MJRobinson
Member
- Location
- Chico, CA, USA
Identifying this Switchboard Panel 240-Delta?
- Thread starter MJRobinson
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kwired
Electron manager
- Location
- NE Nebraska
Can't see the far terminal of the right transformer but if it ties to the far left terminal on the left unit (guessing it does) then you should have a high leg delta system there. Can't tell the voltage without seeing nameplates or measuring.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
The panel itself is rated for use on 208Y120 3 phase 4 wire, or 240/120 3 phase 4 wire delta, 400A with a 100% Neutral. The panel "doesn't care". Some of the breakers USED inside of that panel might care because if it is 3Ph4W delta, any 1 or 2 pole breakers plugged onto B phase would need to be rated for "straight" 240V, not "slash rated", meaning not 120/240V. 3 pole breakers wouldn't matter, neither would it if you have 208Y120V.
MJRobinson
Member
- Location
- Chico, CA, USA
kwired
Electron manager
- Location
- NE Nebraska
Again it appears the supply is 120/240 three phase 4 wire - with a high leg.
The panel is rated for such, but 208/120 supply would still fall within the panel rating.
The panel is rated for such, but 208/120 supply would still fall within the panel rating.
MJRobinson
Member
- Location
- Chico, CA, USA
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Good point.
Took me a while to get it, but I see it now. That's a single pole breaker on B phase...
Single pole QP breakers are only rated 120V.
It's either 3-single poles or a 3 pole missing the handle tie, not real clear but also looks like 30A.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Yep, you might be right, it appears to say "Day Shed" above the first breaker, which might mean it's a feeder to an out building, so should have been 3 pole. But either way it's a violation.
just the cowboy
Inactive, Email Never Verified
- Location
- newburgh,ny
I have seen this mentioned before, when would you EVER use a 1 pole breaker on "B phase?? I was taught high leg is unusable for 1 pole feed.
- Occupation
- Licensed Electrician
I was taught never to use it and I don't but you can hook up to the high leg and make stuff like motors or lights work.
just the cowboy
Inactive, Email Never Verified
- Location
- newburgh,ny
I don't even see how it would run a motor, because if you look at it from a vector stand point it is really sharing 2 phases B phase and half of A or C. A light maybe but not a motor.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
It will run a single phase motor just fine, at 208V and with limited current because it has one and a half winding resistance and probably open delta (higher impedance feering the B wire.)
It will also run a three phase motor as well as a similar delta or open delta since the neutral is not used. But three single pole breakers will not fly for that.
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- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
You CAN use it, but it's DIFFICULT to use it, because as said, MOST of the 1 pole breakers are not going to be rated for more than 120V L-G. But if you use bolt-on breakers, you can do it if you pick the CORRECT breakers. Since I know Siemens, an example is that the QP plug-in breakers are only rated 120V, as are their bolt-in sisters, the BQ series. But if you use the BQD series bolt-ons, i.e. what you would use in a 480/277V panelboard, the single pole breakers are rated for 277V, so those can be used.
The only plug-in breaker arrangement that I know of where you can do this is an I-Line Square D panel. That will cost someone a LOT more money just to get a 208V 1 pole plug-in breaker. That makes it never worth it.
The only plug-in breaker arrangement that I know of where you can do this is an I-Line Square D panel. That will cost someone a LOT more money just to get a 208V 1 pole plug-in breaker. That makes it never worth it.
:thumbsup:
kwired
Electron manager
- Location
- NE Nebraska
There are two pole breakers rated straight 240 volts. They are not something commonly found in stock at your supply house and they are not cheap if you order them.
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