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Old 12-04-2008, 05:09 PM   #1
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diminshing voltage


have 5 outlets on a circuit, the first one on the circuit is a GFCI in the garage. This one and the next read at about 124 volts. when i get to the third on the circuit it drops to about 108 volts and when i try to plug in an appliance it doesn't work. I put in a new receptacle to see if maybe that was the problem but there was no change. what should I do now. this was an earlier post. since then I have found that one of the outlets has a ground wire that i believe was touching the power wire it is oxidized and black could this be causing my problem.

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Old 12-04-2008, 05:21 PM   #2
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diminshing voltage


Did you retest everything after you fixed that ground wire?

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Old 12-04-2008, 05:22 PM   #3
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diminshing voltage


Yes, it probably was acting as a heavy load.

How was it touching?

Retest and please, post your results.
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Old 12-04-2008, 05:43 PM   #4
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diminshing voltage


You must have a very loose connection between the second (120+ volt) outlet and the third (108 volt). With no loads on the circuit, you won't get that much of a voltage drop in a properly connected circuit even over a distance of 200 feet

If your voltmeter is really sensitive, as are many digital models, the 108 volts could be phantom voltage induced where non-connected wires paralleled one another; for example the ground was continous all the way out to receptacle #3 but the neutral which was juxtaposed within the Romex cable was not connected properly to receptacle #2.

With the loose connection (or phantom voltage only), when you measure the voltage at receptacle #3 with a load out there, the voltage will be much lower.

Last edited by AllanJ; 12-04-2008 at 05:47 PM.
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Old 12-04-2008, 09:41 PM   #5
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I retested everything and am still showing 108 volts at all but the first two receptacles on the circuit I made sure everything was tight on all of the receptacles. On the receptacle where i Have the ground that looks green and black, when they wired it they had the ground in connected to the receptacle and the ground out looped around the ground in about 2 inches from the ground screw on the receptacle. the ground in looked like it may have been touching one of the hots where the sheathing was stripped back past the point where it was connected to the outlet
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Old 12-04-2008, 10:12 PM   #6
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With a small load such as a lamp plugged into receptacle #4 and with its switch in the on position, what is the voltage at receptacle #3?

Check receptacles #2 and #3, between the paired screws on each side is a thin metal bridge about an eighth of an inch wide. Do not bend this but check to see if it is cracked (or not there). When the incoming and continuing wires are attached directly to the receptacle, these bridges are needed to continue the power along to the next receptacle. Connections are more reliable when the incoming wire, the continuing wire, and an extra short piece are wire nutted together with just one of the paired screws on each side used to hold the other end of the short piece (pigtail).

Added: Just for kicks, measure all three at receptacle #3: voltage from hot to neutral, from neutral to ground, and from hot to ground with and without the lamp at receptacle #4 "switched on".

Last edited by AllanJ; 12-05-2008 at 04:00 PM.
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Old 12-05-2008, 11:51 AM   #7
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diminshing voltage


Quote:
Originally Posted by samiller1980 View Post
have 5 outlets on a circuit, the first one on the circuit is a GFCI in the garage. This one and the next read at about 124 volts. when i get to the third on the circuit it drops to about 108 volts and when i try to plug in an appliance it doesn't work.
124v-108v = 16v.

At a 1A load this is 16Ω and 16w. 16Ω seems high for a bad connection, but 16w makes a pretty hot wirenut. I guess a very corroded connection could give you 16Ω.

At a 10A load this is 1.6Ω and 160w. 160w in a wirenut would probably make itself known in a big hurry.
I suppose there could be a long, skinny, and very hot, wire in this circuit somewhere.

If you put a 10A load at the very end of cascaded outlets you should see a gradual decrease in voltage from outlet to outlet, let's say a ~1v drop from each outlet to the next, ending up with 120v or so at the last outlet.
If you see a sudden decrease in voltage from one outlet to the next then this is where the problem is.

With 124v you must be close to the pole transformer or you have a bad neutral connection in the panel. I have 122v and the pole thingy is right outside.

Last edited by Yoyizit; 12-05-2008 at 12:24 PM.
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Old 12-05-2008, 02:15 PM   #8
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With 124v you must be close to the pole transformer or you have a bad neutral connection in the panel. I have 122v and the pole thingy is right outside.
The primary side can vary too. The effect isn't as pronounced since it takes a pretty large voltage drop on the primary to show up as much on the secondary, but it does factor in.

My parents rural house runs so low that when you buy a UPS you have to change the setpoint or it cuts in randomly.
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Old 12-05-2008, 03:32 PM   #9
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The primary side can vary too. The effect isn't as pronounced since it takes a pretty large voltage drop on the primary to show up as much on the secondary, but it does factor in.
7200v/240v = a 30:1 turns ratio, so 240v +/- 12v on the secondary gives you 7200v +/- 360v on the primary, ideally.

Low household voltage probably damages motors. They may want to get a buck-boost xformer.
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Old 12-05-2008, 04:57 PM   #10
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Originally Posted by Yoyizit View Post
Low household voltage probably damages motors. They may want to get a buck-boost xformer.
They aren't so low as to cause damage, I think they are running around 117-118 close to the transformer. Still low enough to trip some UPSs unless you turn the sensitivity down.

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