PME supply to detached garage

[Midwest]

My question is not quite in the title.

I've been asked to quote for the above. No extraneous conductive parts in garage, which I intend to supply from spare way in house domestic CU, swa to garage CU utilizing the earthing facility of TN-C-S.

However, one of the reasons they want the supply installed, is to power a portable heater in their mobile caravan that they winter on their driveway, to combat damp etc. Not quite sure of the exact nature of the heater (not a caravan'er myself), but assuming normal low voltage heater on a trailing lead.

Sec 708 electrical installations in caravan parks, Sec 721 electrical installations in caravans.

Reg 708.411.4 ESQCR prohibit the connection of a PME earthing facility to any metalwork in a leisure accommodation vehicle, but not sure where a portable temporary device would fall under these two regs.

I could see the potential of flex to heater being damaged, and standing on true earth and holding onto metalwork of caravan.

Phone my scheme Elecsa, who just referred me to 708.411.4. I could just install and advise against, or go for TT in garage, but is my thinking correct? I suspect they've done it for years, with flex from the house.

 

[Rosco]

My question is not quite in the title.

I've been asked to quote for the above. No extraneous conductive parts in garage, which I intend to supply from spare way in house domestic CU, swa to garage CU utilizing the earthing facility of TN-C-S.

However, one of the reasons they want the supply installed, is to power a portable heater in their mobile caravan that they winter on their driveway, to combat damp etc. Not quite sure of the exact nature of the heater (not a caravan'er myself), but assuming normal low voltage heater on a trailing lead.

Sec 708 electrical installations in caravan parks, Sec 721 electrical installations in caravans.

Reg 708.411.4 ESQCR prohibit the connection of a PME earthing facility to any metalwork in a leisure accommodation vehicle, but not sure where a portable temporary device would fall under these two regs.

I could see the potential of flex to heater being damaged, and standing on true earth and holding onto metalwork of caravan.

Phone my scheme Elecsa, who just referred me to 708.411.4. I could just install and advise against, or go for TT in garage, but is my thinking correct? I suspect they've done it for years, with flex from the house.

If it is for the purpose of having a heater inside the caravan so for instance the caravan is in the driveway then a trailing lead into caravan for the heater, why not suggest installing them a commando socket in the garage (like a caravan park would have) so they can hook up and power the heater internally

 

[Leesparkykent]

Id probably just TT the garage.

 

[7029 dave]

But it is not static, so can't see how that would apply.Seen loads trailing leads out of windows to charge the leisure battery.

 

[HandySparks]

I'd consider putting a socket on the outside of the garage for the caravan and giving just this socket a TT earth.

 

[westward10]

I would use the TN-C-S from the house, Section 708 does not apply. You have been asked to put power in the garage, how they utilise the sockets is up to them.

 

[rolyberkin]

If they are going to plug the caravan in to the supply via the leisure battery/caravan supply point and then use a socket in the caravan it defo needs to be TT. Best way is probably to fit a commando socket on the garage as suggested above and let them plug the lead they will probably already have into that.

 

[Midwest]

Thanks for the advice guys.

I'm not sure they want to hook up the caravan directly, but I will check that. I've just replaced their CU, so now asked for the supply to the garage, mentioning plugging in a temporary heater for the caravan. As I said I did ring technical, but got very lose advise. As I'm not actually connecting the caravan to the earthing facility, not sure that reg applies, not withstanding it could happen accidently.

 

[LeeH]

It's not a caravan site, treat it as such.

 

[Octopus]

Why would you TT a garage when they may use it to plug in their caravan they tow, for a few days a year???????? Thats just daft IMHO

 

[Midwest]

I did email Elecsa technical, I find you get a more fuller response than via telephone. Here is their reply;

'Thank you for your enquiry.

The scope of section 708 applies to caravan/camping parks and similar facilities and not necessarily a domestic situation. However if the conditions are similar there is no reason why the designer cannot take section 708 into consideration.

If we assume 708 does not directly apply then there are no other specific regulation in BS 7671 for the situation described that forbid the exporting of a PME earth, therefore the decision will be down to the designer.

We would advise a risk assessment approach based on the use of installation. We have also attached some articles on this subject for your information'.

The articles are those we've seen posted here before, never the less useful. One does include a reference to the IET Code of Practice for Electrical Vehicle Charging Equipment Installation, but for around £60, its an expensive read and I can't see it giving anymore guidance than I've already received, if at all applicable.

Think I'll do a PME install, when it gets a bit warming to install the swa. In the meantime, I'll see what my client intends to do with the caravan heater.

Thanks for the replies.

 

[Dave OCD]

Funnily enough I had to install a 25 metre run of 4mm 3 core SWA to a shed yesterday in freezing weather, it was a sh1te to bend nicely and work with.

 

[Midwest]

Warm it up the day before!

 

[Octopus]

Warm it up the day before!

And then it will get cold again.

I did a 20 m of 3c 6 mm run a couple of weeks back on a very cold day. When I arrived on site I put it in the clients kitchen until I was ready too run it - and then it was ok.

 

[Midwest]

Think I'll just wait for a few warmer days.

 

[stevethesparks]

How many people do you see using a TT socket to cut the grass with their electric lawnmower?
Its not static, so TT not required.

 

[Midwest]

I suppose such devices would be Class 2, whereas a portable heater would be Class 1?