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260v at thermostate

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RandyPenn

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This doesn't have anything really to do with a garage but hope I can find some help. I am planning an upgrade to my homes main panel. I am in the process of mapping all the circuits in my current panel and stumbled upon something I'm not sure should cause concern. Two of the bedroom in my house have ceiling heat and while testing to find the circuits today they gave me a reading of 260v. Should I be concerned?

Randy
 
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RandyPenn

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Re: 260v at thermostat

The circuit feeds two bedrooms from a 20A double pull breaker. I tested the voltage at the two wires connected at the thermostat, my multi meter reads 260v. I haven't tested at the breaker, just at the thermostat.

Randy
 
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tgb

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Most utilities supply voltage from 228-245ish at the home level, try a different meter, maybe something wrong with transformer on a pole.
 
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RandyPenn

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The tester was set to the right voltage. I checked the voltage at the breaker and got 244v. Seems strange to get the high reading at the thermostat. NOT a fan of ceiling heat.... seems to only work half the time.
 
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pattenp

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If the voltage is 244 at the breaker then the voltage should be the same or a tad less at the device. Check the readings again.
 
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justsam

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It is pretty difficult for the voltage at the load to be greater than the voltage at the source, unless there is some type of step up transformer or the like. How are the heater strips controlled, is there simply an on/off or can they be variable. Not impossible to have an autotransformer in there but not likely.

Is there only one panel that could be feeding these? Is it possible you have a higher voltage at another panel? Again not likely.

What is the meter being used? Do you see the 260 volts when the heater is on, or off, or both. Should be some drop when on.

Be careful working around these line voltage thermostats! Can you measure from a ground, I assume neutral is not present, to each side of the 240 VAC. Are they both around 120VAC?
 
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Chilliwack Murray

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I've seen several experienced technicians make this mistake:

Are you SURE it is showing 260 VAC and not 260 mVAC? If it is indeed showing 260VAC and your source is 240, you likely have a meter that is affected by the shape of the sinewave. In short - some devices can distort the shape of the sinewave and cause some meters to read an inaccurately high AC voltage. Look for a "True RMS" meter.

What make and model meter are you using? Maybe you could attach a photo of the meter setting and display?
 
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RandyPenn

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The meter I'm using is a Harbor Freight special, so I don't have much confidence in it. The thermostat is an old top wheel type. When you take it out it has 2 black wires attached to it and what look like a red and a bunch of white wires in the box/space behind. Not sure about any more than that. My only option is wall heaters but I think thats better than this mess.

Thanks
Randy
 
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RandyPenn

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Re: 260v at thermostat

I'll get some pic tomorrow and post them up. It'll probably read just fine and i'll look like an idiot. I believe the wire was 12 gauge. but I wasn't really paying attention to that.

Randy
 
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Rookie2

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Ceiling heat is 240v , just spent days trying to repair one room. don't worry about the 260v its a combination of the junk meter and the 120 feet of wire coiled in the plaster that is always hot even without calling for heat. The thermostat only turns off one end of the heating loop.
 
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wyliesdiesels

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Rookie2 said:
Ceiling heat is 240v , just spent days trying to repair one room. don't worry about the 260v its a combination of the junk meter and the 120 feet of wire coiled in the plaster that is always hot even without calling for heat. The thermostat only turns off one end of the heating loop.
Click to expand...

That makes no sense!! :lol_hitti Extra wire will cause the voltage to drop NOT increase!. I think the OP has a junk meter!!
 
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APEowner

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It might help (or, it might not and it certainly won't hurt) if the OP updates his signature with a location so we all know what system(s) he's likely to be working with.
 
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RandyPenn

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I borrowed a klein meter from my neighbor and retested everything. The voltage at the thermostat was 246v. I guess when it come to a free multi meter, you get what you pay for....

Thanks
Randy
 
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wyliesdiesels

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APEowner said:
It might help (or, it might not and it certainly won't hurt) if the OP updates his signature with a location so we all know what system(s) he's likely to be working with.
Click to expand...

This is of no relevance in this case because the OP has already told us the voltage reading at the breaker!!
 
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