Hot tub installation !

[devonsparky]

This is a follow up to a thread I started yesterday.

I have been working all day installing a hot tub situated outside on a patio slabbed deck.

Contrary to what I was told, it was TN-C-S supply so here is how I have wired it.

• From Henly blocks - 25mm tails to a one way board (Main Sw RCCB - 50A MCB)

• 10mm 3 core SWA from board to 63A rotary isolator and from rotary isolator to hot tub

• Earth rod with 10mm G/Y back to one way board and then used one core as an earth to the hot tub and connected the armour to the earth bar too.

Time beat me today so I have not connected into the Henly blocks yet and tested .......................... Is this how you guys would have done it. 10 years in the game and an approved electrician and it's still nice to get feedback off of this forum !! ha ha

 

[electric will]

I've got one of these to do this week, same tncs I'm also fitting a earth rod but was going to fit it near the tub, I thought closer to tub the better cus less potential difference within the earth? Or have I just made myself look really stupid?

 

[Guest55]

I've got one of these to do this week, same tncs I'm also fitting a earth rod but was going to fit it near the tub, I thought closer to tub the better cus less potential difference within the earth? Or have I just made myself look really stupid?

nope , youre right.
i would have fitted the earth rod within 2-3 metres of hot tub with earth cable connected to rotary switch.

 

[electric will]

Buff. Still ok to put rcd near original board isn't it? Don't have to be with the rotory isolator where I've split the earth? Also, 3rd core of swa and swa with be took back to met in house db.

 

[devonsparky]

My earth rod is in the only suitable position ............... it is roughly 4-5 metres away from the tub.

Ideally within 2-3 but surely this is good enough. My head is ready to explode !! I'm a pretty experienced electrician but this install has had me researching the regs/guidance notes/forums etc to make sure it is all done correctly. Looking forward to getting it tested and certified and getting out of there. ha ha

How can these 4-8 week courses make someone a Part P sparky when even the most expereiced sparks are always learning !!

 

[devonsparky]

My 3rd core and swa is all connected to my earth rod. The whole hot tub installation is therefore on TT.

 

[Guest55]

Who's Buff ?
;-)
rcd can be at the mains or local to hot hub if using swa , either is ok.
yes , connect swa and earth conductor together at the CU.

 

[Guest55]

The whole hot tub installation is therefore on TT.

no its not , all you've done is connect your earth rod conductor back to the MET of a TNCS supply , which doesnt achieve that much.
the earth rod cable should be connected to the end of the circuit at the rotary switch for the biggest benefits.

 

[electric will]

Auto correct sorry.

 

[devonsparky]

The earth rod cable goes back to the MET of the one way fuseboard I have installed specifically for the hot tub. Surely this makes this fuseboard TT as its L + N comes off of the Henly blocks.

 

[Guest55]

ah , didnt realise you werent taking an earth from the MET for the one way CU , my bad.
what was your earth rod loop reading out of interest ?

 

[electric will]

Don't tell him spike. Theyll only want you to put a 4 or 5 m rod in, don't matter what answer you give.

 

[devonsparky]

ha ha ................... No worries Biff55 !

I haven't finished the job yet so still have to put my one way fuseboard up yet ................ therefore I haven't done any testing yet.

I'm thinking if the earth loop reading needs to come down I can still stick another rod in from the rotary isolator.

I will post the readings if you are interested once I finish the job.

(Is it just me who feels like they are bordering on the side of electrical geek by spending the evening in this forum ?? lol)

 

[SPARTYKUS]

Okay, going to stick my neck out here....

why haven't you used the perfectly good earthing system provided (TNCS) and ... exported it?


bayonet fixed

 

[electric will]

I've started to spend a lot if time on here, nice to get other peoples view on stuff, as there's no one to chat about stuff when your out there. Not just make sure your not breaking the regs it's just nice to see how others would do things.

 

[electric will]

Sparkykus. Your brave, I considered taking tncs the blood tub I'm doing seems to me mainly made of wood and plastic.

 

[devonsparky]

OMG ....... SPARTYKUS ...................... don't go down that route of questioning !!!! It's been answered a million times on these forums !!
This is the whole basis of this thread really .................. Can't export PME so have to make a TT.

Case closed ha ha

 

[Guest55]

last hot tub i did was off TNS , didnt bother with any rods :-D

 

[SPARTYKUS]

I'm not being belligerent or devils advocate, also apologize if Inhave missed something in a previous thread / related thread. I have never installed a hot tub so am
not up to speed on specific regs (if any).

Hence my question.

Unless there's a specific reason, why can't you export it?

 

[electric will]

I'd say as long as its not metal framed and people can't touch exposed metal parts while their stepping in and out, exporting can't be a problem. Can it?

 

[baazab]

Who's Buff ?
;-)
rcd can be at the mains or local to hot hub if using swa , either is ok.
yes , connect swa and earth conductor together at the CU.

is it better at mains so then swa protctect by the rcd?

 

[SPARTYKUS]

There are specific circumstances where you cannot use Tncs (like caravan parks I believe, it has to be rodded, as a fellow forum member I know who works alot for the Caravan Club will testify).


Is a hot tub one of these instances?

The only other problem is with services like water pipes - which means main bonds also need to be extended- which could be a pain.


Apart from that I 'd rather have a Zs of 0.3 than 37 or 17 or 7 .....?

 

[Guest55]

Unless there's a specific reason, why can't you export it?

The Dno's dont approve of extending their PME earth beyond the equipotential zone of the building in which the supply is located.
This is only an issue if there is exposed / extraneous metalwork at or around the hot tub ,
as in the unlikely event of a neutral break this metalwork may rise to a dangerous potential.
hope this helps.

 

[keniff]

I replied in the other thread, I installed my tub using the supplied tncs earthing arrangement also putting a rod in at the tub end. This rod was well below 22 ohms as stated in the regs, the only problem I had was when you got out the tub and one leg was on the floor and one in the water you could feel a shocking feeling, slight difference between true earth and suppliers earth, therefor I disconnected the suppliers earthing and made the tub tt. Alls fine now so that's how I install them from now on!

 

[electric will]

Sparky, that's also my thought, I'm tempted to export now to be honest.

 

[electric will]

That's a point I mentioned that before, potential difference in the earth ( and tub full of water)

 

[Guest55]

There are specific circumstances where you cannot use Tncs (like caravan parks I believe, it has to be rodded, as a fellow forum member I know who works alot for the Caravan Club will testify).


Is a hot tub one of these instances?

The only other problem is with services like water pipes - which means main bonds also need to be extended- which could be a pain.
agreed , so in that instance you have a choice of running a 10mm earth bond from the MET to the outside pipes or , bang in earth rod near hot tub.
most choose the earth rod method if its a long run back inside and they're only using a 6mm cable anyway.


Apart from that I 'd rather have a Zs of 0.3 than 37 or 17 or 7 .....?
so would i lol

.......................

 

[electric will]

But if you export and have rcd protection how can people feel the tingle when getting in and out. This must be potential difference with the value at the met(via tncs) and the ground where the tub is located, part of body in the water and foot on the ground. Surely the max difference would be 50v any more the rcd would trip

 

[keniff]

Well I put my tester in the water and in the ground and was getting 2 volts. Not alot but you could really feel it

 

[devonsparky]

cheers for that 'keithsims' ................... NO exposed metalwork etc at the hot tub but I think if you TT it and the readings are good then this is the way to go.