CHECKING AND ADJUSTING REFRIGERANT CHARGE
ÐThe refrigerant system is fully charged with R-22 refrig- erant, tested, and factory-sealed.
NOTE: Adjustment of the refrigerant charge is not required unless the unit is suspected of not having the proper R-22 charge.
A superheat charging label is attached to the inside of the compressor access door. The label includes a ``Superheat Charg- ing Table'' and a ``Required Suction-Tube (F) Temperature'' chart.
An accurate superheat, thermocouple-, or thermistor-type thermometer, a sling psychrometer, and a gage manifold are required when using the superheat charging method for evalu- ating the unit charge. Do not use mercury or small dial-type thermometers because they are not adequate for this type of measurement.
When evaluating the refrigerant charge, an indicated ad- justment to the speci®ed factory charge must always be very minimal. If a substantial adjustment is indicated, an abnormal condition exists somewhere in the cooling system, such as insufficient air¯ow across either coil or both coils.
Proceed as follows:
1.Remove caps from low- and high-pressure service ®ttings.
2.Using hoses with valve core depressors, attach low- and high-pressure gage hoses to low- and high-pressure serv- ice ®ttings, respectively.
3.Start unit in cooling mode and let unit run until system pressures stabilize.
4.Measure and record the following:
a.Outdoor ambient-air temperature (F db).
b.Evaporator inlet-air temperature (F wb).
c.Suction-tube temperature (F) at low-side service ®tting.
d.Suction (low-side) pressure (psig).
5.Using ``Superheat Charging Table,'' compare outdoor-air temperature (F db) with evaporator inlet-air temperature (F wb) to determine desired system operating superheat temperature. See Tables 8A-8H and 9A-9F.
6.Using ``Required Suction-Tube (F) Temperature'' table, compare desired superheat temperature with suction (low- side) operating pressure (psig) to determine proper suction- tube temperature. See Table 10.
7.Compare actual suction-tube temperature with proper suction-tube temperature. Using a tolerance of ± 3° F, add refrigerant if actual temperature is more than 3° F higher than proper suction-tube temperature, or remove refrig- erant if actual temperature is more than 3° F lower than required suction-tube temperature.
NOTE: If the problem causing the inaccurate readings is a refrigerant leak, refer to Check for Refrigerant Leaks sec- tion on page 23.
EVAPORATOR AIRFLOW AND AIRFLOW ADJUSTMENTS
For cooling operation, the recommended air¯ow is 350 to 450 cfm for each 12,000 Btuh of rated cooling ca- pacity. For heating operation, the air¯ow must produce a temperature rise that falls within the range stamped on the unit rating plate.
Table 6 shows the temperature rise at various air¯ow rates. Tables 11-14 show both heating and cooling air¯ows at vari- ous external static pressures. See Tables 15 and 16 for ICM (Integrated Control Motor) units air delivery. Refer to these tables to determine the air¯ow for the system being in- stalled. See Table 17 for wet coil pressure drop.
NOTE: Be sure that all supply- and return-air grilles are open, free from obstructions, and adjusted properly.
Shut off gas supply then disconnect electrical power to the unit before changing blower speed. Electrical shock can cause personal injury or death.
Air¯ow can be changed by changing the lead connections of the blower motor.
Unit 48SS two- or 3-speed motors (except size 030) are factory wired for low speed operation. Unit 48SS030 is fac- tory wired for medium speed. Units 48SX024,036, and 048 (460 v) two- or 3-speed motors are factory wired for low speed; units 48SX030 and 042 are factory wired for medium speed.
For 208/230-v and A.O. Smith 460-v Blower Motors Ð The motor leads are color-coded as follows:
| 3-SPEED | 2-SPEED |
black | = | high speed | black | = high speed |
blue | = | medium speed | red | = low speed |
red | = low speed | | |
To change the speed of the blower motor, remove the fan motor speed leg lead from the blower relay (BR). This wire is attached to terminal BM for single-phase and 3-phase units. To change the speed, remove and replace with lead for de- sired blower motor speed. Insulate the removed lead to avoid contact with chassis parts.
For 460-v GE Motors Ð The motor leads are color coded as follows:
3-SPEED | 2-SPEED |
black | = | high | black | = high |
blue | = | jumper | blue | = jumper |
orange = medium | red | = low |
red | = | low | | |
To change the speed of the blower motor, remove fan mo- tor speed lead from the blower relay (BR) and replace with the lead for the desired blower motor speed. The motor speed lead is attached to terminal BM. Insulate removed lead end to avoid contact with chassis parts. On 3-speed motors only, connect orange lead to terminal BM of BR. To select high speed on 460-v GE motors, separate the black (female QC) from the blue lead (male QC) and connect the black lead to the BR. Insulate the blue lead to avoid contact with any chas- sis parts.
