Inverters and caravans.

Probably the phase difference between the voltage output by your inverter and that of the mains should both be connected to your caravan at the same time!

** It's on page 243 actually.

** In case some f****it connects up the regular 240 volt AC supply at the same time.

Likely destroy the inverter whether on or off.

....... Phil

1> in case the mains gets connected as well, while the inverter is connected. This would certainly blow the crap out of the inverter, and probably blow the mains fuse as well.

(Its also remotely possible (depending on the design and isolation of the inverter) that 240v could end up across the inverter's battery, If this happened, the battery could even explode, spreading acid everywhere.)

2> possible earthing issues. Since a caravan is electrically insulated from terra firma, unlike a house which has its own earth stake, I dont know what the proper procedure should be for caravan earthing, when run off a generator or inverter - that likely isnt earthed either.

There have been several cases I know of where caravans fitted with inverters have been hard wired to the 240 V reticulated wiring. Two of these cases were on private properties where the owner did the installation themselves. The inverters worked OK on the DC source but of course as soon as the vans were hooked up to the house power - well one burned to the ground and the other resulted in a non-fatal electric shock (no RCDs in the house wiring and connected via extension cords through the kitchen and bedroom windows).

In another case the inverter was installed by an electrician (wired in permanently) who then complained to the supplier when it blew itself to pieces when the mains was connected (again to a non-RCD protected domestic GPO). His letter to the supplier makes interesting reading as it demonstrates the profound lack of knowledge on his part, and the lack of foresight on behalf of the supplier/manufacturer in not warning about not installing the device that way.

Usually there are 'earth' connections to the frame or metal enclosure of the gen/inv itself. These don't function like the earth in a mains installation as there is no MEN connection on the gen/inv output, the earth is for static dissipation rather than safety.. The output of the generator or inverter is floating, the earth pin on the output is connected to frame ground and is safe enough (to a degree) with respect to faults to exposed metal of devices connected to the output. It would require a double fault for a serious hazard to arise (one fault in the gen/inv insulation system and one in the appliance).

In addition to inverters there are a few cases involving camping generators being similarly wired in permanently within motor homes and carvans. The alternators in the smaller camping generaotrs burn very nicely on a 15A GPO until either they melt open circuit or they short to frame, in which case the RCD in the supply should cut in. We did this to one last month to show an importer why they really should have a warning in the instructions.

My company has been investigating and advising importers about these issues for at least two years. The problem being few of the importers have any knowledge of mains power systems. They just see the product at a trade show in China and sell it, with the consequences being dealt with as they arise since they were never foreseen and planned for (proper instructions, warnings, etc).

"Dave"

** Would seem the message got through to Altronics at least.

That is a good sign.

Since it took 20 years for the same pimply faced * fuckwits* to figure out what the codes "A" and "B" indicated on the pots they were selling everyone.

....... Phil

I read with intrest comments made to this post. I do also use an inverter and a genny(not at the same time) to mains power my caravan. There is no possibillity for a second mains supply as I connect either to the

20 amp socket input on the outside of the van. The groups mention of the earth issue got me thinking...... What would be the best way tho earth the caravan frame? If I use an earth stake how long and how deep should that be? Mathew

Earthing the metal body of the caravan is a good precautionary way of reducing the possibility of electric shock due to an electrical fault. The length and depth you bury the earth stake depends on a number of factors, but mainly the conductivity of the surrounding soil. Dry silica soils tend to be higher resistance than wet or moist clay soils, thus normally requiring either a fairly deep penetration or more than one earth stake to achieve a low enough resistance earth.

There's bound to be a good sparkie who reads this NG who knows the regulations and what methods are legal.

Cheers, Alan

"Alan Rutlidge" >>> installation

Forgot to add that the earth wire should most likely be 6mm2 copper with green/yellow insulation.

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I am the same Dave/David that replied above... different office... different PC...

The earth pin the 20 A inlet would be bonded to the frame of the van, and would also be bonded to the generator frame. Earthing a genny or inverter does not provide the type of protection that earthing does for a mains supply - there is no MEN connection in an invertor or generator and so a fault between active and earth would not trip a circuit breaker (note - some gensets are fitted with RCDs and these have an MEN connection**). Earthing the van won't harm anything if you are running from a genset/inverter, but it doesn't make it safer either.

** One importer has been removing the power outlet from chinese made gensets and replacing them with Clipsal RCD integrated power points to make the genset "safer". They couldn't work out why customers were returning them under warranty because the RCD wouldn't function (failed when tested with RCD capable PATS). Clipsal claim the RCDs are functioning perfectly. Why don't they work? ...... Because the importer knows SFA about electrical/electronics and didn't make an MEN connection on the alternator side of the RCD (they just did a wire for wire changeover). So the expensive RCD GPO functions just the same as the plain old GPO it replaced.