Alright, I have a 200 amp main panel in a 36′ x 60′ garage i’m working on. That panel was installed by a separate electrican other than myself. I was told it had a “wild leg” in it and that I shouldn’t place any breakers on the C or third pole, unless it was a double pole breaker and I bridged it between a B and C or a C and A pole.
I placed a 100 amp double pole breaker on a b and c pole to feed a sub panel ( as directed by the licensed electrican )on the other end of the garage. I first tried it out today and had some trouble. One side of the panel is putting out 217 v and the other side is 113 v. (found out the hard way and burnt the board out of a new reznor shop heater!!!)
What is the problem? Should I not have bridged the double pole breaker where there is a “wild leg”? What is a wild leg anyways? I’m very confident in single phase wiring (residential wiring) but am not confident with 3 phase. HELP!!!
upnorthframer
“If you think education is expensive, try ignorance!!!”
Replies
With 3 phase power, two of the legs have 120V to ground and the "wild" one has 240V to ground.
That's about the extent of what I nkow about 3 phase power...
What I think that you have is 240 V delta with one of the transformers centertapped to give you 120 on 2 legs to neutral.
Also know as 4 wired delta.
http://www.achrnews.com/CDA/Archives/639e6dffd0c5a010VgnVCM100000f932a8c0____
http://polk-burnett.apogee.net/pd/dsaud.asp
You can only run a 240 load off the high leg (and another leg) if it is PURELY 240 volt load.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
In responding to one question you answered another, with your links.
Thanks, ted
"In responding to one question you answered another, with your links."Uh?.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"In responding to one question you answered another, with your links."
Sorry bout that. Bit cryptic.
You were providing info on the 208/240 3ph, 4w, panel and its workings to the original poster and dropped in a couple of links.
I read them and I appreciate the information. Most of my commercial projects are 3ph, 4w and there are times when I have to 'direct' some installations. Now I have a much more concise understanding of the voltages and such.
Thus "answered another".
Am I making any sense today?
ciao, ted
Thanks for the thanks.I though that you where critising me for not directly answering his question.On something like this I think it is better to give then background infomation (teach them to fish) rather than giving them fish.And if they can't understand it then that means that is something that they should not be doing..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Agreed.
t
AWESOME Links Bill!!!
I now understand 3 phase 240 !!!
I am a residential guy who has done a lot of everything residential over the years and never afraid of electricity.
Now I understand a little bit about commercial. (I am not going to go bidding anything but at least I understand something I did not this morning)
Thanks
OK, I see it's time to start spreading some bad news ....
First of all, your service is likely a (nominal) 240v Delta service. That means the following:
- Voltage between any two legs is 240;
-Voltage to ground of one of the phase4s is 208v; and,
-Voltage to ground for the remaining two legs is 120v.
In other words, if you are serving an appliance, like a heater, that requires 240v, it matters not which legs you have the breaker on - it's still getting 240.
If you are in need of a 120v circuit, well, you're in the wrong panel altogether. You need to 'start' your project by setting a single-phase sub-panel, and taking all your 120 circuits from that panel only. Naturally, you will have to feed this panel using only the 120v. legs.
Why? Because, if you read the fine print in the label on the panel, you will find that it is listed ONLY as a 'power' panel for a delta service. This means 'no 120v circuits- you need an 'appliance' panel for that.'
Why does the listing limit it to use as a 'power' panel? In an attempt to prevent your inadvertently creating a 208v circuit. Our friends at UL figure that, while an electrician will take care to feed a panel from the correct legs, the consumer is more likely to make an error when he adds a circuit.