Inverter and Auto Transfer Switch

[helix528]

I'm working on a project on my 5th wheel to add an Inverter, with a Auto Transfer Switch. I am trying to make it as automatic and fool proof as possible. I want to power just wall receptacles, and not AC, Micro, Water Heater, Fridge, power converter etc. I've seen some installations where the whole RV is powered by the inverter, and they just shut off breakers for the items they don't want drawing power. I want to avoid this scenario and keep it all automatic. So my idea is to feed power from the one breaker that controls the majority of the plugs. I would pull the romex that is currently on that breaker, and wire it to the output load of the transfer switch, then wire the breaker to the AC Input 1 on the transfer switch, and the input 2 would feed from the inverter. See the attached diagram.

My biggest concern, is with this method, when running on inverter power, the receptacles are not behind the breaker. They are only running through the breaker when on shore power. Is the internal protections of the inverter enough, or is what I've mapped out not going to work?

I cant get the wiring diagram jpg to work, but you can see it here
https://www.dropbox.com/s/l1aadigxn7gwqps/Trailer%20Wiring.jpg?dl=0

[dmck413]

There should be a fuse on the output of the inverter.If this is rated for your wire size you are good. If not add an inline fuse.

[theoldwizard1]

First, if you have not purchased an inverter, buy one with an automatic transfer switch built in. Without those other loads, you probably only about 1000W inverter so checkout a Samlex Inverter/Chrager/Transfer Switch

Second, you are correct about requiring a fuse/breaker AFTER the inverter ! THIS IS PROBABLY NOT CODE COMPLIANT, BUT THIS IS WHAT I WOULD DO.

Get a 240V fused A/C disconnect box. Run the hot from the shore power plug to one of the input of one of the fuses. Split the output of that fuse and run one of the wires to the hot inut of the inverter/charger/transfer box and the other to the non-inverter powered circuits in your RV. Run the hot output of the inverter to the other fuse input and then the output of that fuse to all circuits that the inverter is covering.

HERE IS THE TRICKY PART ! Do NOT connect the neutral leads from the inverter inside the box to the neutral bar ! The neutral from the inverter covered circuits should connect to the neutral of that circuit. The neutral from the shore power cord should only connect to the non-inverter covered circuit and to the inverter input.

ALL grounds can be bonded inside the box to the neutral. The first outlet on both circuits should be a GFCI.


THEORY OF OPERATION
When on shore power, all power passes through the first fuse before going to both the inverter and the non-inverter covered circuit. This would likely be a 30A fuse. The transfer switch passes current from its input to its output and then to the second fuse which would likely be a 15A fuse.
When NOT on shore power, everything on the non-inverter covered circuit is dead (including the battery charger). Everything on inverter covered circuit is powered through the second fuse. Bonding is done inside the inverter/charger/transfer switch.


WARNING ! Proceed at your own risk ! I doubt a licensed electrician would install this !!

[time2roll]

Two branch circuits? Get two transfer switches.

Transfer switch has two input, one output.

Remove the branch circuit from the breaker and panel (H,N,G) and attach to the switch output. Attach new romex from breaker to input 1 and the inverter to input 2 of the switch. Repeat for second transfer switch and you are good to go.

Check that the fridge and converter are not part of these branch circuits. If they are you need to move the converter to another branch or add a breaker to have on a separate circuit. For the fridge you can set to propane only or move same as the converter.

I have mine set up like this and it has been flawless. And yes power goes through the breaker.

https://www.donrowe.com/KISAE-TS15A-Automatic-Transfer-Switch-p/ts15a.htm
20 amp also available.

[wa8yxm]

I will make it as easy as possible

Instead of an "inverter" get an "Inverter/Charger" A suggestion is somethign like the Xantrex Freedom XC-2000 I will give you the counter on that specific in a bit.

It hooks up like this

Main panel--30 amp branch----Freedom XC---Sub panel--TV, MICROWAVE, GFCI or other outlets) Each circuit has itss own Sub Panel Breaker

Notes:
A Sub panel DOES NOT HAVE Neutral and Ground bonded (Neither should an RV's main that is done at the park end of thigns)

Second: On my Freedom XC I really DO NOT LIKE the way the 120 volt wires connect I broke some of the connectors and had to use "other means" to hook it up.
(Thankfully that's not a problem for me).

THe charger on the Freedom. Is programmable

Before that I had a Prosine 2.0 (Basically the same thing. wired the same way but I like the connections way way way better)

[Just_There]

helix528, what load/inverter size are you planning?

[Just_There]

I am planning on a similar scenario. My latest idea:
Use an inverter with automatic passthrough switching, move the outlets to the output of the inverter, wire the AC input of the inverter to the now empty breaker. I would count on the internal breaker of the inverter to protect the outlets/wiring. Your outlets will always be hot unless you shut down the inverter.

[hedge]

hmm, I ran mine just how you outlined... I didn't even think of the breaker. Now you have me wondering if this is ok.

I would think the breaker would protect it when it is the power source and the inverter overload would protect it when running from the inverter wouldn't it?

[opnspaces]

helix528 wrote:
Ok, that makes sense. To put it before the one breaker, I would have to do a sub panel? There is not a way to put it before a single breaker in the existing panel, correct?

Correct, you would need a separate sub panel to run one breaker.

[Tom_M1]

This is what I did with mine. GFCI is the breaker for my outlets. K2 is the relay I added.

[helix528]

Ok, that makes sense. To put it before the one breaker, I would have to do a sub panel? There is not a way to put it before a single breaker in the existing panel, correct?

[2oldman]

helix528 wrote:
Put it before all the breakers?

Just not sure if Inverted power is typically behind a breaker, or if it needs to be.

No, I meant just the one breaker.

Inverted power always goes before the panel for whole-house installations, or sub-panel installations, which are not easy.

I'm sure you'd be ok with your original plan, but down the road you may get more batteries and wish to run your microwave. Then you have to do this all over again.

[helix528]

Put it before all the breakers? I want to avoid doing that, or I will have to manually shut off breakers every time it swaps to inverted power and back on when on shore power.

I don't think I could wire it before the one breaker, unless I did a sub distribution box and ran power from the main box, to the secondary box, and put the switch between the main and secondary boxes. Trying to avoid that complication.

Just not sure if Inverted power is typically behind a breaker, or if it needs to be.

[2oldman]

Could you move the xfer switch to *before* the ac breaker? That's usually how it's done.

For some reason newbies don't get to post links.