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joff · Joined: 11 Jul 2008 Posts: 2 Location: Costa Rica

Ok, so, first let me say I live in rural Costa Rica, and while I think my house was relatively well wired, the general electrical standards here leave a lot to be desired.

Also I should note that I know Tesla was cool and Edison was a dick… and that’s about the limit of my knowledge of electricity.

Anyway, I have this jury rigged pizza oven, two electric broiling elements wired into a gas oven… I know, I know, don’t bother, I won’t listen to reason. I have a timer (cannibalized from the washer) to make sure it only stays on for a few minutes at a time.

The oven, as dangerous as it may or may not be, is not really the problem. The other night I was using it to broil the top of a stromboli on a lower shelf and I kept turning the timer back on… anyway the wires heated up, melted the tape, and shorted out. I guess the breaker didn’t trip because I think it was still shorting when I pulled the plug.

From that moment on the power in the house went haywire, some circuits dropping, others surging, and surging to the point that I lost some light bulbs and hopefully nothing else.

I traced the fluctuations to the cycles of the refrigerators. One is now unplugged but the other is still going. When it’s in its humming cycle (I assume fan) it’s the same as being off, everything is normal, but when it’s in its other cycle (quiet, I assume compressing), the circuit it’s on drops, and the lights on a different circuit surge. (Also it keeps going through the cycle like once a minute.)

I can’t plug the other one in now because the fluctuations get dangerously intense- with one it’s just annoying.

I had an electrician over today… sort of. His name is Rasta and he’s a nice guy, but I don’t know… I mean he knows the rules for wiring, but I don’t know how many brain cells he has left for troubleshooting. Anyway he left here convinced the problem was with the refrigerators.

He said that the short had screwed up the voltage regulators and correctly pointed out that everything seems fine when the fridges are unplugged. But I didn’t understand how that could cause a surge on other circuits- I mean, isn’t that the point of putting things on different circuits (breakers), so that what happens on one will not affect the others? He said some stuff I don’t remember, but I started getting the distinct feeling that he didn’t really know what he was talking about… but obviously he knows a lot more about it than do I, so I don’t know.

Writing that made me come up with an experiment. I rewired the oven, which sucks about as much juice as anything. When I plugged it into the outlet circuit, the lights surge, and the fridge (on the same circuit) dies. When I plug it into the light circuit the outlets surge- I have a fan plugged in and you can hear its rpms increase. This is the same behavior as the fridges, so I believe that proves that the problem is not with them, they just provoke the same response because they use a lot of power.

I’ve checked the other circuits now. It seems they all are affected- when power is used it drains power from that one circuit and causes a surge on all the others.

So that’s all I’ve got. What do you think?

Thanks,
Joff

vince knight · Posted: Fri Jul 11, 2008 9:21 pm Post subject:

At the end of the day ALL the circuits combine on the main buss bar in your distribution panel so the effect will be seen in the whole dwelling.

Vince

joff · Joined: 11 Jul 2008 Posts: 2 Location: Costa Rica

If anybody's curious this problem was solved by this guy:

http://fineelectricco.com/asknew.html

Jeff, you have described the textbook example of a high resistance in
the neutral conductor. The poor connection could be anywhere from the
service cable's neutral connection in your panel all the way back to the
utility transformer.

You're maintaining the 240v between the two hot wires, but the 120v that
should be between each hot and the neutral is being shifted when you add
the large load. One side's voltage rises, and the other side drops the
same amount.

I suggest starting with the power company if possible. Tell them an
electrician told you what I told you, and they need to check the
line-to-neutral voltages at the meter when you place your large load on
the electrical system.

If they see the voltage shift, the problem is on their side of the
meter, and should be their responsibility to repair. If they do not,
then it's on your side, and your responsibility to call an electrician,
one who is good at troubleshooting.

Let me know if this is helpful, and what you find out.

Larry

I got an electrician, printed and translated the above into Spanish and handed it to him. He understood and fixed the problem in about a half an hour.

vince knight · Posted: Mon Jul 14, 2008 8:38 pm Post subject:

Top banana Very Happy

Glad you got it sorted

Vince