RVelectricity: Power adapter overview – What works or doesn’t work?

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By Mike Sokol

Dear Readers,
I just received this picture from Chuck Woodbury, who wondered if I had covered that sort of RV hookup already. The answer is yes, but since many of my adapter articles have been strewn all over the place during the 10 years I’ve been writing for the industry, I’m putting a lot of them together in one place for ease of reference.

Safety first

Note that since safety is my primary concern, I’m not going to suggest or condone anything dangerous. And there are a few adapters that may not be totally code compliant in all states, but which I believe are safe if used properly. However, in all cases you may find that your local electrical inspector (the AHJ, for Authority Having Jurisdiction) has a problem with a certain type of adapter – and it’s within his or her rights to disallow it.

From the beginning (Listen to Emerson, Lake and Palmer here)

For any new RVers out there, you may not have encountered this problem yet. But you should be aware that just because you have a 30-amp or 50-amp shore power cord on your RV, there’s no guarantee that you’re going to find a matching (and working) electrical outlet at your camping spot. That’s why power cord adapters were created.

The problem is that while there are all sorts of RV power adapters available from major sales sites such as Amazon and eBay, not all of them are safe to use with your RV.

So why do we need adapters?

The answer is that not all campgrounds (and campground pedestals) are created equal. Some of them will have all three types of receptacles (a 20-amp, 30-amp and 50-amp outlet), but many of them will be 30-amp only, or maybe just a single 20-amp outlet in some rural campgrounds. Does this mean you’re SOL, or is there a way to plug in anyway?

Yes, but…

The answer is yes, but there’s no way to get blood out of a turnip. That is, you can’t make a 20-amp or 30-amp outlet give you the same amount of power as a 50-amp outlet. And sometimes you can use a 50-amp outlet to power a 30- or even 20-amp RV. You will also find that some older campgrounds have badly worn or miswired pedestals that may be not safe to plug into. And many times there are safe workarounds, but it always has to be done carefully with a full understanding of how much power is available and how much power your RV appliances can demand.

A deeper look….

First, let’s take a look at a full-service pedestal with 50-, 30- and 20-amp outlets. This is typically found in new RV campgrounds, and it does offer the most flexibility (and power) for your RV’s electrical system, no matter what shore power cord it has.

Note that I’m calling this a 100-amp pedestal because it should be capable of providing a full 100 amps of power at 120 volts (50 plus 50 amps). And in many cases it can also supply 30 amps and 20 amps at the same time. But there’s no guarantee it has been wired that way, so caveat emptor.

The candidates

Here, perhaps, is the most common type of adapter you might encounter. Let’s assume you have a 50-amp shore power RV but need to plug into a 30-amp outlet. Yes, technically the 50-amp connector should be wired for 240 volts, but in actuality it’s two separate legs of 50-amp power at 120 volts, and only the largest coaches use 240 volts. So a 30-amp to 50-amp adapter simply feeds the 30-amps of current at 120 volts into both hot legs of your 50-amp shore power cord.

Available power

This works, but with only 3,600 watts of power available compared to the 12,000 watts you should be able to get from a 50-amp pedestal outlet. From a practical standpoint this suggests you’ll need to do some manual load shedding by not turning on too many high-power appliances at the same time.

That means you probably can’t run your convection microwave and air conditioner at the same time, and your daughter’s 1,800-watt hair dryer can’t be combined with any other big wattage item. Don’t worry if you go over your 30 amps of allotted power as the circuit breaker in the pedestal or your RV’s power center should trip. Don’t shoot the messenger though, as it’s only doing its job.

Reverse it…

But what if you have a 30-amp shore power RV and you want to plug into a 50-amp pedestal outlet. Is that safe? Will it feed 240 volts into your 120-volt RV and blow it up? The first answer is if your RV power center is properly wired with a 30-amp master circuit breaker, then using a 50-amp to 30-amp adapter to plug your 30-amp shore power cord into a 50-amp outlet should be safe from overload.

However, note that this is technically a code violation that your campground (or the local inspector) may not allow. Still, the major manufacturers do build these things, and I agree that in many campgrounds the 30-amp outlets are so worn out that they’re a bigger hazard to plug into as it is.

So, as long as your own shore power cord and RV power panel are properly wired and maintained, there shouldn’t be any immediate danger of overheating the wire with too much current. But always be watchful of any hookup like this because there is a fire hazard if something goes wrong in your RV’s power panel.

What about 50- to 20-amp adapters?

Well, those are in their own extreme danger category since it would be way to easy to plug a 14-gauge extension cord (rated for 15 amps of current) into an outlet that can supply 50 amps of current.

And that’s a recipe for extreme overheating and a fire. If you don’t believe me, watch a video of me overheating a 14-gauge extension cord with 30 amps of current. In 5 minutes it’s approaching the boiling point of water, and I’m sure it would have caught on fire in another 5 minutes of over current. Watch this short video HERE.

However, while you really don’t want to use one of these cheap 50- to 20-amp dogbone adapters, I did find a version that includes a pair of 20-amp circuit breakers, one for each 20-amp duplex outlet.

Note that with the little red push-button circuit breakers, and the heavy wire rated for 50 amps of current, I think this version should be perfectly safe to use at a spare 50-amp pedestal if you need to run a couple of deep fryers or whatever for an outside party. You can buy one of these hard-to-find adapters HERE (when they’re in stock).

What about Y adapters?

You can get a double 30-amp male to single 50-amp female Y adapter from companies such as Southwire and Camco. They should work if you can get access to two different pedestals.

However, if both 30-amp outlets on the two pedestals are on the same incoming hot leg, then it’s possible to draw up to 60 amps of current through the 50-amp neutral. But even though that’s technically a code violation, there’s probably limited danger of actual overheating if everything else is clean and maintained. Still, you’ll want to carefully watch for overheating if you’re running a lot of appliances and air conditioners.

The big caveat is those 20/30-amp to 50-amp Y adapters, sometimes called 45-amp adapters since they have a 15-amp and 30-amp male plug feeding a 50-amp female outlet. If the pedestal is wired properly with a GFCI on its 20-amp outlet, then the combined neutral currents will cause the GFCI outlet or breaker to instantly trip. If not, then the GFCI has failed or somehow been disabled, which is a serious code violation.

Hockey puck adapters

I only like dogbone adapters from quality companies such as Camco and Southwire. That’s because nearly every adapter failure I’ve seen has been one of those super-inexpensive puck adapters that were likely not assembled correctly to begin with.

So I would look at any of these with a jaundiced eye. Plus they tend to twist the plug contacts out of the outlet from the weight of the cord hanging off of them, so I think they’re a bad idea in general, unless you can properly manage the cord weight twisting problem.

Electricity can be your best friend or your worst enemy if you don’t understand the rules. So let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.

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Mike
15 days ago

comment image Hi Mike,
While having my RV inspected (PA) I saw the shop had what you refer to as an adapter “Puck” (your picture of something similar is attached). It was made by Progressive Industries whose indoor RV electric monitoring system has worked great these last 4+ years of RVing. SO I bought the 30 AMP (supply) to 50 AMP puck-style adapter. Like you I found that the puck adapter is a bad idea. The weight of my 50 AMP cord immediately caused the puck adapter blades to pull partly out of the newly-serviced pedestal outlet! Knowing this was NOT good, I used a good-quality strap (NOT a bungy cord) which holds the plug in place – and I check it regularly. I wrote Progressive about this and have received no response. I guess I’m going to have to go back to a good dog bone adapter. Thanks for your incredibly timely tip on the inadequacies of these adapters!

WEB
16 days ago

Referring to “A deeper look….” above, now why would you call a full-service pedestal a 100 amp panel? I have wondered where this confusing term comes from. First you say it is because there are 50, 30 & 20A (= 100A) outlets, then you say it has 50 + 50 amps @ 120V. :-/
So is a 14-50R plug is actually a 100 amp plug, cuz it can deliver 100 amps? My 200 amp house panel is actually a 400 amp panel for the same reason or it is rated at whatever combination of breakers I put in there? I even see Home depot calls the full service panel an 80A panel…

WEB
16 days ago
Reply to  WEB

Addendum: I only have access to the 2008 version of the NEC code and it states “Where the electrical supply for a recreational vehicle site has more than one receptacle, the calculated load shall be calculated only for the highest rated receptacle.”

Gene M
18 days ago

It would be nice if you could publish a wiring diagram of a 50a to 30a adapter like the 30a to 50a in this article. Thanks

Al C
18 days ago

One good use for a puck adapter. I use a 30 to 20/15 puck regularly. I plugged a triple tap into the puck and on the triple tap is a digital volt meter and a “correct wiring” tester. Since I have a hardwired EMS, this allows me to get a quick check on the status of a pedestal. Puck adapter is great for this use because it saves a bunch of space and is always ready for use.

BadWolfe
19 days ago

Wow, another great article spelling out the concepts and issues in an easily understandable format. Thanks Mike!
(I had no idea there were all of these variables to consider, I would just see an adapter and want to try it to solve my power needs…. I now see some of them were not good choices.)