auto−reset switch closes when the compressor casing temperature falls to 151−187°F (66°C−86°C), and the compressor is re−energized. This single−pole, single−throw (SPST) bi−metallic switch is wired in series with the 24V Y input signal to control compressor operation.
Crankcase Thermostat (S40) (−036, −042, −048 and
−060 Units Only)
The reference models are equipped with a 70 watt, belly band type crankcase heater. HR1 prevents liquid from accumulating in the compressor. HR1 is controlled by a thermostat located on the liquid line. When liquid line temperature drops below 50° F the thermostat closes energizing HR1. The thermostat will open, de−energizing HR1 once liquid line temperature reaches 70° F .
Defrost Thermostat (S6)
The defrost thermostat is located on the liquid line between the check/expansion valve and the distributor. When defrost thermostat senses 42°F (5.5°C) or cooler, the thermostat contacts close and send a signal to the defrost control to start the defrost timing. It also terminates defrost when the liquid line warms up to 70°F (21°C).
Bi−Flow Liquid Line Filter Drier
The unit is equipped with a large−capacity biflow filter drier which keeps the system clean and dry. If replacement is necessary, order another of the same design and capacity. The replacement filter drier must be suitable for use with HFC−410A refrigerant.
Defrost System
The XP14 defrost system includes two components: a defrost thermostat (S6) and a defrost control (CMC1) (figure 15).
DEFROST CONTROL (CMC1)
The defrost control includes the combined functions of a time/temperature defrost control, defrost relay, diagnostic LEDs and terminal strip for field wiring connections.
P1 − FIELD SELECT |
|
TIMING PINS |
|
TEST |
|
PINS |
|
| DIAGNOSTIC |
P5 − | LEDS |
| |
COMPRESSOR |
|
DELAY PINS |
|
REVERSING |
|
VALVE |
|
| 24V TERMINAL |
| STRIP |
S87 | CONNECTIONS |
| |
LOW PRESSURE |
|
SWITCH |
|
DEFROST |
|
THERMOSTAT |
|
S4 |
|
HIGH PRESSURE |
|
SWITCH |
|
Figure 24. Outdoor Unit Defrost Control (CMC1)
The defrost control provides automatic switching from normal heating operation to defrost mode and back. When the defrost thermostat is closed, the control accumulates compressor run time at 30, 60 or 90 minute field adjustable intervals. When the selected compressor run time interval is reached, the defrost relay is energized and defrost begins.
Defrost Control Timing Pins (P1)
Each timing pin selection provides a different accumulated compressor run time period for one defrost cycle. This time period must occur before a defrost cycle is initiated. The defrost interval can be adjusted to 30 (T1), 60 (T2), or 90 (T3) minutes (see figure 24). The maximum defrost period is 14 minutes and cannot be adjusted.
NOTE part number is listed near the P1 timing pins.
SUnits with defrost control 100269−02: Factory default is 60 minutes
SUnits with defrost control 100269−04: Factory default is 90 minutes
If the timing selector jumper is missing, the defrost control defaults to a 90−minute defrost interval.
Compressor Delay (P5)
The defrost control has a field−selectable function to reduce occasional sounds that may occur while the unit is cycling in and out of the defrost mode.
SUnits with defrost control 100269−02: The compressor will be cycled off for 30 seconds going in and out of the defrost mode when the compressor delay jumper is removed.
SUnits with defrost control 100269−04: The compressor will be cycled off for 30 seconds going in and out of the defrost mode when the compressor delay jumper is installed.
NOTE
when jumpering the TEST pins. Time Delay
The timed-off delay is five minutes long. The delay helps to protect the compressor from short-cycling in case the power to the unit is interrupted or a pressure switch opens. The delay is bypassed by placing the timer select jumper across the TEST pins for 0.5 seconds.
Test Mode (P1)
A TEST option is provided for troubleshooting. The TEST mode may be started any time the unit is in the heating mode and the defrost thermostat is closed or jumpered. If the jumper is in the TEST position at power−up, the control will ignore the test pins. When the jumper is placed across the TEST pins for two seconds, the control will enter the defrost mode. If the jumper is removed before an additional 5−second period has elapsed (7 seconds total), the unit will remain in defrost mode until the defrost thermostat opens or 14 minutes have passed. If the jumper is not removed until after the additional 5−second period has elapsed, the defrost will terminate and the test option will not function again until the jumper is removed and re−applied.
Page 29
XP14 SERIES
