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 ?

 

[PEG]

Hi dude,i'll kick it off with a early point...your feeds,will be feed,singular,as the requirements for pumps/heating will have to be considered together. These may be fed separately from one DB,we do not know,but it will be your assessed and calculated total load from this,that you will need.

With this,you can then determine cable size,and type,taking into account additional factors such as positioning and earthing requirements.

...Now the puck has been slid across the ice...:smiley2:

 

[UNG]

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 ?

How many jets & pumps has this tub got? at 25A it sounds like they are quoting start current not running current as most hot tub pumps run at less than 5A each and they don't normally have more than 2 water pumps and an air pump

 

[SS-2015]

Yeah, I can't imagine it having 2 separate supplies.
Any I've done have been 32a or 40a supply.
I usually put larger cable in too so if they upgrade hot tub at a later date, they can do so with minimal disruption.

 

[Soulsurfer]

Ok so I was hoping the 25 would include start current and be maybe covered with a type C, but is an earth rod needed as opposed to just connect through Rcbo and swa cable as its TNCS as is. But is that not ok for hot tubs as in reduced resistance of persons due to water etc & being outside too ?

 

[Midwest]

Soulsufer, this has come up quite a few times. If you do a search you'll see a few threads on it. No expert in this area myself, but I believe advice is to put in an earth rod (back to isolator for tub), if the area the tub is being sited, is in contact with the general mass of earth; i.e. people stepping out of tub onto grass.

 

[Soulsurfer]

Hi again, right I'm a bit baffled now as a mate local company years in contracting has said he's done loads of hot tubs straight off 61009 Rcbo and isolator. I also hear about running off Rcbo to isolator and then I take it connecting earth only at isolator ? Then from hot tub mains connections take an earth to earth rod in lawn ? Does that seem right and /or reasonable ? Never needed to use any earth rods before and am a little lost here. Not found any other posts that enlighten me either ? Thanks

 

[Midwest]

Hi Soulsurfer. Have a look at reg. 702.410.3.4.3 (ii), read the note (BYB).
Here's a few threads; http://www.electriciansforums.co.uk/electrical-forum-general-electrical-forum/60489-hot-tubs.html
http://www.electriciansforums.co.uk...ectrical-regulations/92700-hot-tub-again.html
http://www.electriciansforums.co.uk...eral-electrical-forum/91475-hot-tub-help.html
And from outside this forum;
IET Forums - HOT TUBS
IET Forums - PME to hot tub
http://*****************forum.co.uk/topic/21558-new-hot-tub-install/

 

[Buckfast]

Soulsurfer, been reading this thread for a few days and as you say this area new to you and therefore you are doing the right thing in asking, and i think you are asking the right questions. Generally when i install hot tubs off a PME supply i do not use the pme earth for hot tub. I would take a supply L+N fused in distribution board to an insulated enclosure with a EN61008 dp rcd rated at 30mA. I would then dig a trench and install an earth tape as opposed to an earth rod, (Tape 3mm * 25mm * 25 metres generally). Then check earth loop impedance of tape, which you require to be as low as possible. Depending how close you are to PME grounding could be as low as 0.40 ohms or even as high as 200 0hms. When you are satisfied that earth loop impedance is satisfactory and will stay that way in all weather conditions etc, carry on with install using TT earth as opposed to PME earth. Label accordingly so that the two never become joined. Hope this helps.

 

[Soulsurfer]

O.k. Thanks Buckfast, I'm sure my wife will like the name, seeings as she's Scottish ! I may have trouble getting 25 metres of tape into the ground as the entire garden is only about 10 metres long. How deep has said trench got to be ? Also only rcbo I saw recently was single pole with a switched Neutral ? Very pricey too.

 

[Buckfast]

Soulsurfer, everything is subjective to the conditions that you have on site and the most important thing that you have to guarantee is a low impedance earth path, and also that this earth path is guaranteed at all times. Around my kneck of the woods it is solid limestone and sometimes 12 inches from the surface is a maximum, and others a little more. If you have a good soil depth then try putting a 5/8th rod in and check impedance. If you can get two in (8ft) even better. With regards EN61008 Rcds, these are just DP Rcds and cost next to nothing. Put a correctly rated Mcb up front of this. Mcb giving overload protection and rcd fault protection.

 

[Soulsurfer]

Apologies if I'm dragging on a bit, but to clarify you would instead of an Rcbo at source just feed out to the enclosure to the Rcd then there will be a 32A rotary isolator and on to the tub cct board. The earth tape & or rods sunk in and terminated back at isolator and enclosure therefore a 2 core swa would suffice from cu to Rcd enclosure. Only thing is the armour being earthed.

 

[Buckfast]

No apology needed. Normally for these installations i am asked for a 32A supply. This can generally be supplied via 6mm SWA. I always use 3 core. I would come from existing distribution board from unprotected side (No rcd) with a 32A B type mcb, L & N only. This i would take to an insulated enclosure where i would have my DP Rcd rated at 30mA. (Not sure how the link to siemens rcd popped up in last post but it was not put there by me ?). I would bring my TT earth also to this enclosure and connect 3rd core of SWA and also armour to this. Often i would also put a rotary isolator here as well as they are easier to lock off. I would then put rotary isolator at other end of SWA and from here make final connection to Hot tub. Make sure that isolator at far end cannot be touched from hot tub. Hope this helps.

 

[Soulsurfer]

Yes that helps a lot, think I'm on the right path as it were, although where I am stuck slightly is I was visualising swa leaving cu out wall and along wall exterior to the insulated enclosure then into Rotary isolator. Are you saying you would have like that plus a rotary isolator at cu end too ? Or from Mcb to insulated Rcd enclosure near cu then isolator all that end before rest outside at far end and isolator again ?

Quote:
"Often i would also put a rotary isolator here as well as they are easier to lock off. I would then put rotary isolator at other end of SWA and from here make final connection to Hot tub. Make sure that isolator at far end cannot be touched from hot tub."

 

[Buckfast]

Soulsurfer, From Mcb in distboard (No Rcd) to Dp Rcd, to rotary isolator. Generally do all this indoors. Then SWA to Rotary isolator at hot tub end, then final connection. I only use rotary isolator at mains end as they are easier to lock off when working out of site in garden. Maybe a little belt and braces but that is just how i do it. I also tend to use SWA lock nuts as opposed to banjo's as the isolators can be a little tight for room.

 

[Soulsurfer]

Excellent that's real good of you, now for my induction into TT :smile5: thanks for helping mate. I totally prefer over cautious than probably ok to be honest too.

 

[davesparks]

Soulsurfer, been reading this thread for a few days and as you say this area new to you and therefore you are doing the right thing in asking, and i think you are asking the right questions. Generally when i install hot tubs off a PME supply i do not use the pme earth for hot tub. I would take a supply L+N fused in distribution board to an insulated enclosure with a EN61008 dp rcd rated at 30mA. I would then dig a trench and install an earth tape as opposed to an earth rod, (Tape 3mm * 25mm * 25 metres generally). Then check earth loop impedance of tape, which you require to be as low as possible. Depending how close you are to PME grounding could be as low as 0.40 ohms or even as high as 200 0hms. When you are satisfied that earth loop impedance is satisfactory and will stay that way in all weather conditions etc, carry on with install using TT earth as opposed to PME earth. Label accordingly so that the two never become joined. Hope this helps.

You are testing earth electrodes incorrectly if the proximity of a DNO earth electrode is affecting the result to such an extent.

Why on earth are you not using the far better PME earth connection for hot tubs? There is no requirement to do this in the regulations, merely a recommendation to install an electrode connected to the main bonding of the installation.

 

[Buckfast]

Your very welcome. Best Regards Buckfast

 

[Midwest]

Why on earth are you not using the far better PME earth connection for hot tubs? There is no requirement to do this in the regulations, merely a recommendation to install an electrode connected to the main bonding of the installation.

Interesting subject, and as I previously stated no expert in this area, and I'm not currently installing a hot tub! The links I posted #8 (note the last one fails) have a discussion on TNC-S supplies to hot tubs. I think it is fair to say the consensus for TNC-S supplied hot tub - in worst case scenario, with tub outside, situated on the lawn for example - is to convert (at tub end isolator) to TT. I recognise that re 702.410.3.4.3 does not preclude the use of a pme earth & recommends adding an 'additional' earth rod to the pme means of earthing.
I've found a couple of pdf's etc on the issue; http://www.google.co.uk/url?sa=t&rc...pe=pdf&usg=AFQjCNGzR0CSqgATvs1_jcKK3XtD-CDM7g
Swimming pools: to bond or not to bond? - IET Electrical
http://www.google.co.uk/url?sa=t&rc...pe=pdf&usg=AFQjCNEkQbO5R9aWPLD16Phth0h2EuQzdg
These are split 2 - 1 in favour of 'recommending' converting to TT earthing.
Lastly, Soulsurfer has not actually described where the hot tub is being installed, perhaps you could advise us of that Soulsurfer?

 

[Soulsurfer]

Hi mate, Hot tub is apparently being installed on a custom laid concrete pad, Pool lads have told me that they are digging up lawn this week to pour the pad and then it will sit there which is about 0.8 to 1 metre off corner of house in back garden area. Small garden almost all grass with metre or so of patio slabs around the edges before the lawn starts.