Specifications

32
ENVISION COMMERCIAL SPECIFICATION CATALOG
The performance standard AHRI/ASHRAE/ISO 13256-1 became effective January 1, 2000 and replaces AHRI Standards
320, 325, and 330. This new standard has three major categories: Water Loop (comparable to ARI 320), Ground Water
(ARI 325), and Ground Loop (ARI 330). Although these standards are similar there are some differences:
Unit of Measure: The Cooling COP
The cooling efficiency is measured in EER (US version measured in Btuh per Watt. The Metric version is measured in
a cooling COP (Watt per Watt) similar to the traditional COP measurement.
Water Conditions Differences
Entering water temperatures have changed to reflect the centigrade temperature scale. For instance the water loop
heating test is performed with 68°F (20°C) water rounded down from the old 70°F (21.1°C).
Air Conditions Differences
Entering air temperatures have also changed (rounded down) to reflect the centigrade temperature scale. For in-
stance the cooling tests are performed with 80.6°F (27°C) dry bulb and 66.2°F (19°C) wet bulb entering air instead of
the traditional 80°F (26.7°C) DB and 67°F (19.4°C) WB entering air temperatures. 80.6/66.2 data may be converted
to 80/67 using the entering air correction table. This represents a significantly lower relative humidity than the old
80/67 of 50% and will result in lower latent capacities.
Pump Power Correction Calculation
Within each model, only one water flow rate is specified for all three groups and pumping Watts are calculated using
the following formula. This additional power is added onto the existing power consumption.
• Pump power correction = (gpm x 0.0631) x (Press Drop x 2990) / 300
Where ‘gpm’ is waterflow in gpm and ‘Press Drop’ is the pressure drop through the unit heat exchanger at rated wa-
ter flow in feet of head.
Blower Power Correction Calculation
Blower power is corrected to zero external static pressure using the following equation. The nominal airflow is rated
at a specific external static pressure. This effectively reduces the power consumption of the unit and increases cool-
ing capacity but decreases heating capacity. These Watts are significant enough in most cases to increase EER and
COPs fairly dramatically over ARI 320, 325, and 330 ratings.
• Blower Power Correction = (cfm x 0.472) x (esp x 249) / 300
Where ‘cfm’ is airflow in cfm and ‘esp’ is the external static pressure at rated airflow in inches of water gauge.
ISO Capacity and Efficiency Calculations
The following equations illustrate cooling calculations:
• ISO Cooling Capacity = Cooling Capacity (Btuh) + (Blower Power Correction (Watts) x 3.412)
• ISO EER Efficiency (W/W) = ISO Cooling Capacity (Btuh) x 3.412 / [Power Input (Watts) - Blower Power Correction
(Watts) + Pump Power Correction (Watt)]
The following equations illustrate heating calculations:
• ISO Heating Capacity = Heating Capacity (Btuh) - (Blower Power Correction (Watts) x 3.412)
• ISO COP Efficiency (W/W) = ISO Heating Capacity (Btuh) x 3.412 / [Power Input (Watts) - Blower Power Correction
(Watts) + Pump Power Correction (Watt)]
Comparison of Test Conditions
Conversions:
Airflow (lps) = CFM x 0.472; Water Flow (lps) = GPM x 0.0631;
ESP (Pascals) = ESP (in wg) x 249; Press Drop (Pascals) = Press Drop (ft hd) x 2990
Performance Standard (AHRI/ISO/ASHRAE 13256-1)
ARI 320
ISO/AHRI
13256-1
WLHP
ARI 325
ISO/AHRI
13256-1
GWHP
ARI 330
ISO/AHRI
13256-1 GLHP
Cooling
Entering Air - DB/WB °F 80/67 80.6/66.2 80/67 80.6/66.2 80/67 80.6/66.2
Entering Water - °F 85 86 50/70 59 77 77
Fluid Flow Rate * ** ** ** ** **
Heating
Entering Air - DB/WB °F 70 68 70 68 70 68
Entering Water - °F 70 68 50/70 50 32 32
Fluid Flow Rate * ** ** ** ** **
Note *: Flow rate is set by 10°F rise in standard cooling test Note **: Flow rate is specified by the manufacturer
Part load entering water conditions not shown.
WLHP = Water Loop Heat Pump; GWHP = Ground Water Heat Pump; GLHP = Ground Loop Heat Pump