Hot Tub help.

[Soulsurfer]

Hey all, friend of mine just getting a hot tub they would like fed and not done one before so wanted to check on any advice with them as it seems quite heavy on the load requiring a 25A & 16A feed
25A supplies jets & pumps etc.. & 16A for heating elements.

House is on a TN-C-S supply 100A. Only 11.5 metre run from CU to point of hot tub but not sure if I can maybe use a multi core swa at 6mm rather than a separate 6mm & 4mm swa's ? Also am concerned that there are issues with earthing arrangements etc. was going to install an Rcbo at source but would that be incorrect ? Also diversity is there any allowable ?

 

[Midwest]

I'm with Buckfast with regards to making the hot tub TT, due to small differences in potential between the TNC-S earth and true earth.

But as Davesparks suggest, earthing the slab with a rod (or similar) back to the MET would negate this potential? I guess if you an get your rod or tape with a suitably low resistance of less than 20 ohms AND are confident it will remain so then TT is the way to go.
Soulsurfer, have you done a test for a rod yet? Is the slab being constructed with reinforcing bars?

 

[Soulsurfer]

No tests for the rod yet, and will see the slab chaps later today and see what's happening, I would imagine they will be using rebar mesh throughout the slab.

 

[Midwest]

Are you going to bond the rebar? Might be worth consideration (as Davesparks alluded to #26), have a look at some of those links I posted #19.

 

[Midwest]

Have you suggested the composite decking to your client?
Here's some pics from the Bishta web site; BISHTA BISHTA Awards 2014 - BISHTA
Perhaps we could see some pics of your finished article?

 

[Soulsurfer]

Problem is finding a decent way to joint onto rebar if it would be safe, BS951 clamps or similar prob wouldn't be good.

 

[uksparks]

But a PME earth is a much better earthing connection than what is normally achievable in a domestic TT. The addition of a supplementary electrode connected to the MET is the only suggestion in the regulations on the matter.

I agree, all the hot tubs I have connected i have just used the PME earth as it is always going to be better than that of a TT in realistic circumstances.

In reality you are never going to loose the neutral, and if you did its literally one in a million chance say WPD.

 

[Midwest]

Problem is finding a decent way to joint onto rebar if it would be safe, BS951 clamps or similar prob wouldn't be good.

You can get specific rebar clamps, probably not from your local wholesaler though.

 

[uksparks]

You can get specific rebar clamps, probably not from your local wholesaler though.

Whats wrong with twisting it round it with a bit of tape for good measure...

 

[uksparks]

Problem is finding a decent way to joint onto rebar if it would be safe, BS951 clamps or similar prob wouldn't be good.

The words of the BYB regulation 514.13.1 states that it can be used for extraneous parts so I guess it would be acceptable, but maybe something else would be more suitable, I most likely wouldn't use a BS951 clamp as there is better out there.

 

[Soulsurfer]

Well if it's a bit of Denso tape ;-) or a big crimp eyelet and it could buzz like one of those wavy wire puzzle things !!

 

[Soulsurfer]

Have seen there are a great many specific rebar clamps with all different earth connecting clamps built on. They look good. Just been back to job to see pool construction lads and they are digging out tomorrow but no rebar and also just a touch of concrete apparently with 4 corner slabs kind of affair ! they were very vague. Looking at job I also have issues with getting an swa out from house as there is only a low wall opposite so it's back to clients to see if I can dig out their slabs on pathway to go underneath or else it really will be free air !! :cheesy:

 

[Midwest]

Have seen there are a great many specific rebar clamps with all different earth connecting clamps built on. They look good. Just been back to job to see pool construction lads and they are digging out tomorrow but no rebar and also just a touch of concrete apparently with 4 corner slabs kind of affair ! they were very vague. Looking at job I also have issues with getting an swa out from house as there is only a low wall opposite so it's back to clients to see if I can dig out their slabs on pathway to go underneath or else it really will be free air !! :cheesy:

Hope the concrete's gonna be nice & thick! Run the swa under the composite decking, you've convinced them to install!