Operating instructions

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 the 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. For
heating operation, the airflow must produce a temperature rise
that falls within the range stamped on the unit rating plate.
Table 7 shows the temperature rise at various airflow rates. Tables
11 and 13 show both heating and cooling airflows at various
external static pressures. Refer to these tables to determine the
airflow for the system being installed (See Tables 14 and 15 for
wet coil pressure drop).
NOTE: Be sure that all supply- and return-air grilles are open,
free from obstructions, and adjusted properly.
Before changing blower speed, shut off gas supply. Then
disconnect electrical power to the unit and install lockout tag.
Electrical shock or explosion can cause serious injury or
death.
Airflow can be changed by changing the lead connections of the
blower motor.
Unit 48GS two- or three-speed motors (except size 030) are
factory wired for low speed operation. Unit 48GS030 is factory
wired for medium speed.
All 48GX 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 9.
To change the speed of the blower motor (BM), remove the fan
motor speed leg lead from the blower relay (BR). This wire is
attached to terminal BM of the integrated gas control (IGC) board
for single- 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 10.
To change the speed of the blower motor (BM), remove fan motor
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 of the integrated gas control (IGC) board.
For low and medium speeds, black must be connected to the
jumper wire. Insulate removed lead end to avoid contact with
chassis parts. To select high speed on 460-v GE motors, separate
the black (female quick connect – QC – from the jumper lead
(male quick connect – QC) and connect the black lead to the BR.
Insulate the jumper to avoid contact with any chassis parts.
COOLING SEQUENCE OF OPERATION
With the room thermostat SYSTEM switch in the COOL position
and the FAN switch in the AUTO. position, the cooling sequence
of operation is as follows:
1. When the room temperature rises to a point that is slightly
above the cooling control setting of the thermostat, the
thermostat completes the circuit between thermostat terminal
R to terminals Y and G. These completed circuits through the
thermostat:
2. The normally open contacts of energized contactor (C) close
and complete the circuit through compressor motor (COMP)
to condenser (outdoor) fan motor (OFM). Both motors start
instantly.
3. The set of normally open contacts of energized relay BM close
and complete the circuit through evaporator blower (indoor)
fan motor (IFM).
NOTE: Once the compressor has started and then stopped, it
should not be started again until 5 minutes have elapsed. The
cooling cycle remains “on” until the room temperature drops to a
point that is slightly below the cooling control setting of the room
thermostat. At this point, the thermostat “breaks” the circuit
between thermostat terminal R to terminals Y and G. These open
circuits deenergize contactor coil C. The condenser and compres-
sor motors stop. After a 30-sec. delay, the blower motor stops. The
unit is in a “standby” condition, waiting for the next “call for
cooling” from the room thermostat.
MAINTENANCE
To ensure continuing high performance and to minimize the
possibility of premature equipment failure, periodic maintenance
must be performed on this equipment. This combination
heating/cooling unit should be inspected at least once each year by
a qualified service person. To troubleshoot cooling or heating of
units, refer to Tables 16–18.
NOTE: Consult your local dealer about the availability of a
maintenance contract.
The ability to properly perform maintenance on this equip-
ment requires certain expertise, mechanical skills, tools, and
equipment. If you do not possess these, do not attempt to
perform any maintenance on this equipment other than those
procedures recommended in the User’s Manual. FAILURE
TO HEED THIS WARNING COULD RESULT IN SERI-
OUS INJURY AND POSSIBLE DAMAGE TO THIS
EQUIPMENT.
Table 9–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 10–Color Coding for 460-V GE Motor Leads
3-SPEED 2–SPEED
black = high speed black = high speed
violet = jumper blue = jumper
orange = medium speed –
red = low speed red = low speed
22