Unbalanced lines

Status
Not open for further replies.
M

macrai

Member
Can an unbalanced load in a dwelling unit cause a fire?

In the complex I just moved into, I have noticed that half of the complex does not receives the full 120v, I haven't put a meter on it yet, but I don't need to because all the lights are dim and the radio shuts down after playing for 15 seconds, and my stove does not work most of the time. the wiring in the house is all screwed up, a 2p40A controls some lights and receptacle and the stove. When you respond to my question keep in mind that I am renting and it is a multifamily dwelling.
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Sounds like a neutral issue. That problem might not very easy to find especially if it's somewhere outside of your dwelling unit. The bad news is that an open neutral can cause under voltage on some circuits and over voltage on others depending on the resistances of the loads. That may eventually fry sensitive electronic equipment. I would start checking by taking voltage measurements everywhere and compare them to each other.
 
G

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
100206-2235 EST

macrai:

Since you are an electrician I think you should try to determine the cause, but not fix it, that is the responsibility of the landlord or power company.

The suggestion above that it may be a neutral problem is a good first guess. I have provided numerous comments on how to troubleshoot for this kind of problem in various threads at this forum. Do some searching for these.

Get a good voltmeter and measure the voltages at the main panel. These would be neutral to ground, neutral to each hot line, and the voltage between the hot lines.

I will suggest as a first criteria that the neutral to ground voltage should be less than 1 V. If it is 10 to 20 V you probably have big trouble with the neutral between the power company transformer and the main panel. Also if 10 to 20 V or more exists, then the voltages between the hot lines and neutral should be quite different. It also means as stated above that you may damage equipment that is on the higher voltage phase.

If line A to neutral voltage is nominal and moderately stable, but line B to neutral is low and varies with load by a large amount, than there is high impedance in the B hot supply from the power company.

Lights dimming a great deal implies a substantial drop in supply voltage to the light.

If voltages look good at the main panel, then there are problems within the house and similar voltage measurements at various points will tell you whether it is hot or neutral wiring problems.

.
 
M

macrai

Member
Unbalanced lines

thank you everyone for your quick responses. Although, I am also a firm believer of not repairing anything on a rental unit, unless I caused it. I will try to figure it out and use it as leverage.
 
M

macrai

Member
Unbalanced lines

Gar I did as you suggested this morning and here are my finding.
At the panel inside the house with everything turned off I read 108v on B,
120v on A. With everything on B read 40v and A steady. Outside at the
main breaker the reading were reversed-A@40V & B@120V. Regardless of reversed condition it seems to be a power company problem. Correct me if I am wrong and thank you very much.
 
G

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
100207-0923 EST

macrai:

I would assume you mis-traced the leads from inside to outside or they are mislabeled.

If you measured directly on the wires to the meter from the power company, not the lugs, then the problem is between the meter and the transformer.

Loaded and unload you should see little difference in voltage between the neutral wire from the transformer and earth. Earth means a screwdriver stuck in the ground (earth).

.
 
Status
Not open for further replies.
Top