How To Troubleshoot a Time Temperature Defrost Failure on a Heat Pump

In this video we go out to an existing customer's home to look at a 3 ton Bryant split system heat pump to troubleshoot an obvious defrost failure during heat mode. This heat pump uses a time temperature controlled defrost so the video pertains to troubleshooting that particular type of control and not a Demand Defrost System that utilizes an outdoor ambient temperature sensor along with a coil temperature sensor. This video will hopefully help out the new guys or anyone interested in trying to troubleshoot whether the failure is related to the defrost board or the defrost thermostat. If I have to replace a defrost board I will always replace the defrost thermostat as well. This one ended up being a failed defrost thermostat and the defrost board tested out fine, so it was left in place. If the defrost board would have been bad, then the unit would not have shifted into defrost after shorting the speed up pin for 5-7 seconds and removing my screwdriver from it. The refrigerant charge seemed ok as well and was not the cause of this particular failure even though the system needed a new air filter and the filter grille cleaned badly. With the dirty filter we were getting a 28 degree temperature split between return and supply without the heat strips firing, which is a little high. With the filter removed and the grille laid down the temperature split dropped down to around 24 degrees. The blower speed is utilizing high speed so no more adjustment is available there pertaining to airflow. This unit is a little short on return airflow because there is a couple of supply drops going into the basement that are not being picked up by a return and being delivered back to the system which is never a good thing. When hooking up probes to a heat pump during heat mode that utilizes the "O" terminal (energize in cool reversing valve), I like to disconnect the "O" call at the outdoor heat pump and fire the thermostat in cooling mode and turn the temperature way down so that the unit will actually fire in heat mode without the heat strips turning on. I feel like I can get a better gauge on how the heat pump is performing without the heat strips interfering. This gives you a better picture of the temperature split of solely the heat pump and a better picture of the true indoor coil temperature. My name is Jake Porter and I am the sole owner & operator of Magnolia Services, LLC. I am a residential HVAC contractor based out of Johnson City, TN. My service area includes: Johnson City, Jonesborough, Unicoi, Erwin, Elizabethton, Hampton, Boones Creek, Gray, Limestone, Lamar, Telford, Watauga, Chuckey, Piney Flats, Bluff City, Blountville, and parts of Kingsport. If you are in my service area and in need of HVAC services, please do not hesitate to contact me at 423-483-7158. Please do not contact me for DIY technical support. Unfortunately, I would need to be able to put my own tools and hands on the equipment in order to assist you. Thanks for watching. Stay safe & best wishes. #hvac #heatingandcooling #heatpumprepair #heatpump #heatpumps #heatingrepair #defrost #defrostboard #defrostthermostat #timetemperaturedefrost #hvaccontractor #magnoliaservices #magnoliaservicestn #tennessee #jakeporterhvac