Garden supply on PME system

[Km1777]

Evening everyone . Currently looking at pricing a job up . It’s a hot tub supply . Outside socket with a few spare ways in an outdoor cu . 10mm armoured cable on 45 amp mcb . To outdoor consumer unit . From there a 32 amp hot tub circuit and an outdoor socket all in armoured . The question is the supply is on a tnc-s earthing system . The outdoor cu will be roughly 22 metres from house down bottom of the garden armoured is buried in ducting for its full length. The hot tub will be sat on some paving flags so possible to get wet/earthy . I phoned the hot tub manufacturer to see if the heating element was a class1 or class2 heater and they didn’t have a clue what I meant . What would you fellas do in this scenario either use pme or drive earth rod into ground below cu and TT the full garden installation. I know this is a constant conversation between sparkies with not a definitive answer as all scenarios are different . There isn’t any extraneous pipe work that needs bonded also .

Thanks

 

[buzzlightyear]

No you don't need a earth rod for hot tube. Use the PME system its hot tube class 2.

 

[buzzlightyear]

National Inspection Council for Electrical Installation Contracting
https://dms.niceic.com › ...PDF
Electrical design considerations for the electrical supply to hot tubs.

 

[Km1777]

National Inspection Council for Electrical Installation Contracting
https://dms.niceic.com › ...PDF
Electrical design considerations for the electrical supply to hot tubs.

That link won’t load . Who said it was class 2

 

[buzzlightyear]

Who said it was class 2

What is that tub wood, plastic or metal.

 

[ipf]

If you're talking TNC-S or TT, I know which one I'd sooner depend on.
You could always rod it too, no harm, unless...
......the question arises, if the main system fails, is the TT satisfactory.
An interesting one. Separate system testing?
I wouldn't be getting too involved or worried.

 

[buzzlightyear]

If the designer chooses not to use the PME earthing arrangement and decides to install a TT earthing system, special care must be taken to avoid simultaneous contact between accessible metallic parts connected to different earthing arrangements, see Regulation 411.3.1.1 of BS 7671:2018+A1:2020. In some cases, it may be necessary to install a TT earthing system for the whole installation to prevent the risk of contact with metallic parts at different potentials.
IET.

 

[Km1777]

Thanks for that guys I was more thinking about difference in potential between the tub and wet paving flags . The tub is plastic . But it’s the heater if class 1 that’s the issue isn’t it in the event of a broken pen