Gategator37
Senior Member
A 120/240v single phase 3 wire panel is showing a 3-pole breaker feeding a 3-phase exhaust fan, this is not possible is it without a buck/boost transformer correct? Thanks
A 120/240v single phase 3 wire panel is showing a 3-pole breaker feeding a 3-phase exhaust fan, this is not possible is it without a buck/boost transformer correct? Thanks sorry, I meant phase converter, not buck/boost
Well, there is another possibility: The panel is being supplied by a high-leg Delta, and a Delta breaker was used.A 120/240v single phase 3 wire panel is showing a 3-pole breaker feeding a 3-phase exhaust fan, this is not possible is it without a buck/boost transformer correct? Thanks
Well, there is another possibility: The panel is being supplied by a high-leg Delta, and a Delta breaker was used.
No, I'm saying that one can get 3ph from an existing 1ph panel by adding one additional wire to the service and routing it to the line side of a specially-made 3p breaker.Are you saying one can get 3 phases from a panel with only two phases, one of which is a delta high leg just by using a special breaker ?
Becuase, either the service was an existing 1ph, and they modified it for this one piece of equipment, or because it was more economical to build it this way new.If the system had a high leg it must be 3 phase, so why didnt they run all 3 phases to the panel ?
Delta breakers were used when you had a majority of single phase loads along with perhaps 1 three phase load. They are called 'delta' because they usually went along with a high leg delta system, though I guess they would work with a wye supply. They are explicitly prohibited in current code.
Essentially you had a three phase feeder to the panel, but one of the feeder legs went directly to a pole on the 'delta' breaker, without hitting the panel main, and without using a bus on the panel. Useful, for example, if you had a single phase residential panel and wanted to add a single 3 phase hvac circuit.
If you used a three phase panel, then you would end up with one bus essentially unused.
-Jon