DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Electrical and Wiring > Voltage not adding up




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Old 10-12-2013, 07:43 PM  
Smontagu
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Default Voltage not adding up

15 year old house.
No other electrical issues known.
Plug and switch not used often.
Wanted to add an outlet and ran into this problem.
Disconnected plug so it can be ruled out.
Replaced switch to rule it out, same problem.
Switch on:
0v at switch
0v hot-ntrl
120v hot-grnd
120v ntrl-grnd

Switch off:
98v at switch
98v hot-ntrl
120 hot-grnd
12v ntrl-grnd

Other switches on the circuit measure:
120v hot-ntrl
120v hot-grnd
>1v ntrl-grnd
They are not effected by the switch.

Not sure what to do?



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Old 10-12-2013, 08:26 PM  
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The switch goes to a blower for the fireplace that is not working now. Not sure why that is.



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Old 10-12-2013, 11:50 PM  
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I meant other outlets on the circuit measure not other switches. Also the switch is normally off. Both the fan and the outlet used to work.

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Old 10-13-2013, 06:58 AM  
JoeD
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Are you really measuring hot to neutral or are you measuring black to white, both of which are connected to the switch. Those voltage readings are correct a switch loop with no neutral in the switch box.
If there really is a neutral (white not connected to switch) then you have an open neutral some where on the circuit.

Tell us everything about what you did to add the new receptacle.

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Old 10-13-2013, 01:41 PM  
Smontagu
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Okay so I don't think the switch is involved. The switch is to a fireplace fan. When I measured the "switch" there was only one measurent, from hot to hot across the switch. When I say hot I mean black. When I say neautral I mean white. When I say ground I mean exposed copper wire.

The first measurement is across the switch. The other 3 measurements are at the outlet. I was not clear sorry.

When installing the new outlet two things happened. First I had to drill a hole in the 2x4 behind the drywall, not easy. Second when I was cramming the outlet back in the box I did not tuck the ground wire away well enough as the breaker tripped when I turned it back on. I adjusted the outlet in the box and it was fine after that.

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Old 10-13-2013, 01:48 PM  
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Also the switch only has two attachments for the black wires. The white and ground wires ae just straight attached with a twist carrot tops. In my mind when the switch is off the reading should be open or 120v. If the switch is on it should be closed and read 0v. Not sure why there is 98 and 12 which only equal 110? Where did the other 10 volts go???

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Old 10-13-2013, 06:24 PM  
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I removed some drywall and confirmed I did not drill into any cables.

I disconnected the switch completely. There are three wires. The supply line, a cable to the outlet I am having trouble with, and a cable to the fireplace fan.

When the switch was wired the fan was on one side and the supply and outlet were on the other side.

Now the supply to the switch with everything disconnected is:
120v blk-grnd
20v wht-grnd
70v blk-wht

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Old 10-13-2013, 08:12 PM  
kok328
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Listen to JoeD, I think he is thinking the same thing as I.
You can't measure voltage through the switch unless you are measuring the in/out to neutral or ground. You most likely have a switch leg to the blower motor in which case both black & white are hots. You have to wire it based on voltage not color.

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Old 10-13-2013, 09:24 PM  
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OK so if understand you properly there are two black and two white wires in the switch box.
You measure zero volts from black to white wire and 120 volts ground to black wire.

You have an open neutral somewhere on the supply circuit. It could be in a working device.
Measuring across a switch is not useful.

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Old 10-14-2013, 12:30 AM  
Smontagu
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Okay forget everything I said before here is what I have...

A switch box with 3 cables going in to it. The switch is removed.

Cable 1- supply
Measurements are
120v blk-grnd
20v wht-grnd
70v blk-wht

Cable 2- goes to mulitiple outlets
Measurements are
All 0v

Cable 3- goes to fire place fan
Measurements are
All 0v

When the switch box was connected the three ground wires were rabbit eared together. The 3 white wires were rabbit eared together. On one side of the switch was the fan black wire, on the other side was the supply and cable to the outlets.

What are the possible causes for having low voltage readings (70volts) from the black to white wires, and having a 20 volts white to ground reading.



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