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Two 30amp plugs to 50amp outlet
We stayed at a campground this past weekend that didn’t have 50amp in the area we were in, only 30amp. I have a 30amp to 50amp yellow cable. We didn’t need A/C and didn’t do any cooking.
The RV power pedalstal had two 30amp receptacles and each had its own 30amp breaker. Early on in our Prevost experience was told by “a guy” at a limited service campground that I should have a “Y connector” which has two 30amp plugs that are tied into a 50amp outlet that I could then plug our 50amp shore power plug into.
When I looked at one on-line, I see it described as a “cheater box”.
Do these things really work? If plugged into separate 30amp outlets with their own respective breakers on the same pedastal, will I get true 240volt, 50amp service? Worth the investment?
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17 Replies
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The answer is probably regarding if they will work.
As long as you have the correct Y adapter and assuming each 30 amp has its own dedicated breaker in the shore power box, it effectively doubles the current available using a single 30.
You essentially will have a 30 amp limit per leg so if you can control or turn off some of the phantom or non-controllable devices, such as HW heater, water pump, air compressor, etc. you can have power available on each leg for one A/C or a combination of devices. A limit for 30 amp should be 24 amps.
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Am I correct in the belief that a 220V appliance might not work if the 2 30 amp breakers in the pedastal were on the same leg of power?
Are our dryers 220? Is there any 220 equipment in our busses?
Would this condition exist in a commercial situation such as an RV park?
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We have a cheater box and it worked perfectly with our ’98 Vantare and was simple to change incoming shore power to 26 amps on each leg as a safety….I haven’t needed to use it on the Liberty and not sure I would as the Heart inverters are a PITA to change the incoming shore power.
Cheers…Diane
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Our coach came with a ‘cheater’ box (50A female connection with two 30A male plugs extending from the box). We also received several extension cords too.
Our inverters have three different settings that we select from the i-pad power section….
-110v/50A
-110v/30A
-220v/50A
We always have it on 220v/50A when connected to regular 50A shore power.
I choose 110v/30 when I connect to our 30A outlet in the storage garage. I’m not sure when I would use the 110v/50 choice.
Mark
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Walt,
I don’t see a problem using the Y adapter and 220 appliances as long as you keep the amperage in check and make 24 amps your limit as Jon suggested.
Note – The cheater boxes that used 30 amp and 20 amp were a real problem from what I remember in the past, usually because of ground fault on the 20 amp.
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Walt, you are correct in assuming if the 2 30 amp are on the same leg because you will not have the potential to get 240 across the two bus bars in your coach electric panel. Having said that if the shore power box has 2 side by side 30 amp breakers the odds are very low they are on the same leg because the internals in shore power boxes alternate the “stabs: so each adjacent CB is on a different leg.
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I have seen some campgrounds that the Y box..2-30amp ends to a 50 amp receptical will not work due to newer style breaker systems that are arc fault…
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When I sold the company there was a lot of discussion about changing the standards for the shore power outlets, specifically changing the 30 amp receptacle to a GFCI like the mandated 20 amp receptacle.
I am not aware that has become the law or is part of the applicable standards, but if and when it does go into effect there are going to be a lot of RVs not capable of getting shore power into them. For a coach to work with a GFCI receptacle in the shore power box it needs to be equipped for a sequential start, which is to establish the ground before closing the circuit to the balance of the connections. To the best of my knowledge the only Prevost conversion that does that is the Thompson conversion which has one of if not the best electrical system design.
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I didn’t notice that anyone pointed out the obvious, so I will… Two 30 amp connections does not make one 50 amp connection as the 50 amp connection is really two legs of 50 amps, I.e. 100 amps.
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That’s true – and if you did this you’d need to set your invertors to a 30 (or like 27) amp limit… since it’s not 50.
On our bus – this seems a lot easier than the dip switches everyone is talking about – it’s just a menu item on the invertor panels. A few button presses and you’re all set!
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I have alway been at site where 50 amp 240 volt shore power has been available. We will be staying at a site that only has a 30 amp 120volt receptacle. Do I need to do anything with my Liberty coach when connecting to that 30 amps other than limiting loads. That said and not sure how Liberty has set up the connections for the case of using only 30 amp shore power will I only have one or the other side or leg of my electrical panel with power?
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Your Liberty is set up to accept a 30 amp service. Remember a couple of things. First a 30 amp service is going to work just fine for up to 24 amps, and over that the breaker might trip.
It will provide power to both legs in your panel, but you really have to consider your coach like all late model coaches is an energy hog. Reset your inverters to a low current draw. If you use a lot of lighting they are going to draw what they are set for so if they are set for 30 amps you are going to trip a breaker.
You have loads beyond your control and you need to be aware they draw a lot of juice. Look at the load your water pump and aux compressor draw. Add in the refrigerator. If you want Webasto heat or a cruiseair or you want to watch TV or heat water you are likely tripping or on the verge of tripping breakers.
Others may disagree, but before I even consider using 30 amp shore power I am going to fire up the generator and live like a king with all the comforts my coach can offer.
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Jon,
So, if I am to understand your input the Liberty is set up to somehow split the 30 amp 120 volt between the two inverters? If so no problem managing the loads. I do choose my generator as a first line of total comfort. That said many of the parks have rigid restrictions on generators especially after hours so will have to be on some 30 amp shore power. I have not changed the setting on the inverters but will check that out.
Thank you for the info,
Jon P
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You just have to be sure you don’t exceed 12 amps (80% of 15 amps) on each leg. Many inverters allow for a change in shore cord size from 50 to 30. You won’t be able to run much of anything if your chargers are on, you’ll have to wait for float.
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Trying to use 30 amp service, regardless of whose conversion you have is a challenge. Even if you have been driving all day when you plug into shore power the inverters will go to bulk charge because driving does not fully charge house batteries.
So you have to make the inverter adjustment right from the start. Using any 24V circuits like lighting imposes loads on the batteries delaying the time required to reach “float”. Then you have to determine how to handle loads beyond your control such as the water pump. Then you need to decide how to deal with important loads like the refrigerator.
If it were me I would plug into the shore power after the generator was running. Then after a period of time the batteries would be in float, and when I went to bed I would turn off the water pump, leave on the aux compressor to make sure the slide seal was inflated, leave the refrigerator on and everything else except one inverter and then shut down the generator.
The transfer switch will always select the generator over shore power.
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