Carrier 48/50AJ Condenser-FanAdjustment, Gas Valve Adjustment, Round Tube, Plate Fin Unit Charge

Condenser-Fan Adjustment

NOTE: Condenser fans on size 060 MCHX units are not adjustable.

1.Turn off unit power supply.

2.Remove fan guard.

3.Loosen fan hub setscrews.

4.Adjust fan height on shaft using a straightedge placed across venturi and measure per Fig. 43.

5.Fill hub recess with permagum if rubber hubcap is missing.

6.Tighten setscrews and replace panel(s).

7.Turn on unit power.

Four-Inch Filter Replacement — The 4-Inch Filter Change Mode variable is used to service the unit when 4-in. filters are used. When the filters need to be changed, set Service Test→F.4.CH = YES. The unit will be placed in Service Test mode and the economizer will move to the 40% open position to facilitate removal of the 4-in. filters. After the filters have been changed, set Service Test→F.4.CH = NO to return the unit to normal operation.

Power Failure — The economizer damper motor is a spring return design. In event of power failure, dampers will return to fully closed position until power is restored.

Refrigerant Charge — Amount of refrigerant charge is listed on unit nameplate. Refer to Carrier GTAC II; Module 5; Charging, Recovery, Recycling, and Reclamation section for charging methods and procedures.

Unit panels must be in place when unit is operating during charging procedure.

NOTE: Do not use recycled refrigerant as it may contain contaminants.

NO CHARGE — Use standard evacuating techniques. After evacuating system, weigh in the specified amount of refriger- ant from the unit nameplate.

LOW CHARGE COOLING

All Units with Round Tube-Plate Fin Condenser Coils — Connect the gage set and a temperature-measuring device to the liquid line. Ensure that all condenser fans are operating. It may be necessary to block part of the coil on cold days to ensure that condensing pressures are high enough to turn on the fans. Adjust the refrigerant charge in each circuit to obtain state point liquid subcooling for specific models as listed in Table 123.

NOTE: Indoor-air cfm must be within normal operating range of unit.

Table 123 – Round Tube, Plate Fin Unit Charge

UNIT	REFRIGERANT	SIZE	LIQUID
48/50	TYPE		SUBCOOLING
		020, 025, 027,
		030, 035, 040,	20 F ± 2 F
AJ,AK,AW,AY	R-22	050, 060
		036	18 F ± 2 F
		041, 051	15 F ± 2 F
		020, 027, 040,	15 F ± 2 F
		050, 060
A2,A3,A4,A5	R-410A
		030, 035	20 F ± 2 F
		025	12 F ± 2 F

48/50A2,A3,A4,A5 Units with MCHX Condenser — Due to the compact, all aluminum design, microchannel heat exchangers will reduce refrigerant charge and overall operating weight. As a result, charging procedures for MCHX units require more accurate measurement techniques. Charge should be added in small increments. Using cooling charging charts provided (Fig. 44-50), add or remove refrigerant until condi- tions of the chart are met. As conditions get close to the point

on the chart, add or remove charge in 1/4 lb increments until complete. Ensure that all fans are on and all compressors are running when using charging charts.

To Use the Cooling Charging Chart — Use the outdoor air temperature, saturated suction temperature and saturated con- densing temperature (available on the ComfortLink™ display), and find the intersection point on the cooling charging chart. If intersection point is above the line, carefully recover some of the refrigerant. If intersection point is below the line, carefully add refrigerant.

NOTE: Indoor-air cfm must be within normal operating range of unit.

Thermostatic Expansion Valve (TXV) — Each circuit has a TXV. The TXV is adjustable and is factory set to maintain 8 to 12° F superheat leaving the evaporator coil. The TXV con- trols flow of liquid refrigerant to the evaporator coils. Adjusting the TXV is not recommended.

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.Switch main gas valve to OFF position.

3.Remove 1/8-in. pipe plug from manifold. Install a water manometer 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. 51).

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.

A

UNIT SIZE	DIMENSION “A” (in.)
020-035, 050	1.30 ± 0.12
036-041, 051, 060	0.87 ± 0.12

Fig. 43 — Condenser-Fan Adjustment

(All Units Except Size 060 MCHX)

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