![background image](http://html.mh-extra.com/html/carrier/weathermaker-48a2020/weathermaker-48a2020_controls-start-up-operation-service-and-troubleshooting-instructions_2560305149.webp)
149
Gas Valve Adjustment
NATURAL GAS
The 2-stage gas valve opens and closes in response to the ther-
mostat 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. Switch main gas valve to OFF position.
3. Remove
1
/
8
-in. pipe plug from manifold. Install a water ma-
nometer pressure-measuring device.
4. Switch 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. 56).
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. Switch main gas valve to OFF position.
10. Remove pressure-measuring device and replace
1
/
8
-in. pipe
plug and screw cap.
11. Turn main gas valve to ON position and check heating
operation.
Main Burners
For all applications, main burners are factory set and should re-
quire no adjustment.
MAIN BURNER REMOVAL (FIG. 57)
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.
7. Remove sensor wire and ignitor cable from IGC board.
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
Replace whenever refrigerant system is exposed to atmosphere.
Replacement Parts
A complete list of replacement parts may be obtained from any
Carrier distributor upon request.
Fig. 56 — Gas Valve (Part Number EF33CW271)
INLET PRE
SS
URE
TAP (ON
S
IDE)
1/
8
-IN. 27 NPT
OUTLET PRE
SS
URE
TAP (ON
S
IDE)
1/
8
-IN. 27 NPT
HIGH-FIRE REGULATOR
ADJU
S
TMENT
S
CREW
LOW-FIRE REGULATOR
ADJU
S
TMENT
S
CREW
ON/OFF
S
WITCH
Fig. 57 — Main Burner Removal
Summary of Contents for WEATHERMAKER 48A2020
Page 112: ...112 Fig 20 Typical Main Control Box Wiring Schematic 48 50A Units ...
Page 113: ...113 Fig 21 Typical Auxiliary Control Box Wiring Schematic ...
Page 114: ...114 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown ...
Page 115: ...115 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown TO NEXT PAGE ...
Page 116: ...116 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont ...
Page 117: ...117 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown ...
Page 118: ...118 Fig 25 Typical Controls Option Wiring Schematic SW1 SW2 OR DEHUMIDIFY SWITCH ...
Page 119: ...119 Fig 26 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown ...
Page 120: ...120 Fig 27 Typical Power Schematic of Greenspeed Low Ambient Option 48 50A 060 Unit Shown ...
Page 121: ...121 Fig 28 Typical Small Chassis Component Location Size 020 035 Units ...
Page 122: ...122 Fig 29 Typical Large Chassis Component Locations Size 040 060 Units ...
Page 185: ...185 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716 ...