Voltage increase when HVAC blower runs.

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Old 12-30-10, 07:08 PM
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Voltage increase when HVAC blower runs.

I have an interesting issue with some electrical in the mobile home my mother resides in. It goes against what behavior I would expect, so hopefully someone here can shed some light on the problem.

Recently she let me know that her gas oven burner would not light anymore. I checked the glow igniter to find that it was glowing orange and not bright orange or white as I would expect. These models are known for losing igniters and for $35 it seemed light a cheap fix. I ordered and installed it to find that although the new one burned brighter, it did not easily get hot enough to light the burner right away.

She then mentioned something funny that had been going on with the electric. The oscillating fan in her room would increase speed when the HVAC blower was running. I tested this, and sure enough, when the blower was running the oven would light promptly and her fan would run faster. I would think the blower would drag the voltage down briefly, but not increase it. I didn't have my voltmeter with me to confirm voltage unfortunately. Any ideas on what could cause this? My first thought was some sort of ground issue, but I'm no AC electrical expert by any means.

Any help or advice appreciated. Thanks.

-Eric
 
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Old 12-30-10, 07:53 PM
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The original post deleted due to new information on the type of furnace.
 

Last edited by ray2047; 12-30-10 at 10:26 PM.
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Old 12-30-10, 08:22 PM
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What is the voltage of the HVAC blower motor? A gas furnace usually has a 120 volt blower motor and an electric furnace usually has a 240 volt blower motor. So, I guess I am asking is the furnace gas or electric? I am guessing it is an electric furnace and there is a loose neutral problem in the service somewhere.
 
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Old 12-30-10, 09:33 PM
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It's a gas furnace w/ 120V motor.
 
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Old 12-30-10, 10:25 PM
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Originally Posted by EricC View Post
It's a gas furnace w/ 120V motor.
Then my original idea is probably wrong. I was thinking electric furnace. Is there anything else on the furnace breaker besides the furnace?
 
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Old 12-31-10, 07:32 AM
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Originally Posted by ray2047 View Post
Then my original idea is probably wrong. I was thinking electric furnace. Is there anything else on the furnace breaker besides the furnace?
Ray, I think I know what you were thinking and I also think you are right. IF the furnce is wired to leg "A" and IF the kitchen circuit is wired to leg "B" and IF there is a loose neutral in the service, both circuits will have increased voltage when both circuits have equipment on and operating.
 
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Old 12-31-10, 09:27 AM
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Originally Posted by CasualJoe View Post
Ray, I think I know what you were thinking and I also think you are right. IF the furnace is wired to leg "A" and IF the kitchen circuit is wired to leg "B" and IF there is a loose neutral in the service, both circuits will have increased voltage when both circuits have equipment on and operating.
CasualJoe, yes I was and now I'm thinking multiwire circuit maybe? This is a mobile home after all. Though not necessarily a multi wire.

EricC, Is the furnace on half of a 2 pole breaker? If you feel ok doing it pull the panel cover and let us know if the breaker for the furnace has both a black wire and a red wire going to it or if it is a single pole breaker if there is a separate single pole breaker next to it with a red wire.
 

Last edited by ray2047; 12-31-10 at 09:46 AM.
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Old 12-31-10, 04:21 PM
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I'll be out there again this weekend and will take a look. Thanks for your help guys.

-Eric
 
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