PIR on Static Caravan Site - PME and Bonding!

[davetheglitz]

ADS, I don't think i said anything about caravans in my previous post concerning EZ, in fact i pointed out i have no experience of static caravan sites!!!!.. I only really know that caravans are normally fed from a plug and socket arrangement, not sure if that also goes for these big static caravans??

I was merely pointing out what many forget or are unaware of with regards to, the so-called exporting of an earthing system via a sub-main cable....

But that being said, your mentioning a TT system here now, and the OP has said nothing about these caravans being provided with a TT system. If you have experience of these static type caravan parks, then i'm sure your right in what you are saying.

What intrigues me is, that i would have thought that the local authorities, and the DNO company for this area would have been involved in the set-up of this site, .....So how come there are no TT Rods at each of these hard standings?? Come to that, are we sure here that the incoming supply is indeed PME?? ...It just maybe TN-S!! If this site is anything like the size of some of these Static sites, that also cater for tourist caravans and have Social blocks, shops and other amenities, it maybe being supplied from it's own Distribution Transformer. So many unanswered and therefore unknown numerable,s here !!! :C

As you say - all needs investigation - but the Zs at the sites were so low it may well be PME. Questions are:- how long ago was it set up, was it done correctly, how many supplies come in, are they all the same, why are some pitches TT - others not and importantly how much money is available to investigate (bottom line - maybe!)!!!!

Lots to take in! I'll report back when we find out more.

 

[ADS]

As you say - all needs investigation - but the Zs at the sites were so low it may well be PME. Questions are:- how long ago was it set up, was it done correctly, how many supplies come in, are they all the same, why are some pitches TT - others not and importantly how much money is available to investigate (bottom line - maybe!)!!!!Lots to take in! I'll report back when we find out more.

Hi Dave,

I'd be interested in hearing how you get on.

If, as you suspect, anything is connected/bonded to a PEN conductor, though, surely that's going to warrant a Code 1, as it contravenes an actual law. (going by the quote in my previous post)

 

[spinlondon]

Not according to the BRB - 708.411.4In the UK the ESQCR prohibit the use of a TN-C-S system for the supply of a caravan or similar construction.

The rest of the Regulation to which your quote is just a note is:

"In the UK where the installation is supplied from a TN system, only a TN-S installation shall be installed. This does not preclude the use of a TN-C-S system for the supply to permenant buildings on such sites, however, consideration should be given to the earthing and bonding arrangements for amenity buildings."

Here is a quote from BS7430 (earthing Code of Practice):

"NOTE Residential caravans which are not normally intended to be moved from a caravan park are regarded as permanent buildings."

So BS7671 allows for permanent buildings of a Caravan site to be PME, and BS7430 considers static caravans to be permanent buildings.

To my knowledge, there is no regulation requiring the caravans to be TT.

Here is the Regulation in ESQCR that refers to caravans:

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

 

[kme]

AH. I missed the word "static" in the O/P.

I was thinking of standard caravan pitches.......apologies.

KME

 

[davetheglitz]

I don't understand the difference - or perhaps my terminology is incorrect.

The site has 32A hookups and a distribution network. The caravans are permanently on site - not tourers.

The DNO does not control the site distribution - so if it was PME and a neutral was lost all bonded or cpc'd metal parts would become live.

Regardless of definitions PME doesn't seem like a good idea - and if anything went wrong it would be down to the inspector for not picking it up. With so much buried and inaccessible I'm not sure how good a job you could do. I would suspect there are several stages of isolation from the incomer - it only takes one bad connection on a neutral main switch to cause a failure with nasty consequences.

If all is TNS then fine - earthing is separate - so if neutral is lost - no problem. If earth is lost - metalwork only becomes live under fault conditions - and RCD will sort it out.

 

[spinlondon]

I don't know the site or the particular DNO's requirements for PME hook up, so I can only state generalities.

The TN-C part of the distribution should be on the DNO's side. There should be no Combined Neutral and Earth in the site distribution.

The impedance between neutral and local earth on the installation side should be below 20ohms. (Most DNO's require this before providing a connection point to their PME system, some may allow a greater impedance.)

Most DNO's will require multiple earth electrodes at various points around the site, depending on size and their own individual requirements.

As such the fact that the DNO does not control site distribution should be immaterial.

Loss of neutral on the site would be no different to loss of neutral in any other installation, and loss of the DNO's neutral should be safeguarded against by the by the provision of multiple earth electrodes around the site, and the low impedance between neutral and local earth.

The only way to test this would involve de-energisation of the whole site, disconnection of both the earth and neutral at the intake and conducting earth electrode resistance tests etc.

Contacting the DNO to ascertain their individual requirements may be a good idea.

 

[ProDave]

As such this is a plug in - so the caravan itself is fine - it's just the services that it's connected to that need urgent attention!

Here is a quote from BS7430 (earthing Code of Practice):"NOTE Residential caravans which are not normally intended to be moved from a caravan park are regarded as permanent buildings."

So BS7671 allows for permanent buildings of a Caravan site to be PME, and BS7430 considers static caravans to be permanent buildings.

To my knowledge, there is no regulation requiring the caravans to be TT.

As these caravans are connected just to a plug and socket, then I would personally treat it as a TOURING caravan site, and provide each socket with a TT earth. They are NOT "residential" they are holiday caravans, even though they might not actually move.

The fact that they only plug the 'vans in on a socket means they probably expect a frequent and regular turnover of 'vans. Indeed many static holiday parks insist a caravan is replaced at 10 years old, sometimes younger, so they are NOT permanent.

Truly static residential caravans are different. They are often set onto bricked up foundations, and wired with a permanent fixed supply, not a plug and socket, so I would be happy with PME on one of those. These usually remain on site for 20 or 30 years or more, until they get replaced.

As one final thought, we lived in a static van on our building site for 2 years while we built our house, and the DNO made it quite clear that the caravan must be TT'd, and not connected to the PME earth they supplied.

For the sake of driving an earth rod in at each caravan point, I can't see the issue. TTing the earth would ensure compliance with regs (whether static or touring 'vans) and would solve the concerns about exporting a PME earth. But it's important to make sure ALL of them are TT'd.

Just my opinion and what I would do.

 

[Larnacaman]

Spinlondon,

You don't ''HAVE'' to shut down the whole site to test those ground rods these days, you can use an Earth Clamp that can basically be used, while the Rod is still connected. Check out Megger Marks site here on the forum. Makers are ACME, and Chauvin Arnoux.

And yes there expensive, but an absolute god-send in built up areas, where conventional testing of rods is all but impossible.

The other thing i know about these types of Static caravan sites, is that they are only allowed to be occupied 10 months of the year, i think that is the law governing these sites. So there is a 2 month down time in which these earth rods could be tested conventionally also.

 

[davetheglitz]

As these caravans are connected just to a plug and socket, then I would personally treat it as a TOURING caravan site, and provide each socket with a TT earth. They are NOT "residential" they are holiday caravans, even though they might not actually move.For the sake of driving an earth rod in at each caravan point, I can't see the issue. TTing the earth would ensure compliance with regs (whether static or touring 'vans) and would solve the concerns about exporting a PME earth. But it's important to make sure ALL of them are TT'd.

Just my opinion and what I would do.

Precisely what I would like to do - but there's over 200 caravans - and I want to check my facts before I suggest this to the site owner.

 

[Chr!s]

Spin

Here is a quote from BS7430 (earthing Code of Practice):"NOTE Residential caravans which are not normally intended to be moved from a caravan park are regarded as permanent buildings."

So BS7671 allows for permanent buildings of a Caravan site to be PME, and BS7430 considers static caravans to be permanent buildings.

No, BS 7671 does not see a residential caravan as a permanent building.

To my knowledge, there is no regulation requiring the caravans to be TT.

I do, BS7671 Section 708

Here is the Regulation in ESQCR that refers to caravans:

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

The guidance on that section is given as "a caravan or similar construction"

Guidance ESQCR

There is a small inherent risk of danger to consumers (resulting from the possible disconnection of the supply neutral conductor under fault conditions) with all PME networks (see comments for regulation 7(1)), however it is DTI

 

[spinlondon]

Amazing Plumber you have quoted my post and then stated that somewhere in Section 708 is a requirement for caravans to be TT'd.

Did you ignore the quoted Regulation from Section 708 contained in my post, or did you just not see it?

I'll re-quote it for you, it's Regulation 708.411.4:

"In the UK where the installation is supplied from a TN system, only a TN-S installation shall be installed. This does not preclude the use of a TN-C-S system for the supply to permenant buildings on such sites, however, consideration should be given to the earthing and bonding arrangements for amenity buildings."

As for BS7671 seeing Residential Caravans as permenant buildings, does BS7671 see them as anything else?

The definition in BS7671 for a caravan, defines it as "A leisure accomodation vehicle, used for touring, designed to meet the requirements for the construction and use of motor vehicles (see also definitions of Motor caravan and Leisure accomodation vehicle).

Whilst a static caravan may have once been a leisure accomodation vehicle, and it may have been designed to meet the requirements of the construction and use of motor vehicles Regulations. The fact that it is now static, and not used for touring means that it doesn't meet the definition of a caravan for BS7671.

In fact there are a great number of caravans that are not intended for touring, and were not designed to meet the requirements of the construction and use of motor vehicle Regulations. Some are so large, that the only way they can be transported on the public highway, is on the back of a low loader.

Whilst ESQCR recogognises BS7671 for compliance, BS7671 recognises BS7430, and also recognises that in some cases BS7671 may need to be supplemented by the requirements and recommendations of other British Standards.

As I said before, I thought plumbers were failed gas installers.

 

[steptoe]

AH,

but Im fairly sure you will find the reason that these so called caravans have wheels on them is for one reason only,!

so they can legally be classed as a caravan, otherwise they may as well be a portacabin like we hire on site,

but thats not a caravan , why?

its got no wheels so is not transportable in the same way, it cant be towed.!

Im a bit lost now,

sort it out please folks,

I want to know if Im going to be staying in a TT caravan next year, a TT tin house on wheels, or something altogether different.!

 

[Chr!s]

"In the UK where the installation is supplied from a TN system, only a TN-S installation shall be installed. This does not preclude the use of a TN-C-S system for the supply to permenant buildings on such sites, however, consideration should be given to the earthing and bonding arrangements for amenity buildings."

And your point is ?

As for BS7671 seeing Residential Caravans as permenant buildings, does BS7671 see them as anything else?The definition in BS7671 for a caravan, defines it as "A leisure accomodation vehicle, used for touring, designed to meet the requirements for the construction and use of motor vehicles (see also definitions of Motor caravan and Leisure accomodation vehicle).

BS 7671 Section 708 states Leisure accomadation vehicles (including caravans) or tents.

Definition Leisure accommodation vehicle in Bs 7671

Unit of living accommodation for temporary or seasonal occupation which may meet the requirements for construction and use of road vehicles

As for BS7671 seeing Residential Caravans as permenant buildings, does BS7671 see them as anything else?

Definitions Mobile home, A transportable leisure accommodation vehicle which includes means for for mobility but does not meets the requirements for construction and use of road vehicles

Residential park home, A factory produced relocatable dwelling designed for permanent residence which may be used for leisure purposes

I suggest all of the above if the construction is that of a caravan or similar, then they all fall under section 708 BS7671 and the ESQCR Regulations.

Whilst a static caravan may have once been a leisure accomodation vehicle, and it may have been designed to meet the requirements of the construction and use of motor vehicles Regulations. The fact that it is now static, and not used for touring means that it doesn't meet the definition of a caravan for BS7671.

It meets the definition of leisure accommodation vehicle

Whilst ESQCR recogognises BS7671 for compliance, BS7671 recognises BS7430, and also recognises that in some cases BS7671 may need to be supplemented by the requirements and recommendations of other British Standards

I totally agree, though the ESQCR is statutory, and the guidance given by the people who write the ESQCR regulations is a " Caravan or similar construction", they don't care if its a static on bricks wheels or even a double decker caravan, nor do they care if its for permanent residence, as far as they are concerned its a caravan and its the construction which poses the risk not whether its mobile or static.

As I said before, I thought plumbers were failed gas installers

Its a myth, Lol

 

[spinlondon]

Sorry Plumber, but you seem to be missing the point.

Section 708 deals with leisure accommodation vehicles, and indicates that ESQCR prohibits the use of TN-C-S to supply such vehicles.

The DNOs are regulated by ESQCR, not by BS7671, and they use BS7430 as a standard for earthing.

The DNO in the OP's case have supplied and allowed the site to be connected to the PME, something that is apparently prohibited by ESQCR.

Now both BS7671 and 7430 indicate that TN-C-S can be used to supply permenant buildings on caravan sites, BS7430 goes so far as to state that static caravans are considered to be permenant buildings.

Different DNO's have differing conditions where they will allow the connection to their PME. I don't know what the differences are across the country, only in Essex and London. Both Eastern and EDF require earth electrodes, EDF however require the impedance to be below 20ohms.

The DNO that serves the site in the OP's case has obviously determined that the site meets their requirements for TN-C-S, despite ESQCR and BS7671. I can only assume that they have deemed the static caravans to be permenant buildings as per BS7430.

As I have already suggested, it would be advisable to contact the relevant DNO to determine their particular requirements.

 

[Chr!s]

Sorry Plumber, but you seem to be missing the point.

I dont beleive i am.

Section 708 deals with leisure accommodation vehicles, and indicates that ESQCR prohibits the use of TN-C-S to supply such vehicles

Agreed

The DNOs are regulated by ESQCR, not by BS7671, and they use BS7430 as a standard for earthing

Agreed, though they often have there own in depth earthing manuals to which they use.

The DNO in the OP's case have supplied and allowed the site to be connected to the PME, something that is apparently prohibited by ESQCR.

Well we don't know that for sure. A large number of caravans on a tt fortuitously connected via services may well have a low Zs due to parallel paths.

If as the op suggests the gas is common to the pme at the main building, there is no breach of bs7671 as the caravans are still tt, though the dnos may require the services to be electrically isolated, though if the parallel resistance of the caravans tt systems is sufficiently low there would be a low risk even if the neutral was to be broken.

Now both BS7671 and 7430 indicate that TN-C-S can be used to supply permenant buildings on caravan sites, BS7430 goes so far as to state that static caravans are considered to be permenant buildings

Agreed, but they are two separate documents and BS7430 is being amended to meet the new harmonised structure, so you may find that note on caravans will no longer exist?

Different DNO's have differing conditions where they will allow the connection to their PME. I don't know what the differences are across the country, only in Essex and London. Both Eastern and EDF require earth electrodes, EDF however require the impedance to be below 20.

Agreed, it would be much better if they all sang from the same hymn sheet.

The DNO that serves the site in the OP's case has obviously determined that the site meets their requirements for TN-C-S, despite ESQCR and BS7671. I can only assume that they have deemed the static caravans to be permenant buildings as per BS7430.As I have already suggested, it would be advisable to contact the relevant DNO to determine their particular requirements.

I don't believe for one minute that the dno have connected caravans to the pme,Why would they breach the ESQCR, its either a fortuitous connection, or some numpty has connected them up not understanding the requirements.

And i would, as you suggest contact the dno to see what installation they think is connected to there network.

 

[binky]

Just a thought, but if common earthing is supplied to each plug in point, would you need to earth rod each van, or could a common rodding point be used??

 

[Chr!s]

Just a thought, but if common earthing is supplied to each plug in point, would you need to earth rod each van, or could a common rodding point be used??

Possibly, though you would need to determine the loading of the cpc's the earthing conductor and the earth electrode(means of earthing), and not just the faults currents but also the functional currents which are likely to flow.

Also i would consider the higher risk of losing electrical continuity(external influences) where all or some of the caravans connected may lose there connection with earth.

All in all i would suggest it to be easier to just tt the individual installations. Or certainly to limit the number of caravans to each means of earthing.

 

[binky]

Also i would consider the higher risk of losing electrical continuity(external influences) where all or some of the caravans connected may lose there connection with earth.

All in all i would suggest it to be easier to just tt the individual installations. Or certainly to limit the number of caravans to each means of earthing.

If using SWA with CPC core you effectively have 2 earths anyway, but splitting into areas/rows may be a good idea for simple maintenance.

200 rods seems a bit excessive to me if unnecessary. Big Earthing and Bonding book has pretty picture showing segregation of pitches from PME and single earth point as one option for TTing vans (though not 200 at a time )

 

[ProDave]

200 rods seems a bit excessive to me if unnecessary. Big Earthing and Bonding book has pretty picture showing segregation of pitches from PME and single earth point as one option for TTing vans (though not 200 at a time )

Most caravan sites don't have one bollard par caravan, but typically 5 caravan sockets per bollard.

So would a good compromise be one earth rod per bollard?

 

[binky]

Sounds good to me, but I suppose the ultimate answer is how likely to sustain damage an earth system is??? Which brings us back to the old addage of justifying what you have done is 'reasonable / satisfactory' for the conditions at the time of installation.