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11-03-2019, 08:45 AM
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#1
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Senior Member
Join Date: Jan 2017
Location: Little Rock, Arkansas
Posts: 2,594
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Can 20 amp and 30 amp be used simultaneously?
Please settle this for me. As if it's possible to settle anything on the Internet
If the post has separate 30 amp and 20 amp breakers can they both be used simultaneously?
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2021 Keystone Outback 221UMD
2018 Tundra Limited 5.7 liter
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11-03-2019, 08:57 AM
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#2
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Senior Member
Join Date: May 2013
Location: Ontario, California
Posts: 2,429
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Yes. each circuit is suppose to have its own circuit breaker.
Someone actually makes an adapter with a 30 amp male plug and a 20 amp male plug and a 50 amp female plug
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[SIGPIC][/SIGPIC]2016 Newmar Dutch Star 4369
Newmar Owners Club
USAF 1966-1969,- Law Enforcement 1969 - 2003, Retired since March 2003
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11-03-2019, 09:11 AM
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#3
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Senior Member
Join Date: Jan 2017
Location: Little Rock, Arkansas
Posts: 2,594
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Quote:
Originally Posted by LJowdy
Yes. each circuit is suppose to have its own circuit breaker.
Someone actually makes an adapter with a 30 amp male plug and a 20 amp male plug and a 50 amp female plug
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Well! I was just trying to settle an argument, but are you saying that if you only have a 30 and 20 on the post you could still run a 50 amp rig with that adapter?
It would seem so, but I'm not an electrician ... never even played one on TV.
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2021 Keystone Outback 221UMD
2018 Tundra Limited 5.7 liter
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11-03-2019, 09:26 AM
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#5
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Community Moderator
Monaco Owners Club
Join Date: Jul 2016
Location: Central, Arkansas
Posts: 11,291
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Depends on several factors. Some rv's won't work on a GFI protected circuit. The 20 amp plug is always a GFI. My 5th wheel won't but my Motorhome will. In some campgrounds it is against policy to plug into both outlets. That is because they use common wiring to power both plugs with a maximum draw of 30 amps total. Also just to stir the pot for those that don't understand it I feel compelled to mention true "50 amp" rv service is 100 amps total @ 50 per leg so it really isn't gaining much. On a pedestal that isn't designed for that type of use the voltage drop will probably not allow you to use both a/c units anyway.
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2004 Beaver Monterey Laguna IV
Cummins ISC 350HP Allison 3000 6 speed
2020 Chevy Equinox Premier 2.0t 9 speed AWD
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11-03-2019, 09:27 AM
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#6
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Senior Member
Join Date: Mar 2015
Posts: 195
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That would totally be dependent on which phase the two plugs were attached to in the breaker box, a 50 amp requires one leg from each phase which is actually two 120 volt phases with a common neutral, if you take a voltage reading from the two large flat blades you will get 240 volts , each leg to neutral will yield 120 volts each. I have never seen an adapter to add a 30 a and a 20a together myself.
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11-03-2019, 09:32 AM
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#7
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Senior Member
Join Date: Jan 2018
Location: Capistrano Beach, California
Posts: 4,465
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Quote:
Originally Posted by EdInArk
Well! I was just trying to settle an argument, but are you saying that if you only have a 30 and 20 on the post you could still run a 50 amp rig with that adapter?
It would seem so, but I'm not an electrician ... never even played one on TV.
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If the post is wired according to the "standard," with a 240vac feed, the 30 amp CB should be powered by one line and the 20 amp CB, by the other. Using two adapters, you would be able to "combine" the feed into your 50amp RV but the amperage available to your RV would be limited to 30amps for anything on that line, and 20amps for anything on the other. You would not have full 50 amp service on each line as you would if connected to a 50 amp post connection.
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Larry, Eileen, and Finley
2004 Alpine 36FDDS
Third motor home, first Alpine, no need for another.
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11-03-2019, 10:54 AM
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#8
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Senior Member
Winnebago Owners Club Solo Rvers Club
Join Date: May 2015
Posts: 1,834
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Can 30 amp and 20 amp be used simultaneously ? Yes, but check the campground rules - I have stayed at several public and private campgrounds that prohibit this in particular if they charge different nightly flat rate prices for camping with 20, 30, or 50 amp electric service.
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Randy - Manhattan, Kansas
2015 Vista 27N
2020 Ford Escape Hybrid
[SIGPIC][/SIGPIC]
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11-03-2019, 11:00 AM
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#9
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Senior Member
Join Date: Jul 2018
Posts: 4,925
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Quote:
Originally Posted by spdracr39
Depends on several factors. Some rv's won't work on a GFI protected circuit. The 20 amp plug is always a GFI. My 5th wheel won't but my Motorhome will. In some campgrounds it is against policy to plug into both outlets. That is because they use common wiring to power both plugs with a maximum draw of 30 amps total. Also just to stir the pot for those that don't understand it I feel compelled to mention true "50 amp" rv service is 100 amps total @ 50 per leg so it really isn't gaining much. On a pedestal that isn't designed for that type of use the voltage drop will probably not allow you to use both a/c units anyway.
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It's a matter of semantics, but it's a *50 ampere, 120/240VAC circuit*. That it is a split-phase service allows it to provide up to 50 amperes of current on each side of the split (and the split point is where "neutral" comes from in this service) but it's still a 50 ampere service. That sounds contradictory with the next paragraph, but it's not...
As for "isn't gaining much" I disagree because doubling the current is 100% MORE. Unless, of course, you consider double to be not much...
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2005 Four Winds Majestic 23A
“To the world you may be one person; but to one person you may be the world.” - Dr Suess
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11-03-2019, 11:25 AM
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#10
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Senior Member
Join Date: Jul 2014
Posts: 35,441
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They run a 120 volt, 50 amp line to a post.
At that post are 2 breakers, a 30 and a 20 amp. There is no second leg for 240 volts.
Yes you can use both, I am right now, so I can run 2 electric heaters in my 30 amp MH. Most are for electric grills and things like that.
ALL 50 AMP SERVICE IS 120/240 VOLTS. Read your power cord plug.
There is no 240 volt service avalable in a 30 amp post. Why would there be, it wasn't used back when they were installed.
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11-03-2019, 12:16 PM
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#11
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Senior Member
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 5,152
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Some campgrounds are wired one way some another. Usually you can use both the 30 amp and 20 amp at the same time. However, You have no way of knowing what the campground branch breaker for your pedestal is. It may be 30 amp, it may be 50 amp. Wiring code usually allows either way.
Some RV's and TT's have simple 50 amp 240 volt main service entrance. They will work with a 30/20 split adapter. Both legs of the service will be live. It will not overload the neutral because it is still limited to 50 amps total.
One leg will trip the pedestal when loads exceed 20 amps, the other will trip the pedestal when you exceed 30 amp loads. If the campground branch for your pedestal is 30 amps, the campground branch breaker will trip when you exceed 30 amps total on the two legs.
The campground may not have a maintenance person working at the time and you may have to wait until the morning of the next business day for a maint. person to arrive and reset it.
Some Rv's and TT's have sophisticated transfer switches and battery management systems. Of course if your BMS can detect the 30 and activate both legs you do not need an adapter. However, some systems will freak out using the adapter.
A rare few 50 amp RV's and TT's have a 240 appliance and therefore a 240 volt circuit. It will most likely not work using the adapter.
By the way, The service entrance for a TT or RV is electrically the same as the service entrance for a home. The main difference is, most homes have a much larger amp capacity. Modern home service entrances are all 240 volt two leg systems, but theoretically they could be 120 volt 30 amp one leg systems like many TT's.
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Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
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11-03-2019, 12:16 PM
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#12
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Senior Member
Join Date: Jan 2017
Location: Little Rock, Arkansas
Posts: 2,594
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Thanks for all the input. Nothing's ever easy is it
We are a 30 amp rig and during cold weather we use a couple of 1500 watt heaters on low -- 700 watts I think. I have two 15 amp breakers for 120 volt outlets, so i plug one into a jack on each one. Problem is that one of us will sometimes start the microwave without remembering to turn off that heater and trip a breaker. I know some folks run an extension cord out the window to that 20 amp jack.
Thanks
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2021 Keystone Outback 221UMD
2018 Tundra Limited 5.7 liter
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11-03-2019, 12:24 PM
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#13
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Senior Member
Join Date: Jul 2010
Posts: 5,336
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I have read over the years on this and other forums that the term “it depends” is appropriate here. Some electrical posts say you can, some no as it depends on how they are wired. And then I have seen at some campgrounds clear and bold lettering that you MAY not use more than one at a time, and if by doing so you damage the system, you will both pay for the repairs and be asked to leave. So check with the CG before you either plug two or more cords into a single post or one of the combo cords.
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Tom
2016 Newmar Bay Star Sport 3004
2021 Jeep Gladiator Sport Willys
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11-03-2019, 12:38 PM
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#14
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Senior Member
Join Date: Jul 2018
Posts: 3,165
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My campground is wired with a 50 amp main breakers feeding 30 amp peds.
The 50 amps are 240 volt feeds to the box. They are 60 amp 240 volt 6 circuit sub panels with no main breaker in them. In the box is a 30 amp single pole breaker and a 20 amp single breaker. 30 feeds a 30 amp RV outlet and the 20 feeds a 20 amp GFI outlet. So yes, there are indeed 240 volts L1 and L2 feeding the power box. The 30/20 adapter mentioned above does cause problems because as mentioned some RV's do not work when using the GFI circuit. I have tested this theory on my two trailers and neither wold work when plug into a GFI circuit.
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2011 Keystone Sprinter 323 BHS. Port Charlotte Fl/Hinsdale MA. Retired Master Electrician. All Motor homes are RV's. All RV's are not Motor homes.
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