Hot tub - TN-C-S

[snipersmith87]

Im after some advice regarding the earthing of a 32Amp hottub. I've yet to install one and am dubious about the risks associated.
The supply is T-N-C-S.
My plan is to put a seperate supply direct from origin via henleys to a 50amp MCB. 10mm 3c SWA approx 25m to a small wooden workshop. Within the workshop I'm locating a seperate DB with 30mA RCBO to supply small power / lighting within and the 32Amp hot tub sited on patio.
6mm 3c swa to rotary isolator. At this point I'm going to lose the supply armour via stuffing gland and internal cpc via wago. I was then going to install an earth rod connected to the load swa cpc and armouring upto hottub.
Can anybody see any issues with my scenario or further advice?

 

[snipersmith87]

That is true but you would hope they have the professional integrity not to back rubbish.

I looked at these myself. I csn see them being very popular for EV chargers....but they're costly.

 

[suffolkspark]

Page 246 of regs book, reg 702.410.3.4.3 (ii) does say if using pme an earth mat or electrode with a resistance of under 20ohm linked to bonding is recommended..... so looks like full TT may be the right option afterall.

The problem I have with one of the tub jobs I've got coming up (different to the one I was on about a min ago) is the manufacturer has said the unit comes with just 3x 13A plugs attached, (one for heater, blower, and jets), top of page 248 says If I've got sockets they need to be atleast 1.25m from the edge of the tub, so that ones gonna require some thought let's see how long they come?

 

[davesparks]

That is true but you would hope they have the professional integrity not to back rubbish.

They likely don't know enough to know whether they are good or not. Whether they have professional integrity or not I doubt they have the knowledge to make that assessment.
The company making the product will certainly not have told them about any of the negatives, they will have blinded them with the marketing BS.

And you can't trust any review where tbe person doing the review is getting a bonus or reward for doing so, they will always be biased.

 

[Midwest]

And you can't trust any review where tbe person doing the review is getting a bonus or reward for doing so, they will always be biased.

Dave has a point there; they may not knowingly be biased, but they will find it difficult to be negative, to the hand that feeds them.

 

[pc1966]

Page 246 of regs book, reg 702.410.3.4.3 (ii) does say if using pme an earth mat or electrode with a resistance of under 20ohm linked to bonding is recommended..... so looks like full TT may be the right option afterall.

Having a good earth mat/rod near the pool like that might pull the PME fault down a bit, but it also pulls up the local "Earth" so folk are less likely to see a dangerous touch potential between them.

The problem I have with one of the tub jobs I've got coming up (different to the one I was on about a min ago) is the manufacturer has said the unit comes with just 3x 13A plugs attached, (one for heater, blower, and jets), top of page 248 says If I've got sockets they need to be atleast 1.25m from the edge of the tub, so that ones gonna require some thought let's see how long they come?

Time for a bit of joinery to put them inside an additional splash shield? You might be luck and find they come with enough flax, but I would like to see that first!

 

[Jonspark]

Slightly different topic but worth checking out the Zappi EV charger as it has some built in protection that states “TN : can be connected to the PME supply. Complies with BS 7671:2018, 722.411.4.1 (iii)”

I wonder if Hot Tub Manufactures have or will adopt this technology?

Just took this from the Jacuzzi manual
“For the equipotential connection as required by specific na- tional standards, the installer must use the terminal provid- ed (standard EN 60335.2.60)in the electrical box ( 11), and marked with the symbol .
In particular, an equipotential condition must be established for all metallic masses surrounding the spa, for example water and gas pipes, metallic platforms, and so on.“

this would suggest the MET to me, thoughts?