Caravan or Mobile Home? Which one is it.......

[Adrian Sadler]

Hiya all

What we have is a holiday home site type effort where there are 13 caravan type looking units of accommodation.

They do not have towing facilities nor are wired for running lights while towing.
They are sat on wind down legs for adjustment.

Mobile Home - A transportable leisure accommodation vehicle which includes means for mobility but does not meet the requirements for construction and use of road vehicles.....

I thought caravan and therefore caravan site but the more I read it - Its a mobile home.

The issue we were having is that the site supplies are PME.
This is ran all the way to these homes.

The homes are fed from a DB attached to each of the outside of these homes (only accessible with tools) - which in turn feeds the internal manufactures CU.

Now - they have installed via the external DB - a 13a IP socket for hot tubs - on RCBO.

Now people are getting electric shocks from the hot tubs.............

4 other firms have been out to site and said there is nothing wrong with the electrics and it must be the tub. They have also stated that it is not classed as a caravan site so section 707 (i think) does not apply.


Here's my view.

Option 1
External DB main sw will be changed to 100ma type s D.P switch. Install MCB to feed the van and leave the hot tub supply on RCBO.
Divorce the earth at this DB and turn into a TT system therefore both the home and tub are same potential as earth and the shocks will go away.
Use the PME on the armouring for decent protection.

Option 2
Unsure on this one....
Leave the Homes on PME and just divorce the earth at the tub end and rod tub only.
The issue I see with this is that you can touch the tub and the metalwork of the home at the same time. If you can do this then IMO there's risk of a shock again.

If we look at the mobile unit regs section 717 - PME shall not be used unless a) its continuosly under supervision of skilled or instructed people and b) means of earthing is tested before connection.

Now a groundsman wouldnt fall under this........

After any ideas or opinions please as this ones doin me head in - along with site owner.

PS - I have chosen option 1 above and applied to one home - no shocks

 

[The Ghost]

Personally I feel sec 708 applies. Along with sec 721. Concerning Caravans or similar... I think the idea of shocks in hot tubs is a death trap and should be completely isolated (as I imagine they already have been) and discussion taken up with the manufacturer on site to advise. There are really two separate issues here and location types imo.

 

[westward10]

So are people barefoot and getting tingles from the water.

 

[Adrian Sadler]

Only getting shocks if a part of you is on the floor outside the tub. Ie. Just dip ya hand in.

To me - solution 1 is the only one. Tried and tested.

But are there any other option? Would you get a shock mixing earths ie. Tt tub and pme lodge?

The site is fed from Scottish Power and in their guides - PME is not permitted for caravan sites nor mobile homes.

The hot tub manufacturer has washed their hands of it all - saying they only make them and wont instruct on the types of earthing as out their remit.
Same with the 'lodge' manufacturers.

Generally the site owner is a naws who says it doesnt happen on them all - staff say it does on most but is people dependant.

Scottish Power are going out to site...

 

[westward10]

I wouldn't deem it a caravan site they are essentially permanent dwellings. Looks like you are getting potential difference between true earth and the PME earth. How is the water being heated.

 

[Adrian Sadler]

I think the wording is 'leisure accommodation'

Its deffo PD issue. Water is heated by the hot tub.

Now while I know where you going with this (i think) with the usual divorce earth at tub and rod it which is a must on pme imo - you can touch the van while in the tub. So there you will again have a PD.

Only route I can think of is to TT the whole install......

 

[Adrian Sadler]

If could get the zs down to 20 ohms id rod the lot but readings from 2x2m rods is around 100 ohms. Installed another rod and it didnt go down....

 

[Richard Burns]

I woudl say that the long run of PME supplied cable to the "houses" means there is a PD between PME earth and true earth.
Trying to get an external hot tub to be safe is not really sensibly possible, but to get it safer and as an alternative to TT for the whole "house" would be to rod the PME at the "house" and so provide a local earth reference, but there could easily still be a pd present and it does not sound as if you can get a very good earth from a rod, 100 ohms is a bit poor for safety when considering avoidance of voltage differences.

 

[Adrian Sadler]

If you rod for tt we have the 200 ohm guide.
If we rodding the pme we need to get to 20ohms or under - not gonna be possible on this site.

Another option maybe to rod literally every db and cu while keeping the pme - then it might get down to below 20 but more luck than judgment

 

[Adrian Sadler]

Are there any DNO lads from Scottish Power on here?

 

[Deleted member 26818]

The LEB would not allow street furniture a connection to their PME, unless the earth electrode resistance was 1 ohm or less.

 

[Adrian Sadler]

I know the DNO ate going out monday. What will they do? Change heads to one with no earth? Install a rcd n rod?

 

[Deleted member 26818]

They can just remove the Neutral earth link.
It's unlikely that they will install a n RCD or rod, not their concern.

 

[bigspark17]

Does the submain cable go into a first db point and split or loop in out from one to another.?? An rcbo will not help with PD issues, the only way to do this imo is to tt the whole site at first db, put an earth matt in if rods arnt doing much 300mA time delay main switch the site.

 

[Adrian Sadler]

Here is the layout of the electrics. Its PME thruout and needs TT
Only issues are that the first dis board is inside a plastic enc (tools needed) and so is the 2 way CU (metal). Again tools needed.

Achieving discrimination on this is starting to do my head in - suggestions?
Cant really put any rcds in the boards with plastic enc over them as the site is largly unmanned. Flicking the rcd inside the van isnt a issue