) chillers operate @ 250 tons each.
3 @ .518 IKW/Ton
Extra pump power is also consumed. T across dirty coil = 7
Load is 750 Tons,
750 x 24 /7 = 2571 gpm
250 tons
250 tons
250 tons
Phone Topics
Outline
19XRV chillers in VPF systems.
19XRV Chillers in Variable Primary Systems
1. Review conventional Primary Secondary System.
2. Review Variable Primary Flow System.
3. Review the Benefits of “Max Cap” in both P/S and VPF systems.
4. Review the Benefits of VFD driven chillers in both P/S and VPF systems.
5. Review chiller selection guidelines for VPF applications.
.
Phone Topics
Variable Primary Systems use variable speed pumps to supply water to the chillers.
OFF = 0 gpm
ON = ??? gpm
(within min / max flow)
Variable Primary Systems
Phone Topics
The chiller controls to a leaving chilled water set point. 44 F
Chiller cools 54F water to 44F.
How much work is the chiller doing?
Variable Primary Systems
OFF = 0 gpm
ON = ??? gpm
54
Phone Topics
The amount of work the chiller does is related to the flow through the cooler.
ECHWT is fixed.
LCHWT is fixed.
Only variable is cooler gpm.
OFF = 0 gpm
ON = 1200 gpm
Tons = GPM x T 24
500 = 1200 x (54-44) / 24
400 = 960 x (54-44) / 24
300 = 720 x (54-44) / 24
44 F54
Variable Primary Systems
Phone Topics
Tons = GPM x T
24
Variable Primary Systems
Primary Secondary
GPM = Constant, T changes as load changes
Variable Primary
T constant, GPM changes as load changes.
Pump only the chilled water necessary to serve the load.
Phone Topics
Variable Primary Systems
Only one set of pumps.
No decoupler line
All pumps are Variable speed.
Flow (gpm) is regulated to
maintain T.
Tons = GPM x T
24
Phone Topics
Variable Primary Systems
Start up.
Coils call for load.
One chiller / pump started.
Min. flow rate of chiller is 500 gpm.
Therefore, 260 gpm must bypass around coils
240 gpm
500 gpm
0 gpm
500 gpm
500 gpm
100 tons
0 tons
0 tons
48.8 F
44 F
260 gpm bypass
500 gpm
0 gpm
0 gpm
EX: 100 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
At 208 tons, the design T (of 10F)
is achieved.
Flow is no longer required to bypass coils.
208 = 500 x 10 24
500 gpm
500 gpm
0 gpm
500 gpm
500 gpm
208 tons
0 tons
0 tons
54 F 44 F
500 gpm
0 gpm
0 gpm
0 gpm
EX: 208 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
At 500 tons, the design T (of 10F)
is achieved with 1200 gpm of flow.
(1) chiller is now fully loaded.
500 = 1200 x 10 24
1200 gpm
1200 gpm
0 gpm
1200 gpm
1200 gpm
500 tons
0 tons
0 tons
54 F44 F
1200 gpm
0 gpm
0 gpm
0 gpm
EX: 500 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
At 550 tons, the design T (of 10F)
is achieved with 1320 gpm of flow.
(2) Chillers are now part loaded.
Flow split equally.
550 = 1320 x 10 24
1320 gpm
1320 gpm
0 gpm
1320 gpm
1320 gpm
275 tons
275 tons
0 tons
54 F44 F
660 gpm
0 gpm
660 gpm
0 gpm
EX: 550 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
At 750 tons, the design T (of 10F)
is achieved with 1800 gpm of flow.
The 2nd pump is turned on.
Flow split equally.
750 = 1800 x 10 24
1800 gpm
900 gpm
900 gpm
1800 gpm
1800 gpm
375 tons
375 tons
0 tons
54 F44 F
900 gpm
0 gpm
900 gpm
0 gpm
EX: 750 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
At 1000 tons, the design T (of 10F)
is achieved with 2400 gpm of flow.
(2) Chillers are now fully loaded.
Flow split equally.
1000 = 2400 x 10 24
2400 gpm
1200 gpm
1200 gpm
2400 gpm
2400 gpm
500 tons
500 tons
0 tons
54 F44 F
1200 gpm
0 gpm
1200 gpm
0 gpm
EX: 1000 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
At 1100 tons, the design T (of 10F)
is achieved with 2640 gpm of flow.
(3) Chillers are now part loaded.
Flow split equally.
1100 = 2640 x 10 24
2640 gpm
1320 gpm
1320 gpm
2640 gpm
2640 gpm
367 tons
367 tons
366 tons
54 F 44 F
880 gpm
0 gpm
880 gpm
880 gpm
EX: 1100 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
At 1500 tons, the design T (of 10F)
is achieved with 3600 gpm of flow.
(3) Chillers are now fully loaded.
Flow split equally.
1500 = 3600 x 10 24
3600 gpm
1800 gpm
1800 gpm
3600 gpm
3600 gpm
500 tons
500 tons
500 tons
54 F44 F
1200 gpm
0 gpm
1200 gpm
1200 gpm
EX: 1500 ton building load
44 F54 F
Phone Topics
Primary Secondary Pumping System Constant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 1200 1 20% 65 0.954 0.551208 1200 1 42% 65 0.619 0.36500 1200 1 100% 65 0.446 0.384550 2400 2 55% 65 0.537 0.332750 2400 2 75% 65 0.479 0.33
1000 2400 2 100.0% 71.8 0.485 0.4361100 3600 3 73.4% 74.2 0.527 0.4441500 3600 3 100% 85 0.59 0.589
Variable Primary Pumping SystemConstant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 500 1 20% 65 0.954 0.548208 500 1 42% 65 0.619 0.358500 1200 1 100% 65 0.446 0.384550 1320 2 55% 65 0.537 0.332750 1800 2 75% 65 0.479 0.328
1000 2400 2 100% 71.8 0.485 0.4361100 2640 3 73.4% 74.2 0.527 0.4421500 3600 3 100% 85 0.59 0.589
When comparing the two systems we find that chiller efficiency is basically equal
Variable Primary Systems
Phone Topics
Compressor HP ~
Mass Flow X Lift
Load
Chiller
CoolingTower
Compressor/Cycle Efficiency
19XRV Chillers in Variable Primary Systems
Why is chiller performance identical for both systems?
KW = Tons x Lift
Phone Topics
Lift is equivalent in both Primary / Secondary and VPF
systems.
Lift is SCT – SST.
SST – based on LCHWT
SCT – based on Tower Performance
Tons – Building load identical in VPF and P/S systems – just adjust flow and T .
19XRV Chillers in Variable Primary Systems
All of this is exactly the same regardless of chilled water system type!
The Efficiency Advantage of VFD Chillers is just as powerful on VPF systems!
Phone Topics
Primary Secondary Pumping System Constant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 1200 1 20% 65 0.954 0.551208 1200 1 42% 65 0.619 0.36500 1200 1 100% 65 0.446 0.384550 2400 2 55% 65 0.537 0.332750 3600 2 75% 65 0.479 0.33
1000 3600 2 100.0% 71.8 0.485 0.4361100 3600 3 73.4% 74.2 0.527 0.4441500 3600 3 100% 85 0.59 0.589
Variable Primary Pumping SystemConstant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 500 1 20% 65 0.954 0.548208 500 1 42% 65 0.619 0.358500 1200 1 100% 65 0.446 0.384550 1320 2 55% 65 0.537 0.332750 1800 2 75% 65 0.479 0.328
1000 2400 2 100% 71.8 0.485 0.4361100 2640 3 73.4% 74.2 0.527 0.4421500 3600 3 100% 85 0.59 0.589
750 3600 3 50% 65 0.562 0.3391000 3600 3 66.7% 71.8 0.533 0.414
When comparing the two systems we find that chiller efficiency is basically equal
Variable Primary Systems
750 1800 2 75% 65 0.479 0.3281000 2400 2 100% 71.8 0.485 0.436
Except when the VPF chiller is able to operate fewer chillers than the Primary / Secondary system.
Phone Topics
Outline
19XRV chillers in VPF systems.
19XRV Chillers in Variable Primary Systems
1. Review conventional Primary Secondary System.
2. Review Variable Primary Flow System.
3. Review the Benefits of “Max Cap” in both P/S and VPF systems.
4. Review the Benefits of VFD driven chillers in both P/S and VPF systems.
5. Review chiller selection guidelines for VPF applications.
.
Phone Topics
Positive Pressure chillers typically can produce above rated tons as entering condenser water drops.
The “Max Cap” Advantage Applied in VPF Systems?
19XRV Chillers in Variable Primary Systems
570570
600600
630630
643643
630 630
Tons
8585ooFF 7575ooFF 7070ooFF <65<65ooFF8080ooFF
550550
Carrier
Others
Phone Topics
Variable Primary Systems
With MAX CAP feature,
At 550 tons, the design T (of 10F)
is achieved with 1320 gpm of flow.
(1) Chiller is fully loaded.
550 = 1320 x 10 24
1320 gpm
1320 gpm
0 gpm
1320 gpm
1320 gpm
550 tons
0 tons
0 tons
54 F44 F
1320 gpm
0 gpm
0 gpm
0 gpm
EX: 550 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
With MAX CAP feature.
At 1100 tons, the design T (of 10F)
is achieved with 2640 gpm of flow.
(2) Chillers are now fully loaded.
1100 = 2640 x 10 24
2640 gpm
1320 gpm
1320 gpm
2640 gpm
2640 gpm
550 tons
550 tons
0 tons
54 F
44 F
1320 gpm
0 gpm
1320 gpm
0 gpm
EX: 1100 ton building load
44 F54 F
Phone Topics
Variable Primary Systems
With MAX CAP feature.
At 1100 tons, the T can be increased from 10F to 11F by
lowering the LCHWT.
(2) Chillers are fully loaded.
1100 = 2400 x 11 24
2400 gpm
1200 gpm
1200 gpm
2400 gpm
2400 gpm
550 tons
550 tons
0 tons
54 F43 F
1200 gpm
0 gpm
1200 gpm
0 gpm
EX: 1100 ton building load
43 F54 F
Phone Topics
Max Cap advantage – increasing evaporator flow.
Good idea on constant speed, not the way to control VFD chillers.
Variable Primary Systems
Primary Secondary Pumping System Constant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 1200 65208 1200 77500 1200 65550 2400 2 55% 65 0.537 0.332750 3600 65900 3600 69
1000 3600 71.81100 3600 3 73.4% 74.2 0.527 0.4441500 3600 85
MAX CAP ADVANTAGE - MORE EVAPORATOR FLOW.
Variable Primary Pumping SystemConstant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 500 65208 500 77500 1200 65550 1320 1 110% 65 0.453 0.433750 1800 65900 2160 69
1000 2400 71.81100 2640 2 110.0% 74.2 0.507 0.4971500 3600 85
Phone Topics
Max Cap advantage holding evaporator flow constant and lowering LCHWT.
Increased lift on chiller – less efficient than increasing flow.
Variable Primary Systems
Primary Secondary Pumping System Constant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 1200 65208 1200 77500 1200 65550 2400 2 55% 65 0.537 0.332750 3600 65900 3600 69
1000 3600 71.81100 3600 3 73.4% 74.2 0.527 0.4441500 3600 85
MAX CAP ADVANTAGE - CONSTANT EVAP FLOW, LOWER LCHWT.
Variable Primary Pumping SystemConstant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 500 65208 500 77500 1200 65550 1320 1 110% 65 0.458 0.443750 1800 65900 2160 69
1000 2400 71.81100 2640 2 110.0% 74.2 0.517 0.5091500 3600 85
Phone Topics
Outline
19XRV chillers in VPF systems.
19XRV Chillers in Variable Primary Systems
1. Review conventional Primary Secondary System.
2. Review Variable Primary Flow System.
3. Review the Benefits of “Max Cap” in both P/S and VPF systems.
4. Review the Benefits of VFD driven chillers in both P/S and VPF systems.
5. Review chiller selection guidelines for VPF applications.
.
Phone Topics
Same reasons you would supply 19XRV on Primary Secondary Systems.
Why Provide Variable Speed Chillers in VPF?
19XRV Chillers in Variable Primary Systems
VFD driven chillers take advantage of reduced lift and/or reduced load hours offering annual power costs unmatched by any constant speed chiller.
.
Phone Topics
Flow ~ V, ATo increase flow, increase flow area or rotor speed
Lift ~ V2
To increase lift, increase diameter or rotor speed
Power ~ Flow x Lift ~ V2
With constant flow and reduced lift, reduce speed to reduce power
Affinity laws for centrifugal fans, pumps and compressors.
V
Diameter
FlowArea
How 19XRV Chillers save kW in P/S & VPF Systems
Ideal Fan Laws Dictate the relationship between speed, flow and lift
19XRV Chillers in Variable Primary Systems
Phone Topics
Methods to Improve Efficiency - Lift Reduction
- Aerodynamics
- Motor efficiency
- Transmission efficiency
- Metering devices
- Refrigerant
- Cycle enhancements
Compressor HP ~
Mass Flow X Lift
Load
Chiller
CoolingTower
Compressor/Cycle Efficiency
19XRV Chillers in Variable Primary Systems
How 19XRV Chillers save kW in P/S & VPF Systems
LiftECWT
Phone Topics
Efficiency improves dramatically as ECWT drops.
19XRV Chillers in Variable Primary Systems
Reduced Lift at 100% tons(500 Tons)
0.30.35
0.40.45
0.50.55
0.6
85 80 75 70 65 60
Entering Condenser Water Temperature
IKW
/ Ton 19XRV
19XR
All points shown are 100% load (500 tons)
19XRV “unlifts” much better then constant speed machine.
Phone Topics
Primary Secondary Pumping System Constant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 1200 1 20% 65 0.954 0.551208 1200 1 42% 65 0.619 0.36500 1200 1 100% 65 0.446 0.384550 2400 2 55% 65 0.537 0.332750 2400 2 75% 65 0.479 0.33
1000 2400 2 100.0% 71.8 0.485 0.4361100 3600 3 73.4% 74.2 0.527 0.4441500 3600 3 100% 85 0.59 0.589
Variable Primary Pumping SystemConstant Speed
Variable Speed
Building Load GPM
Qty of Chillers
Chiller % Load ECWT
Chiller IKW/Ton
Chiller IKW/Ton
100 500 1 20% 65 0.954 0.548208 500 1 42% 65 0.619 0.358500 1200 1 100% 65 0.446 0.384550 1320 2 55% 65 0.537 0.332750 1800 2 75% 65 0.479 0.328
1000 2400 2 100% 71.8 0.485 0.4361100 2640 3 73.4% 74.2 0.527 0.4421500 3600 3 100% 85 0.59 0.589
VFD column better than constant speed column at every point!
* VFD was selected for same FL IKW/Ton – therefore a bit larger and $$$.
Variable Primary Systems
Phone Topics
Outline
19XRV chillers in VPF systems.
19XRV Chillers in Variable Primary Systems
1. Review conventional Primary Secondary System.
2. Review Variable Primary Flow System.
3. Review the Benefits of “Max Cap” in both P/S and VPF systems.
4. Review the Benefits of VFD driven chillers in both P/S and VPF systems.
5. Review chiller selection guidelines for VPF applications.
.
Phone Topics
Minimum flow rate is 1.5 feet / second (intermittent) and 3.0 feet / second (extended)
Maximum flow rate is 12 feet / second.
Rate of change of flow can be up to 30% per minute.
Evaporator should be selected such that design flow rate is at least double the minimum flow rate (if equally sized chillers).
Evaporator flow rate and pressure drops must be carefully coordinated if unequally sized chillers.
VFD chiller selection guidelines for VPF applications.
VPF systems save pump energy – don’t forget to save on chiller energy too.
Remember – you can have both!
19XRV Chillers in Variable Primary Systems