Hot Tub Query

westy8139 · May 29, 2012

Evening gents, first time on here so go easy. Have got a hot tub to install for a customer of mine (i'm fully registered, qualified, self employed etc) and have a query on the earthing arrangement. The house is fed on a TNCS supply, and i know some like to stake down the hot tub in this case, for safety in the event of a dropped neutral. However is this really neccessary? the tub is self contained, not connected to any of the house pipework, the thing is made of plastic. Its not within reach of any other circuit as its right at the other end of the garden. For me, with the unrealiablity of a TT system, the PME seems a better option.

I also have another one to fit in the next month, but the contactors fitting the tub have asked me to leave a 20A supply only protected by a 30ma rcd, so i'll leave the earthing here up to them.

Anyway, would appreciate your thoughts

Rockingit · May 29, 2012

We're into belts and braces territory here. You start with whatever the manufacturers install instructions say, then improve on them if you see fit. If it were me then I'd probably just keep the PME rather than ditching it to TT, given that it has to have RCD protection as well. There's also nothing to stop you keeping the PME and banging in an earth rod at the same time - all you do is make the PME grid a little larger (kind of). At the very least you'll help to keep your disconnections time down.

cbw · May 29, 2012

I actually think ^^^^thats what the BGB says, as a reccomendation??

Page 204 reg 702.410.3.4.3 (ii)

Did one like this a couple of weeks ago so had to look it up.

Guest55 · May 29, 2012

westy8139 said:
Evening gents, first time on here so go easy. Have got a hot tub to install for a customer of mine (i'm fully registered, qualified, self employed etc) and have a query on the earthing arrangement. The house is fed on a TNCS supply, and i know some like to stake down the hot tub in this case, for safety in the event of a dropped neutral. However is this really neccessary? the tub is self contained, not connected to any of the house pipework, the thing is made of plastic. Its not within reach of any other circuit as its right at the other end of the garden. For me, with the unrealiablity of a TT system, the PME seems a better option.

I also have another one to fit in the next month, but the contactors fitting the tub have asked me to leave a 20A supply only protected by a 30ma rcd, so i'll leave the earthing here up to them.

Anyway, would appreciate your thoughts

I think your assessment is correct.
As there is no exposed metalwork on the hot-tub nor any extraneous metalwork via filling tap then
theres nothing to introduce a hazardous touch voltage even if neutral is lost.
Therefore i also would just use the PME earth connection for the hot-tub supply.
RCDs all round , happy days.