50 amp to a 30 and 20 out how to do? HELP!
I'm adding a second ac to my WW trailer, it has a 30 amp service, I am wiring the 2nd ac with seperate wiring and load center and breaker out of the load center will be a plug for the ac. I was looki...
Forum Discussion
wnjj wrote:
Incorrect. They are 180 degrees out. Only one phase of the 3 available phases on the power lines are used for a residence. The single 240V phase is center tapped for the neutral to provide two 120V circuits that are 180 degrees out from each other. 120 degrees wouldn't cancel the neutral current anyway.
Concur... However there a few CGs out there that have a 120/208 volt system derived from a 3-phase system and have the hot legs 120 degrees apart. Typically it would be 120/208 volts connected in "wye" configuration like in the 1st diagram. While there are other configurations, a wye secondary is normally what you'll find since the center is connected to ground and is similar to a 120/240 volt system except the hot legs being 120 degrees apart. Homeowners and RV-ers are normally connected to a transformer with single phase primary and secondary like in 2nd diagram and the hot legs are indeed 180 degrees apart but it's not referred to as "phases" in the industry.
Some info. is here and here.
A 120/208 volt (single phase) system for RVs in CGs is normally not a problem because all loads are typically 120 volts. If you had a dryer or other appliance with resistive heating elements in it, you only get (208/240)x(208/240) = 75 percent of the normal output. Voltage drop in the system would make that even worse. The same standard RV 50 amp plug & recept. works on both a 120/240 or 120/208 volt system in a CG.
