Furnace is blowing bus fuses

I never blew a bus fuse in the 7 years I've lived here. I blew one over the winter, and one blew today.
Anything I can check before calling for service?
I cleaned the filters about 2 months ago. Would clogged filters cause the blower to work hard enough to blow the fuse?
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On Tue, 26 Jun 2007 19:43:52 +0000, Mitch wrote:

It could but less likely than a failing motor. Is the motor direct drive (inside the blower) or belt driven? It's probably something that someone with an Amprobe (clamp on ammeter) would need to test how many amps the blower motor is drawing and if it increases past what its full load rating is as it runs.
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Funny you mention a clogged filter. I watched a tape in class about how amps = work (with a constant voltage and resistance). So in the example they had a vaccum. They showed it running and it's amp draw, and then clogged up the hose. The amps went down. Since the fan was moving less air, it was doing less work, therefore was drawing less amps. Where the problem comes from with clogged filters, is a dp accross the fan, and ofcourse a lower system effeincy.
So now to your point. Do you have anything on the same circuit? Is your fuses time delayed?
tom @ www.BlankHelp.com
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wrote:

A friend told me how they blew a breaker when they ran their toaster oven and microwave at the same time. Ok, no biggie, for them or me.
The problem was that they didn't notice that the breaker was tripped for a full day, when they opened the fridge and the ice was water.
So the fridge was on there too! When she told me the story, she still didn't see that as a problem.
I don't know if the breaker is 15 or 20, but apparenly it has only tripped this one time, even though wouldn't it trip of if the toaster oven wsa on when the fridge started up? This is the same family I'm alsways asking questions about, so this time, regardless of the answer, I'm leaving them on their own. :)
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wrote:

My toaster is on a different circuit, but the microwave and refrigerator are on the same circuit (the most convenient outlet was there). They've been that way for around 5 years with no problem.
--
Mark Lloyd
http://notstupid.laughingsquid.com
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On Tue, 26 Jun 2007 21:34:34 -0500, Mark Lloyd

Interesting. I haven't counted, but I thought the two, with the fridge on startup, would be enough to go over 15, or even 30.
Good to know. Thanks.
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Often when the bearings of a blower motor are quite worn, the fan will start and run while cold but as things warm up (and loosen up) the bearings increase friction and, sometimes, actually let the rotor touch the stator. This stalls the motor and then it's a question of whether the build in thermal protection switches off before the fuse blows.
If that's the case, the situation will only get worse until you can replace the end caps or the entire motor. If the motor is a non-standard speed/voltage/power then it might pay to get a mechanically identical motor and switch out end plates. Otherwise, replace the motor.
A quick check is to occasionally stop the motor and feel the shell to see if it's running HOT (nearly burns your hand) rather than just mildly warm.

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