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Sunday, January 9, 2011

Is It Pre-wired for RV Generator?

We are considering adding a generator to our coach. We want a generator and have heard our model is prewired for one, however we are not sure. How do we tell, and what type should we get? Steven, (Berwick, PA) 

I'm assuming you have an older motorhome Steven. So, to know that a coach is pre-wired for a future generator installation, look inside the proposed generator compartment. It should be equipped with a louvered door to allow for the ventilation requirements of the power plant. Secondly, there will be an electrical box mounted somewhere inside that compartment. Called the generator “make up” box or “J” box, it will contain conductors that run from the generator compartment to the main panelboard distribution box, (breaker box), somewhere inside the RV. Or, it may be routed to a dedicated 30-amp receptacle located near the shoreline cord entrance, such as shown in the photo here.

At the main breaker panel, you may also find a separate circuit breaker labeled for the generator or at least space for one. Some coaches also come from the factory with an automatic transfer switch already installed. This device will automatically switch the source of AC voltage from the shoreline cord to the generator after it is started. If there is no automatic transfer switch on-board and there is a 30-amp receptacle at or near the shoreline cord, then you must plug the shoreline cord into the generator receptacle in order to power the coach. There may also be a plugged fuel line already run into that compartment as well. Plus the compartment will be metal-enclosed.

And don’t forget, you can always contact the coach manufacturer (assuming they are still around!). By providing them the model and VIN number of your motorhome, they should be able to tell you how that particular coach was outfitted as it left the factory.

As far as generator brand, there are quite a few nice models currently available. I’d suggest seeking out information for suppliers having a proven RV track record for starters, but I certainly wouldn’t rule out any of the newcomers to the RV market. I’d probably have to start from scratch and download info from any and everyone who currently makes an RV generator, making sure it is indeed approved for RV use. There are quite a few options today. Do your homework and compare size, output rating, cost, fuel efficiency, etc., prior to making the decision.

Don’t forget, you’ll have to first mathematically “size” the RV to determine how much power you’ll actually need. In other words, based on the 120-volt devices in your rig, how much wattage will you actually require? The answer to this question will determine what “size” generator you should consider. Once you’ve done the math, add another 20-30% for a safety buffer; keeping in mind, you’ll also be plugging in devices like coffee makers, curling irons, etc., in addition to the built-in or “hard-wired” AC loads associated with your particular motorhome. The bottom line; always have more output capacity available than you’ll typically need at any given time.

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