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!

 

[Guest77]

Regarding RCDs, I haven't really taken in what you have said about it yet here, best practice is RCDs at the caravan point rather than away from it IMO, however I will have another read of the OP later and respond again tommorrow, if I can get in before E54 LOL

 

[Guest77]

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!

Well there should have been a code regarding the PME bit on the existing sheets, the inspector didn't know his oninions from his garlic I am afraid, at least you have questioned it, section 7 will have much more.

 

[Doomed]

As I say, TT'ed at the hook up, mixed at the source.
708.553.1.14 & 708.411.4

 

[Carlosfandango]

But it's not tt'd at the hookup, it tt and PME at source.

 

[Plonker 3]

But your are introducing the PME potential to the TT

 

[Guest77]

But it's not tt'd at the hookup, it tt and PME at source.

Thats no issue, I thought you meant mixing at the caravan outlet end, as it is now thats the case, thats why Carlos disconnected the PME earth due to the concern the outlets were PMEd, that is what the thread is basically about.

But your are introducing the PME potential to the TT

Quite right fella, thats why I suggested to carlos he connect the existing earth into a wago in the back of the outlet and rod at that point.

 

[Guest77]

But it's not tt'd at the hookup, it tt and PME at source.

Well then thats fine, the whole thing sounds confusing, but at the source fine, not the outlet. Can you clarify again lol

 

[Doomed]

and one final question - are you sure its PME and not TN-S?

 

[Carlosfandango]

Wait, I'm confusing things here! I explained it better in my first post!! I think?

 

[Carlosfandango]

Definitely pme, not tn-s.

 

[Engineer54]

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!

There is no problem connecting a TT system to any TN supply earthing, although an Ra value of over a 100 ohms isn't going to add anything to a PME system!! From what i can tell from the OP, you are saying that the SWA radials away from the 5 way DB are carrying the same PME supply earth to the caravan hook-ups, which is also fine.

It's at the caravan hook up's where the PME earthing system needs to be isolated from the caravan plug and socket supply , and a TT system earth provided.... The caravan plug & socket hook up points should contain the 30mA DP RCD's not at the 5 way DB as has been stated. That 30mA main switch in the 5 way DB should be changed out for a straight isolator, and the RCD after the meter changed out for a 100 or 300mA S type. Whats the betting the CU in the caravan is also protected by a 30mA RCD too lol!

 

[driverman]

Caravans parks should be tested every year not 3 years as stated by OP. Is it a residential site as opposed to a touring site? PME is acceptable on the distribution side. TT can be created at the hook up's to the caravans.

 

[driverman]

May be true,maybe not., but I heard on the grapevine, that when the new regs come out there will be major changes re caravan site installations. Anyone know anything?

 

[Jamzie]

Statics every 3 years, tourers every year. That's what it used to be, but I've been away from the game for a few years-has it now changed?

 

[Leesparkykent]

professional-electrician.com/.../niceic-advicesupplies-pme-system-caravan-...

 

[Guest77]

Tourers definately every year, I haven't got the BGB with me to confirm 3 years with statics, however ,most holiday parks would have a condition report of the vans every year for insurance reasons I suspect regardless of the regs, it is cheaper insurance if the vans checked annually.

 

[driverman]

Statics every 3 years, tourers every year. That's what it used to be, but I've been away from the game for a few years-has it now changed?

Yes, 3 years for statics, therefore OP's site may well be a static caravan site as stated every 3 years. Depending on the actual static van tn-s is allowed, not to sure about PME though.

 

[Guest77]

Yes, 3 years for statics, therefore OP's site may well be a static caravan site as stated every 3 years. Depending on the actual static van tn-s is allowed, not to sure about PME though.

Don't think it is an issue, TNS the better way, that said without the BGB were all guessing, Murdoch is on now, if he sees this he may put us out of our misery.

 

[driverman]

If residential site, TN-S can be used for direct connection to caravan. TN-C-S can also be used as long as not metal clad units. OP are the static vans metal clad? This could be why previous EICR are satisfactory.

 

[driverman]

Found this , hope it helps

 

[Carlosfandango]

It's a touring site, previous few inspections have been 3 years but I've recommended 1 year due to the findings. I've recommended a spike and individual rcbo at each hookup, doubt it if it ever gets done!!

 

[driverman]

It's a touring site, previous few inspections have been 3 years but I've recommended 1 year due to the findings. I've recommended a spike and individual rcbo at each hookup, doubt it if it ever gets done!!

Any idea why they had an EICR every 3 years? As you say touring site every year.

 

[Carlosfandango]

No idea, the first records show the tests were done every year, but the last two have been every 3. The company that used to do the tests have changed MD and QS so that might explain.

 

[Engineer54]

So, what are your full recommendations for this sites caravan distribution system and hook-up points as stated in your Opening Post??

 

[davesparks]

Personally I wouldn't use isolated rods at each hookup.
I'd be looking to create one large earth nest to give the lowest most stable Ra possible, possibly installing rods at each hookup but having them all linked together.

I know it would technically be a departure but I see no issue with having an earth nest of very low Ra connected to the MET and having the PME connected.