electrical issue


  #1  
Old 07-30-13, 07:24 AM
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electrical issue

Recently, my Rheem furnace that is 4 years old totally stopped working, and it clearly had no power to it. I don't have AC, but I do use the bower in the summer time to occasionally circulate air thorough the house.

I checked the breaker first, but it was not tripped. Then I checked the furnance fuse and it was open so I went and bought a new fuse. The old and new fuse were a fusestat type s 12A fuse. When I put the new fuse in and turned on the power nothing happened. I checked the new fuse and it was now open.

I checked the resistance for the power input to the furnance and i measured 20ohms.
I'm not sure if that is normal, but it isn't a short.

I went back to home depot and got two 15 amp fuses. I put those in and my furnace came right up.

Should I be concerned about this? It seems odd that the 12 amp fuses would be blowing when there is no obvious short.
 
  #2  
Old 07-30-13, 10:58 AM
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Was the 12-A fuse marked dual element (time delay)? It's odd that after four years, the 12-A fuses would start blowing. My guess is that there is something about the motor or capacitor that has increased the starting current draw.
 
  #3  
Old 07-30-13, 11:29 AM
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The first fuse was marked dual element, time delay. I'm also pretty sure the second one was, too.

I wondered if something is aging and increasing the starting draw current. I don't think its the motor because the 2nd 12A fuse blew when I turned the switch at the furnace on to provide power, and not at the thermostat to run it. There was no motor start up current at that time because I didn't turn the motor on.

Maybe there was some start up current going into that big cap for the motor. What should I look for if that cap starts failing worse?
 
  #4  
Old 07-30-13, 05:39 PM
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Hmm, interesting. That would indicate that the electrical loads other than the motor have increased, at least on startup. The motor cap would not draw current unless the motor itself were started. The digital controls for the furnace would also have a DC power supply, probably with a filter cap. Difficult to troubleshoot over the internet - and maybe equally difficult to troubleshoot on the scene.
 
 

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