Caravan site wiring

[nickjohn]

Sorry about asking this question as I think similar posts have been made before but I could not find one along the same lines as this.

A friend of mine has a residential static caravan site (as in the caravans on the site are lived in 24/7 52 weeks a year by the same people).
The configuration of the site wiring is there is a central building incorporating the incoming mains which splits into individual meters for each van, this goes to a 60a sw fuse then into a 60A 30ma RCD then a swa sub main (with the old vans the swa went into the van and connected into a CU incorporating another 60A 30ma rcd and breakers) with the new vans the sparks has installed an external housing adjacent to the van which has a cu with a 60A 30ma rcd and 16A breaker, this then connects to an external 16A socket with a flex into the vans CU - the new vans cu has a 30ma RCD.

He says the vans must have a means of disconnection of the supply adjacent to them as they are mobile homes... some have to be lifted in with a crane so they are not mobile in the true sense of the word.. he also says the vans are limited to what they can use electrically wise as they are mobile homes hence the 16A breaker.

Now the problem is that as the vans are permanent residences they have washers / dryers / toaster / TV's / kettles etc etc which puts more load on them than say a holiday home.

My friend does not understand why we cannot just connect the swa direct into the van as they were before as the swa has an rcd at source which should give the protection necessary, also the small 16A breaker is already causing problems with the resident as it overloads all the time.

Can anyone shed any light on what is the correct connection configuration.

 

[Badged01]

Caravan sites and Caravans are all covered in BS7671 under special locations so have a read of that first. From my limited knowledge of caravan site design I believe mobile homes are classified under the regs the same as caravans so ….

….. the sparks has installed an external housing adjacent to the van …

Correct …… This has to be done to meet current regs, you cant run it straight into the mobile home.

the vans are limited to what they can use electrically wise as they are mobile homes hence the 16A breaker.

Wrong ……The caravans are not limited to 16A, they just have to be connected by a ‘Commando’ socket -- which can supply upto 125A!.

Its definately the standard practise for touring sites to only use 16A, which frustrates me with my campervan because as you have said it limits what appliances you can have running! But for a fixed site I cant see a problem with more than 16A .....

 

[D Skelton]

I'd also be binning the two of the three RCDs wired in series to each caravan! The one at the mains intake and the one at the DB adjacent to the caravan! If a TT system then a type-s could be needed at the mains intake position.

Depending on the max demand at each caravan I'd be looking to feed the SWA into a two way IP rated enclosure directly adjacent to the unit with a 100A main switch and a 32/40A type b feeding a 63A commando socket.

 

[spark 68]

I'd also be binning the two of the three RCDs wired in series to each caravan!

You need to keep at least two of them, as the regs require a 30mA RCD at the connection post 708.553.1.13, and another 30mA device in the van 721.411.1 , even though they won't discriminate.

edit: If the supply to the individual pitches is also TT then a 100mA TD RCD or greater may also be required at the source supply to discriminate with the pitches.

Another poster is also correct in that 16A is the minimum supply allowed, and may be greater if required.

 

[Badged01]

I'd also be binning the two of the three RCDs wired in series to each caravan!

Above poster beat me to it but its a strange setup on caravan wiring with the regs. I havent looked too deeply into the actuals but as explained to me by a "knowledgeable" caravan site electrician over a beer or 10. Because the site has basically got to be a TT system you end up with an RCD at the mains intake to protect cables to the pitches, and RCD at the caravan pitch socket (cos regs say it) and an RCD on the caravan consumer unit (cos regs say it).

So yes 3 RCD's in series ...... I never got to discussing discrimination til after about the 8th beer so cant remember the solution to that!

 

[spark 68]

Hi badged,

The actual supply to the pitch post (cabling wise) can also be a TN system, only you have to seperate the earthing in the case of PME/TNC-S this can be done at the pitch pillar (making it a TT at this end), it does not necessarily have to be done at the supply side , no such problem with TN-S though.

 

[D Skelton]

You need to keep at least two of them, as the regs require a 30mA RCD at the connection post 708.553.1.13, and another 30mA device in the van 721.411.1 , even though they won't discriminate.

721.411.1 will be met by the adherance to 708.553.1.13.

edit: If the supply to the individual pitches is also TT then a 100mA TD RCD or greater may also be required at the source supply to discriminate with the pitches.

This is what I said

as explained to me by a "knowledgeable" caravan site electrician over a beer or 10. Because the site has basically got to be a TT system you end up with an RCD at the mains intake to protect cables to the pitches, and RCD at the caravan pitch socket (cos regs say it) and an RCD on the caravan consumer unit (cos regs say it).

So yes 3 RCD's in series ......

He isn't as knowledgable as you think he is




I stand by what I say, bin the RCD at the mains intake (unless TT in which case a type-s may or may not be needed), RCD at the 2 way IP rated DB adjacent to the caravan and bin the other RCD inside. There is absolutely no advantage to having three RCDs in line on one circuit, if anything, it makes the circuit even more prone to fault. Regardless of hearsay, correct discrimination between RCDs has to be achieved, and the only way to do this is to only have one of them, or, have two with one of them being a type-s.

 

[spark 68]

RCD at the 2 way IP rated DB adjacent to the caravan and bin the other RCD inside

.

This you cannot do, they both fall under different reg sections, the van also has to have a 30mA device inside where ADS is used.

I take it this to ensure you will always have RCD protection, also they are classed as two different installations, the Van ends at the flex,the pitch ends at the post.

Just one of those anomalies.

 

[D Skelton]

.

This you cannot do, they both fall under different reg sections, the van also has to have a 30mA device inside where ADS is used.

I take it this to ensure you will always have RCD protection, also they are classed as two different installations, the Van ends at the flex,the pitch ends at the post.

Just one of those anomalies.

Of course you can, it doesn't matter about the reg sections. 721.411.1 says where ADS is used an RCD shall be provided. Where exactly does it specify where it shall be provided?

They are not classed as two seperate installations, just two seperate sets of regulations covering different types of installation. Does section 701 comprise of a seperate installation in relation to the regs covering the wider scope of the installation throughout the rest of the property? Of course not. Have you ever seen people wiring RCDs in series to protect a bathroom lighting circuit???

 

[spark 68]

It is because the van is classed as mobile, and may be used from a another supply (not necessarily a caravan pitch), the van is covered by section 721, and as such is classed as an installation and wiring system in it's own right.

The same apples to marinas and boats, have a look at GN7, and figure 721 (particularly item 5 in fig. 721) in the BGB.

 

[D Skelton]

It is because the van is classed as mobile, and may be used from a another supply (not necessarily a caravan pitch), the van is covered by section 721, and as such is classed as an installation and wiring system in it's own right.

The same apples to marinas and boats, have a look at GN7, and figure 721 (particularly item 5 in fig. 721) in the BGB.

Potentially so, that's why as professionals and ultimately designers, we have to make judgement calls based on our years of experience, expertise and fundamental understanding of both electrical theory and regulation. In a static caravan, which some may even argue is a fixed installation in it's own right (the word 'static' being a dead giveaway), I wouldn't look at fitting an RCD if the supply to it had been wired correctly, similarly, I'd have no hesitation in ripping an existing one out if the supply was wired correctly and just replacing with a main switch. In a truly mobile caravan I wouldn't entertain not fitting an RCD.

In the latter scenario the risk of being connected to something that isn't RCD protected is far greater that the risk of nuisance tripping occuring. In the former, static caravans tend to stay static, but upon being moved how hard is it really to replace a main switch with an RCD if the supply to the caravan isn't wired correctly, which in itself is highly doubtful as if it wasn't the caravan park simply wouldn't be allowed to operate.

 

[spark 68]

Oh I agree with you, it does seem pointless having two 30mA RCDs in series, but unfortunately they are tested and certified completely separately against different sections.

 

[D Skelton]

Oh I agree with you, it does seem pointless having two 30mA RCDs in series, but unfortunately they are tested and certified completely separately against different sections.

No they're not, they are being tested and certified to be in compliance with BS 7671 as a whole. If you are looking at a static caravan with no RCD in it but one at the supply to it directly outside, in answer to the question on whether or not the installation complies with section 721.411 then the only answer available is yes! 'Is an RCD complying with 415.1.1 provided?' Yes! Who cares where it is provided

 

[spark 68]

When a caravan (static or otherwise) is supplied/sold, it is tested and certified against section 721, the pitch is likewise certified against section 708, you then end up with a degree of overlap we are discussing.

Let me ask you a question, if someone brought to you (or your premises) a static caravan for you to provide an EICR for, would you pass it off with no RCD (no code) ?, bearing in mind you have no idea where it was to be used.

 

[D Skelton]

When a caravan (static or otherwise) is supplied/sold, it is tested and certified against section 721, the pitch is likewise certified against section 708, you then end up with a degree of overlap we are discussing.

Let me ask you a question, if someone brought to you (or your premises) a static caravan for you to provide an EICR for, would you pass it off with no RCD (no code) ?, bearing in mind you have no idea where it was to be used.

Ok, I see what you're getting at now. Yes, on their own merit, whether that is out of the factory or in transit or on the sales yard a static caravan would need an RCD within to comply with section 721. Upon being delivered to site and installed in it's permanent location however, nothing stopping you ripping the bugger out!