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Topic Title: Caravan installation
Topic Summary: Installation spec
Created On: 13 May 2018 03:16 PM
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 13 May 2018 03:16 PM
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Neilmwatts

Posts: 3
Joined: 13 May 2018

Hi can anyone offer me some advice regards electrical install in a caravan. I've looked on a few forums and it appears some say you must use double pole mcb's (along with an rcd obviously). My question is, is this still necessary if you are installing a double pole main switch? Also, on a lot of caravan and leisure sites, the ccu' s offered for caravans are plastic and so don't comply with amendment 3. Could anyone shed any light?
 14 May 2018 09:30 AM
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jonny705

Posts: 223
Joined: 26 September 2015

Hi Neal.

The caravans are wired like a normal house, main RCD or split load RCD D/P, switches protect the installation with normal single pole MCB afterwards.
The Only thing that was different was the chassis was earthed also.
The cables are normal T&E, not seen any kind of de-rating on normal circuits, although cable is buried in the insulation.

The test certificates supplied with the new caravans were all dead tests only, and the RCD was not tested (not on the sheet anyway).
They put in a disclaimer which basically leaves it up to the site owner to supply the correct earthing, overcurrent protection , type of supply suitable etc., so the manufacture cannot be held responsible for any problems once wired up.

I don't think they have to have metal boards as I know a mobile home if worked on does not have to be notified part P style, but although I haven't seen one yet in a caravan or motor home, I may be wrong.

I don't think there is a unique legislation that the caravan manufactures have to follow, some were really well done, some were rough, some had a test sheet with NO information on other than type of MCB etc, a couple had a full test sheet with all R1/R2s I/R etc. on them like you would expect.

I also searched about caravans a while back, and there is very little on how they are actually wired.
 14 May 2018 10:08 AM
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Zoomup

Posts: 5046
Joined: 20 February 2014

British Standard 7671 is the Electricians' bible. It is entitled "Requirements for Electrical Installations. " The current edition is the 17th, but the 18th edition is due to be released this summer. Reg. 421.1.201 says that within domestic (household) premises consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall i, have their enclosure manufactured from non-combustible material, or ii, be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Reg. 132.12. Note 1. Ferrous metal , e.g. steel is deemed to be an example of a non-combustible material. So is your caravan a domestic household premises?

Section 708 of B.S. 7671 deals with Electrical Installations in Caravan/camping Parks and Similar Locations. The PME earthing facility is prohibited from being connected to any metalwork in a leisure accommodation vehicle including a caravan, so TT earthing is essential.

Section 721 is entitled, Electrical Installations in Caravans and Motor Caravans. It does NOT deal with electrical installations in mobile homes, residential park homes or transportable units. It does apply to the electrical installations of caravans for habitation purposes, and applies to touring caravans. Reg. 721.411.1 requires an R.C.D. to provide automatic disconnection of the supply (ADS) that interrupts ALL LIVE CONDUCTORS. So a double pole device is required on a single phase supply. This is normally a 30 mA R.C.D. A single pole switched R.C.B.O. would NOT comply in this instance.

A Residual Current Device is a double pole device so all is well there. The hook up point on a caravan site usually has a 30 mA R.C.D. as does the caravan in its consumer unit. That is good. They should be tested on a regular basis. Single pole M.C.B.s are o.k. inside the caravan in its consumer unit.

But having said that, Reg. 721.43.1 states that each final circuit shall be protected by an overcurrent protective device which disconnects all live conductors of that circuit. This may be to protect users if the supply polarity is reversed at the hook up point or in a supply lead. So yes, officially B.S. 7671 does require double pole M.C.B.s in a touring caravan consumer unit.



Z.

Edited: 14 May 2018 at 10:45 AM by Zoomup
 14 May 2018 10:45 AM
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AJJewsbury

Posts: 17169
Joined: 13 August 2003

The caravans are wired like a normal house, main RCD or split load RCD D/P, switches protect the installation with normal single pole MCB afterwards.

That might be acceptable on a static caravan (i.e. not a caravan but a normal building in BS 7671 terms), but for a tourer, double pole protection is required throughout. Remember that tourers can be taken abroad and there are still places where polarity isn't as consistent as in the UK or even to receive a 230V supply between two phases rather than between phase & N.

- Andy.
 14 May 2018 11:08 AM
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AJJewsbury

Posts: 17169
Joined: 13 August 2003

Also non-flexible cables (e.g. T&E) are prohibited in touring caravans - you need to use conductors with at least 7 strands, typically flex. (Reg 721.521.2) and minimum 1.5mm2 (including c.p.c.s).
- Andy.
 14 May 2018 11:19 AM
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mapj1

Posts: 11223
Joined: 22 July 2004

As of quite recently, double pole breaking RCBOS in normal MCB sizes are becoming available.

Either designs that take L-N double bus-bar example
or with flying leads example

-------------------------
regards Mike
 14 May 2018 11:30 AM
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AJJewsbury

Posts: 17169
Joined: 13 August 2003

I'd be slightly wary of 'single pole switched N' RCBO designs - although they switch both poles they won't have overcurrent protection in the "N" pole, nor (I suspect) is the N contact capable of breaking large fault currents by itself (but rather relies on the "L" contact to have opened first). That's all fine with a correctly polarised earthed neutral scenario, but might end up a bit 'messy' with certain faults if the supply isn't polarised as expected or indeed don't have an earthed N at all. Ditto for French style single pole switched N MCBs.
- Andy.
 14 May 2018 12:06 PM
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Neilmwatts

Posts: 3
Joined: 13 May 2018

Thanks everyone, much appreciated.
 14 May 2018 12:38 PM
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AJJewsbury

Posts: 17169
Joined: 13 August 2003

Also be careful when terminating flex into accessories that normally accept rigid conductors - if the terminals aren't designed to accept the multiple strands of flex directly you might need to 'solidify' the ends of the flex - e.g. by applying bootlace ferrules (not by soldering/tinning!).
- Andy.
 14 May 2018 06:40 PM
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sparkingchip

Posts: 11230
Joined: 18 January 2003

Static or touring?

Each have different requirements.

Andy B
 14 May 2018 07:29 PM
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ebee

Posts: 6529
Joined: 02 December 2004

Originally posted by: mapj1

As of quite recently, double pole breaking RCBOS in normal MCB sizes are becoming available.



Either designs that take L-N double bus-bar example

or with flying leads example



What does this clause mean?

"NOTE - CARRIER'S MAXIMUM INSURANCE CLAIM IS £25.00 AND SIGNATURE IS MANDATORY. FOR EXTRA COVER - CONTACT OFFICE"

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 14 May 2018 09:17 PM
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mapj1

Posts: 11223
Joined: 22 July 2004

reject parcels that look damaged. Or only sign and caveat. Actually I think it means they are using a cheap courier, as most offer a number of cover options.

-------------------------
regards Mike
 16 May 2018 07:55 AM
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jonny705

Posts: 223
Joined: 26 September 2015

Sorry assumed you meant static, if you are doing a motor home or touring caravan, T/E cables become loose due to vibration I have stripped 2 motor homes in the past, and they were wired in a flex-but I don't know what type.

The D/P type as mentioned on mobile types is because a lot of sites abroad are wired wrong hence additional safety; the caravan club recommends a plug tester to check polarity so I assume it must be common.
 16 May 2018 08:44 AM
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Zoomup

Posts: 5046
Joined: 20 February 2014

I have often wondered about the use of electro-mechanical devices like R.C.D.s etc. being used in touring vans and motor homes. Will the devices be affected by continual vibration when the vehicle is on the road, perhaps travelling over bumpy roads with pot holes, or worn bumpy country lanes to sites? Are there stipulations in the manufacturing specs. regarding use after being vibrated. Will vibrations affect operation? Most devices are destined to be installed in static homes, offices or factories that do not vibrate or go on holiday.

Z.
 16 May 2018 09:07 AM
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AJJewsbury

Posts: 17169
Joined: 13 August 2003

I have often wondered about the use of electro-mechanical devices like R.C.D.s etc. being used in touring vans and motor homes. Will the devices be affected by continual vibration when the vehicle is on the road

But somewhat mitigated by the pitch socket also being 30mA RCD protected - hence two RCDs would need to fail (plus the earth fault itself) to result in danger, plus instructions to test the van's RCD every time the supply is connected (presuming people take more notice of such instructions than they do at home).
- Andy.
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