Inverters and caravans.

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Greetings group.
I read in the current Altronics catalog (page 234) that inverters
should only be used for stand alone use.

They should not be connected directly to the fixed wiring in a caravan.

I expect the reason is something to do with safety, but what is the
reason?

Thanks,
Russell.


Re: Inverters and caravans.


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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!


Re: Inverters and caravans.



< snipped-for-privacy@hotmail.com
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**  It's on page 243 actually.


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

     Likely destroy the inverter whether on or off.



.......   Phil




Re: Inverters and caravans.


On 18 May 2006 16:20:05 -0700, " snipped-for-privacy@hotmail.com"

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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.





Re: Inverters and caravans.



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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.

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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).



Re: Inverters and caravans.



"Dave"
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** 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



Re: Inverters and caravans.



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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



Re: Inverters and caravans.



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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
 



Re: Inverters and caravans.



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



Re: Inverters and caravans.



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cases
the
wiring
of
not
of
inverter
is
The
case
any

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.



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