Voltage imbalance

[ExNuke]

Good day,

I have a question on voltage changes in the supply side of some wiring.

One leg that comes into the panel reads 115 VAC the the other 126VAC when no load is applied. The grounds are connected together and connected to an earth ground rod. The neutrals are connected via a bus which are connected to the primary panel via a neutral cable.

When a load (such as a pump or heater) is put onto either of the incoming power legs, the voltage changes to 69 VAC on one leg and 170 VAC on the other leg.

Anyone have a suggestion on where to check? I'm completely stumped.

Thank you.

 

[davidbeach]

Somewhere along the way, the neutral does not make it back to the service transformer. A very good way to destroy all sorts of electrically powered stuff.

 

[nbucska]

or to kill someone...

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[itsmoked]

A buddy electrician had a worker go out to a trailer park to fix something. He dropped the neutral... He had to buy dozens of refrigerators.

 

[Skogsgurra]

Was that "buddy" you? That's how you got your handle? ;-)

Gunnar Englund

http://www.gke.org

 

[itsmoked]

hehehe... NO!

 

[RudyL54]

Two possible things to look at. The neutral should be common to both the panel and the unit. Secondly, the KVA rating of the transformer before the panel.

If one leg is drawing more current than the rating of the transformer, it could bring the voltage down to meet the same KVA rating.

Check the neutral line and the KVA rating.

 

[wfowfo]

"One leg that comes into the panel reads 115 VAC the the other 126VAC when no load is applied."

Assuming you really mean NO load, you have a problem with your transformer.

 

[RudyL54]

Assuming without load, yes there is a problem on the transformer. Now, if you are not 100% sure, have somebody trace and check one leg. You might find something connected to it illegally or undocumented.

 

[ExNuke]

Thanks to all that replied.

Since the power comes in underground to the step-down transformer, goes to the house panel then to a breaker out to the garage underground via aluminum wiring where the problem is located, are you referring to the step-down transformer? The power in the house is fine - we've checked every circuit.

 

[ExNuke]

One more thing, our heat pump and hot tub are both 220 and they run fine. The voltages to these are around 115 when off or on.

 

[davidbeach]

The neutral is likely open somewhere between the transformer and the service.

 

[itsmoked]

Or very high resistance. Crummy split-bolt, etc.

 

[Knight2211]

1 thing I want to clarify, you say that your hot tub is 220, and the voltages to this is around 115 on or off, I assume you mean hot to ground, but both are 115 hot to ground? Where are you reading the 126 and 115 then? I am sure you know that you should have 126 and 115 at the hot tub if it really is 220.........

 

[bigbillnky]

Almost certainly you have a problem in the neutral connection(s). That is the reason your 240 volt loads operate normally.

Do not assume that a tight connection means a good connection, especially when dealing with aluminum conductors. I have personally tested AL compression connections that were open electrically, but physically appeared perfect.

This can be a very dangerous problem, and can effect the proper operation of circuit protective devices. DO NOT attempt to resolve this yourself. This is a problem for someone well experienced with power system issues to correct. Failure to properly correct the problem or problems within this system could have serious consequences for you and your family. Find a professional, and be prepared to bear the cost of replacing at least a portion of the AL wiring system.

Bigbillnky,C.E.F.....(Chief Electrical Flunky)

 

[itsmoked]

bigbillnky; Has a good point. Especially with the mention of hot tubs.

You really need to get to the bottom of this fast. Furthermore an imbalance could easily translate to a fire in any one of numerous devices normally found in a house.

 

[ExNuke]

Thanks again to all that replied. Looks like everyone agrees that it's in the neutral.

The aluminum wiring goes from the house panel to the GARAGE where the service is having the problem. All wiring in the house is copper as is the wiring in the garage. The garage is detached from the house - which at this point sounds like a good thing given the issue.

The voltages as far as the hot tub is in the house and are being read from hot to ground. Those are fine at 115.

The only place we read uneven voltages are the garage, starting at the panels where the aluminum wiring comes in, then down the line - lights, outlets, etc.

I believe that the next step is to move a hot leg to the neutral to replace the current neutral. The garage does NOT need 220 running to it.

I'd really like to replace the aluminum wiring from the house to the garage, but since I'm out of work, I'm gonna have to make due.

 

[itsmoked]

First U should just make some checks with a voltmeter from you house neutral to the aluminum neutral just off the house neutral. Another words probe from the house neutral to the actual aluminium neutral wire strands a 1/4" from where it is attached to the house neutral. Do this while a voltage imbalance is present in the garage. Do it with a DMM set to volts. Tell us what you measure. See if that connection is bad. But don't alter anything yet. You want the answer before you destroy the evidence.

If you don't see more than half a volt do the same on the garage end.


Let us know what you find.