Friedrich VRP12K, Service And Parts Manual

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120 PB
EXTERNAL STATIC PRESSURE
Ductwork Preparation
If flex duct is used, be sure all the slack is pulled out of the flex duct. Flex duct ESP can increase considerably when not fully
extended. DO NOT EXCEED a total of .30 ESP, as this is the MAXIMUM design limit for the VERT‑I‑PAK A‑Series unit.
IMPORTANT: FLEX DUCT CAN COLLAPSE AND CAUSE AIRFLOW RESTRICTIONS. DO NOT USE FLEX DUCT FOR: 90 DEGREE BENDS,
OR UNSUPPORTED RUNS OF 5 FT. OR MORE.
Fresh Air Door
The Fresh Air Door is an “intake” system. The fresh air door opened via a slide on the front of the chassis located just above the
indoor coil. Move the slide left to open and right to close the fresh air door. The system is capable of up to 60 CFM of fresh air @ ~.3”
H20 internal static pressure.
Checking Approximate Airflow
If an inclined manometer or Magnehelic gauge is not available to check the External Static Pressure, or the blower performance data is unavailable for your unit,
approximate air fl ow call be calculated by measuring the temperature rise, then using tile following criteria.
Electric Heat Strips
The approximate CFM actually being delivered can be calculated by using the following formula:
DO NOT simply use the Kilowatt Rating of the heater (i.e. 2.5, 3.4, 5.0) as this will result in a less-than-correct airfl ow calcula -
tion. Kilowatts may be calculated by multiplying the measured voltage to the unit (heater) times the measured current draw of
all heaters (ONLY) in operation to obtain watts. Kilowatts are than obtained by dividing by 1000.
EXAMPLE:
Measured voltage to unit (heaters) is 230 volts. Measured Current Draw of strip heaters is 11.0 amps.
230 x 11.0 = 2530
2530/1000 = 2.53 Kilowatts
2.53 x 3413 = 8635
Supply Air = 95°F
Return Air = - 75°F
Temperature Rise = 20°F
20 x 1.08 = 21.6