GPCH3 Installation Manual
11
In general 400 CFM per ton of cooling capacity is a rule of
thumb. Some applications depending on the sensible and
latent capacity requirements may need only 350 CFM or up to
425 CFM per ton. Check condition space load requirements
data to match CFM and capacity.
After unit is set and ducted, verify ESP with a 1” inclined
manometer with pitot tubes or a Magnahelic gauge and
units have multiple speed blower motors. If factory selected
speed is not utilized, the speed tap can be changed. Never
run CFM below 350 CFM per ton, evaporator freezing or
poor unit performance is possible.
1. Using a digital manometer measure the static
pressure of the return duct at the inlet of the unit
2. Measure the static pressure of the supply duct
3. Add the two readings together.
4. Consult proper table for quantity of air.
If the external static pressure exceeds the minimum or
maximum allowable statics, check for closed dampers, dirty
The blower motor speed for the EEM motor is controlled by
three 24V low voltage leads: green, yellow, and white. The
green lead sets the speed for fan-only mode. The yellow
lead sets the speed for cooling and heat pump heating
The leads are factory connected as follows: Green to T1,
Yellow to T2, and White to T3. T1 is the low speed setting
and is dedicated to fan-only mode. T2 is medium speed
cooling and T3 is medium speed heating. T4 is high speed
cooling and T5 is high speed heating. To adjust the blower
speed, move the yellow and/or white wires to T4 and T5.
See CFM vs ESP tables in this manual.
unit’s refrigerant charge must be checked. All package units
method at the compressor suction line. After superheat is
adjusted it is recommended to check unit sub-cooling at the
condenser coil liquid line out. For charge adjustments, see
superheat and subcooling charts shown for each model.
Refrigerant gas is considered superheated whenever its
temperature is higher than the saturation temperature
corresponding to its pressure. The degree of superheat
equals the degrees of temperature increase above
the saturation temperature at existing pressure. See
Temperature - Pressure Chart.
1. Run system at least 10 minutes to allow pressure to
stabilize.
2.
near compressor with adequate contact and insulate
for best possible reading.
3. Refer to the superheat table provided for proper
system superheat. Add charge to lower superheat or
recover charge to raise superheat.