We stopped at an RV park (an old and poorly maintained KOA) in hot weather. Plugged in the 30 amp cord. The power pedestal looked sketchy -- the socket was chipped and improperly mounted. Fired up the air conditioner. It worked, sort of, but made barely-audible low rumbling sounds and did not put out enough cool air, which is not its usual behavior.Came back home. Plugged into my 20 amp garage circuit -- the a/c worked just fine. Conclusion -- the power in the RV park was not up to snuff. I don't know the technical term, but it was not enough juice.Is there a metering device that can be used to avoid or detect this problem? And how common is this in the US? (I know it is an issue in Mexico.)(Note to moderator: I was going to post this in the Tech forum, but this is a problem that is specific to RV parks, so that is why I posted it here. If it is in the wrong place, please forgive me.)

This Progressive 30 AmpAlso available in 50 amp if necessary.

I suggest you get yourself a Progressive Industries 30 amp EMS. It will drop out (cut off power) if there's anything wrong with the supply. Armed with that information shown on the display, you can inform the park owners, get moved to a different space, or they'll get someone to fix the problem. I did that successfully several times. Even in Mexico.But without the EMS, you can usually get a park to let you move.The rule of thumb is never operate your A/C when the line voltage is outside the range of 108 to 133 Vac. The lower voltages are bad for the A/C motor especially. You should at least have a line voltage monitor inside your RV where you can glance at it before turning on any heavy draw equipment, like the MW or A/C. If it dips too much when you turn something on, there's a high resistance somewhere.I always carry a spare head for my umbilical cord because those can go bad...especially the 30 amp head. I also carried a new receptacle with me in Mexico and would loan it to RV parks when necessary.

Every summer posts appear concerning low voltage at 30A sites and more so in older or non maintained parks. Not many posts for 50A sites.Yes a EMS will detect and shut down with low voltage and no more A/C. Another solution is a autoformer that boots voltage.

The simplest metering device is a voltmeter. Not 'up to snuff' means low voltage.

and running your ac on low volts could cook it.

How to protect against poor RV park power? | Good Sam Community

33 Replies

2naEagle
Explorer
Aug 08, 2018
JoeH wrote:
First I verify the pedestal is OK with tester I made that checks both legs of the 50 amp plug
Assuming all is good there,
I have the following configuration :
pedestal-> surge guard -> autoformer -> progressive EMS.

Then if that fails, the genset AGS will start up.

That is the way I do it also.
I thought I was the only one doing all 3:)
JoeH
Explorer III
Aug 08, 2018
First I verify the pedestal is OK with tester I made that checks both legs of the 50 amp plug
Assuming all is good there,
I have the following configuration :
pedestal-> surge guard -> autoformer -> progressive EMS.

Then if that fails, the genset AGS will start up.
ReneeG
Explorer
Aug 04, 2018
Today's RVTravel.com article on pedestal power is timely. Here's a link to the article along with a printable checklist.
Lynnmor
Explorer
Jul 31, 2018
You can buy the DM55-1 voltmeter for $3.65 on the popular auction site.
profdant139
Explorer II
Jul 31, 2018
Thanks for those tips!!
valhalla360
Navigator
Jul 31, 2018
profdant139 wrote:
Just on an interim basis, before I get the perfect tools, how would I use an ordinary multimeter to monitor the voltage while the air conditioner is running? Or is this something that I would do by unplugging my power cord from the pedestal and sticking the tips of the meter into the socket?

Plug the trailer in and before turning things on:
Check the voltage before turning the air/con on.
Check right after turning the air/con on.
Check periodically (more is better but you have to be reasonable)
Watch the voltage when it kicks on or off (it will typically change a bit but if it doesn't spring back up to a reasonable voltage in a few seconds, consider turning it off.)
loggenrock
Explorer
Jul 31, 2018
Here's an example of a plug in volt meter from Amazon - less than $10 - Yeeco Wall Flat US Plug LCD Digital Voltmeter. Makes a nice little nightlight, too! If I find a tired looking 30A receptacle, I also use the 50A to 30A "dogbone". Many more rigs run 30A, so those receptacles get worn out sooner than the 50's. Like others, I run a Progressive Industries 30A portable "EMS" that has shut power down to our rig multiple times if the park voltage drops - even had 1 place with too HIGH voltage which cut it off. Well worth the somewhat pricey investment.
2naEagle
Explorer
Jul 30, 2018
> How to protect against poor RV park power?

Electrical Management System (EMS)

I Prefer the hardwired.

Autoformer

I also use the Internal Mounting Kit.
pianotuna
Nomad III
Jul 30, 2018
Hi profdant139,

Voltage needs to be checked while "under load".

Stick the prongs of the volt meter into a wall socket in the rv, while the roof air is running. 107 and above you are golden.

I leave a kill-a-watt meter plugged in all the time.

profdant139 wrote:
Just on an interim basis, before I get the perfect tools, how would I use an ordinary multimeter to monitor the voltage while the air conditioner is running? Or is this something that I would do by unplugging my power cord from the pedestal and sticking the tips of the meter into the socket?

Or should I just call 911 before doing that?? ;)
Jim
Explorer
Jul 30, 2018
profdant139 wrote:
Just on an interim basis, before I get the perfect tools, how would I use an ordinary multimeter to monitor the voltage while the air conditioner is running? Or is this something that I would do by unplugging my power cord from the pedestal and sticking the tips of the meter into the socket?

Or should I just call 911 before doing that?? ;)

Because of the watts consumed by the A/C is huge compared to most other electrical items in your RV, just put it where it's convenient for you to take a measurement. Most of us buy the plug it type and put it into one of the outlets in the kitchen area.

That will give you a general sense of what the voltage reaching the A/C is. Of course you'd want to avoid turning on the MW, toaster, or hair dryer at the same time. I use to keep a list of consumption vs. various appliances when I had a 30 amp RV, now with a 50 amp, it's not as important.