Thermostatic Expansion Valve (Txv); Gas Valve Adjustment; Main Burners; Filter Drier - Carrier 48AJ Operating And Service Manual

Thermostatic Expansion Valve (TXV) —
has a TXV. The TXV is nonadjustable and is factory set to main-
tain 10 to 13° F superheat leaving the evaporator coil. The TXV
controls flow of liquid refrigerant to the evaporator coils.

Gas Valve Adjustment

NATURAL GAS — The 2-stage gas valve opens and closes
in response to the thermostat or limit control.
When power is supplied to valve terminals 3 and 4, the pilot
valve opens to the preset position. When power is supplied to
terminals 1 and 2, the main valve opens to its preset position.
The regular factory setting is stamped on the valve body
(3.5 in. wg).
To adjust regulator:
1. Set thermostat at setting for no call for heat.
2. Turn main gas valve to OFF position.
3. Remove / -in. pipe plug from manifold. Install a water
1
8
manometer pressure-measuring device.
4. Set main gas valve to ON position.
5. Set thermostat at setting to call for heat (high fire).
6. Remove screw cap covering regulator adjustment screw
(See Fig. 40).
7. Turn adjustment screw clockwise to increase pressure or
counterclockwise to decrease pressure.
8. Once desired pressure is established, set unit to no call for
heat (3.3-in. wg high fire).
9. Turn main gas valve to OFF position.
10. Remove pressure-measuring device and replace
pipe plug and screw cap.
11. Turn main gas valve to ON position and check heating
operation.
For all applications, main burners are
Main Burners —
factory set and should require no adjustment.
MAIN BURNER REMOVAL (Fig. 41)
1. Shut off (field-supplied) manual main gas valve.
2. Shut off power supply to unit.
3. Remove heating access panel.
4. Disconnect gas piping from gas valve inlet.
5. Remove wires from gas valve.
6. Remove wires from rollout switch.
A48-3729
Fig. 38 — Belt Tension Adjustment
7. Remove sensor wire and ignitor cable from IGC board.
Each circuit
8. Remove 2 screws securing manifold bracket to basepan.
9. Remove 4 screws that hold the burner support plate
flange to the vestibule plate.
10. Lift burner assembly out of unit.
11. Reverse procedure to re-install burners.
Filter Drier —
posed to atmosphere.
Replacement Parts —
parts may be obtained from any Carrier distributor upon request.
2 LEADS, #18 WIRE 1/32 INSULATION,
1 / -in.
600V. MAX., 105°C
8
INLET PRESSURE TAP
(PLUGGED)
1/8 - 27 N.P.T. THDS.
Fig. 40 — Gas Valve (Part Number EF33CB271)
A48-3733
122
Replace whenever refrigerant system is ex-
A complete list of replacement
Fig. 39 — Condenser-Fan Adjustment
REGULATOR
ADJUSTMENT SCREW
(REMOVE COVER)
D-1 D-2
W-1 C1
C2
W-2
RECEPTACLE TERMINAL
Fig. 41 — Main Burner Removal
A48-3730
OUTLET PRESSURE
TAP (PLUGGED)
1/8-27 N.P.T. THDS.
RECEPTACLE AND
TAB COMBINATION
TERMINAL
PILOT CONNECTION
FOR 1/4" O.D. TUBING
(PLUGGED)
A48-5717