Progresive Industries EMS

I was at the same state park last year as I am now and was concerned about low shore power voltage during the hot period of the day. I have a PI unit and the voltage never got low enough that the PI shut it off to my 5'er. I was still concerned about my a/c's and low voltage so I looked up the operating specifications for my two Coleman units. I was surprised to see they are designed to operate at 115V, NOT 120V as I had thought. So the low of 108-109v that I have seen is just 5% or so lower than the design voltage of 115V. Why does my PI shut off at 104? Because 115V less 10% is 103.5V which is the absolute low to operate the a/c's. That is why the PI, and others, are set to shut down the power at 104V.

Well I ordered the ems-pt50c and MY goodness,
why didn't you guys tell me it was so huge !!!

From all the pics I had seen I thought it was 4" wide x 8" tall and maybe 2" deep

This thing is 15" tall and maybe 6" thick and wide !!!!!!!!!!!!


Not that it's a problem - but that almost borders on NOT portable :)

Hi Bobbo,

My goal was to have the rv appear to be on shore power at all times, so in my case there was no "extra" cost. What fits for me doesn't necessarily fit for others.

Yes my "solution" works because I never plug in the rv without checking the power source. I use: kill-a-watt

watt meter



Outlet tester.

outlet tester



ems from PI is good and well designed. If you have a 50 amp RV I think it is worth considering. If you are a 30 amp rv (and I am), then, in my opinion, it is close to the Emperor's new clothes.

pianotuna wrote:
Hi Steve,

I meet low voltage needs by doing double conversion. Converters can tolerate quite low voltage (some right down to 95 volts). I plug in just my converter, and plug the rest of the RV into my inverter.

That would cost more for a newby to properly set up than just getting the PI EMS! It would involve more batteries, a larger inverter, heavier wiring, etc. The PI would be more cost effective.

Also, does your solution protect from reverse polarity, miswired pedestals giving 240v instead of 120v, open grounds, etc.?

Hi renoman,

What else besides the converter was running when it fried from low voltage. I've regularly run my PD at 100 volts and Iota claims 95 volts (at reduced output, of course).

I'm much more likely to get an autoformer than a surge device.

It was my converter frying under low voltage that prompted me to get the PI EMS in the first place. Priceless piece of equipment.

Hi Steve,

I meet low voltage needs by doing double conversion. Converters can tolerate quite low voltage (some right down to 95 volts). I plug in just my converter, and plug the rest of the RV into my inverter.

Actually most of my camping is boondocking so shore voltage is mostly a non issue for me. For example my last trip was 3 weeks and 3000 miles. I only stayed at campgrounds 3 nights.

pianotuna wrote:
Hi renoman,

If the local power grid takes a direct "hit" from a lightening strike your PI ems will not protect you from the surge. So, it would be better to go and unplug. (don't forget a hard hat Lol)

The PI is the best of the best that RV'ers can afford. It doesn't meet my needs for low voltage protection, so it is useless to me.

renoman69 wrote:

pianotuna wrote:
Hi,

I'd simply move to my inverter.

.......run out to the breaker panel and fiddle with the power cord in the pouring rain and hail? No thanks. I love my PI EMS.

Please explain your low voltage need and how you are meeting it. Enquiring minds.

Had issues with power at a campground over the 4th of July - low voltage - dropped below 104 volts many times. I like out remote indicator - nice to see what the voltages are at the campground and how much current the rig is drawing.

Progressive Electrical Management System - Hardwired 50A w Digital Remote Display.

Hi renoman,

Yes it does--but only at 104 volts. I go no lower than 108, so the ems is useless for me personally.

If I could find a 4000 watt PSW inverter that was reliable I'd buy one and just plug in the converter 100% of the time.