50 amp to a 30 and 20 out how to do? HELP!

myredracer wrote:

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.

I stand corrected. You are absolutely correct. No wonder people have trouble with electrical terminology. Home wiring is single phase, yet can have two "phases" created by a transformer that are 180 degrees apart, but it is still considered single phase. 50 amp service delivers 100 amps of potential 120V power in it's two separate legs, but we still call it 50 amp service. And I am sure there are numerous other terms that defy logic. Go means stop and stop means go. Thanks for the clarification.