Hot tub installation question.

[HappyHippyDad]

Evening all..

I have been asked to supply power for a hot tub. However, I am having difficulty finding out the information I need from the company selling the hot tub!

I mainly wanted to find out 2 things, the power that the unit requires and any cable size that is stated in the manufacturers instructions, neither of which the company new. They just said that it needs a 32A MCB. The customer states he was told it needs a 21A isolator switch??? So basically I'm none the wiser!

I have tried to find the Manufacturers instructions online to no avail. It is a 'Villeroy and Boch R6L' if anyone is clever enough to find a site which shows the wattage of this unit!

3 questions:

1. If it is a 32A MCB then would you agree that 4mm cable is OK? Both VD and Zs would be ok:
VD is 10.56V @ 32A and 30 Meters.
Calculated Zs= 0.72ohms (Ze=0.22 TNCS)
The reason I ask this question is because 6mm seems to be the 'norm' from scouring the net, but the calcs work out fine for 4mm.

2. Some hot tubs recommend a rotary isolator. Is this generally required?

3. Some hot tubs require a type C MCB. Is this generally required?

Cheers all.

PS... It has RCD protection.
Pps... I would like all the replies to be yes,no,no please

 

[Leesparkykent]

Installation and Electrical Requirements

It states what's needed in Amps, you can obviously work the rest out though if needed.

 

[Leesparkykent]

Evening all..

I have been asked to supply power for a hot tub. However, I am having difficulty finding out the information I need from the company selling the hot tub!

I mainly wanted to find out 2 things, the power that the unit requires and any cable size that is stated in the manufacturers instructions, neither of which the company new. They just said that it needs a 32A MCB. The customer states he was told it needs a 21A isolator switch??? So basically I'm none the wiser!

I have tried to find the Manufacturers instructions online to no avail. It is a 'Villeroy and Boch R6L' if anyone is clever enough to find a site which shows the wattage of this unit!

3 questions:

1. If it is a 32A MCB then would you agree that 4mm cable is OK? Both VD and Zs would be ok:
VD is 10.56V @ 32A and 30 Meters.
Calculated Zs= 0.72ohms (Ze=0.22 TNCS)
The reason I ask this question is because 6mm seems to be the 'norm' from scouring the net, but the calcs work out fine for 4mm.

if the calcs work out that 4mm is ok...then 4mm is ok. Personally I would put 6mm In based on your calcs above as the VD is close to the mark

2. Some hot tubs recommend a rotary isolator. Is this generally required?

section 702 I think without looking

3. Some hot tubs require a type C MCB. Is this generally required?

Not always, but no harm in putting it on a type C if Zs complies
Cheers all.


PS... It has RCD protection.
Pps... I would like all the replies to be yes,no,no please

PS...if you are using the TNCS earthing you may have to install a rod/s connected to the MET (can't remember the max Ra stated ... <20Ω off the top of my head)

 

[HappyHippyDad]

Thanks Lee.

You're right it is section 702. It states that switchgear should be outside of zone 1, but I want to know if a rotary switch is needed? If it is for isolation purposes for maintenance then it has the MCB, however if MI (if i can ever find them) state it is required then I will fit one.

The site you have linked just says a 'disconnect device must be incorporated in to your fixed wiring in accordance with local and national regs ( sounds very American). It also states to use a 32A MCB but gives no indication as to the wattage of the tub.

 

[Hellmooth]

I recently ran a supply for a hot tub, the manufacturer stated it needed a 32A supply and ran in 4mmm artic flex from the isolator, but didn't give details of current demand! I was supplying power and lighting as well so ran a 10mm SWA to a garage board, i then ran the 4mm artic flex to an isolator (recommended minimum 2m from edge of hot tub) and then to the hot tub which was supplied with its own RCD!

 

[Hellmooth]

Isolator is definitely needed hippydad, min 2 metres from edge of hot tub, I fitted a 32A rotary with my set up!

 

[HappyHippyDad]

Isolator is definitely needed hippydad, min 2 metres from edge of hot tub, I fitted a 32A rotary with my set up!

Thanks Hellmooth

You've said an isolator is definitely required which it will have as it has an MCB. Is the rotary isolator simply for maintenance, if so I can't see why the MCB can't be used, unless the rotary has another purpose? Also, unless local isolation is required.

 

[davesparks]

Basic common sense says you fit an isolator local to any piece of current using equipment, this has been standard practice for as long as anyone here has been in the industry.

 

[HappyHippyDad]

Basic common sense says you fit an isolator local to any piece of current using equipment, this has been standard practice for as long as anyone here has been in the industry.

That's fair enough, there have been quite a few debates over the years on this site as to whether local isolation is required by the regs or whether it is simply down to good practise. Fan isolators come to mind... Must have discussed a 1000 times, so a fair enough question to ask and discuss I think.

 

[Hellmooth]

Yes the isolator is for local isolation, the mcb could be in the house so isn't a great idea........

 

[Midwest]

I have no experience of installing a supply to a hot tub/Jacuzzi etc, however I have read quite a few threads on this subject on this forum. You might want to do a search on that. Think converting TNC-S to TT supply was one consideration, depending on location of tub. Local isolator is pretty much essential, common sense applies, I think.

 

[davesparks]

There's no need to convert from a perfectly good TNCS to a less good TT! A supplementary earth electrode connected to the MET with an Ra less than 20ohms is recommended, and is a very good idea in my opinion

 

[D Skelton]

There's no need to convert from a perfectly good TNCS to a less good TT! A supplementary earth electrode connected to the MET with an Ra less than 20ohms is recommended, and is a very good idea in my opinion

You're right in that there is no need, however in my opinion it would be prudent.

With any other type of outbuilding or external supply on TN-C-S (barring maybe an all metallic outbuilding or static caravan) I'd agree wholeheartedly but hot tubs are different in that you're wet and barefoot when you're stepping out of them. That reference to true earth become even more important!

I've installed four hot tubs so far and the method I have used every single time (they've all been TN-C-S for some reason?) is a dedicated supply split at the origin to an external IP rated board near the hot tub with a 100mA s-type RCD and 10mA RCD in series with the suitably rated OCPD in this enclosure, and a rotary isolator. Each one has been rodded as a TT with the rod sited close to the hot tub and a maximum Ra of 20ohms.

What baffles me is that on two occasions all that was required by the instructions was an IP rated RCD 1363 socket outlet to plug the hot tub in to?! One of which was already installed in this way when I came across it on a periodic!

 

[Midwest]

Hmmm, very interesting subject. Done some searching on the net, don't think I would have one of these tubs anyway. Safety standard for whirlpool baths is IEC 60335-2-60, I think. If you do a google search on that, there's interesting pdf file by Low Voltage Directive Administration Cooperation (sorry can't cut and paste). It gives some examples of persons receiving electric shock, because of the construction of the products and inadequate insulation of live parts and heating elements, and poor instruction (by the manufacturer) on how to safely connect to the power supply. I wouldn't get in one!