Caravan hookups

[Carlosfandango]

I was asked to test five caravan pitches for someone I've done a few jobs for. Now, I'll admit my knowledge on TT systems is not vast so I'm looking for a bit of advice. The install has been tested by a large local contractor every three years. When I got there the setup was as follows. BS 1361 cutout - meter- 63 amp 100mA rcd - 16mm Swa - 5 way db (63amp 30mA main switch) (roughly 20m away),then out to the hookups via 10 amp mcb's. There was a 10mm earth out to multiple rods connected to the RCD steel enclosure (as told by customer). There was also a 16mm earth to the PME cutout? I know this is incorrect so I disconnected it and got 110 ohms Ra. This is obviously classed as stable but not ideal. My problem is, why did this other contractor not pick up on this, or am I the one that's wrong?? Before anyone else pipes up I know there are other faults ie no overload protection on the supply to the 5 way db!
Thanks for reading!

 

[telectrix]

63A fuse or MCB to protect the SWA. it could be argued that the PME connection is OK as it gives a good low Zs. in the event of a neutral failure, the TT would act as a back-up and prevent problems caused by a supply N failure.

 

[Carlosfandango]

No fuse or mcb, just an rcd main switch.

 

[Guest77]

PME, is a huge no no for caravan outlets, having PME running within the armoured to the caravan socket fine from the meter, you then drop the earth off in the back off the socket in a wago or other terminal away from the caravan outlet, and then whack a 5ft rod or two together making 10ft in the ground at the caravan socket point and connect the earth from the rod to the outlet, this way the armoured is protected vis a OCPD from the meter end with a pme earth, but the caravan outlet is TT, isolated from the PME and therefore keeps BS7671 happy.

 

[Plonker 3]

The cutout fuse will act as the OCPD for the 5 way board depending on how the SWA is run so there is no chance of it being damaged etc although the DNO may not like it. What size is the main bullet?

 

[Carlosfandango]

100 amps

 

[Plonker 3]

Time to stick a relevant sized RCBO in place if the RCD then.

 

[Guest77]

Just to add, TT systems need double pole isolation, Haven't got the BGB with me right now but it is highlighted in there for sure.

 

[Carlosfandango]

Like I say it was just a condition report (maybe didn't say that actually?) so I'll just put recommendations. Is it better to have a rod at each outlet or can you TT the lot? Obviously there's no discrimination with the one rcd protecting all the outlets (30mA at the 5 way) so that's another discrepancy.

 

[Doomed]

I have seen several sites which started their life as agricultural that have PME and TT at the source.
As long as the hookups have TT earthing you are OK.

 

[Guest77]

Hmm, I can't see that, I have no issue with it but the regs quite clearly state PME a no no on caravan sites, if you connect a TT system and a PME together then in theory you have PMEd it, I cannot see that being acceptable so I have to disagree, I won't say anymore on the matter until I get to confirm via the BGB the actual reg numbers, and they will be in there for sure.

 

[Carlosfandango]

Guess what my Sunday morning will consist of!!

 

[Plonker 3]

I need to reference the BGB too before committing. Will have to be tomorrow before i can though as currently in the pub lol.

 

[Guest77]

Like I say it was just a condition report (maybe didn't say that actually?) so I'll just put recommendations. Is it better to have a rod at each outlet or can you TT the lot? Obviously there's no discrimination with the one rcd protecting all the outlets (30mA at the 5 way) so that's another discrepancy.

No problem TTing the lot on one rod if you can get the RA at the furthest point to be a resonable reading, it is easy to rod individually though the way I mentioned in my first post, either way really, the PME bit though, a definate no no on a caravan site for Touring cavarans, may be different for static vans.

 

[Carlosfandango]

Thanks guys, I was doubting myself as I have the previous 15 years test sheets and there is no mention of any of the issues I found!