Question about hot tubs

[Wilko]

Also, by TTing the remote installation it will likely retain RCD protection if DNO experiences the dreaded floating N fault. All very unlikely, I know.

 

[Nigel]

Maybe because IET guidance says that when outdoors you should?

(Extract from wiring matters)
All electrical work should comply with BS 7671. There are no specific requirements for electrical installations associated with hot tubs in BS 7671. However, where a hot tub is located outdoors in the open air, for example a garden, IET Guidance Note 7 Special Locations recommends that the requirements of Section 702 (swimming pools and other basins) should be applied. The requirements for swimming pools are given in Section 702 of BS 7671:2008+A3:2015. IET Guidance Note 7 also sets out the risks.

But it's only guidance and down to risk assessment at design stage by whoever is designing and installing I suppose.

My understand, for what its worth as it was imparted a long time ago, is that any metallic parts of the installation would be earthed. The extraneous conductor in this case would be the ground especially when wet and with bare feet.

I understand that it is classed as a swimming pool. That is obvious. But BS7671 says no such thing about TT’ing a swimming pool blindly. If there is nothing to earth or bond then what is the risk of electric shock?

And are you seriously saying that we need to bond the ground? Can you explain to me how we would go about this? I will get my popcorn.

 

[Nigel]

Also, by TTing the remote installation it will likely retain RCD protection if DNO experiences the dreaded floating N fault. All very unlikely, I know.

Will an RCD work without a neutral?

 

[Strima]

Why anyone would TT a hot tub with no extraneous metallic parts available to touch is beyond me.

Possibility of step voltages on wet ground?

 

[Midwest]

Not hot tub bod meself, but read suggestions here (with PME) of using that earthing facility, and local rod. These hot tub parties can get pretty raunchy apparently, lots of water being splashed around, & bodies everywhere.

 

[Devonchris]

And are you seriously saying that we need to bond the ground? Can you explain to me how we would go about this? I will get my popcorn.

If the extraneous metal part is in the ground then its acting as a conductor between it and the ground. In this case just put a clamp on. Where you are in direct contact with the ground put a rod in. The effect is the same, you are ensuring that they are all at the same potential.

 

[Midwest]

Think he's still cooking his popcorn. Either that or he's watering his Pampas grass.

 

[Nigel]

Possibility of step voltages on wet ground?

From what? Everything is non-conductive?

 

[Wilko]

Will an RCD work without a neutral?

The local test button no, but the safety function yes. Also, with TT the rising N does not mean CPC has to rise. Any fault current that did still flow will travel via L through the RCD etc and return to transformer via rod or Us. So the RCD detects imbalance in L to N and trips in the usual way, hopefully .

 

[Nigel]

If the extraneous metal part is in the ground then its acting as a conductor between it and the ground. In this case just put a clamp on. Where you are in direct contact with the ground put a rod in. The effect is the same, you are ensuring that they are all at the same potential.

How can you make non-conductive materials the same potential? Hot tubs are plastic. The frame is plastic. The pipework is plastic.

Can someone please explain why we would TT PLASTIC

 

[telectrix]

How can you make non-conductive materials the same potential? Hot tubs are plastic. The frame is plastic. The pipework is plastic.

Can someone please explain why we would TT PLASTIC

and don'tforget to put a rod in the water.

 

[telectrix]

anyway electrics and hot tubs are perfectly safe. ask these guys:

 

[Wilko]

Can someone please explain why we would TT PLASTIC

Ha ha, good question. If the installation is double insulated then I guess it makes no odds.

 

[Nigel]

Ha ha, good question. If the installation is double insulated then I guess it makes no odds.

Exactly, which almost all hot tubs are. The issue only arises when there is other conductive things around such as steel conduit an outside tap. Then we would need to look at possibly changing things.

I suppose my point is every installation will be different and that is why blanket decisions like TT it makes us lazy sparks.

 

[Wilko]

BTW - I'm working on my Alzheimer prevention just now so my usual 12 posts or 12 minute warranty is void ...