An amazing (to me) thing happened at our house yesterday. About mid morning, we started to notice several of our lights were out. Also, the stove had no power, but the fridge did. 3 of my GFCI circuits could not 'test' or reset at all indicative of no power.

Several circuits were fine others were out. It was really weird. We called the Edison and they said it sounded as if a phase was out.

I thought residential was single phase? Sure enough, they came out and hooked up a temporary voltage box of some sort and we were then able to get the heat back on. Today they are coming over to dig up my power line.

They asked if I had been digging recently in the yard. They noticed that I had installed a fence and asked me when it was installed. (Its been 18 mos).

Are there 3 phases to the house to give us the 240V for the stove, AC and other and then single phase from the panel to the services?

What might have caused this phase to drop out if not my digging? I did have utilities protection come out 18 mos ago when I dug post holes for my fence. Could the damage have been done that long ago and just now showed up? Could anything else cause this short of someone damaging the underground line or a faulty wire? A tree root for example?

Any help would be appreciated. I feel like the Edison is setting me up for liability and I would like to be armed with some information. My understanding is they are responsible for the connection to the house no matter what unless they can prove I hit the line while digging, or didn't call utilities protection service.

thanks

wildandblue

can't tell from your info if you live in a cold climate, but freezing and thawing of the ground can damage your wire or a lightning strike even far off that causes a power surge. Also if a lot of things are in use when a brownout occurs you may not be able to start every circuit at once...things like the freezer with a motor in it use twice as much power to start as they do to run. Is the fence or the posts metal mesh that could have caused a ground fault?

KeepItSimpleStupid

Residential is generally single phase. Very few parts of the country have 3 phase.

The delivery is a high voltage single phase supply in the killovolt range.

The secondary of this distribution is 240 Votls, but it's center tapped. The center tap is connected to ground/neutral. This means that the house gets two 120 volt lines 180 degress out of phase. You connect to the two 120's and get 240V, You connect between one of the 120 and ground, you get 120V.

Yes, I know it's confusing.

jforce

Thanks for the replies. I live in a cold climate. Lots of thawing and freezing of late. Fence is wood. No we definitely lost a phase according to the Edison. KISS, your answer is not confusing. I do get it. And it makes sense that the stove (240V) would not work, and the furnace would not kick in, while the fridge did (120V). I just am trying to understand this a bit better in case they try to tell me I did it. Thanks again.

KeepItSimpleStupid

Your mistake was not having the power line marked.

Only you know if heavy equipment was used in the installation and the equipment was repeatively run over the power line. In all likeliness the power line break is no where near the break.

The confusing part is there are "two phases" in residential, 180 deg apart, but it's referred to as "single phase" because there is only one high voltage wire supplying power.

Now, just to make things a bit more complicated. You have 240 V systems that use L1,L2 and ground. Some that use L1,L2, Ground and Neutral and some yet that get grandfathered and connect the Ground and Neutral together at the appliance. The latter are some ranges and dryers. The latter use a little 120 V to drive the controls and motors.

I'm glad you understand it.

jforce

I did have the power line marked for the fence install. Thought I mentioned that in the orig post....are you referring to my fence install?

KeepItSimpleStupid

I didn't know about the fence install. Your probably OK and you don't have to worry. It's just normal "wear and tear" for the climate.