Bryant R-22 service manual Function Light Code and Display Location

TABLE 15—FUNCTION LIGHT CODE AND DISPLAY LOCATION

CODE	T’STAT	UNIT	DEFINITION	*	POSSIBLE CAUSE
Constant flash	—	X	No demand	9	—
No pause			Stand by
1 flash	—	X	Low-speed operation	8	—
w/pause
2 flashes	—	X	High-speed operation	7	—
w/pause
3 flashes	X	X	Ambient thermistor failure	6	—
w/pause
4 flashes	X	X	Coil thermistor failure	5	—
w/pause
3 flashes					Thermistor drift, wrong location
					Incorrect wiring
pause	X	X	Thermistor out of range**	4
					Incorrect refrigerant charge
4 flashes
					Dirty indoor/outdoor coil
5 flashes			Pressure switch trip		Dirty outdoor coil
	X‡	X		3	Refrigerant overcharge
w/pause			(LM1/LM2)
					Wrong indoor coil
6 flashes					Low refrigerant charge
	X	X	Compressor PTCs out of limit	2	Compressor mechanical problem
w/pause†
					Dirty indoor/outdoor coil
Constant light					Equipment or electrical service
No pause	X	X	Board failure	1
					not grounded
No flash

*Function light signals order of importance; in case of multiple-signal request, 1 is most important.

†Signal at thermostat will occur after 3 consecutive attempted restarts and lockout has occurred.

‡ Will be energized if pressure switch remains open for 1 hr. **Check both thermistors to determine which is faulty.

	70
	60						HIGH SPEED
	HIGH
		SPEED		CAPACITY			BALANCE POINT
	50
(1000'S)
	40
	LOW
BTU	SPEED		CAPACITY					STRUCTURE
	30							BALANCE POINT
	20					LOW SPEED
						BALANCE POINT
	10
	50	60		70	80	90	100	110	120

TEMPERATURE (°F)

A91282

Fig. 35—Typical Cooling Balance Points

DEFROST

The 2-speed control logic for the defrost function is the standard time and temperature initiated, time or temperature terminated. Defrost occurs only at outdoor temperatures less than 50°F. The control initiates defrost when the outdoor coil thermistor is 30°F (±

2)or less, and the selected defrost time (interval) has been accumulated during unit operation. Termination occurs when the coil thermistor reaches 80°F (± 5) or the defrost period reaches a maximum of 10 minutes.

Defrost always occurs in high speed unless the stage–2 latch POT is set at ZONE. During defrost the unit operates in high speed, energizes the reversing valve (O) and auxiliary heat (W2), and de-energizes the outdoor fan. Upon termination, there is a 20-sec delay in the outdoor fan being energized. If the stage–2 latch POT is set to ZONE and the heat pump is in low speed, it defrosts in low speed.

—32—

FIELD-INITIATED FORCED DEFROST

By placing a jumper across the speedup terminals for a minimum of 5 sec and then removing it, the unit initiates a defrost cycle. (See Fig. 34.) The cycle occurs only if the outdoor ambient is less than 50°F, regardless of outdoor coil temperature. The cycle terminates when the coil thermistor reaches 80°F ( ± 5) or the defrost period reaches a maximum of 10 minutes.

FURNACE INTERFACE

This feature provides a heat-pump lockout upon a demand for auxiliary heat (W2) and must be used when interfacing a heat pump with a gas/oil furnace. Field selection of the furnace- interface option is done by connecting the factory-supplied jumper to the ON position of the 3 terminal connectors. (See Fig. 33.)

When the option is selected, the heat pump will be locked out of operation any time there is a thermostat demand for W2 or the outdoor ambient is below the balance-point POT-setting selection. (See Fig. 34.) When the unit requires defrost, auxiliary heat (W2) energizes the furnace. After defrost is terminated, the heat pump shuts down and the furnace satisfies the thermostat. To utilize this function, the economic and/or thermal balance point must be determined. See the appropriate heat pump balance-point work- sheet available from your distributor or branch.

BALANCE POINT

This feature can be used in 2 different options: furnace interface or electric-heat staging. Refer to the Furnace Interface section for its application. If the heat pump is installed with a fan coil with multistages of electric heat, this option can be used to stage the banks of heat by outdoor ambient. This eliminates the need for accessory outdoor thermostats.

When using this option to stage electric heat, first stage is energized by a W2 demand, and second stage is energized by a W3 demand. Select the W3 desired temperature by rotating the balance-point POT. (See Fig. 34.) Temperatures that may be selected are 10°, 15°, 20°, 25°, 30°, 35°, 40°, and 45°F. The POT is factory set at 45°F.

LOW-SPEED HEATING WITH AUXILIARY HEAT

If the system is operating in low-speed heating and there is a demand for auxiliary heat (W2), the system changes to high-speed operation. W2 is energized unless the low-voltage control wiring is configured as described in Fig. 36.