50A breakout - 30A & 20A for 2nd A/C in 30 amp RV

[rickfraza]

In 2019 I added a second air conditioner to my 30A Class C. The A/C was added on a completely separate 110V-20A circuit from the RV. The idea was to plug the RV into the 30A and the A/C into the 20A outlets at the RV park pedestals. Since this isn't always reliable, I looked for another method using the 50A outlet. The trouble was that a 50A to 2 x 30A dogbone over fused the A/C, and possibly the RV itself since each leg provides 30A and the breaker might not flip until 50A. Dogbones of all types provide no fuse/breaker protect. I asked for help from the forum and got several replies, but never built a 50A-30A-20A conversion box since there would have been multiple boxes and cables. Recently I found the exact all-in-one box that I needed. The Connecticut Electric CESMPSC41GRHR Power Outlet box sold at Home Depot provides a 30A-110V and 20A-110V breakers for the 30A and 20A GFCI outlets in the box. I called the company on the number listed on their website and tech support was very helpful. I ordered the box on Amazon. I bought some 4 wire cable (AWG 8-600V-black/red/white/green) from Home Depot. I wired it to a 50A-110V RV plug purchased at my RV store. I wired the black to the 30A-110V breaker pole, the red to the 20A-110V breaker pole, the white to the neutral bus lug, and the green to the ground bus lug. The box comes with a wiring diagram affixed to the inside cover. I wanted to go through the top rather than use the knockouts so I bought a hub for the top of the box to insert the cable and a cable clamp so the cable could not be pulled from the box. The entire process took about an hour after all the parts were gathered. It should be noted that this box does not protect against high or low voltage, only against over-fusing. You'll need a surgeguard with a voltage regulator for that. This was a simple project for someone who is accustomed to working with electricity. For those that aren't familiar, I'd advise finding an electrician to wire the box for you. Electricity can be deadly.

[Retired_JSO]

I placed a second a/c in 2 separate 30amp trailers over the years plunging the second unit into the 20 amp pedestal plug. Never had a problem. Eve had 3 50/amp units over the years with either duel or triple a/c units . On one of the 50 amp units, I tried a split 2, 30 amp plugs to a 50 amp since many Georgia state parks have a twin 30 amp pedestal, I’ve attached the 50 amp units to a pedestal with 2 30 amp outlets and it blew breakers up stream in a main junction box. When I attached 1 of the 30amp legs to the pedestal 20 amp outlet, it blew the 20 amp GFCI. The only way to work it out is to have the new unit on a separate input cord using the pedestal 20 amp and the 30 amp to the dedicated 30 supply.

[theoldwizard1]

Overkill. The 50A to two 30A doggone would fine assuming escort goes through a fuse/breaker before the load.

The following would be much cheaper. Start with a FUSED A/C disconnect box. Wire a 50A male plug to the inlet side. Wire a 30A female to one fuse and a 20A female to the other. Install cartridge fuses in the appropriate slots.

You can always buy short extension cords with pre-molded plugs and cut off the end not being used.

[larry_cad]

The 30A feed to the RV would be fine since there is already a 30A main breaker in the RV that feeds various, smaller breakers, including a 20A breaker to the original A/C unit. The new A/C unit would need it's own, separate 20A breaker in the line feeding the new A/C. That breaker would have to be mounted outside of the RV breaker box, in it's own enclosure. Addin

[wra]

That was a lot of money for being paranoid. Do you worry about plugging in a 3 amp TV set into a 20 amp home outlet? I hope not. You are essentially doing the same thing when plugging in a 13 amp air conditioner into a 50 amp plug. The current drawn is no more than the appliance needs. Your RV breaker is also in the line limiting the current to 20 amps. Don't over think AC power.