Is a hot tub governed by section 702?

[RF Lighting]

To diverge slightly off topic here, the original discussion with my colleague which prompted this discussion was actually in relation to earthing arrangements on a PME supply.

Regulation 702.410.3.4.3 (ii) says on the note that where a PME earthing facility is used that it is (b)recommended[/b] that an earth rod or mat should be installed and connected to the supplementary bonding (paraphrasing)

Two things. Why would this not be mandatory rather than a recommendation if it’s actually required, and why not prohibit the use of PME all together for this type of installation rather than rodding the bonding?

 

[JohnW2]

Certainly when I did my most recent regs course, there was no reference made at all to any GN’s, OSG or electricians guides, all though I do think the earthing and bonding and the testing guidance notes should be compulsory reading as a minimum.

All such documents (even the OSG and mutterings of NIC) can be useful at times, provided one remembers that (even if written by the IET) they only represent someone's opinion regarding interpretation of BS7671, not the least because it can be interesting, and sometimes thought-provoking, to be exposed to other people's interpretations of BS7671 - but that makes no difference to what BS7671 'actually says'.

If BS7671 'as it is actually written' is silent, unclear, ambiguous or even just 'wrong' about some issue, then that remains the case regardless of what may be written in any 'guide', even if written by the IET. Those who wish to, or are constrained to, comply with BS7671 presumably have to comply with BS7671 'as written', regardless of any opinions (even those expressed by the IET) about interpretation.

Kind Regards, John

 

[JohnW2]

To diverge slightly off topic here, the original discussion with my colleague which prompted this discussion was actually in relation to earthing arrangements on a PME supply.

Hardly off-topic'!!

Regulation 702.410.3.4.3 (ii) says on the note that where a PME earthing facility is used that it is recommended that an earth rod or mat should be installed and connected to the supplementary bonding (paraphrasing) ... Two things. Why would this not be mandatory rather than a recommendation if it’s actually required, and why not prohibit the use of PME all together for this type of installation rather than rodding the bonding?

Two excellent questions, but I can't read their minds!

Anyway, to essentially repeat myself yet again, my view would be that IF they did decide that the earth rod/mat was required (not just 'recommended') OR that PME was not allowed at all, in the case of a "swimming pool" (presumably because they felt that such was required 'for safety'), then why would anyone think that the same degree of electrical safety should not be required if the container full of water was called a hot tub?

In other words, why would anyone think that the lack of explicit mention of hot tubs in 702 was anything other than an 'oversight'? A 'large something full of water', in proximity to electricity, does not become any more or less safe depending upon what one calls it!

Kind Regards, john

 

[RF Lighting]

I agree. I know I often say it, but we have to remember that BS 7671 is a minimum standard that must be complied with, but in my opinion one should always strive to do the best job you can.

I put some steel conduit in a wall today. Not required by the regs, but it’s a better job. It’s the same thing to me.

I can't read their minds!

Ha ha perhaps I phrased that badly! It just seems a strange regulation to me and thought it could raise some interesting points, or maybe were both missing something blindly obvious.

 

[JohnW2]

I agree. I know I often say it, but we have to remember that BS 7671 is a minimum standard that must be complied with, but in my opinion one should always strive to do the best job you can.

Very true, but I think what we're discussing is 'worse' than that (albeit probably just due to 'oversight' in writing the regs) - since I really don't see any rational (or even safe/'responsible') reason why even the minimum (safety) requirements should be any less for a hot tub than for a swimming pool.

Ha ha perhaps I phrased that badly! It just seems a strange regulation to me and thought it could raise some interesting points, or maybe were both missing something blindly obvious.

I don't think it was you that phrased it badly' but, rather, "they" who did, when they wrote the regs.

For a start, I'm not at all sure that it is really appropriate for "regulations" to make 'recommendations' - that is probably the place of 'guidelines', in relation to things that are not 'required (by regulations), albeit they probably should (unlike the OSG!) make it clear that they are just 'recommendations', rather than giving many people the impression that they were 'required' (by regulations).

To my mind, regulations should be prescriptive, either requiring something or not. One might suspect that the 'recommendation' you refer to means that the authors could not even agree amongst themselves about whether or not it should be 'required'.

As for your second question, IF they decided to 'require' (rather than merely 'recommend') the earth rod/mat when a PME earth was used, rather than simply 'not allow' a PME earth at all, I suppose that could be because they felt that having the rod/mat rendered a PME earth 'safe enough' (and that, in some circumstances, having the PME earth as well as the local rod/mat might 'increase safety')?

Kind Regards, John

 

[RF Lighting]

It’s certainly a strange one and I’m sure Bernard will be along at some point to remind us of the flip side that is an open circuit CNE connection, which would be less safe than a straight TT circuit!

Perhaps this is where the IET disagree also...

 

[JohnW2]

It’s certainly a strange one and I’m sure Bernard will be along at some point to remind us of the flip side that is an open circuit CNE connection, which would be less safe than a straight TT circuit!

No doubt, but if he is going to invoke scenarios of vanishingly small probability (person being in vicinity of hot tub, fault making something touchable 'live', the person touching that something and a supply CNE fault - all simultaneously), then maybe we could flip his flipside back again, by pointing out that in the equally 'vanishingly improbable' scenario of an extreme period of drought, a TT earth might not facilitate operation of an RCD in the event of 'need', whereas a TN-C-S one would

Perhaps this is where the IET disagree also...

Yes, possibly - as I said, they certainly seem 'undecided'. Maybe, even, Bernard is a clandestine member of JPEL/64!

Kind Regards, John