Using an adapter to plug 30 amp RV to 50 amp service

[RV Wizard]

Agreed.

[Gary - K7GLD]

Originally Posted by Dmiles

So, did I really boil it down, or did I add to the confusion?

Actually, the "short answer" is, using the 50 amp dogbone adapter isn't likely to hurt, and very well MIGHT help, in most situations...

[ruddpatter]

Paul R. Haller; excellent response, thanks.

[NeilV]

Originally Posted by Dmiles

My MH uses 30 amp service. I bought a 30 to 50 amp adapter for those times when I'm at a CG where 50 amp is all that is available (it has happened twice).

Got me to thinking, why not just use 50 amp service whenever it's available? I would be assured better quality power, and everything in my MH is protected with breakers, so, why not?

Anyone have any ideas on why I shouldn't do this?

The 30 amp breaker at a campground many times trips during brown outs or because it just has aged to the point that it is no longer capable of handling a 30 amp load. In these situations I will use the 50 to 30 dog bone to plug my 30 amp rig into the 50 amp socket so my autoformer can correct the low voltage situation without tripping the breaker or to overcome a faulty 30 amp camp ground breaker.

This will protect your equipment as you will not be getting additional power loss/voltage drop as the 30 amp breaker starts to fail. You may even notice that while the 30 amp breaker will be running hot along with your power cord everything may start to cool down once you plug into the 50 amp with the dog bone.

The risk is that if you have a short between the 50 amp dogbone and your 30 amp main breaker inside the coach then you could damage your power cord and electrical gear between those two points. If that concerns you you could put an inline 30 amp breaker beween the 50 to 30 amp dog bone to protect your power cord however that would be your call.

For me I know the condition of my power cord along with its connecting plugs and have a 30 amp SurgeGuard in line with a 30 amp AutoFormer to protect me against power faults between the power post and the coach so I am comfortable with doing this.

[CamperHome]

Originally Posted by Flagelpater

This would be okay if only a 50 amp receptical were present but if a 30 amp were there, that one should be used because the pedestal would provide the protection.

I understand everything everyone is saying except for one thing... If someone could dumb it up for me. What is the "protection" that will not be provided for a 30amp system when plug is plugged into the 50amp pedestal with an adapter?

[TripleEEE]

Originally Posted by CamperHome

I understand everything everyone is saying except for one thing... If someone could dumb it up for me. What is the "protection" that will not be provided for a 30amp system when plug is plugged into the 50amp pedestal with an adapter?

NeilV sums it up for you below....

Originally Posted by NeilV

The 30 amp breaker at a campground many times trips during brown outs or because it just has aged to the point that it is no longer capable of handling a 30 amp load. In these situations I will use the 50 to 30 dog bone to plug my 30 amp rig into the 50 amp socket so my autoformer can correct the low voltage situation without tripping the breaker or to overcome a faulty 30 amp camp ground breaker.

This will protect your equipment as you will not be getting additional power loss/voltage drop as the 30 amp breaker starts to fail. You may even notice that while the 30 amp breaker will be running hot along with your power cord everything may start to cool down once you plug into the 50 amp with the dog bone.

The risk is that if you have a short between the 50 amp dogbone and your 30 amp main breaker inside the coach then you could damage your power cord and electrical gear between those two points. If that concerns you you could put an inline 30 amp breaker beween the 50 to 30 amp dog bone to protect your power cord however that would be your call.

For me I know the condition of my power cord along with its connecting plugs and have a 30 amp SurgeGuard in line with a 30 amp AutoFormer to protect me against power faults between the power post and the coach so I am comfortable with doing this.

[hilgert]

It does not matter in a properly wired, properly maintained campground with decent power. However having all three...properly installed, properly maintained, and decent power... are very often not the case in many RV parks. Sometimes even having one of those is considered a bonus.

Typically, campground pedestals with both 50A and 30A (and 20A) will alternate (from pedestal to pedestal) between legs for the 30A service (from one of the 50A legs), with one leg for the 30A outlet, and (if available) the opposite leg for the 20A outlet, so which leg you are on for 30A *should* not matter. But there is lots of "silly and stupid" out there, so don't count on it...bring a voltmeter and check for yourself.

NeilV noted one issue with hooking a 30A cord to a 50A outlet is that the 30A power cord is not protected between the 50A breaker and the 30A house (RV) breaker. However, there are a few possible but improbable conditions where this might be an issue, and the 30A breaker in the RV should trip if current is over 30A. As NeilV also noted, 30A outlets can suffer from past high-current issues (someone with 30A running the AC, microwave and hot water element would likely be drawing at/more than 30A). Before I upgraded our Sunseeker from 30A to 50A I always favored 50A receptacles with a 30A dogbone for this reason.

In some parks I've measured voltage dropping significantly when the AC comes on, so I installed a 50A Hughes Autoformer which provides a voltage boost down to 95 volts input on either phase (part of my 30A to 50A conversion). Immediately after the autoformer I have a Progressive Industries EMS, which will disconnect on low/high voltage (or other conditions like a missing neutral). They are both connected prior to the transfer switch, and the two in combination simply won't allow low/high/bad power to pass onto the panel in the motorhome...we either get good power, or no power at all. Both are plug-in models (easy to bypass if issues arise with either) installed in a locked storage bay so they are out of sight of interested parties that might want to borrow them forever. There are 30A versions of both.

[70ChevelleSS]

Well everyone has thanked Paul for his great write up so let me just add this.

It's a lot of information the OP didn't ask for and it also contains some misinformation.

First off it's 120 volts per hot leg, not 110. 110 would be considered a brownout.

Second there are coaches that use the 2 hot legs for 240 volt loads, such as a clothes dryer. Not that common but there are some.

Third, on a 50 amp RV all power coming in the 2 hot legs does not return on the neutral leg. That would have the potential of 100 amps running back on the neutral leg, 50 amps from each hot leg. Pretty sure that would burn up the neutral wire which is rated for 50 amps. Note that all 3 wires in the cord, 2 hots and neutral, are all the same gauge rated for 50 amps each. If there are equal loads on both hot legs than ZERO amps flows back through the neutral line. In a 120/240 volt panel only the imbalance in loads on the 2 hot legs returns on the neutral leg. Which would be a maximum of 50 amps. That assumes one hot leg fully loaded and no load at all on the other one.

Bottom line, it won't hurt to use the 50-30 adapter. The 50 amp breaker at the pedestal is there to protect the supply lines feeding the pedestal and the outlet, not the cord you plug into it. It's the job of the 30 amp breaker in the RV to protect the cord. No different than your home, 15 amp breakers protect the 14g wiring and the 15 amp outlets not what you plug into them which may only have 16g or even 18g wires. A direct short in a 30 amp cord will trip a 50 amp breaker. The 30 amp cord is just not rated to handle 50 amps on a sustained basis.

As mentioned it's hit or mess as to whether the power will be better using the 50 amp outlet. Depends on how the park is wired and who is using what in the park. Also mentioned is the outlet itself. The 50 amp outlets are much more robust than the 30 amp ones. So a better connection and less change of voltage drop at the outlet.

[steveha]

This has been one of the more informative threads I've read for a while.. I have one thing to add. This spring I ran into two CG's with 50A only.
One beautiful place in TN, TVA/Cherokee Dam-Cherokee Lake even supplied a dog bone if you didn't have one...

[DAN L]

Dmiles

I would still use my portable Progressive Industries surge protector.

[70ChevelleSS]

Originally Posted by DAN L

Dmiles

I would still use my portable Progressive Industries surge protector.

Not a bad idea whether using 30 or 50 amp supply.

[CamperHome]

Originally Posted by hilgert

"I have a Progressive Industries EMS", "Both are plug-in models", "installed in a locked storage bay so they are out of sight"

Hilgert, thank you so much for the helpful info.

If it would not be too much trouble could you please tell me exactly how does one convert a 30a to a 50a camper.

Also could you please send me the model of the EMS unit,

and a make/model and where you installed the locked storage bay (or are you talking about the one that is part of the camper). If so sux because my electric in in back(ish) of the camper and the bay is in the front. We have a Keystone Cougar.

one more thing... if you have the make/model of anything else I need to for this process I would greatly appreciate that info too.

[hilgert]

Originally Posted by 70ChevelleSS

...
First off it's 120 volts per hot leg, not 110. 110 would be considered a brownout.
...

I agree that anything below 110 is something to begin worrying about. My Progressive Industries EMS-PT50X shuts off power below 104V and above 132V (and other undesirable conditions), BUT my Hughes Autoformer will give a 10% boost to low voltage. Since the EMS is after the Autoformer, in reality I'll never see below 104V (wish I could set it higher). I do have two displays inside the RV on two plugs on two different phases, and if I saw either below 110V (after boosting when using the AC) I'd consider switching to generator or leaving the park.

Note that electricians (especially ones that have been around for a long time) often toss 110/115/120 around when talking...it's all understood to be 120V (goes back to the old days of 110, then 115, and now 120V). I'm an electrical engineer by education (but not by career), and I use when talking to folks in Lowes or Home Depot.

Originally Posted by 70ChevelleSS

...
The 50 amp breaker at the pedestal is there to protect the supply lines feeding the pedestal and the outlet, not the cord you plug into it.
...

RV park pedestals are most typically supplied by lines servicing multiple pedestals. This would mean that the current carrying capacity of the lines feeding the pedestal(s) is several multiples of 50A (maybe 200A or above). The 50A/30A/20A breakers at the pedestal are therefore primarily there to protect the cords plugged into the pedestal...as the lines to the pedestal can carry MUCH more than 50A.

This is part of the reason for brownouts at many RV parks in the summer...when *everyone* has their AC units on the resistance of the feeder lines causes a drop in voltage. This happens in our stick-and-brick houses as well...just typically a much smaller voltage drop.

Originally Posted by 70ChevelleSS

...
It's the job of the 30 amp breaker in the RV to protect the cord.
...
The 30 amp cord is just not rated to handle 50 amps on a sustained basis.

Correct..but...just like in a house it's possible to plug in an appliance with a smaller cord that could burn up at currents lower than the breaker for the receptacle. I know I've experienced a few burned cords in my life, where the house breaker for that circuit did not trip (as the cord burned up before the breaker heated up enough to trip).

In the improbable (but possible) event of a short between the 50A pedestal breaker and the 30A RV breaker (say in the transfer switch), more than 30A could flow before the 30A breaker. Another scenario would be that something crushed/cut the cord (maybe one misses with a shovel or something) and shorted it out. In both cases the 50A pedestal breaker would (hopefully) trip, but the 30A RV breaker may not see even a single amp of current due to this...as the short is *before* the RV breaker.

Originally Posted by 70ChevelleSS

As mentioned it's hit or mess as to whether the power will be better using the 50 amp outlet. Depends on how the park is wired and who is using what in the park. Also mentioned is the outlet itself. The 50 amp outlets are much more robust than the 30 amp ones. So a better connection and less change of voltage drop at the outlet.

100% agree...which is why when we had 30A I always favored using a dogbone off of 50A. We have been to one park that had ONLY a 50A outlet (this was a park in Florida near relatives that was mostly a mobile home park, but had a few slots for RVers, and had loaner dogbones if needed).

[hilgert]

Originally Posted by CamperHome

Hilgert, thank you so much for the helpful info.

If it would not be too much trouble could you please tell me exactly how does one convert a 30a to a 50a camper.

Also could you please send me the model of the EMS unit,

and a make/model and where you installed the locked storage bay (or are you talking about the one that is part of the camper). If so sux because my electric in in back(ish) of the camper and the bay is in the front. We have a Keystone Cougar.

one more thing... if you have the make/model of anything else I need to for this process I would greatly appreciate that info too.

With a great deal of time, effort and cost (how to convert). For your situation you would want to consider external units...running 50A cable from the back to the front storage, and then back again, is a lot of work and money, and I doubt you could do this such that the lines were all protected/inside. For me I "just" had to run it from a new inlet (replaced the 30A inlet) to a storage bay that was about 6 feet away (external bay for kitchen garbage can we never used), then to a nes transfer switch, and then to the other side of the motorhome. Fate smiled upon me as there was "just enough" room to cram through a 50A cable and a few extra 20A lines for future expansion from one side of the motorhome to the other...but it was very tight. The wife threatened a divorce me as she was doing the pushing and I was doing the yelling.

To do this properly you'd need (for your Cougar) a lot of cable, a new 50A inlet, a new transfer switch (assuming you have a generator with an auto transfer switch), the EMS (if you wanted it) and (in my case) the Hughes Autoformer (I'd buy it direct from Hughes). You'd then also need new 50A shore cables, adapters in case you are at 30A or 20A sites (or storage...we have 120V 20A service in our covered storage spot), and such. All told I'm well north of $1000 for this project.

***This is not a small project, and I would not have done it if I was not able to run all the lines 100% inside the RV (behind cabinets, etc.). If you are not handy, or don't have a friend that knows how to do this, I'd not attempt it yourself.

The EMS I used is the My Progressive Industries EMS-PT50X (there is a 30A version as well).

EDIT: If you are looking to add a 2nd AC or something, often times people with 30A just run a separate 20A cord from the 20A pedestal outlet to the AC. If a pedestal with 50A/30A/20A is properly wired, the 30A and 20A will each come from separate legs (although 20 + 30 is 50, so it would not matter). If it's only 30A and 20A, then it's possibly just one phase, and 30A might be the total limit.