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!

 

[ImpededLoop]

Fair enough. I stand corrected!

 

[happysteve]

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.

A departure from a statutory regulation? You're a braver man than I am...:angel_smile:

 

[davesparks]

Statutory regulation?

 

[happysteve]

The Electricity Safety, Quality and Continuity Regulations 2002. Part II, 9. (4).

 

[Carlosfandango]

Recommendations I've suggested are,
1. Fit 63amp mcb in 100mA rcd enclosure to protect 16mm cable. (currently protected by dno 100amp fuse)
2. Disconnect existing earth rod at supply end and pme supply cable to outside dist. board.
3. Replace 30mA rcd at dist board and fit main switch, replace 10 amp with 32amp mcb's that supply hookup sockets (currently there is a 6mm 3core that supplies 2 x sockets, 2 live cores sharing a neutral)
4. Fit new hookup enclosures containing 2 x10 amp 30 mA rcbo and 2 x 16 amp socket outlets ( caravan club apparently recommend 10a mcb?)
5. Isolate pme supply at hookup and install earth rod at each one.
What's your thoughts? I know it's not ideal but short of ripping it all out and starting again, which isn't gonna happen!!

 

[davesparks]

The Electricity Safety, Quality and Continuity Regulations 2002. Part II, 9. (4).

Which says:
(4) The distributor shall not connect his combined neutral and protective conductor to any metalwork in a caravan or boat.

I am not a distributor and I would not be connecting a CNE conductor to anything.

Exactly how would I have made a deviation from this ???

 

[Guest111]

For what it's worth I used to do a lot of camping and every site I've been on has had one earth rod per hook up point,also best practice is to use an individual mcb/rcd per outlet as there is always some numpty who'll try and use 2 heaters and a kettle and trip the breaker.

 

[Engineer54]

[

Recommendations I've suggested are,
1. Fit 63amp mcb in 100mA rcd enclosure to protect 16mm cable. (currently protected by dno 100amp fuse)
Make that an S type 100 or 300mA RCD......

2. Disconnect existing earth rod at supply end and pme supply cable to outside dist. board.
I wouldn't bother disconnecting the earth rod connection, leave it in....

3. Replace 30mA rcd at dist board and fit main switch, replace 10 amp with 32amp mcb's that supply hookup sockets (currently there is a 6mm 3core that supplies 2 x sockets, 2 live cores sharing a neutral)
Not sure what you mean by (2 live cores sharing a neutral)??

4. Fit new hookup enclosures containing 2 x10 amp 30 mA rcbo and 2 x 16 amp socket outlets ( caravan club apparently recommend 10a mcb?)
Fine, so long as the RCBO's are DP not SP!!

5. Isolate pme supply at hookup and install earth rod at each one.
Fine, remember the hook up cabinet can be PME, it is the supply to the caravan that needs to be isolated and on a TT earth... The hook-up cabinets i've seen for caravan pitches have two small earth bars, one for the incoming earth (pme) and one for the TT earth.

What's your thoughts? I know it's not ideal but short of ripping it all out and starting again, which isn't gonna happen!!

What do you mean by '(currently there is a 6mm 3core that supplies 2 x sockets, 2 live cores sharing a neutral)'' ?? 2 line cores run in parallel from existing 10A MCB in 5 way DB, or 2 line conductors supplied from 2 separate MCB's in the 5 way DB??

BTW how many caravan pitches are there on this caravan touring site?? And what other buildings are being provided for, like club house, shop(s), shower rooms etc??

 

[Carlosfandango]

There's 5 pitches, no other buildings at all. Very small site. Two lives fed from two mcbs. I know shared neutrals is a no no but my reckoning, right or wrong, was that as it's 6mm cable and fed by 10 amp then the neutral will be capable of carrying the load?

 

[Engineer54]

There's 5 pitches, no other buildings at all. Very small site. Two lives fed from two mcbs. I know shared neutrals is a no no but my reckoning, right or wrong, was that as it's 6mm cable and fed by 10 amp then the neutral will be capable of carrying the load?

Surely if all 5 ways of this 5 way DB are being used that would, be 10 caravan pitches and 5 hook-up cabinets?? Or are you saying only 3 of these MCB's are being presently used??

Makes you wonder how anyone can get such a small installation wrong, It would have cost almost the same amount of money initially to do things right in the first place!!

 

[happysteve]

Which says:
(4) The distributor shall not connect his combined neutral and protective conductor to any metalwork in a caravan or boat.

I am not a distributor and I would not be connecting a CNE conductor to anything.

Exactly how would I have made a deviation from this ???

From the ESQCR 2002, Explanatory Notes ("This is not part of the Regulations"):

Regulation 9 contains requirements for distributors operating protective multiple earthing systems, including the circumstances in which earthing terminals of consumers' installations should not be connected to the distributor’s combined neutral and protective conductor.
​

Also BS7671 (non-statutory) cites the ESQCR 2002 in 708.411.4:

The ... ESQCR 2002 prohibit the connection of a PME earthing facility to any metalwork in a leisure accommodation vehicle (including a caravan).
​

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.

A departure because bs767 1 says you must not have PME connected to the caravan pitches. But with the earth nest connected I see no reason why you shouldn't have PME connected,

It's not BS7671 you'd be making a departure from, it's the ESQCR 2002.

As for "I am not a distributor," if you believe that this means that the statutory regulation does not apply to you then I will stand by my earlier statement about you being a braver man than I am...

Sorry, i didn't quite understand that you meant connecting the PME to the caravan. I thought you were only talking about PME up to the pitch hook-up cabinet, which is fine. Personally i wouldn't connect the PME through to the caravan, too much responsibility if something did go wrong no matter how good the TT earthing on the PME was....

... and braver than Engineer54 as well by the sounds of it. You must have stones the size of melons.

 

[Carlosfandango]

Surely if all 5 ways of this 5 way DB are being used that would, be 10 caravan pitches and 5 hook-up cabinets?? Or are you saying only 3 of these MCB's are being presently used??

Makes you wonder how anyone can get such a small installation wrong, It would have cost almost the same amount of money initially to do things right in the first place!!

There are 2 posts each with 2 hookups on each, fed by 1 x 6mm 3 core to each, then 1 hookup on the outdoor db itself, making 5 hookups. To the remote hookups red is one live, yellow another, blue a shared neutral and the armour serving as an earth. Hope that makes sense?

 

[Engineer54]

Yes that makes sense, not the most intelligent way of doings things mind!! lol!!

 

[Richo77]

What about if it was a tn-s Earth system. Would you still have to disconnect the tn-s Earth and then use a TT system on the commando socket to the touring caravan? I think you would still have to use a TT but not sure.

 

[Jamzie]

No Richie. TN-S is permitted