Bryant 598B Subcooling Temperatures, Xii. System Functions And Sequence Of Opera- Tion

TABLE 4—SUBCOOLING TEMPERATURES

	TXV TYPE EXPANSION DEVICE
UNIT	HIGH CAPACITY ONLY
	SUBCOOLING AT SERVICE VALVE
024	14°F
036	15°F
048	12°F
060	16°F

NOTE: If subcooling charging conditions are not favorable, charge must be weighed in accordance with unit rating plate ± 0.6 oz/ft of 3/8-in. liquid line above or below 15 ft respectively.

EXAMPLE: To calculate additional charge required for a 25 ft line

set: 25 ft - 15 ft = 10 ft x 0.6 oz/ft = 6 oz of additional charge.

XII. SYSTEM FUNCTIONS AND SEQUENCE OF OPERA- TION

The outdoor unit control system has special functions. The following is an overview of the two-speed control functions:

A. COOLING OPERATION

This product utilizes a 2-stage cooling indoor thermostat. With a call for first stage cooling (Yl), the outdoor fan and low capacity compressor are energized. If low capacity cannot satisfy cooling demand, high capacity is energized (Yl and Y2 or Y2 only) by the second stage of indoor thermostat. After second stage is satisfied, the unit returns to low-speed operation until first stage is satisfied or until second stage is required again. When both one stage and two stage cooling are satisfied, the compressor will shut off.

NOTE: If unit has not operated within the past 12 hours or following a unit power-up, upon the next thermostat high- or low-speed demand, unit operates for a minimum of 5 minutes in high speed.

NOTE: When two-speed unit is operating at low speed, system vapor (suction) pressure will be higher than a standard single- speed system or high-speed operation. This normal operation is due to the reduced capacity operating with typically larger indoor and outdoor coils.

NOTE: Outdoor fan motor will continue to operate for one minute after compressor shuts off, when outdoor ambient is greater than or equal to 100°F.

B. STATUS FUNCTION LIGHTS

A system control STATUS function light is located on the outdoor unit control board (see Fig. 12). The STATUS light provides signals for several system operations. See Table 5 for codes and definitions. Table 5 also provides the order of signal importance.

NOTE: Only one code will be displayed on the outdoor unit control board (the most recent with the highest priority).

C. FACTORY DEFAULTS

Factory defaults have been provided in the event of failure of outdoor air thermistor, coil thermistor, and/or furnace interface jumper.

D. ONE MINUTE SPEED CHANGE TIME DELAY

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

E. COMPRESSOR OPERATION

When the compressor operates in high capacity operation, the motor rotates clockwise. Both the lower and upper pistons are eccentric with the rotating crankshaft and both compress refriger- ant. When the compressor operates in low capacity the motor reverses direction (rotates counterclockwise). The lower piston becomes idle and the upper piston compresses refrigerant. The start and run windings are reversed.

—12—

TABLE 5—CONTROL FUNCTION LED CODE

CODE	DEFINITION	SIGNAL
		IMPORTANCE*
Constant flash	No demand	10
No pause	Stand by
1 flash	Low-speed operation	9
w/pause
2 flashes	High-speed operation	8
w/pause
3 flashes	Outdoor thermistor failure	7
w/pause
4 flashes	Outdoor coil thermistor failure	6
w/pause
3 flashes
pause	Thermistor out of range	5
4 flashes
5 flashes
pause	Low pressure switch trip	4
1 flash
5 flashes
pause	High pressure switch trip	3
2 flashes
6 flashes	Compressor VC/VH trip	2
w/pause
Constant light
No pause	Board failure	1
No flash

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

TABLE 6—DUAL CAPACITY COMPRESSOR

(WINDING RESISTANCE AT 70° ± 20 °)

WINDING	024	036	048	060
Start (S-C)	2.280	1.850	1.457	0.740
Run (R-C)	0.770	0.745	0.552	0.356

F. CRANKCASE HEATER OPERATION

The two-speed control energizes crankcase heater during unit off cycle.

G. OUTDOOR FAN MOTOR OPERATION

The outdoor unit control energizes outdoor fan any time compres- sor is operating. The outdoor fan remains energized during the 1 minute speed change time delay and if a pressure switch or compressor overload should trip. Outdoor fan motor will continue to operate for one minute after the compressor shuts off when the outdoor ambient is greater than or equal to 100°F.

H. COMPRESSOR VOLTAGE FAILURE (6 FLASHES)

The control senses the voltage of the compressor run winding. If compressor voltage (Vc) is less than 90v when control board is calling for compressor operation, control shuts compressor off for 15 minutes with outdoor fan running. After 15 minutes (provided there is a call for Y1 or Y2), control attempts to start compressor. During this time, a code of 6 flashes appears at control board. If Vc trip occurs 3 consecutive times during a Y1 request, then low capacity operation is locked out and control responds to Y2 requests until a reset occurs. If 3 consecutive trips occur in a combination of Yl and Y2 or all Y2 requests, then both low and high capacity operation will be locked out. The compressor voltage failure (6 flashes) can be caused by:

•compressor internal overload trip (refer to Table 6 for correct winding resistance).

•no 240 volt power supply to outdoor unit.

•failed compressor contactor(s).

•failure of start relay to pick up properly.

•improper wiring.