Combining inverter and converter in same system

[blurtheline]

Hi, first let me apologize if this question has been answered and I missed it!

I'm building a trailer with 110v and 12v. I have a WFCO converter that is wired to my shore power inlet, my 12v lines, and my deep cycle battery. As-is, the system is working great when I'm connected to shore power (I get 110v, 12v, and the battery charges), good when I'm disconnected from shore power (12v works), but I also need 110v when I'm not connected to shore power - so I bought an inverter.

My question is - how do I connect the inverter to the system so that I can "seamlessly" go from shore to non-shore. If I try and connect it into the existing setup I get issues (GFCI and reverse current) that I'm seeing with the testers I have. Is there some type of diode that I need to put in the circuit? Sorry, I'm a beginner to this stuff - but no shocks so far

Thanks, Art

[SSchumacherCO]

I figured this out for my own application a while back but I can't find the drawing. Seems to me that I switched the 120VAC load between shore power and the output from the inverter using a DPDT relay with a 120VAC coil. When there is no shore power the inverter is connnedted. When shore power is present the relay coil switches out the inverter and connects the 120VAC circuit directly. A second relay could also disable the 12VDC input to the inverter as well so it isn't needlessly running. My only concern is that with shore power the coil on the relay is always energised. This shouldn't be a problem but just sort of bugs me. At one point I was looking for latching relays to get around this. This sounds much more complicated than it really is. If I can find the drawings I'll post them.

[madjack]

...automatic is good, however if you get a manual throw DPDT switch, you know when it is engaged and not havvta worry about a coil burning out(or up)...
madjack

[jss06]

I agree with the relay method. Carry a couple of spare relays with you so that you have one handy if it burns out. Also look for the heavier duty relays that are rated at 100% duty cycle.

Another possibility. Why not just wire two outlets? One powered off the inverter the other powered off the shore power?

[brian_bp]

SSchumacherCO's system is a home-made auto-changeover or transfer switch. As madjack said, you can also do it manually.

Three wasy to make the changeover manually, instead of automatically:

1. Unplug equipment (maybe all gathered on one power bar) from one source and plug into the other
2. double-pole, double-throw (DPDT) switch (or just a SPDT - if neutral can be shared)
3. feed power from each source though a circuit breaker, with the breakers placed in opposite directions (such as in facing sides of a breaker panel); link the breaker handles with bars, so that only one can be turned on at a time

For the automatic approach, there are commerically produced transfer switches which work essentially as already described; sometimes they are built into combined inverter/charger units (the all-in-one solution).

Diodes? Not in an AC power system.

[blurtheline]

Thanks everyone for the good information, it sounds like a manual or seperate system is the way to go.

I'm still confused though on a related note (thanks for the patience!)

As I mentioned I'm using a WFCO unit. When it's plugged into shore power things work fine. But - I just ran a test where I disconnected the battery from the WFCO and then used my inverter (connected to the battery seperately) to power the WFCO. Under this scenario my 110v circuit testers go crazy (all lights on, I'm not even sure what that means). Why would power from an inverter cause this? Do I need to ground the battery to the trailer frame?

Thanks!!!

[jmullan99]

SSchumacherCO's system is a home-made auto-changeover or transfer switch. As madjack said, you can also do it manually.

That is what I do. Converter wired direct to shore power. Inverter direct to batteries. Breaker panel is fed by a plug that I either plug into my on-board shore power outlet, or plug into inverter. Simple and safe.

[radven]

Another good option is to get a combination Inverter / Charger, and do away with the Converter. This way, you accomplish everything you need in a single box.

I am planning to use a Xantrex Freedom 458 in our next trailer.

A very nice, small, affordable Inverter / Charger is the Xantrex HF series. Check Xantrex.com for more details.

Cheers!

- Chris