Heat Pump Controls

Each unit is factory provided with a Unit Protection Module (UPM) that controls compressor operation and monitors the safety controls that protect the unit. The UPM is a printed circuit board and is found in the heat pump module.

Safety controls include the following:

•High pressure switch located in the refrigerant discharge line and wired across the HPC terminals on the UPM.

•Low pressure switch located in the unit refrigerant suction line and wired across terminals LPC1 and LPC2 on the UPM.

The UPM includes the following features:

Anti-Short Cycle Timer

Five minute delay on break timer to prevent compressor short cycling.

Random Start

Each controller has a unique random start delay ranging from 270 to 300 seconds to reduce the chances

of multiple units simultaneously starting after initial power up or after a power interruption, creating a large electrical spike.

Low Pressure Bypass Timer

The low pressure switch is bypassed for 120 seconds after compressor start-up to prevent nuisance low pressure lockouts during cold start-up in the heating mode. If the low pressure switch remains opened after 120 seconds, the unit enters a soft lock.

Brownout/Surge/Power Interruption Protection The brownout protection in the UPM board will shut down the unit if the incoming power falls below 18 VAC. The unit will remain off until a minimal incoming power of 18 VAC is detected. Once proper power is restored, the unit will start-up within the random start time period.

Malfunction Output

The controller has a set of wet contacts for remote fault indication or dry contacts for communication with a DDC controller or BMS. The fault output will depend on the dip switch setting for “ALARM”. If set to “CONST”, a constant signal will be produced to indicate a fault has occurred and the unit requires inspection to determine the type of fault. If it is set to “PULSE”, a pulse signal is produced and a fault code is detected by a remote device indicating the fault. The remote device must have a malfunction detection capability when the UPM board is set to “PULSE”.

Test Dip Switch

A test dip switch is provided to reduce all time delay settings to five seconds during troubleshooting or verification of unit operation. Note that operation of the unit while in test mode can lead to accelerated wear and premature failure of the unit. The “TEST” switch must be set back to “NO” for normal operation.

Freeze Sensor

This is optional and can be set to ignore or monitor a freeze sensor. There are two configurable freeze points, 35°F and 15°F. The unit will enter a soft lockout until the temperature climbs above the set point and the anti- short cycle time delay has expired.

NOTE

If unit is employing a fresh water system (no anti- freeze protection), it is extremely important to have the “Freeze” switch set to 35°F in order to shutdown the unit at the appropriate leaving water temperature and protect your heat pump from freezing if a freeze sensor is included.

Crankcase Heater

A crankcase heater is installed around the base of each compressor in the unit to boil-off any liquid refrigerant that may be absorbed into the oil during idle periods. It is recommended the heater operate 24 hours prior to the compressors being started.

Model ERCH-HP Energy Recovery Unit 25

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