Furnace blowing fuse
- Thread starter Ashcroft
- Start date
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John From Detroit
Well-known member
Likely too small a fuse. but the blower is a major power sucker. My Atwood feeds it via a circuit breaker... The "Stalled" current draw on a motor can be very high.
I have another motor on my RV turned a 25 amp fuse into a flash bulb. but only draws 10 amps running by measurement.
Make sure of two things. ONE the blower turns freely.. (you can access one of the two blower wheels from outside easily) and 2 that you are using the SPECIFIED fuse. even if 20 amp is the right size it may be you need a slow blow.
I have another motor on my RV turned a 25 amp fuse into a flash bulb. but only draws 10 amps running by measurement.
Make sure of two things. ONE the blower turns freely.. (you can access one of the two blower wheels from outside easily) and 2 that you are using the SPECIFIED fuse. even if 20 amp is the right size it may be you need a slow blow.
If the circuit is meant to be run on a 20 amp fuse, do not put a put a higher rated fuse in it's place! There's a reason it has a 20 amp fuse and not something larger. John is pointing you in the right direction though on the motor. The motor may be starting to go bad, or just needs a drop or two of oil in the bearings. Unfortunately, some motors don't have bearings that can be lubed. There may also be a direct short or a possible grounded spot in the wiring. As John said, check to make sure nothing is impeading the rotation of the blower. May be a varmit dead and dried up or who knows what else. If nothing there, then try unhooking the wiring to the motor and see if it still blows the fuse. If it does, there's a wiring issue. If it doesn't blow the fuse, the motor is then the guilty party.
Gary RV_Wizard
Site Team
A 20A fuse ought to be sufficient for a motor that draws 5-10 amps when running. A fan should not have a high initial amp draw because it is supposed to be free-spinning (light load). Atwood specifies 18 gauge wire for the power supply, so it had better not be high amps!
I'd first check the squirrel cage fan to verify it turns freely and loo for any obvious dangling or damaged wires.
I'd first check the squirrel cage fan to verify it turns freely and loo for any obvious dangling or damaged wires.
Gary RV_Wizard
Site Team
There is only one motor but it turns two fans, one on either end of a single shaft. One fan pushes combustion air/exhaust through the burner and the other circulates heated air through the RV.
An extra-slow blow type of fuse might help, but it is not required by the furnace design and would be sort of a band-aid fix. If the slow-blow solves the problem, it tells you the excess power draw is of short duration and not very large, but it is still something that ought not to be happening. Besides, standard automotive blade-type mini-fuses are not particularly fast acting to begn with. If a fuse blws quickly, it's probably more than slightly overloaded.
An extra-slow blow type of fuse might help, but it is not required by the furnace design and would be sort of a band-aid fix. If the slow-blow solves the problem, it tells you the excess power draw is of short duration and not very large, but it is still something that ought not to be happening. Besides, standard automotive blade-type mini-fuses are not particularly fast acting to begn with. If a fuse blws quickly, it's probably more than slightly overloaded.
