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Observe that compressor, condenser fan, and evaporator
blower motors start. Observe that compressor and outdoor fan
shut down when control setting is satisfied and that indoor
blower shuts down after 30 second fan time delay expires.
3. When using an auto-changeover room thermostat, place both
SYSTEM and FAN switches in AUTO positions. Observe that
unit operates in heating mode when temperature control is set
to “call for heating” (above room temperature) and operates in
cooling mode when temperature control is set to “call for
cooling” (below room temperature).
IMPORTANT:
Three-phase, scroll compressor units (50GS048,
50GX030-060) are direction-oriented. These units must be
checked to ensure proper compressor 3-phase power lead orienta-
tion. If not corrected within 5 minutes, the internal protector will
shut off the compressor. The 3-phase power leads to the unit must
be reversed to correct rotation. When turning backwards, scroll
compressors emit elevated noise levels, and the difference between
compressor suction and
discharge pressures may be
dramatically lower than normal.
CHECKING AND ADJUSTING REFRIGERANT CHARGE
The refrigerant system is fully charged with R-22 refrigerant,
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 chart is attached to the outside of the service
access panel. The chart includes the required suction line tempera-
ture at given suction line pressures and outdoor ambient tempera-
tures (See Fig. 15–27).
An accurate superheat, thermocouple- or thermistor-type ther-
mometer, a sling psychrometer, and a gauge manifold are required
when using the superheat charging method for evaluating the unit
charge. Do not use mercury or small dial-type thermometers
because they are not adequate for this type of measurement.
NOTE:
Allow system to operate in the cooling mode for a
minimum of 10 minutes before checking or adjusting refrigerant
charge.
When evaluating the refrigerant charge, an indicated adjust-
ment to the specified 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 airflow across either coil or both coils.
Proceed as follows:
1. Remove caps from low- and high-pressure service fittings.
2. Using hoses with valve core depressors, attach low- and
high-pressure gauge hoses to low- and high-pressure service
fittings, 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 fitting.
d. Suction (low-side) pressure (psig).
5. Using “Cooling Charging Charts” compare outdoor-air tem-
perature (°F db) with the suction line pressure (psig) to
determine desired system operating suction line temperature.
See Fig. 15-27.
6. Compare actual suction-tube temperature with desired
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 refrigerant 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 section.
INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS
For cooling operation, the recommended airflow is 350 to 450
cfm for each 12,000 Btuh of rated cooling capacity.
Tables 8 and 9 show cooling airflows at various external static
pressures. Refer to these tables to determine the airflow for the
system being installed.
NOTE:
Be sure that all supply- and return-air grilles are open,
free from obstructions, and adjusted properly.
Disconnect electrical power to the unit and install lockout tag
before changing blower speed. Electrical shock can cause
serious injury or death.
Airflow can be changed by changing the lead connections of the
blower motor.
Unit 50GS two- or three-speed motors (except size 030) are
factory wired for low speed operation. Unit 50GS030 is factory
wired for medium speed.
All 50GX units are factory wired for low speed and may need to
be wired for medium or high speed in the field.
FOR 208/230V
For color coding on the 208/230V motor leads, see Table 6.
To change the speed of the indoor fan motor (IFM), remove the fan
motor speed leg lead from the time delay relay (TDR). This wire
is attached to terminal–3 of TDR for single-phase and 3-phase
units. To change the speed, remove and replace with lead for
desired blower motor speed. Insulate the removed lead to avoid
contact with chassis parts.
FOR 460-V GE MOTORS
For color coding on the 460-v GE motor leads, see Table 7.
To change the speed of the indoor fan motor (IFM), remove fan
motor speed lead from the time delay relay (TDR) and replace with
the lead for the desired blower motor speed. The motor speed lead
is attached to terminal–3 of TDR. For low and medium speeds
Table 6—Color Coding for 208/230–V Motor Leads
3-SPEED
2-SPEED
black = high speed
black = high speed
blue = medium speed
-
red = low speed
red = low speed
Table 7—Color Coding for 460-V GE Motor Leads
3-SPEED
2-SPEED
black = high
black = high
violet = jumper
blue = jumper
orange = medium
-
red = low
red = low
14
Summary of Contents for 50gs sizes 018-060
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