Neutral problem

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kbrandt

Member
Location
arizona
Got a call today from a HO who is getting 30 volts on some outlets while reading 300 on other outlets which are supposed to be 120 volts.

Told her to call power company before I made a hour drive and they said it was good on their side 120/240,ran into this before and it was always a neutral problem on the power company side.

This is 4 year old house. I'am going to check for loose neutrals in panel and was wondering about other threads on this subject.I looked but couldn't find any. I may hook up my generator to the panel and see what it reads,but I only have a 120 volt generator.(yes I will disconnect utility side first)

Any suggestion before I drive an hour over to their house would be great.
 
480sparky

480sparky

Senior Member
Location
Iowegia
The biggest problem I have with HO's who use their own meters is they don't know to look for the 'V' on their auto-ranging meters. Anyone who sees 300volts on at 120/240volt system should look for 'mV'. Methinks the HO isn't telling you the whole story, just what they think they know.
 
e57

e57

Senior Member
Location
San Francisco, CA
I usually tell them to shut off the main CB - then I head out right away! Why bother with the POCO who is going to tell them its OK over the phone or show up too late - Not unlike the TelCo's "Inside wiring problem" crap.

You go - you charge, you find it, and 50-50 it's a panel change IMO.

IMO this is one of the most dangerous electrical situations - and not one to be handled over the phone. (Computers, refridgerators, coffee machines, ect. have a tendency to spontaneously combust with this type of problem - Do not use house loads to examine this problem!)

Heres a recent thread about this type of problem:
http://forums.mikeholt.com/showthread.php?t=87986&highlight=super+beast
 
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W

wireman71

Senior Member
I'd bring something along to jumper/lug the neutral on the service loop if it's overhead. Could be a bad connection there.
 
480sparky

480sparky

Senior Member
Location
Iowegia
Or else someone with a trencher snagged the neutie and it finally corroded away. If that's the case, time for a fault locator!
 
e57

e57

Senior Member
Location
San Francisco, CA
electricman2 said:
Why is the A/C tech checking outlets?
Click to expand...
They probably called him saying, "every time the AC comes on all the lights get weird." He probably went thinking he'd find a seized compressor. Sometimes the first clue of this type of situation is the reaction of other 120 loads to the addition of a 240 load. Ovens are another initial perceived culprit.
 
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K

kbrandt

Member
Location
arizona
Went to HO house today and here's what I found.

12-3 romex, one circuit feeding refer and the other feeding livingroom outlets.Shared neutral one breaker on A phase the other on B phase.

Neutral on circuit in panel burned to a black color, so I start to unscrew from neutral bar and it just fell out, was never screw down tight.

It was sending 205 volts to refer, HO had plugged into other outlet, lucky for him.

Grounds and neutrals loose in panel also.

Thanks for replys, thought I'd let you know how it went just incase you run into the same situation.
 
Z

zgozvrm

Member
Location
Northern California
Strange voltage readings

Strange voltage readings

I had a similar problem once when I used to work for a well drilling company. I was trouble-shooting a 480V irrigation pump. The first thing I would usually do is check the incoming voltages. I used an adjustable wrench to unbolt the cover to the panel, then I placed it on top. All my line-to-line voltages were good, as were my line-to-ground measurements (using the enclosure as a ground). Not finding any problem in the panel, I decided to close it up and check out the motor. As I reached on top of the panel for my wrench, I got a pretty good jolt. I grabbed my DMM and touched one probe to the panel enclosure and stuck the other one directly into the ground (which was dry, bare dirt). My meter showed 600 volts! I had the power company come out and take a look at the problem...they eventually found a bad ground at the transformer.

Other times, I have seen line-to-line voltages of 600 volts on a 480 volt system (with no load). If I recall, this was only on one pair of line wires (the others L-L readings were normal). This always seemed to coincide with the loss of a fuse at the transformers.

I'm still not sure how this can happen, but it sounds similar to this 300V problem.
 
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