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Reference Calculations
Heating Calculations:
HE
LWT = EWT -
gpm x 500
HC
LAT = EAT +
cfm x 1.08
TH = HC + HW
Legend
Abbreviations and Definitions
cfm
= airflow, cubic feet/minute
EWT = entering water temperature, Fahrenheit
gpm = water flow in gallons/minute
WPD = water pressure drop, psi and feet of water
EAT
= entering air temperature, Fahrenheit (dry bulb/wet bulb)
HC
= air heating capacity, MBtu/h
TC
= total cooling capacity, MBtu/h
SC
= sensible cooling capacity, MBtu/h
kW
= total power unit input, kilowatts
HR
= total heat of rejection, MBtu/h
HE
= total heat of extraction, MBtu/h
Operating Limits
Operating Limits
Air Limits
Min. Ambient Air
Rated Ambient Air
Max. Ambient Air
Min. Entering Air
Rated Entering Air db/wb
Max. Entering Air db/wb
Water Limits
Min. Entering Water
Normal Entering Water
Max. Entering Water
Nominal Water Flow
Notes:
Minimum/maximum limits are only for start-up conditions, and are meant for bringing the space
up to occupancy temperature. Units are not designed to operate at the minimum/maximum
conditions on a regular basis. The operating limits are dependent upon three primary factors:
1) water temperature, 2) return air temperature, and 3) ambient temperature. When any of the
factors are at the minimum or maximum levels, the other two factors must be at the normal level
for proper and reliable unit operation.
AFFINITY SERIES OUTDOOR PACKAGED HEAT PUMP INSTALLATION MANUAL
Cooling Calculations:
HR
LWT = EWT +
gpm x 500
SC
LAT (DB) = EAT (DB) -
cfm x 1.08
LC = TC - SC
SC
S/T =
TC
Cooling
(°F)
(°C)
-10
-23.3
80
26.7
100
37.8
50
10.0
80.6/66.2
27/19
110/83
43/28.3
30
-1.1
50-110
10-43.3
120
48.9
1.5 to 3.0 gpm per ton
(1.6 to 3.2 l/m per kW)
HWC = hot water generator capacity, MBtu/h
EER
= Energy Efficient Ratio
= Btu output/Watt input
COP = Coefficient of Performance
= Btu output/Btu input
LWT = leaving water temperature, °F
LAT
= leaving air temperature, °F
TH
= total heating capacity, MBtu/h
LC
= latent cooling capacity, MBtu/h
S/T
= sensible to total cooling ratio
Heating
(°F)
-10
70
85
40
68
80
30
30-70
90
31
(°C)
-23.3
21.1
29.4
4.4
20.0
26.7
-1.1
-1.1
32.2
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