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Old 03-22-2017, 06:10 PM   #1
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A/C panel on wall

I have a 2007 Surfside. Took it in today because the rear air conditioner has never cooled the rear bedroom correctly. I bought it from a dealer two years ago and is a scam artist . Today the dealer told me this motorhome is not designed for both air-conditioners to run at the same time . It was advertised with 50 amp service and it only has 30 . The control panel on the wall has one thermostat and both air-conditioners have always come on since I bought it with the shed lights coming on intermittently . Can someone show me a picture of what their control panel on the wall looks like so I know if this has been changed out as well ?
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Old 03-23-2017, 06:12 PM   #2
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A 50 amp RV has two 120v 50 amp lines, for a total of 100 amps (12,000 watts) of 120v power. The plug has 4 prongs. 30 amp RV service is on line of 30 amps, (3,600 watts) of 120v power. The 30 amp plug has only 3 prongs. It's very common for a 30 amp RV that has 2 A/C units to use a control panel to control the amperage draw by alternating front and rear A/C. If you have a generator, it's very possible it might be 5,000-5,500 watts and can run both A/C with no problem.

Not sure the dealer was a scam artist, perhaps they just mis-stated the RV features. NEVER take a salesman's word, always verify, verify, verify. OR...get it in writing.

What make, model, of control panel (Electrical Management System) do you have? Easier for folks to understand and let you know if it's a National installed EMS or not. Question is, does it do it's job?


xrated, thanks for catching my brain fart. I was still able to edit my post!
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Old 03-23-2017, 06:18 PM   #3
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Originally Posted by BFlinn181 View Post
A 50 amp RV has two 120v 50 amp lines, for a total of 100 amps (6,000 watts) of 120v power. The plug has 4 prongs. 30 amp RV service is on line of 30 amps, (3,600 watts) of 120v power. The 30 amp plug has only 3 prongs. It's very common for a 30 amp RV that has 2 A/C units to use a control panel to control the amperage draw by alternating front and rear A/C. If you have a generator, it's very possible it might be 5,000-5,500 watts and can run both A/C with no problem.

Not sure the dealer was a scam artist, perhaps they just mis-stated the RV features. NEVER take a salesman's word, always verify, verify, verify. OR...get it in writing.

What make, model, of control panel (Electrical Management System) do you have? Easier for folks to understand and let you know if it's a National installed EMS or not. Question is, does it do it's job?
A 50 amp RV has two 120v 50 amp lines, for a total of 100 amps (12,000 watts) of 120v power

Fixed that ^^^^^ for ya!
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Old 03-23-2017, 07:14 PM   #4
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Originally Posted by Topgunwinner View Post
I have a 2007 Surfside. Took it in today because the rear air conditioner has never cooled the rear bedroom correctly. I bought it from a dealer two years ago and is a scam artist . Today the dealer told me this motorhome is not designed for both air-conditioners to run at the same time . It was advertised with 50 amp service and it only has 30 . The control panel on the wall has one thermostat and both air-conditioners have always come on since I bought it with the shed lights coming on intermittently . Can someone show me a picture of what their control panel on the wall looks like so I know if this has been changed out as well ?
I just bought the exact same RV last week and am in the process of figuring out how everything is wired. Of course, yours may be different from mine but here's what I know about mine so far.

Although NRV called it a 50A unit it is not exactly a true 50A service. The shore cord does have a 50A male connector but that's where the 50A wiring ends. What others tell you about 50A is valid data but does not apply to the way NRV wired my unit.

What it actually has is one shore cord leg with a 30A breaker feeding to the main panel. All loads except one A/C are fed thru that panel. The other leg of the shore cord feeds the second A/C thru a 20A breaker independent of the main panel.

When plugged into a 50A service you can run both A/C's with no issues as long as you don't turn on other loads and draw a total or more than 30A (including A/C) thru the main panel. In the event you overload the main panel, by using a hair dryer or toaster etc., there is a current sensing unit that will shut down the A/C that operates thru the main panel in the bedroom. The A/C running on the dedicated 20A leg will continue to operate.

If you open the drawer unit to the rear of the main DC/AC breaker panel. remove the drawer racks and remove the bottom panel of the cabinet you will find your converter and the control unit for current sensing and air conditioner staging.

I have yet to dig into the schematics for the current sensing unit and air conditioner control circuitry. Additionally, I'm not exactly sure how things work when you plug the motorhome into a 30A service pedestal.

As I dig into it more I will be glad to share whatever I find out if you want to PM me. I can take a picture of my thermostat but I bet ours are exactly the same. I'll do that tomorrow. Since I've only had the unit for less than a week I'm sure there are a lot of things you can probably tell me about it too.
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Old 03-23-2017, 07:41 PM   #5
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Quote:
Originally Posted by hohenwald48 View Post
I just bought the exact same RV last week and am in the process of figuring out how everything is wired. Of course, yours may be different from mine but here's what I know about mine so far.

Although NRV called it a 50A unit it is not exactly a true 50A service. The shore cord does have a 50A male connector but that's where the 50A wiring ends. What others tell you about 50A is valid data but does not apply to the way NRV wired my unit.

What it actually has is one shore cord leg with a 30A breaker feeding to the main panel. All loads except one A/C are fed thru that panel. The other leg of the shore cord feeds the second A/C thru a 20A breaker independent of the main panel.

When plugged into a 50A service you can run both A/C's with no issues as long as you don't turn on other loads and draw a total or more than 30A (including A/C) thru the main panel. In the event you overload the main panel, by using a hair dryer or toaster etc., there is a current sensing unit that will shut down the A/C that operates thru the main panel in the bedroom. The A/C running on the dedicated 20A leg will continue to operate.

If you open the drawer unit to the rear of the main DC/AC breaker panel. remove the drawer racks and remove the bottom panel of the cabinet you will find your converter and the control unit for current sensing and air conditioner staging.

I have yet to dig into the schematics for the current sensing unit and air conditioner control circuitry. Additionally, I'm not exactly sure how things work when you plug the motorhome into a 30A service pedestal.

As I dig into it more I will be glad to share whatever I find out if you want to PM me. I can take a picture of my thermostat but I bet ours are exactly the same. I'll do that tomorrow. Since I've only had the unit for less than a week I'm sure there are a lot of things you can probably tell me about it too.
Interesting! Your shore cord has a 50 amp, 4 prong, plug. To plug into a 30 amp outlet, you'll need an adaptor. That adaptor will connect the one hot (30 amp) prong to the two hot prongs of the 50 amp plug. The 30 amps won't be split evenly, 15A and 15A, but will use up to 30 amps in one leg, (the one with the 30A breaker) The other leg can only draw as many amps are left to draw from the 30A pedestal. If you try to draw more, the breaker in the pedestal would trip. I'd guess your EMS panel should do it's job of shedding amperage to keep you within the 30A limit.

50A RV service, as I said earlier, is two legs of 50A. What I left out is that the two legs are 180 out of phase of each other. Your EMS detects when the two legs are in the same phase (as would be the case in a 30A to 50A adaptor) and goes to work limiting it appropriately.
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Old 03-23-2017, 07:45 PM   #6
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BFlinn181 wrote:
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xrated, thanks for catching my brain fart. I was still able to edit my post!
No worries.......I have them myself, but probably no more than 15 to 20 day!
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Old 03-24-2017, 07:17 AM   #7
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BFlinn181,

Your assessment is mostly correct but not 100%. Since one leg of the 50A shore cord feeds thru a 20A breaker, that circuit will be limited to 20A regardless of what any EMS might do and regardless of what adapters are used. The reason there is a 20A breaker is that particular (probably A/C) circuit is wired with #12 wire and the other (main) leg is wired with #10.

I have not yet determined if the unit even has an EMS but suspect it does have at least a current sensing air conditioner control of some sort. I'm still investigating. If anybody has any technical documentation it would sure be helpful. I have the owners manuals but they provide limited information.

Additionally, I believe these units were originally furnished with a 1,000 watt inverter. The one in my unit appears to have been removed. There is a space on the wall where a control panel used to be and all the wiring for an inverter is taped and bundled in one of the compartments. In the brochure it states that units ordered with 2 air conditioners have to also be ordered with "50A service", 5500 watt generator and the 1,000 watt inverter.

For some reason there is a branch circuit labeled "INVERTER" in the main panel. I can't imagine what that branch circuit might be for. I don't think they would back feed the main panel thru a branch breaker. The unit does have a converter so I doubt it had an inverter/charger from the factory. I suppose it's possible the unit originally had an inverter/charger that was removed and a stand alone converter was installed.

Another thing I have to track down is why are there two breakers in the main panel labeled "A/C 1" and "A/C 2"? That would seem to indicate the 20A shore leg does not feed one of the A/C units. In that case, what does it feed?

The hunt continues today then the rains come and I will have to put off the quest for answers until things clear up again. The joys of purchasing a used motorhome. I think this unit has had 3 owners before me. No telling what the previous "experts" have modified. It's a difficult task running down wires with no drawings. Also, all wires are encased in that black corrugated chaff protection so they all look alike.
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Old 03-24-2017, 09:17 AM   #8
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I never suggested the 20A leg could be tricked into handling more than 20A. If your breaker panel has a factory labeled breaker for an inverter, it most likely was equipped with an inverter/charger. A straight inverter would get all it's power from your 12v house batteries and it's 120v output wouldn't be wired through the breaker panel. You might check if the 'inverter' breaker is now wired to power the converter/charger. A 1,000 watt inverter is pretty small, it would have limited capacity.

In a typical RV 50A power panel, the two legs of 50A power are split between the two sides of the panel. At the top of the panel are two 50A CB, one for each leg. Everything on one side is powered by one 50A leg, the other side is powered by the second leg of the 50A shore cord. The challenge for the builder is to evenly split the loads to both legs of the 50A service.

I find it puzzling that National would, in 2007, build an RV with 50A cord and power panel, but only limit one leg to 20A. The price difference in #10 and #12 wire is very little, and the added complication of needed a power shedding EMS is just not worth it.

In older RVs, from the '90's, before there were many 50A pedestals in campgrounds, RVs big enough to require two A/C often had 30A service to one A/C and all outlets in the RV, the second A/C is only available when the generator is used. To operate the second A/C on shore power, an EMS had to be used that ensured both A/C wouldn't try to operate at the same time.
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Old 03-25-2017, 09:17 AM   #9
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Yeah, I'm more and more convinced the unit was 30A only from the factory and someone "upgraded" it to 50A in a jury rigged sort of way. So far it all looks safe.

This is my 7th motorhome and all have had their own little quirks.

Since electricity was my field in my working days I'm sure I'll get it all run down eventually. There is someone else on here looking for information about the same unit but I'm not sure how much help I'll be to them since my unit appears to be unique.
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