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.)
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.
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.
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).