Johnson Controls RC Series Engineering Manual page 6

RC SERIES ENGINEERING GUIDE
Performance Standard (AHRI/ISO/ASHRAE 13256-1)
The performance standard AHRI/ASHRAE/ISO 13256-1 became effective January 1, 2000 and replaces ARI 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 instance 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 water flow in feet of
head.
Fan Power Correction Calculation
Fan 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 cooling capacity but de-
creases heating capacity. These Watts are significant enough in most cases to increase EER and COPs fairly dramatically over ARI
320, 325, and 330 ratings.
• Fan 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) + (Fan Power Correction (Watts) x 3.412)
• ISO EER Efficiency (W/W) = ISO Cooling Capacity (Btuh) x 3.412 / [Power Input (Watts) - Fan Power Correction (Watts) + Pump
Power Correction (Watt)]
The following equations illustrate heating calculations:
• ISO Heating Capacity = Heating Capacity (Btuh) - (Fan Power Correction (Watts) x 3.412)
• ISO COP Efficiency (W/W) = ISO Heating Capacity (Btuh) x 3.412 / [Power Input (Watts) - Fan Power Correction (Watts) + Pump
Power Correction (Watt)]
Comparison of Test Conditions
Cooling
Entering Air - DB/WB °F
Entering Water - °F
Fluid Flow Rate
Heating
Entering Air - DB/WB °F
Entering Water - °F
Fluid Flow Rate
Note *: Flow rate is set by 10°F rise in standard cooling test
Part load entering water conditions not shown.
WLHP = Water Loop Heat Pump; GWHP = Ground Water Heat Pump; GLHP = Ground Loop Heat Pump
Conversions:
Airflow (lps) = CFM x 0.472;
ESP (Pascals) = ESP (in wg) x 249;
ISO/AHRI
ARI 320 13256-1 ARI 325
WLHP
80/67 80.6/66.2 80/67
85 86 50/70
* **
70 68
70 68 50/70
* **
WaterFlow (lps) = GPM x 0.0631;
Press Drop (Pascals) = Press Drop (ft hd) x 2990
6
ISO/AHRI
13256-1 ARI 330
GWHP
80.6/66.2 80/67
59 77
** ** **
70 68 70
50 32
** ** **
Note **: Flow rate is specified by the manufacturer
ISO/AHRI
13256-1 GLHP
80.6/66.2
77
**
68
32
**