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Hot tub lighting

AMC
Hi All
Ive been trawling the forums to try and make a judgement on which regs to follow.
Ive a client with a Wood fired Hot Tub, it has a blower and lights fitted. The manufacturer states the appliances is Class 2.
The hot tub has a internally mounted rccb 30ma, flex and European style plug which will be jointed to a swa cable under the tub.
Reading guidance from the Niceic and the IET I find a difference in opinion so I thought I’d ask you.
Niceic takes the view that Hot tubs are not covered under BS7671 so general wiring REG’s apply. However if fitted next to a swimming pool section 702 applies.
IET takes the view: “How could an electrical designer claim as a defence that the risks of electric shock for a hot tub installed outdoors is any less than that of a swimming pool, fountain or paddling pool, as defined in the scope of Section 702?”
So assume section 702 applies.

The hot tub has been placed on a slabbed patio area with two steps up to another patio area. There are ground mounted floor lights within 2 meters of the tub on the steps above the tub level.These floor lights are fed from a selv constant current driver with a max output voltage of 70V DC.

So if section 702 applies these lights would not be suitable looking at 702.55.4
So would you advise applying section 702 or general BS7671 regs?
My problem now is that each light is around £350ea and the ground works have been completed, so to change the lights/wiring would be very costly.
Also the earthing arrangement for the installation is TN-S. Which is ok for the class 2 hot tub?
Any advice appreciated.
Parents
  • 0

    I guess the main question is:  Should a plug and play type hot tub which is being permanently connected comply to section 702?

    By your helpful and appreciated replies Id say yes.

    Ive since realised the fittings are available in a 24v DC constant voltage format. So hopefully I can get these changed, before they are shipped.

    Regarding the earthing:

    702.410.3.4 Application of protective measures against electric shock

    NOTE: Where a PME earthing facility is used as the means of earthing for the electrical installation of a swimming pool or other basin, it is recommended that an earth mat or earth electrode of suitably low resistance, e.g. 20 ohms or less, be installed and connected to the supplementary protective equipotential bonding.

    The chances of an earth stake getting lower than 20 ohms on the rocky ground are very slim.The tub is fed off a local distribution board in a shed, which in turn is fed via a 30m x 10mm swa run back to the main plant room. Near the main plant room in a service void there are structural steel rsj's embedded in the foundations with a sub 20 ohm reading.

    I'm thinking of connecting the earth core of the SWA via a separate earth bar in the plant room to this steel work as an earth electrode. I could keep the armour connected to the TN-S system and isolate it via a plastic gland at the shed and use the TT connected 10mm core as the earth. The above reg doesn't specify where the electrode or earth mat is located.

    Or am I interpreting the reg wrong : earth electrode of suitably low resistance, e.g. 20 ohms or less, be installed and connected to the supplementary protective equipotential bonding.

    Should the structural steel work as an earth electrode be connected to the main earth terminal (TN-S) as a supplementary protective equipotential bonding?

    If so Ill have a TN-S which could be PME, supplemented by a TT system. At this rate my head is hurting more than a perceived electric shock!

Reply
  • 0

    I guess the main question is:  Should a plug and play type hot tub which is being permanently connected comply to section 702?

    By your helpful and appreciated replies Id say yes.

    Ive since realised the fittings are available in a 24v DC constant voltage format. So hopefully I can get these changed, before they are shipped.

    Regarding the earthing:

    702.410.3.4 Application of protective measures against electric shock

    NOTE: Where a PME earthing facility is used as the means of earthing for the electrical installation of a swimming pool or other basin, it is recommended that an earth mat or earth electrode of suitably low resistance, e.g. 20 ohms or less, be installed and connected to the supplementary protective equipotential bonding.

    The chances of an earth stake getting lower than 20 ohms on the rocky ground are very slim.The tub is fed off a local distribution board in a shed, which in turn is fed via a 30m x 10mm swa run back to the main plant room. Near the main plant room in a service void there are structural steel rsj's embedded in the foundations with a sub 20 ohm reading.

    I'm thinking of connecting the earth core of the SWA via a separate earth bar in the plant room to this steel work as an earth electrode. I could keep the armour connected to the TN-S system and isolate it via a plastic gland at the shed and use the TT connected 10mm core as the earth. The above reg doesn't specify where the electrode or earth mat is located.

    Or am I interpreting the reg wrong : earth electrode of suitably low resistance, e.g. 20 ohms or less, be installed and connected to the supplementary protective equipotential bonding.

    Should the structural steel work as an earth electrode be connected to the main earth terminal (TN-S) as a supplementary protective equipotential bonding?

    If so Ill have a TN-S which could be PME, supplemented by a TT system. At this rate my head is hurting more than a perceived electric shock!

Children
  • 0 in reply to AMC
    AMC said:

    I guess the main question is:  Should a plug and play type hot tub which is being permanently connected comply to section 702?

    By your helpful and appreciated replies Id say yes.

    This is not really an engineering question. The real one is whether a judge would include a hot tub within the definition of, "Swimming pools and other basins". 702.11 (scope) includes e.g. paddling pools, but excludes natural features.

    I do not think that there is any doubt: the common feature is that nearly naked people can stand within the structure. I would say that the size and depth are irrelevant.

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