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

[htwheelz67]

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 looking at this....splitter cable

plus a 50 amp ext cable vs 2 cables, I figure I can make my own but at the end of a 50 amp cable. I am unclear how to do it. I want one 30 amp outlet and one 15/20 amp outlet, I'm using 2 dometic hi eff a/c's so they will each run off 15 amp breakers. I'm not too proficient in 240 volt 4 wire wiring.

[2oldman]

That adapter looks fine.

[myredracer]

First, be aware that even though the AC units may be high efficiency and draw only 1000 watts when running, that is at 120 volts. AC units draw more current as the voltage goes down and is opposite to resistive devices (heaters, coffee makers, etc.). When AC units start up, they have a momentary inrush current and for a high eff. AC is about 50 amps. If you read the manual for them, you will find that the min. wire is #12 ga. and breaker size is 20 amps. Running two AC units on the same supply would require a 40 amp breaker and if both started simultaneously, the inrush current would be 100 amps. Some find they can do it on 30 amps but they are risking damage to the AC units. If the voltage is much less than 120, a 30 amp breaker will trip. Don't forget there would also be additional load from converter, fridge, etc.

I would wire the new one on a separate 20 amp cord/circuit and plug it separately into the 20 amp receptacle on the pedestal using a 20 amp power inlet like Park Power. All pedestals always have a 20 amp (GFCI) receptacle by code (unless it's a really old CG) whether or not it has 30 or 50 amps or both. This would allow you to always plug into the 30 & 20 amp recepts. on a pedestal or to plug into a 50 amp one using that adapter with a 30 & 20 amp connector on it.

Note that CGs have a max. of 20 percent 50 amp recepts. by code. (NEC). As of the 2005 code edition, only 5 percent of CGs were required to have 50 amp recepts. in pedestals. Finding a 50 amp recept. can be extremely difficult unless you go to a high end RV park, some casinos or some gov't CGs.

If you do decide to always plug into the 20 amp recept., note that the pedestals and CG wiring are never designed to have both the 30 amp and 20 amp recepts on a pedestal running at the same time. Drawing close to 50 amps at 120 volts on a 30 amp only pedestal can cause excessive voltage drop which will eventually damage AC units. Never run the AC units below 105 volts. From a voltage drop perspective, plugging into a 50 amp recept. with an adapter would be better.

Having a permanently mount voltmeter inside is highly recommended to monitor the CG voltage. Even better, get an EMS unit that will automatically shut power off. Progressive Industries has the best one. There isn't one available for 20 amps tho.

Using an adapter introduces one more potential failure point in the shore power connection due to overheating from a bad connection. Never plug in live - shut off pedestal breaker(s) first. Failing to do this will lead to pitted and dirty plug blades and inside a recept. cause overheating and resistance. Always make sure your plug blades are kept clean.

[wa8yxm]

For use on a 50 amp site that is a good choice less you want to fully upgrade the RV.. I like your plan by the way.

The other option is to upgrade to 50 amps, new power center (if you do not have generator with a transfer switch all you need is a new center and a new cord)

But bring that 2nd A/c out to a "Break out" spot (Plug and outlet) so you can "Split" it off when on a 30 amp site

But if you are currently comfortable with 30 amp service, that is Overkill.

One suggestion: Carry a 12ga extension cord, Sears or K-mark cords with the push button on the outlet are my favorite, but any good 12ga cord will do, say 25 Feet is likely long enough (my Sears cord is 100' but I only use it .. rearley, I have a 10 and 20 foot for routine use) On a 30 amp site you use that cord to the park's 20 amp outlet

On a 50 amp site use your splitter

I think you will be very happy.

One final caution:
People will talk about the "Danger" of plugging a 30 amp cord into a 50 amp breakier,... yes there is danger. very slight.. The 30 amp breaker inside the RV (and the 20 amp on the 2nd A/C) will provide protection against nearly all problems. A short in the shore cord will trip the 50 before anything bad happens, and a short "Downline" the breakers inside the RV

Iun fact, if you accidently try to draw 35 amps the big difference is you won't have to go out in the driving rain to reset the park breaker.. you will like that.

[westend]

At the end of the day what you have with 50 amp RV service or conventional 240V service is two legs of 120V each, a neutral, and a ground. How you break that out to different connections is determined by what fits your needs.

You don't mention about any power inlets you have but the assumed 30 amp RV power inlet of either an attached cord or an exterior plate mount inlet. If you establish either a cord or plate inlet for the new 120V A/C service, you will want to split the 240V service and connect appropriate connection to that service. Sometimes, this is most elegantly done by building a breakout box that has either a 30 amp outlet and 15 amp outlet (two receptacles) or passing through one leg of the 50 amp service and having a single 15 amp receptacle.

An alternative to a break out of the 240V service is to connect with the traditional 30 amp cord and have an additional 120V cord to the pedestal as most campground pedestals have both.