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Old 01-19-2021, 01:48 AM   #1
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THOR #21795
Plugging 50 amp MH into 30 amp 240v socket

Hello, I have a 2011 Thor Hurricane class A motorhome. It has the large shore power cable with a 4-prong plug. I understand this is a 50 amp plug but does that mean the coach runs on a 240 volt power system? I have a 3-prong 30 amp, 240 volt plug socket in my garage that is used for a compressor or welder. Would it be safe to plug the coach into this socket using the 4-prong female to 3-prong male "dogbone" adapter? We don't really need to run much inside the coach over winter except maybe some occasional lights and occasional furnace. The main concern would be keeping the batteries charged. Any advice or help on this would be greatly appreciated! I don't want to risk damaging anything by using this plug socket. Thanks in advance for your help!

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Old 01-19-2021, 02:25 AM   #2
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Don't do it because you'll fry the coach. 50 amp is basically 240 broken down into 2 separate 120 V circuits.
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Old 01-19-2021, 02:34 AM   #3
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Old 01-19-2021, 02:38 AM   #4
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Plugging 50 amp MH into 30 amp 240v socket

X2. Don’t do it!
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Old 01-19-2021, 02:47 AM   #5
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If you just want to run the furnace and keep the batteries charged use an adapter and plug into the normal 120V 15a house plug.

Just don't try to run an A/C or something that way.
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Old 01-19-2021, 02:49 AM   #6
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Originally Posted by Pete'sMH View Post
X2. DON’T DO IT! But you should be able to replace the outlet with the needed 4 hole one. The “extra” hole allows the two legs to be separate which your coach needs. With a bit more work and a junction box you could add the proper outlet adjacent to the one you have.
I thought the "Dogbone" adapter would allow for this by consolidation of the neutral and ground? So that's not the case? I am new to 50 amp powered coaches so that's why I want to gather as much info as possible. So would it be better in the interim to just step the 4-prong 50A plug down to a standard 3-prong 110v house socket and use that to keep the batteries topped off? Any problems associated with that?
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Old 01-19-2021, 02:51 AM   #7
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X3

Do not do it, however like Pete says if you no longer need the 240v it can be converted to a 120v 50amp outlet.

FYI don't think of the 120v50a cord going to your mh as 240v50a it is NOT.

Next time your in a 50a campground take a look at the breakerS in the pedestal, they'll both be 50a.

Then you can start thinking of you power cord as 2 120v 50a circuits wrapped in 1 sheath.



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Old 01-19-2021, 02:52 AM   #8
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Originally Posted by JamieGeek View Post
If you just want to run the furnace and keep the batteries charged use an adapter and plug into the normal 120V 15a house plug.

Just don't try to run an A/C or something that way.
Ok. I can do that. I don't intend to run anything except maybe the occasional light or two and the furnace on occasion but probably not for more than an hour or so at a time.
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Old 01-19-2021, 02:57 AM   #9
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X3

Do not do it, however if you no longer need the 240v it can easily be converted to a 120v 50amp outlet.

FYI don't think of the 120v50a cord going to your mh as 240v50a it is NOT.

Next time your in a 50a campground take a look at the breakerS in the pedestal, they'll both be 50a.

Then you can start thinking of you power cord as 2 120v 50a circuits wrapped in 1 sheath.



This does make sense. I have seen what you describe at the campground power pedestal. Thanks for the info!
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Old 01-19-2021, 04:18 AM   #10
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Originally Posted by abjbrtd View Post
X3

Do not do it, however like Pete says if you no longer need the 240v it can be converted to a 120v 50amp outlet.

FYI don't think of the 120v50a cord going to your mh as 240v50a it is NOT.

Next time your in a 50a campground take a look at the breakerS in the pedestal, they'll both be 50a.

Then you can start thinking of you power cord as 2 120v 50a circuits wrapped in 1 sheath.




Actually, that's exactly what it is.

The OP could utilize the 240 VAC 3 prong source except it has no neutral, only a ground (or is it the other way around), and there is no "dogbone" adapter that would convert his 50 Amp plug to this receptacle.
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Old 01-19-2021, 04:42 PM   #11
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Originally Posted by 16ACE27 View Post
Actually, that's exactly what it is.

The OP could utilize the 240 VAC 3 prong source except it has no neutral, only a ground (or is it the other way around), and there is no "dogbone" adapter that would convert his 50 Amp plug to this receptacle.
As I have had explained to me, my understanding was that the 240vac 3-prong has the ground and neutral combined. So this would not be split properly into the two legs of 120vac that go into the coach by using a 4-prong female to 3-prong male dogbone (which does fit into that receptacle). Am I understanding that correctly?
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Old 01-19-2021, 05:32 PM   #12
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no '3 prong' 240v outlet has any 'combined' Neutral and Ground - it actually has NO Neutral, ONLY a ground.

now, your 50amp 240v RV NEEDS both, not just one, so, no, you can't just 'plug into' this 240v outlet, even with an adapter.

technically: the reason a 50amp 240v RV needs the Neutral is because there is NEVER time when both 'sides' of the 240v power is balanced - the Neutral wire then provides that balancing. RVs, like your home's Main Panel, have a a Neutral because many things can be powered at the same time, but not 'equally' between the two 120v 'sides' of the panel.
For most other 240v outlets with only 3 wires, and no Neutral, they work for those appliances because the 'heating' element/power needs are exactly the SAME on both 'sides' of the power - so no Neutral is required, though most NEW Clothes Dryers use a 4-wire scheme now since a human can be TOUCHING the metal appliance WHEN a power leakage might happen - the Neutral wire then provides a secondary path, versus the human.
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Old 01-19-2021, 06:10 PM   #13
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Originally Posted by TurnerFam View Post
no '3 prong' 240v outlet has any 'combined' Neutral and Ground - it actually has NO Neutral, ONLY a ground.

now, your 50amp 240v RV NEEDS both, not just one, so, no, you can't just 'plug into' this 240v outlet, even with an adapter.

technically: the reason a 50amp 240v RV needs the Neutral is because there is NEVER time when both 'sides' of the 240v power is balanced - the Neutral wire then provides that balancing. RVs, like your home's Main Panel, have a a Neutral because many things can be powered at the same time, but not 'equally' between the two 120v 'sides' of the panel.
For most other 240v outlets with only 3 wires, and no Neutral, they work for those appliances because the 'heating' element/power needs are exactly the SAME on both 'sides' of the power - so no Neutral is required, though most NEW Clothes Dryers use a 4-wire scheme now since a human can be TOUCHING the metal appliance WHEN a power leakage might happen - the Neutral wire then provides a secondary path, versus the human.
Fully understood. This was the kind of info I was looking for. I will not be using that receptacle. I would like to eventually convert it over to a 4-prong setup that will be appropriate for my MH. Thanks very much for your help and advice!
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Old 01-19-2021, 06:21 PM   #14
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This is a great forum! I learn new things everyday!
Thank you to all contributors.
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Old 01-19-2021, 06:46 PM   #15
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Question: I've got this old receptacle that was used for a dryer in my garage...What (if anything....); can I do with it?

https://www.thorforums.com/forums/at...1&d=1611082306
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Old 01-19-2021, 07:06 PM   #16
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So.... is the house side 3 prongs or 4 prongs, more importantly how many wires were run there?
The National Electrical Code currently requires 4-prong dryer outlets in all new home construction. Existing homes may still use 3-prong outlets. The switch to a 4-prong outlet was due to a flaw in the 3-prong outlet design. In a 3-prong outlet, the ground and neutral wires are contained in the same prong.
The little difference is the how the ground (or neutral) appears.... as an angle or round or U prong? Tells you the NEMA configuration of the receptacle. Note that RV plugs grounds are all U or round shaped..... NOT angle shaped.

So don't do it directly, the mentioned adapters would fit any how. However, can you replace the house side receptacle with the proper one for the RV? Depends. IF you have four wires (black, red, white and green) inside the house AND they are all connected at the panelboard properly you can install what you need. But this is more of a local electrician project to insure that you have the 120VAC from black to white and 120VAC red to white with ground connected (4 prong).

If the wiring in the house side is Black White and Green in the cable you can still get this wired but would need to change the breaker in the panelboard to single pole 30A then install a RV receptible. If the cable is Black Red and white or green (older) as a 3 - wire then you would need to wire and relabel the conductors.

Or just use the dogleg to 30A to 20A and run a few items that you need to keep it alive. Can't run an A/C much on 15A, 20A OK for just one.
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Old 01-19-2021, 07:14 PM   #17
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Unless I am missing something here?

I have 30 amp plug on side of house, I hook my RV up to it all the time. Had it install to keep power to our rig 24/7

240 volts is 240 volts.

I have 50 amp plug from rv, I plug into 30 amp dongle, 30 amp surge. Works like a champ!! Just can't run both ac's at same time.

If you are a 50amp rig and go to a park that only has 30 amp plug, what do you do if this is unsafe?
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Old 01-19-2021, 07:41 PM   #18
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Quote:
Originally Posted by pneumatics View Post
So.... is the house side 3 prongs or 4 prongs, more importantly how many wires were run there?
The National Electrical Code currently requires 4-prong dryer outlets in all new home construction. Existing homes may still use 3-prong outlets. The switch to a 4-prong outlet was due to a flaw in the 3-prong outlet design. In a 3-prong outlet, the ground and neutral wires are contained in the same prong.
The little difference is the how the ground (or neutral) appears.... as an angle or round or U prong? Tells you the NEMA configuration of the receptacle. Note that RV plugs grounds are all U or round shaped..... NOT angle shaped.

So don't do it directly, the mentioned adapters would fit any how. However, can you replace the house side receptacle with the proper one for the RV? Depends. IF you have four wires (black, red, white and green) inside the house AND they are all connected at the panelboard properly you can install what you need. But this is more of a local electrician project to insure that you have the 120VAC from black to white and 120VAC red to white with ground connected (4 prong).

If the wiring in the house side is Black White and Green in the cable you can still get this wired but would need to change the breaker in the panelboard to single pole 30A then install a RV receptible. If the cable is Black Red and white or green (older) as a 3 - wire then you would need to wire and relabel the conductors.

Or just use the dogleg to 30A to 20A and run a few items that you need to keep it alive. Can't run an A/C much on 15A, 20A OK for just one.
House side is a 3-prong, 240v receptacle. Like you'd use for a dryer or welder (or in my case, an air compressor). My motorhome shore power cable has the 4-prong plug connector.
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Old 01-19-2021, 08:44 PM   #19
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macdaddy1111 has the set up. The 30A on the wall is 120VAC and runs from one single pole breaker in the panelboard. In fact this is the best way when a park only has 30A on the pedestal. One A/C with a few other items only.

What Bob has is old. Old. Don't use it, remove it. BUT you can repurpose the cable but need to replace the receptacle itself and then change the wiring in the panelboard to match. Written on the cable should be the wire size and # of conductors.

Search for NEMA plugs charts on the web and you can see the multitude of stuff that is out there.
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Old 01-19-2021, 09:24 PM   #20
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Thanks!
I know that setup is 58 years old...
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