The timing sequence to 1/60 of original time. Install jumper wire on speed-up terminals. Remove protective cover from TP1 and TP2 speed-up terminals. Zero indicates defrost thermostat is closed and operatingĩ. Using ohmmeter,Ĭheck resistance across defrost-thermostat leads. After a few minutes in heating, liquid-line temperature atĭefrost thermostat should drop below closing set point ofĭefrost thermostat of approximately 30☏. Restart unit in heating, allowing frost to accumulate onĨ. Disconnect outdoor fan motor lead from OF2. Jumper between DFT and R terminals on control board asĥ. Resistance reading may be zero (indicating closedĭefrost thermostat) or infinity (∞ for open thermostat) dependingĤ. Wires connected to DFT and R terminals on controlīoard. Thermostat leads are the black, insulated Disconnect defrost-thermostat leads from control board andĬonnect to ohmmeter. Remove control-box cover for access to electrical componentsģ. Troubleshoot the board, perform the following items.ġ. Restart in defrost if room thermostat is satisfied during defrost. The board has a feature that allows the heat pump to
This control board utilizes screw terminals for the low-voltageįield wiring.
This ensures operational problems are not attributed to the defrostcontrol To make sure unit operates properly in heating and cooling modes. NOTE: This procedure allows the service technician to checkĬontrol board and defrost thermostat for defects. That indicate whether or not board is defective. Troubleshooting defrost control involves a series of simple steps Theirįunctions are described in the sections to follow. Theĭefrost period is field-selectable, depending upon geographic areasĪnd defrost demands. The board is set at factory for 90 minutes. Jumper (labeled W1 on the circuit board) to the terminal for theĭefrost time desired. The defrost-control board can be field-set to check need for defrostĮvery 30, 50, or 90 minutes of operating time by connecting the
Timer and defrost relay found on older defrost systems. Solid-state defrost boards used on heat pumps replace electromechanical
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