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Old 02-12-2015, 09:28 PM   #1
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Do all 50 amp coaches have an EMS?

2002 38' Diplomat
Keith & Shirley
Durant, OK
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Old 02-12-2015, 10:16 PM   #2
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Originally Posted by ruffian View Post
Do all 50 amp coaches have an EMS?
No they don't .... however, a quality Progressive EMS can be added. I installed the hardwired unit in my last two MHs. I would do it again.

George R. - Fulltiming since January '03
2007 Newmar Mountain Aire 3991
2012 Chevy Malibu LT1
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Old 02-12-2015, 11:55 PM   #3
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With 220V, we have line 1 & line 2. Each is 120 V 50A, when plugged into a 50 A receptacle. We can assume the internal electrical loads, like AC 1 & Ac 2 are wired to separate incoming 120 volt lines.

So when 50 A service is unavailable and we have to downgrade to a 30 A service, how are we able to chose to use those appliances wired to Line 2?

Are power panels without an EMS using only one of the two incoming 50 A 120V legs to energize the main buss in the coach electric panel. Without an EMS, how does the system power the appliances normally powered by the 50A leg dropped when using a 30A adaptor?

My EMS has been acting up and because of the high cost of parts to repair it, as a test, I disabled Line 2 of the incoming 220V source. Connecting the main buss together in the power center gives me a total of 50 amps to run everything needed if I use a little care about turning on the electric HW heater while running both AC's, then starting the MW. I know it won't quite work.

So instead of counting on an EMS to count amps for me, I do it manually. Very little effort and goes a long way towards simplifying my panel.
2002 38' Diplomat
Keith & Shirley
Durant, OK
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Old 02-13-2015, 06:26 AM   #4
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Originally Posted by ruffian View Post
Do all 50 amp coaches have an EMS?
EMS Energy Management System that sheds loads when you try to draw too much power on 30 amps... NO

EMS Progressive Industries calls their Surge Guards Energy Mangers,,, NO

My coach as an example, Neither of the above (I do have a portable surge guard but it is not part of the choach)

Owner's Brain... There used to be a TV show, Green Acres, where the lead characters were Mr. and Mrs. Oliver Wendell Douglas.

Mr. Douglas understood that the generator they used for electricity had limits and it would run long and well provided only he used electricity.

But alas even though all the appliances had a number on them and you could not plug in more than a given nmber (Forget what it was) his wife would plug in way more than the genny could handle and OFF went everything.

In short, His brain was an EMS.. her's. not so much.

I call that Eva Gabor Disease since she played the wife. Many have that problem.
Home is where I park it!
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Old 02-13-2015, 06:34 AM   #5
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Both L1 & L2 are powered when a 50/30 Adapter is used to plug to a 30A outlet, so you don't have to choose. However, you do have to be aware that the available power is limited to only 30A (3600 watts) instead of the 100A (12,000 watts) you have with 50A/240v shore power.

When you have thermostat-controlled power usage (fridge, water heater, a/c), some people fund it hard to manage the demand themselves. That's where an EMS helps - it watches the loads for you and shuts off appliances when demand exceeds supply. But you may still lose power unexpectedly when the EMS Sheds a load you were using. No real magic - it just avoids tripping the external shore power breaker.

A straight-forward alternative approach is to run the fridge and water heater on propane when the shore power is limited, thus taking those appliances out of consideration.

I think you will find, however, that the vast majority of 50A rigs do come with an EMS. Only the most basic (low priced) models will lack it).
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
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