Checking External Static Pressure; Checking Temperature Rise - Goodman [A/G]PG Service Instructions Manual

SERVICING
6. Braze all joints, leak test, evacuate, and recharge system.
7. Start up the unit and record the pressure drop across the
cleanup drier.
8. Continue to run the system for a minimum of twelve (12)
hours and recheck the pressure drop across the drier. Pres-
sure drop should not exceed 6 - 8 PSIG.
9. Continue to run the system for several days repeatedly
checking pressure drop across the suction line drier. If the
pressure drop never exceeds the 6 - 8 PSIG, the drier must
be adequate and is trapping the contaminants and it is
permissible to leave it in the system.
10. If the pressure drop becomes greater, then it must be re-
placed and steps 5 through 9 repeated until it does not
exceed 6 - 8 PSIG.
NOTE: The cause for burnout MUST be determined and cor-
rected BEFORE the new compressor is started.
S-200 CHECKING EXTERNAL STATIC PRESSURE
The minimum and maximum allowable duct static pressure is
found in the Technical Information Manual.
Too great of an external static pressure will result in insuffi-
cient air that can cause icing of the coil, whereas too much air
can cause poor humidity control, and condensate to be pulled
off the evaporator coil causing condensate leakage. Too much
air can cause motor overloading and in many cases this con-
stitutes a poorly designed system. To determine proper air
movement, proceed as follows:
1. Using a draft gauge (inclined manometer) measure the static
pressure of the return duct at the inlet of the unit, (Negative
Pressure).
INCLINED
MANOMETER
SUPPLY
Total External Static
2. Measure the static pressure of the supply duct, (Positive
Pressure).
44
3. Add the two readings together.
NOTE: Both readings may be taken simultaneously and read
directly on the manometer if so desired.
4. Consult proper table for quantity of air.
If the external static pressure exceeds the minimum or maxi-
mum allowable statics, check for closed dampers, dirty filters,
undersized or poorly laid out ductwork.
S-201 CHECKING TEMPERATURE RISE
Temperature rise is related to the BTUH output of the unit and
the amount of air (CFM) circulated over the heat exchanger.
All units are designed for a given range of temperature increase.
This is the temperature of the air leaving the unit minus the
temperature of the air entering the unit.
The more air (CFM) being delivered through a given unit the
less the rise will be; the less air (CFM) being delivered, the
greater the rise. The temperature rise should be adjusted in
accordance to a given unit specifications and its external static
pressure.
1. Check BTUH input to unit. Do not exceed input rating
2. Take entering and leaving air temperatures.
3. Select the proper speed tap or dip switch setting for direct
4. Take motor current draw to determine that the motor is not
RETURN
stamped on rating plate.
drive units.
overloaded during adjustments.
SUPPLY
T
SUPPLY
T
RETURN

Checking Temperature Rise

RETURN
T T
RISE = SUPPLY - RETURN