Hot tubs....

[keniff]

So hot tubs, would you use the pme supply and get that slight tingle when getting out or rod it? Can't find a reg on it so it's a bit unclear. Your thoughts please!!

 

[Strima]

All depends on the installation, cable run etc and manufacturers instructions. Seen quite a few hot tubs but no stakes in.

 

[keniff]

Yeah see iv acquired one, no instructions etc, wired it with swa to mini consumer unit built in the tub, using the provided pme tncs earthing. I don't get a tingle but the mrs does lol

 

[Dcf]

I've just done a big swim spa on a three phase pme connection,
The regs state that if it's pme then it requires an earth rod with a resistance of 20 ohms or less .its tucked away in the special locations bit about pools.
ive also seen plenty without rods though.

 

[Strima]

The regs state that if it's pme then it requires an earth rod with a resistance of 20 ohms or less

That's going some with rods to get it down that low, I know it is possible but come on, 20 ohms, would end up spending more on rods than anything else.

 

[keniff]

I've just done a big swim spa on a three phase pme connection,
The regs state that if it's pme then it requires an earth rod with a resistance of 20 ohms or less .its tucked away in the special locations bit about pools.
ive also seen plenty without rods though.

Just found that reg, it says when pme is used to supply the pool or basin it is recommended to use a rod for equipotential bonding, that would mean the frame etc would be on a rod and pme? Surely it's one or the other?

 

[Dcf]

Just found that reg, it says when pme is used to supply the pool or basin it is recommended to use a rod for equipotential bonding, that would mean the frame etc would be on a rod and pme? Surely it's one or the other?

That was my thoughts exactly.
i ran a 10 mm earth wire from the db to the pump unit and another 10mm from the unit to the rod.i got it down to 23ohm at the rod end.its in the regs for a reason I suppose but it's not that clear what that reason is.good old wiring regs you would think that after 17 editions it would be black and white though instead of a murky shade of grey

 

[keniff]

So you had pme and TT connected together? Strange but that's how I read it also. Might just bang a rod in doubt I will get it down to 20 in my area but it's only a "recommendation" I suppose

 

[spark 68]

While looking through GN7 (for something else) hot tubs are mentioned in chapter 13 of GN7 amd1,
it says basically where a hot tub is in a room other than a bathroom then section 701 (location containing a bathroom or shower) is to be applied in full.

Where the hot tub is located outdoors then section 702 (swimming pools etc.) applies in full.
Wrt 702, supplementary bonding is required for all extraneous conductive parts in zones 0,1 and 2 irrespective of whether they are simultaneously accessible or not.

 

[Engineer54]

Very much depends on the location and what the tub is mounted on. If you have positioned the tub on bare ground/grass, then your asking for trouble!! The best mounting/positioning is on a hard wood decking base, with a decent distance of surrounding decking. Concrete or concrete and slabs is only a little better than bare ground, especially if there is reinforcement in the concrete.

Nothing wrong at all with combining a rod to a PME supply. What i have to laugh at though, is that your BS7671 calls for a 20 ohm Ra on a hot-tub with a PME connection, but 200 ohms on a TT system covering the whole installation!!! It's not as if 20 ohms is going equal out, say a 0.35 ohm PME earthing. I know what they are trying to do, but you'ld be Better of making the hot-tub a TT and be done with it, but not a 200 ohm TT...lol!!!

 

[spark 68]

Hi E54,

As far as PME goes, I think this probably the time to consider TTing it, as you would for caravan pitches etc.

Edit: just read your post saying basically the same thing, lol

 

[keniff]

Well it's on a concrete base untill decking goes down, I'll bang a rod in but best I get in this area is about 100 with a few rods! Thanks guys

 

[Engineer54]

Well it's on a concrete base untill decking goes down, I'll bang a rod in but best I get in this area is about 100 with a few rods! Thanks guys

You surprise me, What area of East Sussex are we talking about??

 

[keniff]

Hastings it's very rubbly here seem to get nice readings in the what i think clay areas, but not alot are TT around here

 

[Englishsparks]

IS the Mrs insured?

If so dont worry about.


Seriously! I would follow the manufacturers instructions, so why not google it for the info.

Yeah see iv acquired one, no instructions etc, wired it with swa to mini consumer unit built in the tub, using the provided pme tncs earthing. I don't get a tingle but the mrs does lol