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I have a 30 amp RV outlet in my garage that I want to use to power a couple of 10 amp battery chargers. The battery chargers have 15 amp plugs.

I'm thinking of getting a 10 gauge copper cable, putting a TT-30P on one end, and a metal junction box with a strain relief on the other. The box would have two 15 amp outlets, each with their own 15 amp circuit breaker. Then I could set the box on my workbench and plug everything in.

I'm not sure how to fit the breakers in the box yet. I'm hoping to find a 3 gang cover plate that's blank in one position and has holes for outlets in the other two spots. Then I could put panel mount breakers in the blank part of the cover.

Would this be safe and legal? Is there an existing product that would do the same thing for a reasonable price?

This question is similar to this one: Safe breakout for an RV outlet. The main difference is that I'm doing everything indoors.

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  • If fitting breakers is a problem, then fuses still exist.
    – Simon B
    May 27, 2022 at 10:39
  • You can use NEMA 3R stuff indoors. So this is a dup.
    – Harper - Reinstate Monica
    May 27, 2022 at 18:00

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Put in an actual small subpanel. You can mount in in a box and attach receptacle boxes to it. If you actually have room in your garage (a permanently mounted subpanel has to have a large working space in front of it) you could actually put the subpanel on the wall, move the 30A feed to go into the subpanel and connect the RV receptacle (on a 30A breaker) and the new 15A or 20A circuits, so you would have all the options always available.

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First, make sure the RV outlet actually is the voltage it seems to be. Because idiots exist.

Just use a UL-Listed splitter

You are proposing to build a splitter. DON'T. The main problem is the "breakers" end up having to be hobby-electronics-Chinese tier stuff, since they don't sell approved breakers in that form-factor. Closest you can get is this, but it will be awkward to mount in a 2-gang box (and they're not cheap).

However, they make molded adapters which take a TT30 and turn it into dual NEMA 1-15's. They are UL Listed, because UL will allow this if the unit has integral fuses. (UL does not require that the fuses be replaceable, they are typically molded-in). However typically in these units, there is one 15A fuse per socket, and a single device which exceeds 15A has a problem, so fuse blows are unlikely.

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  • I like the idea of buying a splitter with fuses in it, but I'm having a hard time finding one that's UL listed, or that has fuses. I guess I could get one that doesn't have fuses and plug in a couple of power strips that have breakers. But that seems kinda messy.
    – mrog
    May 31, 2022 at 5:09
  • I finally found a cord that could work. I don't know if it's UL listed or not, but it has some over current protection. firmanpowerequipment.com/collections/accessories-parts/products/…
    – mrog
    May 31, 2022 at 8:08

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