50 and 30 amp outlets on same circuit

[Martian]

Hi. This is the plan-I have a 50 amp rv outlet installed by the rv port. My trailer is a 30 amp cord. Am I breaking any electrical rules if I daisy chain a 30 off f the 50 amp outlet? It is only set up for one rv and adding the 30 outlet will eliminate using a dog bone all the time. Thanks to the ac gurus ahead of time!

[Jim_HiTek]

The danger is that someone, perhaps the next owner of your property, may try to plug a 50 amp and a 30 amp device in at the same time. So...

The main line for 50 amp should have a 50 amp CB on it of course. And so should the 30 amp right at the T where you branch off the 50 amp line. So you are protecting the 30 amp device (or RV) AND the 50 amp line is also protected from overload.

That's what I'd do, but you can just call your local building/electrical inspectors and have them come out and look at your setup. They'll give you the proper guidance. Sometimes you need to go to their office and schmoose the secretary first to get someone to talk to or to come out. Carry a drawing of your setup with you. I use to do that all the time for free professional advice. They get to know you and are happy to answer questions (usually) if you give them the proper respect. And it's FREE! Sometimes had to get a building permit but that was cheap compared to fines or damage from doing the job incorrectly.

[MingusPirate]

Don't do it. It would be against the electrical code. If you have a fire for any reason you could be at fault.
Next, the 50 amp is at 240 volts, where the 30 amp is 120 v. I have heard of a licensed electrician wiring a 30 amp rv receptacle like a dryer which is 240 v, because they look similar. That burns up a lot of equipment.
Stick with the dogbone.

[wolfe10]

Actually, if breakers at the house main supply are sized to handle 80 amps on the leg you are using for the 30 amp hot as well as the 50 and the wire is sized appropriately, I see no issue with doing it.


Would be be better to run a separate hot with its own 30 amp breaker in the house main supply box-- yes.

[amosnandy]

Originally Posted by MingusPirate

Don't do it. It would be against the electrical code. If you have a fire for any reason you could be at fault.
Next, the 50 amp is at 240 volts, where the 30 amp is 120 v. I have heard of a licensed electrician wiring a 30 amp rv receptacle like a dryer which is 240 v, because they look similar. That burns up a lot of equipment.
Stick with the dogbone.

Sorry, but you are wrong. With a Dog bone plugged into a 50 amp outlet, you would need to draw 50 amps before any protection is afforded. A short or for that matter, even a heavy load plugged into a 50 amp outlet could cause a 50 amp to 30 amp dogbone or the 30 amp cord to overload and burn. When a 30 amp RV is plugged into a 50 amp outlet with a dogbone the first protective device is the 30 amp breaker in the distribution panel. In reality, 50 amp to 30 amp dogbone are not UL listed.

The proper way to run a 30 amp RV off a 50 amp circuit is to wire a 30 amp outlet off one leg of the 50 amp breaker, to a 30 amp breaker to a 30 amp receptacle.

The OP has it correct as long as he puts a 30 amp breaker in the line from the 50 amp to the 30 amp.

[Persistent]

Jim Hitek has the correct plan. The 30 amp 120 volt circuit can be connected to one hot leg of the 50 amp 240 volt cable.

There must be a 30 amp branch breaker before wire is down sized and outlet is down sized. All connections must be made inside an approve box. The box must be suitable for 50 amp 240 volts and large enough to meet code.

I recommend a 50 amp 240 volt sub-panel with room for 50 amp 240 volt, 30 amp 120 volt, and 20 amp 120 volt branch breakers. Connect the 30 amp to one leg and the 20 amp to the other leg. Of course the 50 amp will connect to both legs.

RV pedestal boxes like these are widely available and much more convenient. Use the breakers as disconnects for plugging in properly.

Here is an example. You can probably find one that cost a lot less.
https://www.amazon.com/TL137US-Tempo...08&sr=8-2&th=1

[Injuneer]

I guarantee you that all of you who complain about those "dog bone" adaptors being a fire hazard due to being able to put a 30 amp cord into a 50 amp receptacle also have lamp cords rated at perhaps 5 amps or less plugged into your 15 or 20 amp 120 volt receptacles at home, don't you?

[amosnandy]

Originally Posted by Injuneer

I guarantee you that all of you who complain about those "dog bone" adaptors being a fire hazard due to being able to put a 30 amp cord into a 50 amp receptacle also have lamp cords rated at perhaps 5 amps or less plugged into your 15 or 20 amp 120 volt receptacles at home, don't you?

It’s been 30 years since I have seen a lamp cord rated at 5 amps. In order to be UL listed the cord on any electrical device must be rated to handle the current it is able to plug into. Most lamps use a 14 gauge wire.

[CRV2]

If you only need a 30a connection, then what I suggest to do is to simply change the 50a receptacle and the 50a circuit breaker to a 30a setup. This should be simple to do depending on what you have setup already.

What type of outlet box do you have? Can it handle multiple outlets, if so then perhaps I would do it differently. ~CA

[HenryH001]

Originally Posted by Injuneer

I guarantee you that all of you who complain about those "dog bone" adaptors being a fire hazard due to being able to put a 30 amp cord into a 50 amp receptacle also have lamp cords rated at perhaps 5 amps or less plugged into your 15 or 20 amp 120 volt receptacles at home, don't you?

Yes however the difference is the one lamp is all the cord supports and it might be limited to a 40 watt bulb.

You can’t compare it to a circuit with multiple plug-ins.

[CRV2]

Every circuit protected by a breaker is designed to have lower electrical loads (lights, appliances, etc) plugged into that circuit than what the breaker is designed to trip (break) at. For example, there is nothing wrong with plugging in a 1/2 amp electric toothbrush into a circuit protected with a ~20a breaker (or more or less). Same concept here applies.

[twinboat]

Originally Posted by amosnandy

Sorry, but you are wrong. With a Dog bone plugged into a 50 amp outlet, you would need to draw 50 amps before any protection is afforded. A short or for that matter, even a heavy load plugged into a 50 amp outlet could cause a 50 amp to 30 amp dogbone or the 30 amp cord to overload and burn. When a 30 amp RV is plugged into a 50 amp outlet with a dogbone the first protective device is the 30 amp breaker in the distribution panel. In reality, 50 amp to 30 amp dogbone are not UL listed.



The proper way to run a 30 amp RV off a 50 amp circuit is to wire a 30 amp outlet off one leg of the 50 amp breaker, to a 30 amp breaker to a 30 amp receptacle.



The OP has it correct as long as he puts a 30 amp breaker in the line from the 50 amp to the 30 amp.

[QUOTE=amosnandy;6020117]

In reality, 50 amp to 30 amp dogbone are not UL listed.




The ones I looked up are.

[carybosse]

Originally Posted by Jim_HiTek

The danger is that someone, perhaps the next owner of your property, may try to plug a 50 amp and a 30 amp device in at the same time. So...

The main line for 50 amp should have a 50 amp CB on it of course. And so should the 30 amp right at the T where you branch off the 50 amp line. So you are protecting the 30 amp device (or RV) AND the 50 amp line is also protected from overload.

That's what I'd do, but you can just call your local building/electrical inspectors and have them come out and look at your setup. They'll give you the proper guidance. Sometimes you need to go to their office and schmoose the secretary first to get someone to talk to or to come out. Carry a drawing of your setup with you. I use to do that all the time for free professional advice. They get to know you and are happy to answer questions (usually) if you give them the proper respect. And it's FREE! Sometimes had to get a building permit but that was cheap compared to fines or damage from doing the job incorrectly.

Hopefully, I make sense on my comments, and hopefully someone can help me understand some of this.

First, the best thing to do is to have a panel rated for 80 amps and to hang a single pole, 30 AMP breaker (120 VAC) off the panel to supply the 30 AMP power and hang a double pole, 50 AMP breaker (240 VAC) to supply the 50 AMP power.

If you pull one leg of the 50 AMP circuit to supply the 30 AMP circuit, doesn't it really need to be set up for 60 AMPs? In theory, I would think that each leg of the 50 AMP circuit is only 25 AMPs.

I wired a 30 AMP circuit in my garage a few months back for very little money. Granted, I had the junction box in my stash, only needed the breaker, a few feet of wire, an outlet, and a faceplate. The junction box was actually the hard part, Home Depot and Lowes were out, but then I discovered I already had one left over from another project. Second issue was the short piece of wire to go from the breaker box to the outlet. The issue with that was finding an employee to cut the wire. I actually hit 4 big box home improvement stores before I found an employee. I did help several customers find what they were looking for, but didn't receive a commission on the sales.

If I wanted a 30 AMP and a 50 AMP, I would just bite the bullet and run separate circuits. In my mind, I can't see a lot of difference in the costs over the trying to cobble something off the the existing 50 AMP circuit.

It has been a while since I did any complicated wiring, but while in college, I had to help setup a piece of concrete test equipment that required a 480 VAC, 3-Phase circuit. I can't remember now if it was a 100 AMP circuit or a 100 HP pump, I just know wrestling with that copper was not fun.

Oh, and all of these things we are talking should technically require a permit and an inspection, with a licensed electrician required to install, in probably almost any jurisdiction in the US.

[twinboat]

Originally Posted by carybosse

Hopefully, I make sense on my comments, and hopefully someone can help me understand some of this.







If you pull one leg of the 50 AMP circuit to supply the 30 AMP circuit, doesn't it really need to be set up for 60 AMPs? In theory, I would think that each leg of the 50 AMP circuit is only 25 AMPs.



.

Each leg of 50 amp service has the potential of 50 amps at 120 / 250 volts.

If your only using 120 volts, you can draw 50 amps from each leg, up to 100 amps.

RV 30 amp service only use 1 leg at 120 volts. Max amp draw is 30 amps.