Fuse will blow whenever the heat pump kicks in. Using an infinity thermostat, a four wire system. The furnace works fine and i am temporarily running a manual thermostat across R and W for now.
Which components in the heat pump would you suspect in blowing the 3 amp fuse in the furnace. Could it be the control board itself in the heat pump or the compressor contactor coil. Should i measure the resistance of all the components in the heat pump running low voltage?
Thanks in advance
carrier 58mcb-120 furnace and carrier 25hna660 heat pump
Re: 3 amp fuse blows on a carrier 58mcb furnace board
Ok, If 3 amp fuse is blowing in the air handler unit when switch is turned to cool check to see if outside unit jump starts and stops when this happens. If this is the case wiring is fine check main relay in outdoor unit. There will be a spring contact on main relay (Black relay close to where wires come into unit), check for corrosion or carbon build-up on little round contacts. If you can clean contacts with a small piece of sand paper. Make sure all breakers are off before removing cover! You might have to remove relay in order to clean it. Make sure you write down exact locations of any wires you remove. This should fix the problem.
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Re: 3 amp fuse blows on a carrier 58mcb furnace board
Hi!!! Does your ac unit work fine?If not check your low voltage problem..You have a low voltage problem check the wire going out to your condensor make sure that they are not touching..Good luck..Check low voltage wires..short in progress..
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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
Depends on what type of heat you have...if it is electric, it could be your thermostat (some electric heaters use contactors & rely on the thermostat to switch the fan on). Heat pumps also use the thermostat to switch the fan on in heat & cool mode. Most electric furnaces use a sequencer to switch the low speed of the fan whenever there is a call for heat. Gas furnaces use either a fan/limit controller (if the unit is older) OR a circuit board based on time (after the thermostat calls for heat). SO depending on the type of system you have, it could be a bad sequencer, controller, relay, thermostat, or control board.
You either have something wired wrong or you have a direct short in the system. Are you starting the A/C or the furnace? If it's the A/C, it could be a shorted compressor, capacitor, fan motor or it's wired wrong.
The first thing i would do is shut off all the power to the unit and disconnect all the wiring from the thermostat. then i would install a jumper wire from R to W on the circuit board and see if the furnace runs good. if it runs good and does not blow a fuse, your problem is in the wiring between the t-stat and the furnace. If this does not help, please indicate if your system is a straight a/c, furnace system. or if it is installed with a heat pump. also does it make any difference what the temperature is outside. for example, does the fuse only blow when the temp drops down into the 30s or does it not make any difference.
Red wire to R on thermostat red on furnace and red on heat pump Same with white except w1 on thermostat. Blue to common on thermostat common of furnace (probably brown but will be marked) and blue to common on heat pump. yellow to Y on thermostat and straight to heat pump. Orange to O on thermostat and straight to heat pump. If wired correctly with no shorts fuse problem should be solved. commonly people leave enough wire exposed inside the t-stat for wires to short together. This will blow the fuse. Hope this helps. I understand the frustration.
I would suspect you have a problem in the defrost circuit of your heat pump. there are a couple of things you can try. first just run the system on emergency heat and see what happens. you could have a defrost board that is shorting when it kicks into defrost. it sends a signal back to the furnace so it will come on during defrost. if you do not blow a fuse as long as you are running in emergency heat, i would suspect the defrost control board. also you could have a dead short in the wire that runs from the "w" terminal on furnace control board, out to the heat pump. keep in mind that any of the wires could be the cause and i am just tying to give you the most common things. your furnace will still run if you unhook all the low voltage wiring out at the heat pump. if you do this and stop blowing fuses. you know it is something on that wiring. goodl luck.
Your old stat is wired for a traditional thermostat and not a communication stat like the new infinity you have. There is a module plug on the furnace board that will need to be connected to the new thermostat for it to work. The wires that are wired now are from a terminal strip inside the furnace. Please contact your local Carrier dealer. They may be able to get that harness for you