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Hydronic Loop Performance:Design vs. Installed
Why design and modeling data don’t always match a building’s actual performance
David Kandel
New Mexico Association of Energy Engineers May 26, 2015
Agenda
Hydronic Loop Performance: Design vs. Installed• Design and Modeling Assumptions & Coil Behavior• Performance Problems
• Valve Sizing• Valve Authority (Static vs Dynamic Balancing)• Coil Performance
• Potential Solutions
Valve Specs
• Design / Modeling Assumptions• Proper Valve Sizing• Stable System Pressures• Perfect Valve Authority
Valve / Coil Performance
Coil Performance
Co
il P
ow
er /
Flo
w
Flow / Control Signal
ΔT
BTUh
Valve GPM
Resulting Coil Output
ΔT
Agenda
Hydronic Loop Performance: Design vs. Installed• Design and Modeling Assumptions & Coil Behavior• Performance Problems
• Valve Sizing• Valve Authority• Coil Performance
• Potential Solutions
Hydronic Valve Sizing
P
gpm Cv
Example:• Coil Requires 250 GPM• Design DP for valve, 4 psi • DP of Valve not to exceed 5
psi
1252
250
4
250 Cv
Hydronic Valve Sizing
Example:• Coil Requires 250 GPM• Design DP for valve, 4 psi • DP of Valve not to exceed 5
psi
1252
250
4
250 Cv
Hydronic Valve Sizing
2GPM
P
Cv
Checking DP
Example:• Coil Requires 250 GPM• Design DP for valve, 4 psi • DP of Valve not to exceed 5
psi
Hydronic Valve Sizing
psi7.790
250 P
2
2GPM
P
Cv
Checking DP
psi2.2170
250 P
2
Piping Options
Coil Balance Valve
Control Valve
Coil Control Valve
Coil Flow Limiting
Valve
Control Valve
No Balancing DeviceOversized Control Valves
Coil Control Valve
Coil Control Valve
Near Pump:• High ΔP causes massive
overflow
ΔP35 psi
ΔP8 psi
Far From Pump:• Oversized Valve cause
overflow• No Protection from pressure
changes
Traditional Balancing ValveOversized Control Valves
Near Pump:• Major Valve Authority issues• No Protection from pressure
changes
Balance Valve
Balance Valve
Far From Pump:• Minor Valve Authority issues• No Protection from pressure
changes
Coil Control Valve
Coil Control Valve
ΔP35 psi
ΔP10 psi
Flow Limiting ValveOversized Control Valves
Near Pump:• Major Valve Authority issues• No Protection from pressure
changes below full flow
Far From Pump:• Minor Valve Authority issues• No Protection from pressure
changes below full flow
Coil Control Valve
Coil Control Valve
ΔP35 psi
ΔP10 psi
Flow Limiting
Valve
Flow Limiting
Valve
Agenda
Hydronic Loop Performance: Design vs. Installed• Design and Modeling Assumptions & Coil Behavior• Performance Problems
• Valve Sizing• Valve Authority• Coil Performance
• Potential Solutions
15
Valve Authority
Branchp
valvepCoil
Balance Valve
branch
valve
p
pA
Static BalancingFull Flow
Near Pump:• High Branch Differential• High Pressure Drop on
Balancing Valve
Balance Valve
Balance Valve
Far From Pump:• Low Branch Differential• Low Pressure Drop on
Balancing Valve
Coil Control Valve
Coil Control Valve
ΔP20 psi
ΔP10 psi
4PSI
4PSI
2PSI
4PSI
4PSI
12PSI
100%
Static BalancingManual Balancing Valves
• 100% flow• No pressure drop• 100% flow• 12 psi pressure drop
• 20% flow• ? psi pressure drop
Static BalancingManual Balancing Valves
• Limit the maximum coil flow…
• What happens below max flow?
Static BalancingAutomatic Balancing Valves
Control Valve + Automatic Balancing valve = PI Valve
Static BalancingLess than Full Flow
Near Pump:• Massive overflow
Balance Valve
Balance Valve
Far From Pump:• Small overflow
Coil Control Valve
Coil Control Valve
ΔP20 psi
ΔP10 psi
5PSI
< 4PSI
1PSI
14PSI
< 4PSI
2PSI
20%
Dynamic Balancing
Dynamic BalancingAll Flows
Near Pump:• Exact GPM
Far From Pump:• Exact GPM
Coil PI Valve
CoilPI Valve
ΔP20 psi
ΔP10 psi
0 to 100%
Agenda
Hydronic Loop Performance: Design vs. Installed• Design and Modeling Assumptions & Coil Behavior• Performance Problems
• Valve Sizing• Valve Authority• Coil Performance
• Potential Solutions
Valve / Coil Performance
Coil Performance
Co
il P
ow
er /
Flo
w
Flow / Control Signal
ΔT
BTUh
Valve GPM
Resulting Coil Output
ΔT
Low Delta T at the Coil
T500Q(Btu/h) GPMPower Output:
Operating in the Waste Zone1. Pumping more Water2. Reduced Delta T3. No additional BTUs
Low Delta T at the Coil
Coil Degradation
Heat Transfer of Coil Degrades Over Time• Damage to coil or fins• Air-side fouling• Water-side fouling
Coil Degradation
Coil Performance
Co
il P
ow
er /
Flo
w
Flow / Control Signal
ΔT
BTUh
Valve GPM
Resulting Coil Output
ΔT
Coil Performance
Coil Degradation
Wa
ste
Zon
e
Co
il P
ow
er /
Flo
w
Flow / Control Signal
ΔT
Agenda
Hydronic Loop Performance: Design vs. Installed• Design and Modeling Assumptions & Coil Behavior• Performance Problems
• Valve Sizing• Valve Authority• Coil Performance
• Potential Solutions• Pressure Independent Valves• Delta T Limiting
Pressure Independent ValvesBetter Performance
• No Issues with oversizing• Perfect Valve Authority• Stable control, part load and full load
Pressure Independent ValvesPI Valve Technologies
Mechanical Regulator Flow Meter
Pressure Independent TechnologyMechanical Regulator
Pu Pd
Pd
Pressure Independent TechnologyMechanical Regulator
Pu Pd
Pd
Pressure Independent TechnologyElectronic Pressure Independence
Real Time Flow Measurement
Unrestricted Flow Pattern
Advantages of Electronic PI ValvesDP Reset Strategy
DP reset can now be employed with Pressure Independence
Advantages of Electronic PI ValvesDP Reset Strategy
At Design• “Critical Zone” valve full
open at 5 psi
Coil ePIV
Coil ePIV
100%
5PSI
100% Open
9PSI
9PSIAdvantages of Electronic PI ValvesDP Reset Strategy
At High Demand• “Critical Zone” valve full
open at 5 psi
Coil ePIV
45%
5PSI
At Reduced Demand• “Critical Zone” valve driven
open, as pump reduced as far as possible.
40%
50% Open
8PSI
65% Open80% Open90% Open
8PSIAdvantages of Electronic PI ValvesVFD Reset Strategy
At High Demand• “Critical Zone” valve full
open at 5 psi
Coil ePIV
45%
5PSI
At Reduced Demand• “Critical Zone” valve driven
open, as pump reduced as far as possible.
4PSI3PSI2PSI
40%35%30%
7PSI6PSI
Pressure Independent TechnologyDelta T Limiting
Pressure Independent TechnologyDelta T Limiting
Delta T LimitingCase Study: Large Tech Company in North Carolina
Position Control 240 GPM
144 GPM
96 GPM
Pressure Independent
P.I.+DT Management
Hydronic Loop Performance: Design vs. Installed• Design and Modeling Assumptions & Coil Behavior• Performance Problems
• Valve Sizing• Valve Authority• Coil Performance
• Potential Solutions• Pressure Independent Valves• Delta T Limiting
