Motorhome Electrical Modification Help

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  #1  
Old 02-11-14, 09:07 AM
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Motorhome Electrical Modification Help

Hi all. I have an older motorhome with 30-amp service. As a result, there is a switch above the microwave that will allow you to run the microwave OR the front a/c unit, but not both. The rear a/c unit is wired directly to the generator and therefore only runs when it's fired up. The generator feeds the breaker panel, too, so the only way to run both a/c units currently is with the generator running. This is fine with me (and a required limitation given the 30-amp service), however what's not fine is only being able to run the front a/c unit under shore power.

I could easily install a switch after the existing micro/AC switch to switch between the a/c units. BUT, that would mean disconnecting the generator from the rear unit. What sort of switching arrangement could I install to safely add the ability to power the rear a/c unit under shore power while preserving the ability to run both units off of the generator?
 
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Old 02-11-14, 11:27 AM
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Do you plan on having both A/C units on the generator at the same time? Will the generator be able to handle the load? I assume there was a reason the mfg did not put both units on the generator.
 
  #3  
Old 02-11-14, 11:51 AM
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Actually it's the opposite (I apologize that it's difficult to describe in text). The manufacturer limited the load for the shore power to 30-amps. As a result, only one a/c unit is wired up to the breaker panel.

Both a/c units are hooked up to the generator from the factory - one through the breaker panel (there's an automatic transfer switch to switch between shore power and generator power feeding the panel) and the other directly to the generator (there's a breaker somewhere according to the diagram, but it's separate from the main panel). This way, both a/c units will run off the generator but only one (the front one) will run when plugged into the shore power.

Since the rear unit (again, only runs via the generator) cools the bedroom, I would like to have the option to switch between the 2 a/c units when plugged into shore power. I don't intend to try to run both as that would overload it the system. But, the way it's wired up from the factory is that the rear unit will only run with the generator and the front will run on both shore power and generator. Some newer units still have this arrangement to limit the draw from campground utilities, but they do give you the option of choosing which a/c unit to run when plugged in. I'd like to wire up that capability while still being able to run both off of the generator as I can today.

The easiest way to do it is to install another switch to switch the shore power between the 2 units, but I would have to disconnect the rear unit from the generator to prevent the possibility of feeding it from both the generator and shore power simultaneously. Unless, of course, I can install some sort of automatic or manual switch. Which is my question
 
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Old 02-11-14, 12:30 PM
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Here is a like to so Cam Switches. They have some rated 25 Amps 250V.
http://www.kayceeindustries.com/pane...20switches.pdf

I think what you have is an existing transfer switch with your panel as the load that switches between the 30amp cord and the generator. At the generator you probably have two breakers, one for the rear A/C and one that goes to the transfer switch that supplies the panel. In the panel you have a breaker that supplies the Front A/C. You could install a Cam Switch for the rear A/C being the load and with 2-positions (1)=Gen and (2)=Panel. You just have to remember to not run both A/C units at the same time on the Generator. Don't know if you have any room in the panel to add a breaker to supply the alternate feed to the rear A/C through the Cam Switch.
 
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Old 02-11-14, 01:07 PM
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Yes, that's exactly what I have. I have not located the generator breakers yet, but I haven't looked too hard either. They may be under a cover in the generator compartment.

The main panel is in a closet across the hall from the transfer switch (which seems inconvenient from a wiring perspective, but that's how they did it).

The generator wiring diagram shows what you describe: one feed directly to the 2nd ac unit and the other to the transfer switch which in turn feeds the panel. I like your idea, but the issue is running both A/C units with the panel (shore power), not the generator. I would have to remember not to run them both when it's plugged into a 30-amp campground service. The system is designed to run both a/c units off of the generator (though one is fed through the breaker panel and the other from the generator directly).

I also have room in the panel for another breaker for the rear a/c but I'm having a hard time envisioning how/why I would do that....
 
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Old 02-11-14, 03:33 PM
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Here is what I was thinking to control of the A/C units with a Cam Switch.Name:  RV AC Units ON Gen.jpg
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In the Generator position you can run both units.
In the second position you can be on shore power and turn off the rear unit
In the third position you can run the rear unit from shore power and the front unit will not operate.

You can talk with the Cam Switch supplier and they can set up the correct configuration for each position.
 
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Old 02-11-14, 05:22 PM
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Wondering if you can change the power center to 50 amp and hard wire the rear a/c to the breaker box so you can run both at the same time....

Just a thought.

What motor home is it?

What panel do you have? parallex?
 
  #8  
Old 02-12-14, 06:37 PM
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Thanks bahtah - that looks like it would work! The diagram is great!

Lawrosa - I don't know what I would need to do to bump it up to 50 amps. I'm new to the camping thing, but from what I understand the 30-amp service is more common at campgrounds. Bumping it up to 50-amps might limit my options. But if I were to go that route, I would assume that I'd have to upgrade the shore power cable as well as possibly the cabling between the transfer switch and panel. I'm not sure what brand the panel is, but it's in an '84 Tiffen Allegro. It appears as if back then they used residential-type stuff. It looks like a residential panel, surface mounted. There's a lot of open spots in it for breakers.
 
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