Hydronic Loop Performance: Design vs. Installed

Why design and modeling data don’t always

match a building’s actual performance

David Kandel

Rocky Mountain ASHRAE November 6, 2013

Agenda

Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems

• Valve Sizing • Valve Authority • Coil Performance

• Potential Solutions

Valve Specs

• Design / Modeling Assumptions • Proper Valve Sizing • Stable System Pressures • Perfect Valve Authority

Valve / Coil Performance

Coil Performance C

oil P

ower

/ Fl

ow

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

Pgpm Cv�

�

Example: • Coil Requires 250 GPM • Design DP for valve, 4 psi • DP of Valve not to exceed 5

psi

1252

2504

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

2504

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

psi7.790250 P

2

����

����

2GPM P ���

����Cv

Checking DP

psi2.2170250 P

2

����

����

Piping Options

Coil Balance Valve

Control Valve

Coil Control Valve

Coil Flow Limiting Valve

Control Valve

No Balancing Device Oversized Control Valves

Coil Control Valve

Coil Control Valve

Near Pump: • High ΔP causes massive

overflow ΔP

35 psi

ΔP 8 psi

Far From Pump: • Oversized Valve cause

overflow • No Protection from pressure

changes

Traditional Balancing Valve Oversized 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

ΔP 35 psi

ΔP 10 psi

Flow Limiting Valve Oversized 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

ΔP 35 psi

ΔP 10 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�

valvep�Coil

Balance Valve

branch

valve

ppA

��

�

16

Valve Authority

Valve Opening (%)

Flow

(%)

branch

valve

ppA

��

�

Balance Valve

Balance Valve

Coil Control Valve

Coil Control Valve

ΔP 20 psi

ΔP 10 psi

4 psi 4 psi 2 psi A = 0.4

4 psi 4 psi 12 psi A = 0.2

17

Valve Authority

0 40 60 80 100

20

40

60

80

100

10

30

50

70

90

10 20 30 50 70 90

Valve Opening (%)

0.2

1

Valve Authority Distortion

Flow

/ C

oil O

utpu

t (%

)

Valve Opening (%)

Flow

(%)

branch

valve

ppA

��

�

18

Valve Authority

0 40 60 80 100

20

40

60

80

100

10

30

50

70

90

10 20 30 50 70 90

Valve Opening (%)

0.2

Valve Authority Distortion

Flow

/ C

oil O

utpu

t (%

)

Agenda

Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems

• Valve Sizing • Valve Authority • Coil Performance

• Potential Solutions

100

90

20

40

60

80

10

30

50

70

Coo

ling

Out

put (

%)

0 40 60 80 100 10 20 30 50 70 90

Water Flow (%)

110 120 130 140 150

Cooling Output %

Water ΔT

Wat

er Δ

T

Power Saturation Point

Waste Zone

Understanding Coil Behavior

Operating in the Waste Zone 1. Pumping more Water 2. Reduced Delta T 3. No additional BTUs

Coils Heat Transfer Coefficients

• Air film coefficient of sensible heat transfer between air and the external surface of the coil

• Water film coefficient of heat transfer between the internal coil surface and the coolant fluid within the coil

• Unit conductance of the coil material Based on a coil design with a clean, non-fouled surface

Coil Degradation

Heat Transfer of Coil Degrades Over Time • Damage to coil or fins • Air-side fouling • Water-side fouling

Coil Degradation

Coil Performance C

oil P

ower

/ Fl

ow

Flow / Control Signal

ΔT

BTUh

Valve GPM

Resulting Coil Output

ΔT

Coil Performance

Coil Degradation

Was

te Z

one

Coi

l Pow

er /

Flow

Flow / Control Signal

ΔT

Coil Performance

Coil Degradation

Was

te Z

one

WW

More GPM to produce the same BTU

Coi

l Pow

er /

Flow

Flow / Control Signal

ΔT

Coil Degradation Cost of Operating in the Waste Zone

Coil Degradation Cost of Operating in the Waste Zone

55 gpm

320 kBTU/hr

325 kBTU/hr

65 gpm

1 2

Coil Degradation Cost of Operating in the Waste Zone

1 2 BTUh 320,000 325,000 1.6% GPM 55 GPM 65 GPM 18% Pump hp Hp increase = (65/55)3 65%

3

1

2

1

2���

����

�GPMGPM

HPHP

?

1 2 Δ BTUh 320,000 325,000 1.6% GPM 55 GPM 65 GPM 18%

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 • Direct BTU Control

Pressure Independent Valves Better Performance • No Issues with oversizing • Perfect Valve Authority • Stable control, part load and full load

Pressure Independent Valves PI Valve Technologies

Mechanical Regulator Flow Meter

Pressure Independent Valves PI Valve Technologies

Mechanical Regulator Flow Meter

Delta T Limiting BTU Monitoring

BTU Meter

Delta T Limiting BTU Monitoring

BTU Control Maximizing Load to Flow Ratio

Coil Performance C

oil P

ower

/ Fl

ow

Flow / Control Signal

BTUh

Valve GPM

Resulting Coil Output

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 • Direct BTU Control

Questions?