I would like to feed my small 300W inverter into an isolated 'house' circuit that I've identified that powers a few convenient 120v outlets on one side of my trailer (and is isolated from microwaves, converters, etc).My plan is:-Cut the 120v wire for this one circuit as it comes out of the breaker (15a) and heads into the wall.-Put a DPDT switch inline at that cut (the 2 +/- wires).-Wire the 2 +/- output wires from my inverter to the other input of the DPDT.-Now I can flip a switch and that circuit goes from normal shore power to inverter powered. And if I forget and leave it in the wrong setting at some point, I can't damage anything (like accidentally powering my converter from my inverter, etc)So wondering if I've overlooked anything. And also want to ask what I should be doing with the grounds. The DPDT has only 2 poles for the +/- wires. What to do with the bare copper grounds? Should I splice the 3 (the two inputs and one output) together, even though the switch itself isn't grounded? Also, should the chassis ground of the inverter itself be wired to the same bare copper ground wire as the 120v bus is.Any advice would be appreciated.Thanks

DPDT means Double pole - double throw??

That's right. I think DPST (single throw) is two wires just breaking the circuit... where DPDT is switching between two different circuits (inverter vs. shore power in this case).

I recommend a $50 automatic switch over the DPDT toggle.Yes all three grounds should be tied together.Inverter chassis ground should go direct to the frame or main ground bus so that it remains grounded during service.BTW no +/- it is Hot and Neutral.This switch plugs direct into inverter and has terminals ready for the cut wire.

Could you point me to what type of switch you mean @smkettner? I'm not sure what you mean - what causes it to switch automatically?nm - just saw your update

This is the one I used. It switches as soon as the Inverter is powered up.This can be important as you should NOT bond the Ground and Neutral together. That is never done at sub-panels or connections below the main panel (ie the first panel after the power arrives from the transformer)I lead the power from the trailer breaker panel to the transfer switch, then back to the panel to connect to the load.

Inverter wire into RV 'house' circuit question | Good Sam Community

3_tons
Explorer III
Oct 01, 2014
DPDT means Double pole - double throw??
chilly81
Explorer
Oct 01, 2014
That's right. I think DPST (single throw) is two wires just breaking the circuit... where DPDT is switching between two different circuits (inverter vs. shore power in this case).
time2roll
Nomad
Oct 01, 2014
I recommend a $50 automatic switch over the DPDT toggle.
Yes all three grounds should be tied together.
Inverter chassis ground should go direct to the frame or main ground bus so that it remains grounded during service.

BTW no +/- it is Hot and Neutral.

This switch plugs direct into inverter and has terminals ready for the cut wire.
chilly81
Explorer
Oct 01, 2014
Could you point me to what type of switch you mean @smkettner? I'm not sure what you mean - what causes it to switch automatically?

nm - just saw your update
n7bsn
Explorer
Oct 01, 2014
This is the one I used. It switches as soon as the Inverter is powered up.

This can be important as you should NOT bond the Ground and Neutral together. That is never done at sub-panels or connections below the main panel (ie the first panel after the power arrives from the transformer)

I lead the power from the trailer breaker panel to the transfer switch, then back to the panel to connect to the load.
ken_white
Explorer
Oct 01, 2014
I used a DPDT 120 VAC industrial quality relay that had 30A contact ratings.

I did bond the neutral to ground together on the inverter side of the relay and the grounds are bonded togther.

Since the hot and neutral are both switched, there are no ground loop issues and everything works 100% safely and correctly.

As stated above, any of the automatic transfer switches will work as well.
RoyB
Explorer II
Oct 01, 2014
GOOGLE shows a couple of MANUAL CHANGEOVER SWITCHes if you want to go that way verses RELAY TYPE CHANGEOVER method.

ALL PHOTOS from GOOGLE Images

All wiring must be done inside enclosed electrical boxes as shown.

The MANUAL SWITCH has add-on banks depending how many 120VAC circuits you want to tap into and switch between Shore Power and INVERTER.
C3 CONTROLS LINK
MORE TRANSFER SWITCHES LINK

I personally would just run a couple of extension cords out of the small wattage INVERTER 120VAC receptacles and have one located at the home entertainment center area and the other one at the bedromm location. Then just plug in what you need to be running off the INVERTER. I would perhaps do the wiring changes if the whole 120VAc DISTRIBUTION PANEL was being switched between SHORE POWER and GENERATOR or INVERTER, Sure would save a lot of work just for a couple of circuits.

submitted for different ideas only
Roy Ken
wa8yxm
Explorer III
Oct 01, 2014
With the grounds you have two choices, and you may find they are both the same.

Step one, With the Inverter NOT POWERED, check to make sure the ground pin on the outlet is actually connected,, Good chance it is not, if this is the case it makes life real easy cause both options are thus the same.

Option: 1: Connect both Mains (Shore/generator) and inverter ground wires together

Option 2: Connect the Mains ground to the load line and forget the line from the generator
96Bounder30E
Explorer II
Oct 01, 2014
OP.......I did exactly what you are describing about 10 years ago to power my Prowatt 300 watt entertainment center only inverter....

Except, I did one thing different.......I used a 3 pole double throw toggle switch.....the third pole turns the inverter power on and off........one throw of the switch turns the inverter on and switches the circuit input from shore/generator power to inverter power......all of my connections were done within 1' of the fuse/circuit breaker panel......

This system makes it completely fool proof for my wife and kids to watch TV/DVD/SAT while dry camping.....

Again, this was installed in 2003 and has been completely trouble free ever since.....one of the best mods I ever did.......

If you need any help wiring it up I'd be happy to assist........
chilly81
Explorer
Oct 01, 2014
Those are some nice options. I hadn't realized the automatic switches were fairly reasonable. In fact they seem cheaper than the high grade manual switches (which are very nice though - Blue Sea really makes nice stuff but it does cost).

@Bounder, that's clever about using a 3rd pole to turn on the inverter itself. I think I might try going that way to start. The 3pdt switches I can find are super cheapo looking or they cost $25 with shipping. That's vs. like $60 for one of the auto switches. But I'd have to wire up a switch to turn the inverter on and off anyway... maybe I'll go that route.

Thanks for the ideas and ground clarifications. Think I'm ready to go.