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Old 09-12-2017, 01:18 AM
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mccutter mccutter is offline
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Default Power out, but 9v AC on one leg of 220v?

As you know, a hurricane passed through FL yesterday. It knocked power out at my shop but fortunately not at home, so I can still work there.

Anyhow, at the shop is an old under-monitor power strip. It is this flat thing made to go under a CRT and has a row of toggle switches for various functions such as "monitor" "computer" "printer", etc. It is easily 10-years old and does NOT have a battery in it. I have it under the desktop shop computer in the office. There is a LED indicating power on and I notice it is illuminated! WTH? So I check the outlet with a meter and there is 9v on the hot side. I go out to the shop and check the welding outlet and one leg is 0v and the other is 9v.

Also, when the 220v air compressor is turned on it makes a humming noise.

So what would be causing this?
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Old 09-12-2017, 03:33 AM
BukitCase BukitCase is offline
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There's a good chance some dimwit has a genny on and is backfeeding the power lines WITHOUT throwing his main disconnect at the panel - normally, if it were happing CLOSE to you you'd see a much higher voltage - but if it's further away, and more "customers" services are bleeding it down just by being connected, I guess it'd be possible to only measure 9 VAC -

That's the only way I can think of this could happen, other than maybe a faulty transfer switch on a system that was actually done RIGHT... Steve

Oh, and a 220 compressor will STRANGLE any genny smaller than maybe 10KW - I know, I forgot to switch my 22 RUNNING amp 5 horse 80 gal. off a couple years ago before connecting the 8 KW genny, and it grunted and popped its breaker almost immediately (the genny, that is - the compressor hummed pretty good for about a second :=)
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Old 09-13-2017, 11:57 PM
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Backfeed was what I was thinking, also... Power is still out but everyone around us has it. I even went out and cut the tree off the feeder wires to the building so there would be no excuse for them to turn us back on. Might also be the transformer we are all hooked to, who knows... All the breakers are off but there are lights on the building that should let us know when power is back.

Thanks for the reply, Bukit...
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  #4  
Old 09-14-2017, 03:23 AM
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Bob, I have found similar situations with the main breakers or individual breakers turned off in these old rent houses I used to work on.
I just called it "transient voltage" & stopped worrying about it.
I suspect that there are potential for voltage leaks in several places in the wiring, especially with some of the older houses, possibly even some low voltage leaks being carried by the neutral since that's the only incoming cable without a disconnect.

A couple of years ago I was sent to see about a situation in a duplex occupied by 3 fruitcake boys, all family members. Their complaint was a couple of dead outlets in the dining area but the real kicker was that the overhead fixture in the kitchen would only light up if the ceiling fan light in the living room was also on. That fan light was on 3-way switches at opposite ends of the living room.

When I got there I found some other oddities: when that kitchen light & ceiling fan light were on, the kitchen light was far brighter than it should have been and two of the living room outlets were carrying 240 volts instead of 120. So were the "dead" dining room outlets. In fact, one of the Brothers Karamazov or whatever their name was, plugged in a little plastic area fan and it ran at a runaway speed for about ten minutes before it smoked. Surprised me it lasted that long.

This was similar behavior to the interrupted neutral situations I had encountered a few times but not quite, and not at all in this case.
I was not able to figure it out. Harold sent in a sho-nuff electrician to straighten it out and he wound up punting too. After screwing with it for a couple of hours he ripped out the 3 way switch option which left the dining area outlets still dead but somehow stopped the over-voltage danger and removed the potential liability from it too, I suppose.
I never will know what that was all about.

There are some strange things happening in household wiring now & then. Sometimes it turns out to be head-slap simple & sometimes it never does submit to explanation unless just the right person with just the right experience happens along to diagnose it.
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Old 09-14-2017, 11:46 AM
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GWIZ GWIZ is offline
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Had a power failure maybe 12 years ago noticed the Incandescent lights were glowing about 30% when turned on.

Decided at that point to unplug the fridge. figure if the voltage got up to 75% just may fry the motors.

Obvious back feeding. guessing the more solar roofs we get it may become a real problem.

Damn, I guess the money maker will be an automatic low voltage disconnect for the fridge.
Gee, I wounder if the newer computerized fridge's have a low voltage shut down
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Old 09-14-2017, 12:14 PM
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MAC702 MAC702 is offline
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Quote:
Originally Posted by GWIZ View Post
...Damn, I guess the money maker will be an automatic low voltage disconnect for the fridge.
Gee, I wounder if the newer computerized fridge's have a low voltage shut down
I've a buddy with a place in Freeport in the FL panhandle. I was working there all last month.* One of my projects was a surge protector. He has one of those new fridges and, after a power spike, the fridge had to have the board replaced.

While my experience is limited with them, I did some research and installed an Eaton whole-house surge protector on his main panel.

This is different from the conditions described in this thread, but I can confirm that the fridges are now far more susceptible to power problems.

*I missed both hurricanes by not that much time. I drove through the Houston area, and spent a lot of time in Tampa and the Keys.
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Old 09-14-2017, 12:49 PM
BukitCase BukitCase is offline
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My nearly new "too smart for its own good" freezer, during the last power outage, taught me to check FREQUENCY on a genny - bought an 8kw genny from Costco about 10 years ago, didn't think to check the freq. output, runs fine and nothing complained, but...

During the last power outage I switched over, everything worked fine EXCEPT the newest freezer, which wouldn't come on at all. After the normal amount of "blue air" I "shot all the usual suspects", freezer had power available, still no go.

Power came back about 5-6 hours later, switched back to mains - "too smart" freezer came back on as if nothing had happened.

During that time, our OLD Sears freezer that we bought USED in 1977, RAN FINE. Not knowing how long the outage would be, we consolidated stuff into the old one for the duration, so nothing lost.

Checked the genny afterward, but NOT with a load (still haven't, 'nuther thing on the "should do" list - unloaded, it was at just under 250 volts across the 240 plug, and 64 hZ - not sure WHICH of those "Mr. Smarty" didn't like (maybe both) but I'm never gonna unplug that old Sears, just in case it has a pinhole leak on the low side... Steve
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