30A 220v instead of 50A 220v

[YC1]

RV Electric

It is critical the OP fully understands the 30 amp outlet for an RV is not 240 volts.

[Timon]

First a 30A 240V circuit is only good for 24A/5,760W. A 50A is good for 40A/9,600W. Remember you can only use 80% of the rated breaker.

OK, let me be very blunt. If you are doing this with a permit the inspector would fail the install. They will not allow you to put a 50A receptacle with #10 wire.

Just put in the 3/4" conduit and the #6 wire and do the job the right way. The only real cost difference is the wire and the conduit. The breaker, receptacle, outlet box and cover cost about the same. The cost to install is basically the same. I'll bet later you'll find a reason to have the 50A circuit and will be kicking your self for not doing it right the first time.

Use this box if you only want just the 50A box.

Use this box if you want to have a 50A, 30A and 20A just like the RV parks. This would be my favorite since you have a 120V circuit for other uses shuc as heater tape or work lights.

It really bugs me when people try wiggle around the rules just to save a few bucks.

[CJ7ole]

Originally Posted by Timon

Use this box if you want to have a 50A, 30A and 20A just like the RV parks. This would be my favorite since you have a 120V circuit for other uses shuc as heater tape or work lights.

That box is a 30 amp with a 20 amp receptacle. I don't know how they get a 70 amp rating with just a 20 and a 30 amp single pole breakers.

Maybe something more like this:http://www.campingworld.com/shopping...-amp-gfi/77649 or this one: http://www.homedepot.com/p/GE-100-Am...32SS/203393689

[nothermark]

FWIW if all one is doing is storing the unit while keeping the batteries charged 30A 240 VAC is overkill. If one lives in the cooler parts of the country it is still ample. OTOH if one is trying to live in it...

[Timon]

Originally Posted by CJ7ole

That box is a 30 amp with a 20 amp receptacle. I don't know how they get a 70 amp rating with just a 20 and a 30 amp single pole breakers.

Maybe something more like this:30/50 Amp Power Outlet Box with 20 Amp GFI - Connecticut Electric Inc CESMPSC75GRHR - Electrical Hatches & Outlets - Camping World or this one: GE 100 Amp 3-Space 3-Circuit 240 Volt Unmetered RV Outlet Box with 50/30/20-Amp GCFI Circuit Protected Receptacles-GE1LU532SS - The Home Depot

Oops, copied the wrong like. Edited the post So here is the correct link.

[dpinvidic]

Limiting a 50 amp plug to 30 amps is "Micky Mouse".
Yes, your stuff will run.
But when there is a new owner, he will probably be pretty mad if he was counting on a Standard 50 amp plug and only getting 30 amps.

As another poster said, if only for storage, 20 amps is fine.
Just do it right the first time and you won't have any regrets.

Regards,
Dan

[dpinvidic]

Originally Posted by Timon

Oops, copied the wrong like. Edited the post So here is the correct link.

I am curious as to what the electrical code requires for the main input wiring.
You would have to use wire BIGGER than #6 to allow BOTH receptacles to be used at the same time. But the input might have a breaker that is not the sum of the full loads. They might count on not using the full amperage of both outlets at the same time.

regards,
Dan

[Rockwood27]

I believe the 50-30-20 amp boxes require a cable rated for 80 amp draw. One leg is 80 amps (50 + 30) and the other is 70 amps (50 + 20). Maybe a 2 or 4 gauge copper wire?

[Mr_D]

Originally Posted by 70ChevelleSS

You would never use the 12,000 watts a 50 amp 240 volt circuit would provide.

Our rig will.
2 -2000 watt elements in the AquaHot
Electric Floor heating in bath and living room
3 15,000 BTU heat pumps
240 volt dryer
Advantium micro/convection
plus all the other electronics

[Timon]

Originally Posted by Rockwood27

I believe the 50-30-20 amp boxes require a cable rated for 80 amp draw. One leg is 80 amps (50 + 30) and the other is 70 amps (50 + 20). Maybe a 2 or 4 gauge copper wire?

OK, let's go over this. The box has its own breakers so it's a sub panel. In this case you can have the ability to draw more current than the main breaker in the feeding panel can supply. Example I have a sub panel that s fed by a 70A breaker but if I loaded every breaker in that sub to the max I'd pull over 100A. If I did then the breaker in the main panel would trip.

Take this case you have 3 breakers in the sub at 50-30-20 but the main is only rated at 50. BTW, the breaker protects the wire not what's plugged in. If you connected all three and you pulled the max each breaker handles you would trip the 50A in the main panel. This is how it's designed to work.

Here is a link to a wire run calculator. If you fill in the numbers it will give you the required wire gauge for a given run. Make sure you use 240 if your feeding both legs. Also, the ground wire can be smaller than the feed wires. A #8 ground can handle upto #4 feeds. Also the ground can be bare which saves room in the conduit.

[hvac45]

10 gauge is only good for about 25 ft. @ 30 amps. I would run #8 wire

[70ChevelleSS]

Originally Posted by Timon

First a 30A 240V circuit is only good for 24A/5,760W. A 50A is good for 40A/9,600W. Remember you can only use 80% of the rated breaker.

OK, let me be very blunt. If you are doing this with a permit the inspector would fail the install. They will not allow you to put a 50A receptacle with #10 wire.

Just put in the 3/4" conduit and the #6 wire and do the job the right way. The only real cost difference is the wire and the conduit. The breaker, receptacle, outlet box and cover cost about the same. The cost to install is basically the same. I'll bet later you'll find a reason to have the 50A circuit and will be kicking your self for not doing it right the first time.

Use this box if you only want just the 50A box.

Use this box if you want to have a 50A, 30A and 20A just like the RV parks. This would be my favorite since you have a 120V circuit for other uses shuc as heater tape or work lights.

It really bugs me when people try wiggle around the rules just to save a few bucks.

Who said you can only use 80% of a breakers capacity? NEMA standards say a 20 amp breaker with a constant 27 amp load must trip in less than 1 hour. At 40 amps it must trip in less than 2 minutes. For a 30 amp breaker and a 60 amp load it must trip in under 4 minutes. At 100% load a breaker can run indefinitely. Where do the standards say you can only use 80% of the capacity?

[mel s]

Originally Posted by shiggs68

I'm curious why you say this is a no-no? The OP is talking a standard 50 amp ganged breaker RV circuit except using a ganged 30 amp breaker and smaller wire as it would be easier to work with. The OP is not talking this setup for a 30 amp RV.
That type installation would be exactly like what is installed for a residential clothes dryer except possibly the outlet.
TravellingRVDoctor, LLC

shiggs68
You are correct
Apparently the OP intends to wire a 240V 50A receptacle protected by a 2 pole 30A breaker so he can connect a 50A RV shore power cord which is perfectly safe and acceptable.



240V 50A receptacle



2 pole 30A breaker



50A RV cord plug

I misunderstood his intent.
Sorry
Mel
'96 Safari

[Old Scout]

Cant believe how much "attention" this issues gets on IRV2.....I am not a certified electrician but think several of the replies on this thread are--and they have done a good job of sorting out the pro/cons. Think the "red flag" here is the misunderstanding that the OP is going to use a std dryer configuration, and that some how, a 120v leg is going to get on the neutral leg of the RV and create a true 240v condition and thus "burn everything up." Notwithstanding local and national wiring codes for proper wire size, amps and length of run; if you apply std wiring protocols and use std residential and RV plugs and receptacles, its pretty unlikely you will "burn anything down."

Here are the key issues in my simple mind:

1] An RV wired for 50 amps [eg, 2-120v legs, 1-neutral, 1-ground] can accept either 50 amps or 30 amps as long as:
a. use all four conductors as defined in 1] above, or
b. 30 amp only, use a std three conductor config [eg, 1- 120v leg, 1-neutral, 1-ground]

2] The important phrase here is: "if you wire 'it' correctly!" This past summer, my sister had a "friend of a friend" rewire an RV plug in her gararge to accommodate a new dryer. He rewired another RV plug for me [30 amp, 1-120v leg] but managed to reverse polarity of the plug-in. My surge protector caught it and refused the connection. If you dont wire the plug "correctly" --this conversation about 30/50 amp, or 120 vs 240 wont matter much.

3] Most new Class A rigs are 50 amp, and if surge protector equipped, they want a neutral and a ground. Dont even think about trying to use a GFI plug if rig is S/P equipped.

4] Given the modest difference in cost, or if you never think you will use more than 20 amp service, the idea of going 30 Vs 50 [what, to save money?]doesnt seem to make a lot of sense to me.