Bryant R-22 service manual Ambient Temperature for HIGH- LOW-SPEED Operation

HEATING OPERATION (HEAT PUMP ONLY)

The 2-speed products utilize a 2-stage-heating indoor thermostat. The first stage of heating is heat-pump operation (Y1). Auxiliary backup heat is controlled by second stage (W2). There is a 2° differential between first and second stage. The control board determines the compressor speed based on ambient temperature. See Table 14 for ambient temperatures at which speed changes occur. When high-speed, heat-pump heating is required, the control provides a Y2 (24vac) signal back to the thermostat to energize high-speed-indicator LED.

TABLE 14—AMBIENT TEMPERATURE FOR HIGH- AND

LOW-SPEED OPERATION

UNIT	AMBIENT TEMPERATURE (°F)
SIZE	High Speed	Low Speed
036	30 or less	31 or greater
048	33 or less	34 or greater
060	40 or less	41 or greater

LED FUNCTION LIGHTS

When using the factory-authorized indoor thermostats with the 2-speed outdoor units, there are 2 locations where system-function LED-indicator lights are available. The indoor thermostat provides indicator lights for high- and low-speed operation, system mal- function, and auxiliary heat for heat pumps. The 2-speed control board has an LED which provides signals for several system operations. See Table 15 for LED functions, indicator locations, and definitions. Table 15 also provides the order of signal importance if more than 1 signal should occur. The signal to the indoor thermostat is supplied by the low-voltage ″ L″ lead.

THREE-SECOND TIME DELAY

Any time the control receives a 24v input, such as Y1 or Y2, there is a 3-sec time delay before the control function is initiated. This helps prevent nuisance trips and thermostat ″ jiggling.″

ONE-MINUTE SPEED-CHANGE TIME DELAY

When the compressor changes speeds from high to low or low to high, there is a 1-minute time delay before the compressor restarts. The outdoor fan motor remains running.

FIVE-MINUTE TIME DELAY

The 2-speed-control logic contains a 5-minute time delay that prevents the unit from short cycling after a thermostat-off cycle or power interruption. The unit can be forced to operate immediately by momentarily touching a jumper between the speed-up terminals of the control board. (See Fig. 33 and 34.) The speed-up feature will not bypass any other function or time delay.

HIGH VOLTAGE						LOW VOLTAGE
L2	LO	HI	CCH ODF			LM1 LM2 DFT1 DFT2 T1	T2 S2	S1 PW2 PW1
				O	C
						1	P1		18
K1	K2	K3	K4	K5	K6	K7
							FURN INT
								OFF	ON
						SPEED-UP
							STAGE 2	DEFROST BALANCE
							LATCH	TIME	POINT

LED 1

A93569

Fig. 33—Two-Speed Control Board

TWO-MINUTE LOW-SPEED MINIMUM

If the unit has not operated within the past 30 minutes, the unit operates for a minimum of 2 minutes in low speed upon the next thermostat high or low demand.

—31—

LM1 LM2 DFT1 DFT2 T1	T2	S2	S1	PW2 PW1
1		P1				18
K7
		FURN INT
			OFF		ON
SPEED-UP	90	95	50		25	30
85		100			20	35
ZONE		105 OFF	30	90	10 15	40 45
STAGE 2			DEFROST		BALANCE
	LATCH		TIME		POINT

A93568

Fig. 34—Speedup Terminals

CRANKCASE-HEATER OPERATION

The 2-speed control energizes the crankcase heater during the unit’s off cycle when the outdoor ambient is below 75°F.

OUTDOOR FAN-MOTOR OPERATION

The 2-speed control energizes the outdoor fan any time the compressor is operating. The outdoor fan remains energized during the 1-minute, speed-change time delay and if a pressure switch or compressor PTC overload should trip.

If the outdoor fan motor won’t run, check the header-pin housing. (See Fig. 37.) There should be NO jumper wire between Terminals 15 and 16.

Heat Pumps

After the termination of a defrost cycle, the outdoor fan delays come on for 20 sec. This allows the refrigeration system to recover the outdoor coil heat and minimize the ″ steam cloud″ effect.

SECOND-STAGE LATCHING

When low-speed cooling operation no longer satisfies the first stage of the indoor thermostat, the indoor temperature will increase by 2° until second stage is energized. After high-speed cooling satisfies second stage, it returns to low-speed cooling operation. If desired, the installer may select to have high-speed cooling by energizing Y1. High speed will stay energized until Y1 is satisfied. This eliminates the temperature drop between the first and second stages of indoor thermostat, holding room temperature closer to set point.

To utilize this function, the unit capacity should be plotted versus the heat gain of the structure, which provides the system’s balance point when the structure requires high-speed capacity. (See Fig. 35.)

Second-stage latching can be selected by rotating the potentiom- eter (POT) to the desired outdoor second-stage latching tempera- ture (See Fig. 34.) The temperatures that can be selected are 85°, 90°, 95°, 100°, and 105°F. The POT is factory set at 105°F.

ZONE SELECTION

If the stage–2 latch POT is set to ZONE position, the compressor operating speed in either heat or cool mode is determined by the Y1 and/or Y2 inputs. The system operates in low speed with a Y1 input and high speed with Y2 or Y1-and-Y2 input. This allows the multistage-zoning system to determine what speed is needed regardless of outdoor temperature or switchover point.

DEFROST TIME SELECTION

The defrost interval can be field selected, depending on local or geographic requirements. It is factory set at 90 minutes and can be changed to either 30 or 50 minutes by rotating the defrost-time POT. (See Fig. 34.)