Heatcraft Refrigeration Products PRO3 Refrigeration Sequence of Operation, Electrical Connection

PRO3 Side Mount Packaged Refrigeration System

Electrical Connection

1.Refer to all local codes for proper connection.

2.A knock-out is provided for 1" conduit on the side of the condensing unit section above the electrical box. See FIGURE 12.

3.Wire will be brought into the electrical box through the bottom of the electrical box and connected to the top of the contactor.

Refrigeration Sequence of Operation

1.Power is provided to the temperature control, compressor contactor and cooler evaporator fans.

2.The temperature controller closes and energizes the compressor contactor, starting the compressor, evaporator and condenser fan(s).

3.When the system reaches the desired box temperature, the temperature control will de-energize the compressor contactor. Evaporator fans will continue to operate at this point. 

4.When the fixture temperature rises above the set point

and minimum off-time has elapsed, the temperature control will close and re-energize the compressor contactor.

Coolers: Air-defrost Operation

Air defrost units are pre-programmed for 4 defrost per day. These periods are reprogrammable. When the coil temperature reaches 38°F, the control will terminate the defrost cycle.

For programming information see pages 7-16.

Cooler with Electric Defrost and Freezer Temperature/Defrost Control

PRO3 packaged refrigeration system cooler with electric defrost and freezer units come factory equipped with an electronic temperature/ defrost control.

For programming information see pages 7-16.

Table 1 Model PST Default Temperature Control Settings

Cooler with Electric Defrost and Freezer Sequence of Operation

Power is provided to the temperature control and compressor contactor. The drain line heater as well as the crankcase heaters will also have continuous power supplied to them.

The temperature controller energizes the compressor contactor, starting the compressor and condenser fan(s). The evaporator fans will be energized by the electronic controller.

When the system reaches the desired box temperature, the temperature control will de-energize the compressor contactor and the evaporator fans.

When the temperature rises above the set point and minimum off- time (4 minutes) has elapsed, the temperature control will close and re-energize the compressor contactor.

1.During normal operation, at the preset times of day, the temperature/defrost control will de-energize the compressor contactor and evaporator fans and energize the defrost heaters. These functions are controlled through relays on the controller.

2.When the coil has defrosted fully and has reached the  preset coil temperature (as sensed by the coil temperature sensor) the defrost heater de-energizes and the fan delay and drip sequences begin.

3.The temperature/defrost control energizes the compressor contactor, starting the compressor and condenser fan(s).

4.Freezer evaporator fans will be energized by the temperature/ defrost control when the coil temperature reaches 35°F or fan delay time has elapsed.

Application:

Temperature set

points

Defrost start times

Defrost	Drip Time	Fan Delay
Duration
	Minutes

Defrost

Termination

Set Point

Cooler: 35˚ F	Every 3 hours of	60	–	–	38˚ F
	compressor run time
Cooler w/ Electric		40	2	2	65˚ F
Defrost: 34˚ F
Freezer: -10˚ F	4 times / day	40	2	2	65˚ F

PRO3 Side Mount Packaged Refrigeration System Installation and Operations Manual, May 2008 7