Distribution at a Caravan Park

[SYKRAPS]

HI,

I reaslise that this subject does cause some conflicting opinions but I would like to ask a question to some more experienced guys in this matter regarding the distribution around a Caravan Park.

At the park in question I have been asked to cost for upgrades and possible extensive re-wiring due to a potential massive change in the park layout, but as of yet I have not gained access to the distribution area as it is under lock and key and some nugget has lost the key. I suspect that the park is installed wrong as TN-C-S as there is not an earth rod to be seen throughout the site (this is still to be proved).

My thoughts for the the hook ups is to wire them in groups of 4 with a double length earth rod per group of 4 at the last hook up and then to wire these back to an external distribution point which will serve 6 sets of 4 hook ups with again a double length earth rod and to devorce the DNO earth at the external distribution point so basically just TT the hook ups and the external distribution points.

My 1st question would be whether anyone can provide a link or product code for a suitable external distribution enclosure that will be pre constructed.

My 2nd question would be if you had the choice of re-wiring the positions would you use standard SWA or Split Concentric cable, I have been led to believe that with Split Concentric there is a financial saving and its easier to work (I have never used it myself). Both options would be ducted btw.

My 3rd question is would you fit a time delayed RCD unit in the origin DB or in each of the external distribution points, I am leaning towards the later so that in the event of a fault in one of the vans less people are inconvenienced.

I should perhaps also point out that 16a 30ma DP isolation will be present at each hook up for the 16a socket outlet, I have found these pre constructed for around £50 + VAT with internal metering (can anyone beat this).

Cheers Guys in advance.

 

[markc123]

Most caravan parks are TNS....TNCS is forbidden so if it is then thats defo wrong. TT Would be okay, but as TNS is allowed then this will be cheaper. Install in SWA its more suited to the job regardless of price.....dislike the idea of having 4plots linked... although its not wrong and alot of parks do it....over time you will have all 4vans tripping out through the fault to one pad...ive experiwnced it hundreds of times. Feed singally if poss...in the log run it saves unwanted hassel and call outs. I would fit an rcd in every outside db as this is the norm. And that sounds about write price wise for a box....remember section 7 of the regs...the bottom of the outside socket should be at least 0.5meter from the floor. Mark

 

[Engineer54]

Not going to have time to answer all your questions as i'm on my way out to site...

My 2nd question would be if you had the choice of re-wiring the positions would you use standard SWA or Split Concentric cable, I have been led to believe that with Split Concentric there is a financial saving and its easier to work (I have never used it myself). Both options would be ducted btw.

No you can't use Split concentric, not unless your going to duct these cables. They are not mechanically protected, so cannot be used in underground installations without some form of mechanical protection. The DNO have they're own set of rules, so don't go by what you have seen on DNO installations. Even they will only use concentric cable underground from the road joint to the service cut-out....

The other thing is that they are not as easy to terminate as you might think, most will look like an amateur's pig's ear of a job. They really need a heat shrink breakout to make a decent job of terminating them, and they aren't exactly cheap!!

Oops sorry, just noticed you said they would be ducted!! lol!! Very expensive exercise using Ducted cables for a caravan park. Normally they only use direct buried SWA installations. Fine if you can swing it with the owners, but i reckon they will baulk at the cost involved!!

​

 

[SYKRAPS]

OK I see your logic with regards to 1 plot and 1 wire and just pick a central point for the external distribution points so probably not that much more expensive with regards to cable, so would you then earth rod each hook up or just the external distribution point?

 

[SYKRAPS]

Not going to have time to answer all your questions as i'm on my way out to site...

My 2nd question would be if you had the choice of re-wiring the positions would you use standard SWA or Split Concentric cable, I have been led to believe that with Split Concentric there is a financial saving and its easier to work (I have never used it myself). Both options would be ducted btw.

No you can't use Split concentric, not unless your going to duct these cables. They are not mechanically protected, so cannot be used in underground installations without some form of mechanical protection. The DNO have they're own set of rules, so don't go by what you have seen on DNO installations. Even they will only use concentric cable underground from the road joint to the service cut-out....

The other thing is that they are not as easy to terminate as you might think, most will look like an amateur's pig's ear of a job. They really need a heat shrink breakout to make a decent job of terminating them, and they aren't exactly cheap!!

​

It is all going to be ducted but I will take your point on board.

I look foward to you response to my other points at a later time.

 

[markc123]

My new regs are in the van, and as im in bed the old 17th regs book (red book) will have to do for noe.....im not sure if its the same section but it should be....section 708 of part 7 tells you everything you need to know buddy....and according to that you cant even use TT so like i said TNS. Mark

 

[SYKRAPS]

My new regs are in the van, and as im in bed the old 17th regs book (red book) will have to do for noe.....im not sure if its the same section but it should be....section 708 of part 7 tells you everything you need to know buddy....and according to that you cant even use TT so like i said TNS. Mark

I think that this comment is not totally correct

 

[telectrix]

nothing wrong with TT on a caravan site. as long as all hook-ups are 30mA RCD.

 

[MDJ]

Denmans do a really good double 16 amp caravan unit with the rcds in the unit, you could buy 2 and have then side by side or back to back on a decent riser, I use them quite regulary myself, I would also use a large 5ft rod with a thread on it in the ground next to the 4 units, if the reading isn't good enough screw another on and go down 10 feet haha, connect the earth in the supply cable into a connector or wago by itself and then use the earth into the 4 sockets from the rod and convert to TT.

 

[markc123]

I think that this comment is not totally correct

Yes i realise its not correct, it was late and i was cranky forgive me.I did say in my first comment that TT was acceptable though, i must of been to 50different caravan parks in my time - and still do alot of work for park resorts and other small family run caravan parks now, and none of them are TT...surely as TNS is allowed and common practice this would be cheaper for you? And trust me on the single feeds, ive had one on a block of 4 this year where the outside RCD was faulty, they plug a faulty appliace inside so the mains went and all 4vans lost power....you cant be sure even when youve found the faulty rcd that this was the problem, so you have to fully test all 4vans and its a nightmare.

 

[telectrix]

having 4 hook-ups on 1 post fed by 10mm SWA is ideal as long as you fit 1 RCD and 1 MCB for each hook-up. that way a fault in any van will only trip out the supply for that 1 van.

 

[richy3333]

My new regs are in the van, and as im in bed the old 17th regs book (red book) will have to do for noe.....im not sure if its the same section but it should be....section 708 of part 7 tells you everything you need to know buddy....and according to that you cant even use TT so like i said TNS. Mark

WHAT? You sure about that comment? I've worked on loads of caravan sites and the majority are TNCS/TT installs. If it's changed somebody better tell the Caravan/Camping & Caravanning club PDQ

 

[telectrix]

708.411.4 . that seems to rule out TNC-S .

 

[richy3333]

708.411.4 . that seems to rule out TNC-S .

TNCS supply from the distributor and converted to a TT system

 

[Engineer54]

I think you have most things covered in your initial review of layout. Not quite sure of what your stating with regards to the protection within the hook-up units. As Tel states they should each consist of one MBC and one RCD for each outlet socket, or alternatively a DP RCBO for each outlet socket!! I'd still recommend that you stick to SWA for all your underground cabling. The armouring can then be used as additional linking out of ALL the Earth rod positions...

I always recommend 100mA S type, to backup the the 30mA RCD's as they are not the most reliable form of protection just yet, as to totally rely on a single RCD on a TT installation!!

As all these RCD's will be mounted in external enclosures, i personally would install a 100mA S type for each distribution cable covering the 4 plots. Expensive i know, but well worth the cost in my opinion.

I would also make a fairly accurate site cable routing plan/drawing for future reference for both yourself and the park owners. ...You won't realise just how important these things can be, until you need it!! ...lol!!