1/2 power - weird ?

Old 08-03-02, 08:16 AM
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Exclamation 1/2 power - weird ?

With only one leg of my 220 circuit active, I have this scenario:

No 220 appliance works (duh)

I have two AC units.
If I turn one blower off - the lights dim(in half the house). If I turn both off, the light go out (in half the house).

It seems that there must be a back feed or something through the AC units when the blowers are running (the cooling does not work at all - no 220) that powers the other circuts ?

Is this cause for alarm ?

Is it safe to run the blowers so that I have (110) power through the house, or better to live with 1/2 power (until the power company fixes the cable)?


I woke up this morning with no power in the bedroom. Then found out the about half of the house was down. Measured the voltage at my breaker box. 1 leg of 110 was hot, the other was dead. Called power company. A little while later, (as it got warmer), the AC (blower) came on and the lights all came back. Great, I thought - the power company had got me back up. In a few minutes the power company called to see if we had a problem, and we thanked them for a quick job. They were puzzled and said they had not dispatched anyone yet - but that someone would be out shortly to check it out.
They arrived and said they had a bad leg ground and would have to dig up the cable and repair. 5 min later, they came back to say that they had a major outage across town that they had to go to, but they would be back. They suggested turning off AC until they fixed the problem.
Old 08-03-02, 09:13 AM
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You are getting 120 volt power from phase one through your 220 volt rated equipment serving power to phase two of your panel.

IF you have fuses as your main overcurrent device then you most likely have a blown main fuse.

If you have a breaker as your main overcurrent device look for a loose connection somewhere between the buss bar of your main service rated panel to the transformer of your serving utility company. The loose connection is often at the main lugs in your panel, or inside you meter base, or at the squeeze ons where you weatherhead conductors are connected to the Utility company, or the squeeze ons on the pole at the utility company transformer.

Often times this loose connection has been heating a while. Look for bubbled insulation of the conductors at the point of connection or for melted electrical tape at the weaherhead or transformer.

Let us know what you find.

Old 08-03-02, 09:55 AM
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The power company says it a problem on their side - a bad splice in the underground cable.

They have connected a device that re-routes around the bad splice, and all my power is working correctly now - 110 and 220. They will return on Monday to dig and repair. (This must be a common problem- they had a unit on wheels to hook up through the meter)

Of course, today is the day I have out of town guests and a sweet 16 birthday party for my daughter...rolleyes: Looks like things will work out OK if I don't run into more power issues.

I don't loose lights if the AC units are on or off now.

The AC units are fused, but the main has a 200 amp breaker. I did set the thermostat lower than normal last night to accomidate more people in the house, so the load was heavier - maybe the straw that broke the splices back...

From your comments, it sound like feeding phase 1 into phase 2 through a 220 device would be expected in this type of situation ? (ie., it is "as designed", and there is not a improper wiring problem.):
Old 08-03-02, 11:50 AM
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You had what was suspected. A 220 volt unit such as a water heater etc. makes a contact between line one and line two. This is how 220 works. When one hot line looses power the power from the other hot phase will travel through your element or motor windings etc. allowing a reduced voltage to energize the dead phase through the 220 volt element etc.

This is not a good condition but happens any time a 220 volt appliance is on while one of the phases have lost power.

That is why I suggested you look for one blown fuse of two main fuses or a loose connection on the lines between the main breaker and hte Utility transformer. That is what was found in your case [broken wire between your main breaker and you transformer. You lost one phase but had lights on that dead phase when your 220 volt appliance was turned on allowing voltage to pass through the 220 volt appliance from line one enegizing line two with a reduced voltage. Usually this produces dim lights on the dead 1/2 of your home.

You did no wrong, just a diagnostic use of knowledge suggesting what you problem was as you discribed.

The above has a term called "back feed", also causes misdiagnosis in a trouble shooting problem on a certain 220 volt appliance testing and finding voltage that has been back fed from the second hot line making you think you have proper connections when in reality the tester mislead you because of this back feed charicteristics.

Hope this helps


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