Inverter wiring and mains hookup

[GreenBongo]

If I fit an inverter do I need to have a method of isolating the output when the mains hook up is connected?

Where have people fitted their inverters? I'm looking at a 1000W unit, I understand that on full power that would drain the LB pretty quickly but it would be nice to have the capability for short term use with the engine running.

[francophile1947]

Don't see why. The inverter works from the battery and the only connection your hook-up lead will have is to a battery charger.

[GreenBongo]

My hook up lead goes, via a consumer unit, to several mains sockets so if I connect the hook up then I would be putting mains power into the output of the inverter. There is no battery charger.

[mikeWalsall]

I would have thought a high out put inverter would need quite hefty cables connected to the leisure battery..

[GreenBongo]

It does, its certainly not something you would plug into the cigarette lighter socket. It comes with some hefty cable but not a very long length so I need to source some more from an auto-electrics place.
I wanted to wire it up so the sockets would work from either the inverter or the mains hook up, I'm now thinking about using a relay that will disconnect the inverter output automatically when the mains hook up is plugged in.

[dave_aber]

What you need is a contactor - mains operated 2-pole relay.

when hook up is present, the contactor energises and feeds the mains input to the 240v outlets (via an RCD or RCBO of course). When mains input isn't present, the contactor relaxes and connects the inverter output to the same 240v outlets (via the same RCD etc).

You should consider getting a longer 240v outlet cable on your inverter, and keeping the short heavy 12v cables supplied and finding somewhere suitable to locate the inverter close to the battery.

With the very high current on the input side, the voltage drop can be significant unless you scale the cables up in diameter as well as length. You also end up with very high-current cables running for the length of the vehicle, so these need to be adequately fused as there is a very real possibility of a short and fire. Much safer to run long 240v cables (in a suitable conduit), as these will be carrying approx 1/20th of the current compared to the 12v side.

[GreenBongo]

Yes, that's what I'm leaning towards. I haven't worked out where I can fit the inverter near the front of the vehicle, its a fairly large unit.

[GreenBongo]

25mm2 starter cable is around .15V drop per meter at 170A so that wouldn't be too bad, I reckon you'd get a higher drop across the fuse. Under 'normal use' the current would be much less, 170A is the max rating of the cable and a tad more than the peak current of the inverter. I'll have to check the battery specs to see what fuse I would need.

[dave_aber]

If you are using 175a cable, then that's what you are protecting with the fuse, so 150-160a fuse (as is available) is what you want.

[GreenBongo]

The 170A is a continuous rating as is the fuse rating, both will handle a lot more than that for a short duration. The short circuit current of the battery will determine the interrupt rating and how fast the fuse will blow. I don't think the short circuit current is that high on a leisure battery so the interrupt current shouldn't be an issue but a relatively low current may not blow the fuse fast enough if its the wrong type.

[dobby]

Yes, that's what I'm leaning towards. I haven't worked out where I can fit the inverter near the front of the vehicle, its a fairly large unit.

Best place is behind the glove box on the cross brace tube that spans under the dash and across the vehicle, get some extra large jubilee clips or similar to hold it. The tube acts as a heat sink as well.