The control fuses keep blowing tells me one or more of the control that operate the control on 24 volts is malfuctioning. Most controls operate at about 5 watts and on a clamp on amp meter normally pull about 0.2 amp (p = current x voltage, 5 watts = 0.2 amps x 25 volts) I install 75 watt 24 volt transformer with a resettable overload to save on fuses. I reset the transformer and quickly go to the controls and determine the amp draw. When I find the one >0.2 amps I found the problem. The things to check is the emergency heat sequencer, fan control sequencer, reversing valve for heat pumps, main contactor on the condensing unit and any other 24 volt control loads. I have had to replace the themostat wire because the increase current for the thermostat wire can cause the entire length of wire to form a long heater and cause insulation degradationa and cause the thermostat wire to short out and blow the fuses. Hope this helps
Answers & Comments
The control fuses keep blowing tells me one or more of the control that operate the control on 24 volts is malfuctioning. Most controls operate at about 5 watts and on a clamp on amp meter normally pull about 0.2 amp (p = current x voltage, 5 watts = 0.2 amps x 25 volts) I install 75 watt 24 volt transformer with a resettable overload to save on fuses. I reset the transformer and quickly go to the controls and determine the amp draw. When I find the one >0.2 amps I found the problem. The things to check is the emergency heat sequencer, fan control sequencer, reversing valve for heat pumps, main contactor on the condensing unit and any other 24 volt control loads. I have had to replace the themostat wire because the increase current for the thermostat wire can cause the entire length of wire to form a long heater and cause insulation degradationa and cause the thermostat wire to short out and blow the fuses.
Hope this helps