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NDS OUTDOOR SPLIT INSTALLATION MANUAL
Reference Calculations
Heating Calculations:
Cooling Calculations:
LWT = EWT +
LAT (DB) = EAT (DB) -
LC = TC - SC
S/T =
HR
GPM x 500
SC
CFM x 1.08
SC
TC
LWT = EWT -
LAT = EAT +
TH = HC + HW
HE
GPM x 500
HC
CFM x 1.08
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, MBTUH
TC = total cooling capacity, MBTUH
SC = sensible cooling capacity, MBTUH
KW = total power unit input, kilowatts
HR = total heat of rejection, MBTUH
HE = total heat of extraction, MBTUH
HW = hot water generator capacity, MBTUH
EER = Energy Efficiency 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, MBTUH
LC = latent cooling capacity, MBTUH
S/T = sensible to total cooling ratio
Operating Limits
Cooling
Heating
Air Limits
Minimum ambient air, DB
-10°F [-23.3°C]
-10°F [-23.3°C]
Rated ambient air, DB
80.0 [26.7°C]
70°F [21.1°C]
Maximum ambient air, DB
120 [48.8°C]
85°F [29°C]
Water Limits
Minimum entering water
30°F [-1°C]
20°F [-6.7°C]
Normal entering water
50-110°F [10-43°C]
30-70°F [-1 to 21°C]
Maximum entering water
120°F [49°C]
90°F [32°C]
Normal water flow
1.5 to 3.0 gpm per ton
[1.6 to 3.2 l/m per kW]
Operating Limits
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.
