Need Some Electrical Help

**Paul & Deb** · 03-26-2015, 05:54 PM

I'm placing an order for an Onan generator I am having installed and need some advice. As part of the system I will need a 50 amp transfer switch. I have decided on an automatic switch but I have a choice of either a 10 or 12 circuit switch. They are both the same price but I don't know which one I should get. When I look at my power panel in my 337RLS I have 11 breakers and 11 fuses. My totally uninformed feeling is that I should purchase the 12 circuit model but I don't really know if the number of fuses in my panel has any bearing on how many "circuits" I will want to be switching with the transfer switch.

Anyone have knowledge of this stuff that could give me some guidance?

I don't know of this helps pr not:

scott42blue · 03-26-2015, 06:17 PM

50 amps will be 50 amps regardless of how may circuits involved. Not to be rude but, I would strongly suggest you try to work with a local RV or Marine place to install gen set. Many issues, including back feeding, grounding ,fuel source, ventilation for gen and CO. Onan has a great installer manual that goes in detail how to do it.
Be safe

**Paul & Deb** · 03-26-2015, 06:23 PM

Thanks for responding Scott but your comment doesn't address my question unless I am missing something. I know I need a 50 amp transfer switch but are you saying I could get a 50 amp transfer switch with 1 circuit (if such a thing existed) and that would work? I take it you're telling me that it doesn't matter how many circuits are involved, it only matters that since I have a 50 amp service trailer I just need to worry about getting a 50 amp transfer switch.

**Abqscott** · 03-26-2015, 06:57 PM

I have an Onan 5500LP that I have had in two rigs. The transfer switch essentially sends all of its power to the main panel mine does not have it broke down into individual circuits works great. My first install was completed by our local Cummins/Onan dealer. When we moved it into our new Solitude we did it. I don't think local RV dealers work on near as many as the semi repair shops do and they did a good job.

**Paul & Deb** · 03-26-2015, 07:46 PM

Originally Posted by Abqscott

I have an Onan 5500LP that I have had in two rigs. The transfer switch essentially sends all of its power to the main panel mine does not have it broke down into individual circuits works great. My first install was completed by our local Cat/Onan dealer. When we moved it into our new Solitude we did it. I don't think local RV dealers work on near as many as the semi repair shops do and they did a good job.

Do you happen to know the brand and model number of your switch Scott?

**Cate&Rob** · 03-26-2015, 07:53 PM

Hi Poppy,

The connections on the transfer switch are not the same as the circuits in the AC breaker panel. The transfer switch (manual or automatic) switches the power coming INTO the breaker panel.

There are four wires feeding power into the AC panel. Two "hot" wires, usually called L1 and L2, red and black or black and black. One common or neutral wire, usually labeled N and white in colour. The fourth wire is the ground or safety ground and is green.

To supply power from an on board generator, rather than shore power, all four of these connections have to be completely disconnected from shore power and appropriately connected to the generator. This is really important, because if not done correctly, the shore power plug prongs can become live and this is dangerous.

A common (no pun intended) misunderstanding is that the ground (green) wire does not need to be part of the switching . . . but it does. This would take a long explanation, but to simplify, ground and common (green and white) come together only at the source of the power. For shore power, this is way back at the main campground power panel . . . but for your generator, this is at the generator.

As noted earlier, if you are not really comfortable with the logic behind this, hooking up the generator might best be contracted out to a qualified electrician.

Just my 2 cents worth . . .

Rob

scott42blue · 03-26-2015, 08:03 PM

You need a 50 amp automatic transfer switch. It will connect to shore power or generator automatically. I would buy one from a RV place as most electrical supply houses or big box retailers will not understand what you need. When in doubt bigger is always better with electrical stuff. If not sure I would buy 12 circuit over 10. Do a search on Amazon for RV transfer switches ( 50 amp )
Also RVs are a little different than houses as they split the 2 hot legs and may need a bigger ( white ) or neutral wire. Loads can become unbalanced when different demands are put on system.
Hope this helps

scott42blue · 03-26-2015, 08:16 PM

Rob has given excellent advise !!

**Abqscott** · 03-26-2015, 08:20 PM

Originally Posted by Poppy's 5th Wheel

Do you happen to know the brand and model number of your switch Scott?

I think the brand is Parallax.

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**Cate&Rob** · 03-26-2015, 09:15 PM

Hi scott42blue,

Thanks for the endorsement !
I am relatively new to RVs but have been amazed to learn that many campers think plugging into the "50 A" receptacle gives them 20 amps more than plugging into the "30 A" receptacle. They don't understand that the 240 vs 120 voltage difference actually gives them 70 more amps at 120 V . . . and some associated potential risks of bringing 240 volts aboard.

Rob