Carrier NP034-074 specifications Electric Heat 50 Series Units Only, Gas Heat 48 Series Units Only

Fig. 62 Ð Typical Compressor Overtemperature,

High- and Low-Pressure Switch Locations

Table 11 Ð Pressure Switch Settings (psig)

SWITCH	CUTOUT	CUT-IN
High	426 6 7	320 6 20
Low	27 6 4	67 6	7

Control Circuit, 115 V Ð This control circuit is pro- tected against overcurrent by a 5-amp circuit breaker. Breaker can be reset. If it trips, determine cause of trouble before resetting.

Control Circuit, 24 V Ð This control circuit is pro- tected against overcurrent by a 3.2-amp circuit breaker. Breaker can be reset. If it trips, determine cause of trouble before resetting.

Electric Heat (50 Series Units Only)

OVERCURRENT Ð Heaters are protected by fuses in the power circuit, located in the heater control box. As with cir- cuit breakers, determine the cause of fuses tripping before replacing them. Do not replace with larger fuses. All fuses are 60 amp.

OVERTEMPERATURE Ð Heaters are protected by limit switches mounted in the heater box. They reset automati- cally once they cool.

Gas Heat (48 Series Units Only)

LIMIT SWITCHES Ð The maximum supply-air tempera- ture is controlled by a limit switch located in the gas section. The limit is designed to trip at 100 F above the maximum temperature rise shown in Tables 1A and 1B.

When the limit trips, the gas valve is deenergized. Once the unit cools, the gas valve is reenergized.

ROLLOUT SWITCH Ð This switch senses any ¯ame or excessive heat in the main burner compartment and deen- ergizes the gas valve. If this occurs, the gas heating system is locked out until the rollout switch is reset manually. Reset by pressing the button on the rollout switch. See Fig. 39.

When the rollout switch trips, it likely indicates a ¯ue block- age. Inspect the unit for any obstruction in the ¯ue system, for holes on the ¯ue box, or for a defective centrifugal switch or loose combustion blower. See Fig. 63 for proper location of the rollout capillary.

TROUBLESHOOTING

Economizer Ð The economizer control consists of an electronic control board mounted on the back of the cover plate of the economizer motor with the adjustments and elec- trical plugs accessible through the top of the cover. The econo- mizer control is factory wired to the terminals on the motor. All potentiometers and adjustments are a part of the control board.

Fig. 63 Ð Location of Rollout Switch Capillary Tube

ECONOMIZER MOTOR CHECKOUT Ð The motor may be checked out separately from the control board. See Table 12 for motor checkout. To check out the motor, apply 24 VAC power to terminals T0 and T2 of the control board.

NOTE: The connections to motor terminals T1 and R must remain in place.

Table 12 Ð Economizer Motor Checkout

MOTOR	PROCEDURE	EXPECTED RESULT
TEST		AND RESPONSE
A	Remove wire connected to	Motor drives open. If not,
	terminal W on the motor.	replace the motor.
B	Remove wire connected to	Motor drives closed. If not,
	terminal B on the motor,	replace the motor.
	leaving W wire discon-
	nected (Test A).

CONTROL BOARD CHECKOUT Ð To check out the con- trol board motor, conduct the following 4 tests.

Test 1:

1.Apply 24 VAC power to terminals T0 and T2 of control board.

2.Remove mixed air sensor connected between terminals S1 and S2.

3.Remove outdoor-air enthalpy sensor between terminals 11 and SO.

4.Refer to Table 13.

Table 13 Ð Economizer Control Board Checkout,

Test 1

MOTOR	PROCEDURE	EXPECTED RESULT
TEST		AND RESPONSE
A	Turn minimum position	Motor drives closed. If not,
	potentiometer fully	check minimum position
	counterclockwise.	jumper between
		terminals Z and Y, and
		check terminal W and T1
		connections to motor.
B	Turn minimum position	Motor drives open. If not,
	potentiometer fully	check terminal B and R
	clockwise.	connections to the motor.

Test 2:

1.Apply 24 VAC power to terminals T0 and T2 of the con- trol board.

2.Apply 24 v between terminals 1 and T2, and jumper ter- minal T0 to terminal 1.

3.Remove the mixed-air sensor connected between termi- nals S1 and S2, and replace it with a 5490-ohm resistor.

4.Remove outdoor-air enthalpy sensor between terminals 11 and SO, and replace it with a 1.2 kOhm resistor.

5.Turn the minimum position potentiometer fully counter- clockwise.

6.Refer to Table 14.

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