Bard CH5S1, CH4S1, CH3S1 installation instructions Defrost Cycle, Defrost Control Board

DEFROST CYCLE

The defrost cycle is controlled by temperature and time on the solid state heat pump control.

When the outdoor temperature is in the lower 40°F temperature range or colder, the outdoor coil temperature is 32°F or below. This coil temperature is sensed by the coil temperature sensor mounted near the bottom of the outdoor coil. Once coil temperature reaches 30°F or below, the coil temperature sensor sends a signal to the control logic of the heat pump control and the defrost timer will start accumulating run time.

After 30, 60 or 90 minutes of heat pump operation at 30°F or below, the heat pump control will place the system in the defrost mode.

During the defrost mode, the refrigerant cycle switches back to the cooling cycle, the outdoor motor stops, electric heaters are energized, and hot gas passing through the outdoor coil melts any accumulated frost. When the temperature rises to approximately 57°F, the coil temperature sensor will send a signal to the heat pump control which will return the system to heating operations automatically.

If some abnormal or temporary condition such as a high wind causes the heat pump to have a prolonged defrost cycle, the heat pump control will restore the system to heating operation automatically after 8 minutes.

The heat pump defrost control board has an option of 30, 60 or 90-minute setting. By default, this unit is shipped from the factory with the defrost time on the 60 minute pin. If circumstances require a change to another time, remove the wire from the 60-minute terminal and reconnect to the desired terminal. Refer to Figure 12.

There is a cycle speed up jumper on the control. This can be used for testing purposes to reduce the time between defrost cycle operation without waiting for time to elapse.

Use a small screwdriver or other metallic object, or another

¼inch QC, to short between the SPEEDUP terminals to accelerate the HPC timer and initiate defrost.

Be careful not to touch any other terminals with the instrument used to short the SPEEDUP terminals. It may take up to

10 seconds with the SPEEDUP terminals shorted for the speedup to be completed and the defrost cycle to start.

As soon as the defrost cycle kicks in remove the shorting instrument from the SPEEDUP terminals. Otherwise the timing will remain accelerated and run through the 1-minute minimum defrost length sequence in a matter of seconds and will automatically terminate the defrost sequence.

FIGURE 12 — DEFROST CONTROL BOARD

	SW	SW	TIME (SEC)
	1	2
	OFF	OFF	30
LOW PRESSURE BYPASS TIMER SWITCH	ON	OFF	60
	OFF	ON	120*
*(FACTORY SETTING 120 SECONDS)	ON	ON	180
	OFF
		ON

ACCUMULATED DEFROST TIME TIMER (FACTORY SETTING 60 MIN.)

MIS-2668 A

Manual 2100-455M

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