Jacuzzi/Hot tub isolation

[unphased]

Hello all

Hope I can clear my head about a design I am wrestling with for a customer. One aspect of the design is to install a 32A supply to a hot tub.

Just to summarise the job so you can picture what I am trying to achieve.

The customer has had a shed built in the corner of his garden. It is a concrete block walled shed, not timber. He is having a hot tub installed in the opposite corner with a pergola over it and surrounding it with timber decking. The garden slopes from the back down towards the house then there are steps down to a patio paved with brick paviors and there is a brick retaining wall about 450mm high across the garden along the patio. The fuseboard is in the front part of the house inside the garage. There is no electrical supply yet to the shed. Only supply is serving brick wall lights along the retaining wall switched from the conservatory.

The cable distance from fuseboard to shed via the perimeter of the garden is around 30m. Therefore I was thinking of a 40A or 50A supply to the shed and wiring everything from the shed in to the garden area including the 32A supply to the jacuzzi, a couple of floodlights, one on the pergola and one on the shed, decking lights and the internal shed light and sockets.

I am looking at using a wise box to remote switch the lighting wirelessly. So I want to put all the kit in the shed. The distance between the shed and the jacuzzi is about 8m.

I am pretty much clear in my mind about everything except one thing. Is it acceptable to have the isolator for the hot tub inside the shed? It will make life sooooo much easier if it can as I can wire up everything in the shed. I have not wired a hot tub before. The hot tub company are being unhelpful about giving me any information. Section 702 in simple terms restricts the isolator closer than 2m but is there any rreason why I should not put it in the shed 6m away from zone 1?

Soirry for the long winded description I am trying to avoid people asking me more questions, I just want clarification on this one point.

Thank you.

 

[gavindrummond]

What system do you have supplying the house? Ie: TT. TNS TNCS.

 

[unphased]

Hi gav. I knew someone was going to ask this. Its PME, mate.

 

[gavindrummond]

Also I worked for bathstore and remember selling these. If the customer has a heart condition or blood pressure issue they have to consult the doctor before even thinking of having one installed as it can cause heart attacks. But then again if the missis is in the tub along with Viagra and a bad heart that will cause heart failure too lol

 

[unphased]

:^O I don't believe my customers have any issues with their hearts.

 

[gavindrummond]

I can't really help out as I'm a student phase but what I would suggest is look at the regs and the on site guide that should clarify things hopefully

 

[unphased]

We are all students my friend. No worries. I was also wondering about the connection from the isolator to the hot tub. So many questions. Originally I was going to put a switched socket on a post just outside zone 1 fitted with a commando socket and wire a 4mm2 3-core flex to a commando plug and connect the flex direct to the tub. Then I am wondering whether flex can be used outdoors? YY and SY has to be purchased in 100m lengths (apparently) but I could get 4mm2 flex in cut lengths. Then I wondered about putting the isolator in the shed (hence my query) and putting the commando socket on the outside of the shed.

 

[gavindrummond]

I'm not sure phase I don't own a copy of the regs or the on-site guide yet. I think the older more experienced ones can help you out with this conundrum. will be watching and taking notes though

 

[Andy™]

We are all students my friend. No worries. I was also wondering about the connection from the isolator to the hot tub. So many questions. Originally I was going to put a switched socket on a post just outside zone 1 fitted with a commando socket and wire a 4mm2 3-core flex to a commando plug and connect the flex direct to the tub. Then I am wondering whether flex can be used outdoors? YY and SY has to be purchased in 100m lengths (apparently) but I could get 4mm2 flex in cut lengths. Then I wondered about putting the isolator in the shed (hence my query) and putting the commando socket on the outside of the shed.

YY & SY can be bought in metre lengths. i usually get cable from UK cables - google them and see if you have a branch near to you

 

[unphased]

Thank you Andy.

 

[steptoe]

Hi gav. I knew someone was going to ask this. Its PME, mate.

are you sure it is PME and not simply TNCS ?

yep, YY and SY can be got in metre lengths, who told you it had to be in 100m lengths? a rubbish wholesaler?

 

[Phoenix]

TNCS without PME is surely a very rare beast though steptoe isn't it? I may have come across it once... and certainly wouldn't be found on a domestic in the middle of a housing estate.

The DNO have to ensure the network is upto PME standards before connecting customers earths to the neutral conductor.

The one time I have seen TNC-S exist alone, is where the DNOs transformer was located in the mains room of an educational building (I had to get the DNO rep out to get access and sort out a dual access arrangement in order to access the customers main panel board). A 4/5m piece of waveform cable came out the transformers terminal box, and swept along the floor from the transformer end of the room to the switchgear end, where it went into the service head with the CT chamber on top. Looked like there had been a dividing wall at some time, but looke dlike been demolished to make way for a transformer replacement some time in the past.

Certainly would not expect to see TNCS without PME where there is any real distance between the tx and consumer, excepting DIY PME conversions done without the permission of the DNO.

Apologies if I missunderstand!

Back to the point in question. I've got a similar installation to do later on this year for a relative, I'm planning on making the cabin installation a local TT system... using the TNCS/PME doesn't sit right with me in this instance

 

[unphased]

Hi Phoenix. Yes I had come to the same conclusion. I am okay with most of the installation, it's just this hot tub circuit. The hot tub has controls on the top of it so it can be locally switched on and off from the tub. Putting the isolation switch inside the shed is what I cannot decide. Cannot see a reason why not (yet).

 

[Andy™]

providing its accessible, i cant see any problems with it being in the shed either. i would use a rotaty isolator though so it can be locked

 

[Phoenix]

There is a general requirement which is echo'ed by the hot tub manufacturers that the isolation switch must be clear and accessible... standard stuff.

As to where you can put it, in absence of anything more specific I'd resort to section 702 of the regs and treat it as a swimming pool, this states its permitted to install a switch or socket outlet in zone 2 of the swimming pool as long as its protected by a 30mA RCD*. Or if not possible to locate elsewhere within zone 1 but at least 1.25m from the border of zone one and at leat 1 foot above floor, as long as its 30mA rcd protected*

*other protection methods allowed are electrical separation or SELV, non of which are going to be relevant to your install.

General requirements require a minimum of IPx4 in zone 1, or IPx2 in zone 2 (indoor locations, no cleaning with water jets likely)

How big is the cabin, Can the customer locate the hot tub so that one wall is at least 1.25m from the edge of the hot tub (and preferably 2m) ? I'd then install a IP54 rotary isolator.

Where are you locating the distboard for the pool cabin? .. I'd personally favor a second bit of it partitioned off from the main room (otherwise you are into the realms of weather proof dist boards!)

 

[steptoe]

TNCS without PME is surely a very rare beast though steptoe isn't it? I may have come across it once... and certainly wouldn't be found on a domestic in the middle of a housing estate.The DNO have to ensure the network is upto PME standards before connecting customers earths to the neutral conductor.

The one time I have seen TNC-S exist alone, is where the DNOs transformer was located in the mains room of an educational building (I had to get the DNO rep out to get access and sort out a dual access arrangement in order to access the customers main panel board). A 4/5m piece of waveform cable came out the transformers terminal box, and swept along the floor from the transformer end of the room to the switchgear end, where it went into the service head with the CT chamber on top. Looked like there had been a dividing wall at some time, but looke dlike been demolished to make way for a transformer replacement some time in the past.

Certainly would not expect to see TNCS without PME where there is any real distance between the tx and consumer, excepting DIY PME conversions done without the permission of the DNO.

Apologies if I missunderstand!

Back to the point in question. I've got a similar installation to do later on this year for a relative, I'm planning on making the cabin installation a local TT system... using the TNCS/PME doesn't sit right with me in this instance

I would say quite the opposite ime, thjere are more non-PME'd TNCS systems in place then there are PME systems.

remember if you are running a cable that distance from the origin you will need to ensure the integrity of the PME system on your extended EZ.

 

[unphased]

The main issue I have is running cables back and forth around the garden. The shed is new and is blockwork. I thought that by running a supply to the shed would minimise the length of cables and I could then use the shed CU for all the outside circuits. I have already consulted section 702 and I have taken in to account the zones. So roughly 8m of flex from the shed to the tub would connect it.

 

[sammers230]

If the hot tub is next to a bordering wall in the garden couldn't you fit a rotary IP54 isolator to that following distances set out in section 702, then it would be pretty local to the tub. if not the surely the shed would be ok in my opinion as long as it is clearly labeled as already mentioned.

 

[unphased]

Hi Canoe, I've just been reading the product descriptions for YY, SY cable on UK cables website. I cannot determine whether these cables are suitable for trailing across the ground (underneath timber decking) as for SY it says suitable outdoors if protected. Also, standard 3093Y flex might be okay. What would you use? Could be better off with standard SWA to withing a metre of the tub then switching to flex off a IP box for the last metre to connect in?

Edit: PS the tub is outdoors under a pergola.

 

[PC Electrics]

I'd use a rotary isolator, not a commando socket. And I would position it on the outside of the shed so it's accessible when the shed is locked up but the spa is in use.

I usually use H07RN-F from isolator to spa. Unless you think swa is called for, most spas will take an swa entry.

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You should find out the full load current of the spa. You might be able to make the circuit 25A (use Hager). Also design the circuit to the max current without any diversity as most spas take anything from 6 to 12 hours to warm up from cold and can run at full chat when in use