WSHP-PRC001-EN 41
Selection
Procedure
New Performance Ratings
All performance data in this catalog is rated to the new ARI-ISO 13256-1 standard . The following information should be
used in gaining a clearer understanding of the differences on the new ARI-ISO standard versus the ARI 320/330 standards
of today.
The ARI-ISO 13256-1 standard includes adjustment to include pump wattage and fan wattage. For these new calculations,
review SP-1 for ISO pump penalty adjustment calculation and SP-2 for fan wattage adjustment calculation.
Differences in test conditions for ARI-ISO versus ARI 320/330 are listed below.
SP-1: ISO pump penalty adjustment calculation
ISO Pump Penalty (GPM, Feet of pressure drop)
1. Calculate the pump penalty for the ISO standard
2. Calculations must be done in SI (International Standard) units
Note: GPM = Gallons per minute, the actual flow of water.
FtHd = The measured water side pressure drop in feet of head
Flow = GPM x 0.0631 Convert GPM to liters per second.
PressDrop = FtHd x 2990 Convert feet of water to pascals
Pump Penalty = Flow x PressDrop / 300 Note: 300 is a constant
SP-2: ISO fan wattage adjustment calculation
ISO Fan Wattage Adjustment (CFM, SP)
1. Calculate the fan watt factor for the ISO standard
2. Subtract watts from total watts
3. Calculations must be done in SI (International Standard) units
Note: CFM = Cubic feet per minute of air-flow
SP = External static pressure in inches of water glass
Flow = CFM x 0.472 Convert CFM to liters per second.
ESP = SP x 249 Convert inches of water to pascals
Fan Watt Adjustment = Flow x ESP / 300 Note: 300 is a constant
Test Conditions
ARI 320 ISO WLHP
(water loop heat pump)
ARI 330 ISO GLHP
(ground loop heat pump)
Cooling Capacity F F F F
Entering-Air (Dry Bulb) 80 80.6 80 80.6
Entering-Air (Wet Bulb) 67 66.2 67 66.2
Entering Water 85 86 77 77
Leaving Water 95 Note 2 Note 2 Note 2
Fluid Flow Rate Note 1 Note 3 Note 3 Note 3
Heating Capacity
Entering-Air (Dry Bulb) 70 68 70 68
Entering Water 70 68 32 32
Fluid Flow Rate Note 1 Note 3 Note 3 Note 3
Note 1: Flow rate is set by standard rating, cooling test.
Note 2: As determined by the flow rate to be specified by the manufacturer.
Note 3: Flow rate specified by the manufacturer.
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