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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 80.6/66.2
Max. Entering Air db/wb
Water Limits
Min. Entering Water
Normal Entering Water
Max. Entering Water
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
Heating
(°F)
(°C)
(°F)
45
7.2
45
80
26.7
70
100
37.8
85
50
10.0
40
27/19
68
110/83
43/28.3
80
30
-1.1
20
50-110
10-43.3
30-70
120
48.9
90
DUAL COMPRESSOR PACKAGED HEAT PUMP INSTALLATION GUIDE
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
(°C)
7.2
21.1
29.4
4.4
Notes: Minimum/maximum limits are only for start-up
20.0
conditions, and are meant for bringing the space up to
26.7
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)
-6.7
water temperature, 2) return air temperature, and 3) ambient
temperature. When any of the factors are at the minimum or
-1.1
maximum levels, the other two factors must be at the normal
32.2
level for proper and reliable unit operation.
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