Use of ECBs

[Alan Douglas]

do I rely solely on an exported PME connection from the house once the cable is connected or do I sink an earth spike at the caravan end as well

I realize it won't help over there, but the National Electrical Code here requires an additional Earth ground for any detached structure. The question comes up periodically on forums such as Garage Journal that deal with sheds and outbuildings. We can do our own electrical work as long as it is inspected and approved.

[pwdrive]

Looking on the web over here there seems to be different views, some say the house PME is fine others say there should be an earth spike, it seems to boil down to weather or not there are any exposed metal parts in the caravan, in our case the only exposed metal is the copper water pipes, they ultimately are connected to the plastic underground water pipe which supplies the water to the caravan.

Lawrence.

[AlanBeckett]

I take a pessimistiv view and stuff the Regs. The Garden/Garage/Aviary/Greenhouse etc are fed by a 30A Breaker in the main Consumer Unit. The Cable down the Garden is 4-Core SWA with two Cores and the Armour Earthed. I tried putting an RCD in the way but it tripped regularly due, I suspect, to leaks and Phase Shifts. So I took it out and now each area has its own small Consumer Unit and 30mA RCD. Despite being PMEd the 'Outside Circuits' are undoubtedly 'Earthed' via my big Aluminium Greenhouse, which has multiple Earth connections via another section of SWA from the Garage.
I'm not having any problems and I'm still here.

Alan

[pwdrive]

Having read your last post I think I made a mistake in the description of the SWA cable I laid, I think it's 4 core and not 3 core as I originally stated.

To me the feed to an outbuilding from the house is similar to installing an outdoor garden socket down the garden, they are both remote and are earthed back at the house if the PME is exported, as you've already mentioned, two spare cores in the SWA plus the protective sheath, plenty there to handle any earth currents.

One day I'll get it all connected..

Lawrence.

[pwdrive]

Jeeze Alan, I'm not with it this morning, a correction again, I've just now checked our SWA it is three core after all, 3 x 10 mm is what's stamped on it.

According to this article I just found exporting PME and using that alone in the outbuilding is no problem, the TN-C-S supply, which ours is specifies a 10 mm earth conductor so the spare core in our SWA will do for that.

http://www.napitonline.com/downloads/CP%...Supply.pdf

Lawrence.

[Radio Fixer]

Sparks was supposed to come yesterday but didn't make it. My wife wooed him with the promise of coffee and homemade cake and he turned up this morning.

Reconfigured the panel so that there are two RCD areas, much as before, but the utility room sockets, which are where the frozen cabinets are plugged into, now go to a separate 30A RCBO. Then there is another 6A RCBO for outside lights etc.

So to me a pretty good setup and I'm happy with it.

Re-labelled by white stick on paper but I will get around to doing something better. Maybe a CorelDraw exercise when I get time.

You obviously understand things well Alan ... thanks to both you and Lawrence.

Gary

[ppppenguin]

The best, if most expensive, way of complying with 17th edition wiring regs is a separate RCBO for each circuit. Circuits without RCD protection are only allowed in certain specialised situations in domestic premises. Very roughly, the wiring for such circuits must be surface mounted, or in armoured, pyro or other cable with an earthed outer. I think it can then feed lights or fixed appliances without further restriction but I may be wrong. It can certainly be used for fire/burglar alarms. It is possible to feed a socket outlet for a frdge/freezer but this must be clearly marked that it is only for that purpose. Ideally use a different sort of socket such as BS4343 or even old fashioned 15A BS546.

17th ed requires that the circuit be split between a minimum of 2 RCDs. This outlaws using an RCD as the main switch where one trip and the whole place is in darkness.

I'm glad I rewired my house under 15th ed regs. RCDs needed for all sockets outside the equipotential bonding zone, basically outdoor/shed/garage etc. Also any sockets that may get used for kit outside the equibond zone. Typically downstairs ring if adequate outdoor sockets aren't provided. I also protect my lab bench with an RCD. It's only common sense.

Guide to different earthing arrangements. PME has common earth/neutral conductor up to the meter. The DNO then provides you with an earth terminal whichis connected to their combined earth/neutral. http://en.wikipedia.org/wiki/Earthing_system