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Engineering Design Guide HBH/V SERIES Heat Controller, Inc.
To convert Inch-Pound (English) to SI (Metric)
Air Flow Correction Table
400 CFM per ton of cooling capacity is nominal rated airflow for all models (bold print)
Use multipliers directly with unit data for correcting unit performance at other airflows than nominal
Entering Air Correction Tables
Entering air corrections should be multiplied directly to unit performance data to derive performance at entering air condition other
than ARI/ISO/ASHRAE 13256-1
ARI/ISO/ASHRAE 13256-1 uses entering air conditions of Clg- 80.6ϒF DB/66.2ϒF WB and Htg- 68ϒF DB/59ϒF WB shown in bold
Discontinued Standards ARI 320, 325, and 330 used entering air conditions of Clg- 80ϒF DB/67ϒF WB and Htg- 70ϒF DB
Cooling Corrections
Sens Clg Cap Multiplier - Entering DB ϒF
Ent Air
WB ϒF
Total Clg
Cap
70 75 80 80.6 85 90 95
Power Heat of
Rej
60 0.852 0.828 0.980 1.097 1.129 * * * 0.996 0.878
65 0.974 0.595 0.808 1.004 1.017 1.194 * * 0.998 0.979
66.2 1.000 0.539 0.767 0.967 1.000 1.152 * * 1.000 1.000
67 1.004 0.501 0.740 0.939 0.955 1.124 1.233 1.276 1.002 1.010
70 1.034 0.636 0.810 0.844 1.016 1.136 1.220 1.005 1.029
75 1.069 0.514 0.612 0.826 0.973 1.127 1.010 1.058
Heating Corrections
Ent Air
DB ϒF
Htg Cap Power
Heat of
Ext
60 1.059 0.947 1.100
65 1.019 0.981 1.032
68 1.000 1.000 1.000
70 0.995 1.010 0.989
75 0.980 1.037 0.960
80 0.967 1.063 0.934
Total Cap Sens Cap Power Heat of Rej
1.019 0.902 0.964 1.007
1.013 0.928 0.976 1.003
1.007 0.953 0.988 1.000
1.004 0.977 0.994 1.000
1.000 1.000 1.000 1.000
0.998 1.023 1.006 1.000
0.997 1.047 1.012 1.000
Cooling
CFM Per Ton
of Clg
% of
Nominal
300 75%
325 81%
350 88%
375 94%
400 100%
425 106%
450 113%
Airflow
Htg Cap Heat of ExtPower
0.957 1.061 0.922
0.968 1.040 0.946
0.979 1.020 0.970
0.989 1.010 0.985
1.000 1.000 1.000
1.011 0.997 1.015
1.021 0.994 1.030
Heating
Air Flow Water Flow Ext Static Pressure Water Pressure Drop
Airflow (L/s) = CFM x 0.472 Water Flow (L/s) = gpm x 0.0631 ESP (Pa) = ESP (in of wg) x 249 PD (kPa) = PD (ft of hd) x 2.99
Reference Calculations
BTUH = BTU( British Thermal Unit) per hour
CFM = airow, cubic feet/minute
COP = coefcient of performance = BTUH output/BTUH input
DB = dry bulb temperature (°F)
EAT = entering air temperature, Fahrenheit (dry bulb/wet bulb)
EER = energy efciency ratio = BTUH output/Watt input
EPT = external pipe thread
ESP = external static pressure (inches w.g.)
EWT = entering water temperature
GPM = water ow in U.S. gallons/minute
HE = total heat of extraction, BTUH
HC = air heating capacity, BTUH
HR = total heat of rejection, BTUH
HWC = hot water generator (desuperheater) capacity, Mbtuh
IPT = internal pipe thread
KW = total power unit input, kilowatts
LAT = leaving air temperature, °F
LC = latent cooling capacity, BTUH
LWT = leaving water temperature, °F
MBTUH = 1000 BTU per hour
S/T = sensible to total cooling ratio
SC = sensible cooling capacity, BTUH
TC = total cooling capacity, BTUH
WB = wet bulb temperature (°F)
WPD = waterside pressure drop (psi & ft. of hd.)
Conversion Table - to convert inch-pound (English) to SI (Metric)
Legend and Glossary of Abbreviations
LWT = EWT -
HE
GPM x 500
LAT = EAT +
HC
CFM x1.08
LWT = EWT +
HR
GPM x 500
LAT (DB) = EAT (DB) -
SC
CFM x1.08
LC = TC - SC
S/T =
SC
TC
Heating
Cooling
Selection Procedure
3