42 WSHP-PRC001-EN
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Procedure
ISO Cooling Data Calculations
Examples for cooling calculations in reference to ARI-ISO 13256-1 is listed below. This step-by-step example, utilizes the
unit information as shown in SP-3, to verify the ISO calculations found in SP-4.
SP-3: Unit information
Unit Information
Total Unit Watts 1129
Air Flow, CFM 609
Static Pressure at the unit (in. wg) 0.12
GPM 5.97
Total Pressure Drop across water side (Ft. of water) 2.08
Air Side Capacity
Sensible Capacity (Btuh) 14000
Latent Capacity (Btuh) 7572
Total Cooling Capacity before adjustment (Btuh) 21572
Sensible/Total Heat Ratio 0.649
Explanation of Cooling Calculations
STEP 1:
To calculate the fan power adjustment, refer to SP2 on Page 41
for the procedure on how to calculate the fan power adjustment
factor.
In this example:
CFM = 609
SP = 0.12
Fan Power Adjustment
=(CFM x 0.472) x (SP x 249) / 300
=(609 x 0.472) x (0.12 x 249) / 300
=29 Watts
STEP 4:
To calculate the ARI-ISO 13256-1 Cooling Capacity Rating, add
the Cooling Capacity Adjustment (Btuh) to the Total Cooling
Capacity.
In this example:
ARI-ISO 13256-1 Cooling Capacity Rating = 21572 + 99
Result:
ARI-ISO 13256-1 Cooling Capacity Rating = 21671
STEP 2:
To calculate pump penalty, refer to SP1 on Page 41 for the
procedure on how to calculate the pump penalty.
In this example:
GPM = 5.97
FtHd = 2.08
Pump Penalty
=(GPM x 0.0631) x (PressDrop x 2990) / 300
=(5.97 x 0.0631) x (2.08 x 2990) / 300
=8 Watts
STEP 3:
To calculate capacity adjustment, multiply 3.413 times the
Fan Power Adjustment factor rounded to the nearest inte-
ger.
In this example:
Capacity adjustment = Fan Power Adjustment x 3.413
Result:
=29 x 3.413
=99 Btuh
STEP 5:
To calculate ARI-ISO 13256-1 Ratings Power Input (watts), add
the actual total measured watts to the pump penalty, then sub-
tract the Fan Power adjustment watts.
In this example:
Power Input = 1129 + 8 - 29
Result:
Power Input = 1108
STEP 6:
To calculate the Energy Efficiency Ratio, divide the ARI-ISO
Cooling Capacity by the ARI-ISO Power Input watts.
In this example:
Energy Efficiency Ratio = 21671 / 1108
Result:
Energy Efficiency Ratio = 19.56
SP-4: ISO calculations
ISO Calculations
ARI-ISO Power Adjustment
Fan Power (watts) 29
Pump Penalty (watts) 8
ARI-ISO Capacity Adjustment
Fan Power (Btuh) 99
ARI-ISO Ratings
Cooling Capacity (Btuh) 21671
Power Input (watts) 1108
Energy Efficiency Ratio (EER) 19.56
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