Bryant R-22 service manual Cycle-ProtectorDevice, V. Crankcase Heater, Vi. Time-Delayrelay

T3 T1 T2

HN67ZA002

A91438

T2

T1

T3

HN67ZA003

A91439

	T2
	T1
	T3
HN67ZA008
	A94005
	T3 BLK
T1 YEL	T2 VIO
	T3 BLK
HN67PA025
	A91440

Fig. 15—Cycle-Protector Device

Cycle-protector device is simple to troubleshoot. Only a voltmeter capable of reading 24v is needed. Device is in control circuit; therefore, troubleshooting is safe with control power (24v) on and high-voltage power off.

With high-voltage power off, attach voltmeter leads across T1 and T3 and set thermostat so that Y terminal is energized. Make sure all protective devices in series with Y terminal are closed. Voltmeter should read 24v across T1 and T3. With 24v still applied, move voltmeter lead from T1 terminal to T2 terminal across T2 and T3. After 5 ± 2 minutes, voltmeter should read 24v, indicating control is functioning normally. If no time delay is encountered or device never times out, change control.

V. CRANKCASE HEATER

Crankcase heater is a device for keeping compressor oil warm. By keeping oil warm, refrigerant does not migrate to and condense in compressor shell when the compressor is off. This prevents flooded starts which can damage compressor.

Crankcase heaters come in 2 basic types: wraparound-(bellyband) type that is wrapped externally around compressor shell, and insertion-type that is inserted into compressor oil well in shell of compressor. Both types are used in outdoor units.

On units that have a single-pole contactor, the crankcase heater is wired parallel with the contactor contacts and in series with the compressor. (See Fig. 18.) When the contacts are open, a circuit is completed from the line side of the contactor, through the crankcase heater, through the run windings of the compressor, and to the other side of the line. When the contacts are closed, there is

—16—

no circuit through the crankcase heater because both leads are connected to the same side of the line. This allows the heater to operate when the system is not calling for heating/cooling. The heater does not operate when the system is calling for heating/cooling. On units with 2 or 3 pole contactors, the crank- case heater is connected to the line side of the contactor and is not controlled by the contactor contacts.

The crankcase heater is powered by high-voltage power of unit. Use extreme caution troubleshooting this device with power on. The easiest method of troubleshooting is to apply voltmeter across crankcase heater leads to see if heater has power. Do not touch heater. Carefully feel area around crankcase heater. If warm, crankcase heater is probably functioning. Do not rely on this method as absolute evidence heater is functioning. If compressor has been running, the area will still be warm.

With power off and heater leads disconnected, check across leads with ohmmeter. Do not look for a specific resistance reading. Check for resistance or an open circuit. Change heater if an open circuit is detected. Some crankcase heaters in this series of units are equipped with a crankcase-heater switch. This energy-saving device shuts off power to heater when temperatures are high enough that heater is not needed. Be sure this switch is functioning normally before condemning crankcase heater.

VI. TIME-DELAY RELAY

The time-delay relay (TDR) is a solid-state-controlled, recycle- delay timer which keeps the indoor blower operating for 90 sec after thermostat is satisfied. This delay enables the blower to remove residual cooling in the coil after compression shutdown,