Thoughts on two circuits and two gang switch ?

[holmslaw]

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[JohnW2]

Where an installation, item of equipment or an enclosure contains live parts that are not capable of being isolated by a single device† and no interlocking arrangement is provided to ensure that all the circuits concerned are isolated prior to gaining access, then Regulation 537.2.1.3 requires a durable warning notice to be provided......

Those regs have nothing to do with light switches. They are about 'parts' fed by two or more supplies ie mains/generator/battery/ups etc.

I don't really see why a light switch doesn't qualify as an 'item of equipment or enclosure'. However, as I said, I'm sure that warnings are very rarely provided for hall/landing two-way switching, for which there is very often no provision for isolation 'by a single device' (other then the installation's main switch - which I doubt is in the spirit of what is intended).

Kind Regards, John.

 

[SimonH2]

But more nice "sweeping" curves..................This bloke certainly gets about!

It wasn't me - we just found it like that when we moved the cabinet.

but worth leaving a clear note at the consumer uint to say which switch boxes have more than one MCB or RCBO supplying them.

That certainly makes sense, and one might argue its actually required (as part of 'identification'/documentation), but I wonder how often it's actually done, given that such a situation is presumably extremely common - quite probably more the rule than the eception for lighting switches in halls/landings etc.

More to the point, have you ever seen it done ?

 

[SimonH2]

Those regs have nothing to do with light switches. They are about 'parts' fed by two or more supplies ie mains/generator/battery/ups etc.

The only warning label required on light switches is to warn of the presence of 400volts.

Oh dear, I haven't inadvertently kicked off another discussion on the finer point of the regs have I ? I'll go and get some popcorn if that's the case

 

[sparkticus]

Those regs have nothing to do with light switches. They are about 'parts' fed by two or more supplies ie mains/generator/battery/ups etc.

The only warning label required on light switches is to warn of the presence of 400volts.

Yea thanks, I did wonder about that. The exact wording in the regs book for 537.2.1.3 reads "contains live parts connected to more than one supply"


As opposed perhaps to "contains live parts connected to more than one circuit "

 

[sparkticus]

More to the point, have you ever seen it done ?

No, I have never seen it and I regularly see lighting grid switch systems switching multiple circuits across multiple phases. There is almost always the 400 Volt warning.

 

[JohnW2]

but worth leaving a clear note at the consumer uint to say which switch boxes have more than one MCB or RCBO supplying them.

That certainly makes sense, and one might argue its actually required (as part of 'identification'/documentation), but I wonder how often it's actually done, given that such a situation is presumably extremely common - quite probably more the rule than the exception for lighting switches in halls/landings etc.

More to the point, have you ever seen it done ?

Nope - but, there again, my exposure to electrical installations has been limited. However, even without such experience, as I implied before, I feel sure that a specific/explicit note at the CU about light switches would be rare, although the information might well be implictly there in terms of the labelling of CU and documentation of the installation. As for a 'warning label' on the switch itself (which some are arguing may be required by 537.2.1.3), I feel sure that most householders would veto (or remove) that!

Kind Regards, John.

 

[sparkticus]

I feel sure that most householders would veto (or remove) that!

Or let it reside under the wallpaper / thick coat of emulsion

 

[ban-all-sheds]

Yea thanks, I did wonder about that. The exact wording in the regs book for 537.2.1.3 reads "contains live parts connected to more than one supply"


As opposed perhaps to "contains live parts connected to more than one circuit "

So what if the two circuits come from two different CUs, and there's no isolation switch before them, making the only single point of isolation the cut-out fuse?

 

[JohnW2]

So what if the two circuits come from two different CUs, and there's no isolation switch before them, making the only single point of isolation the cut-out fuse?

As I explained recently, that's one of the (several) reasons why 2-way cross-floor (hence cross-phase) light switching in my house is done with ELV and relays. In my case, even the cut-out fuses would not represent a single point of isolation, because we would be talking about different phases (as well as different switch-fuses and CUs), hence different cut-out fuses.

Kind Regards, John.

 

[sparkticus]

So what if the two circuits come from two different CUs, and there's no isolation switch before them, making the only single point of isolation the cut-out fuse?

Yes, that is a very good point. I have been unclear about 537.2.1.1 for quite some time.

1) In what context is it written? holmslaw indicates it is for multiple generator situations which is what others have told me.
2) What does "supply" mean in this context ? Does it mean the generator(s) source of electrical energy feeding that enclosure and the related parts of the installation or does it mean the final circuit causing parts to be live within that enclosure?

 

[aptsys]

I can't see the illusion What are you guys seeing that I'm not? The pictures seem to make sense.

 

[JohnW2]

Yes, that is a very good point. I have been unclear about 537.2.1.1 for quite some time.

It's actually 537.2.1.3 we've been talking about. 537.2.1.1 is simply the introductory clause of the section on Isolation, indicating that there must be a means of isolation of live conductorys for every circuit. It is also the clause which implies that DP isolation is required for TT installations.

1) In what context is it written? holmslaw indicates it is for multiple generator situations which is what others have told me.

The context is simply that of the first 'General' subsection of the main section on Isolation. I presume that holmslaw's interpretation is based on ....

2) What does "supply" mean in this context ? Does it mean the generator(s) source of electrical energy feeding that enclosure and the related parts of the installation or does it mean the final circuit causing parts to be live within that enclosure?

Holmslaw is presumably interpreting it as meaning the former. BS7671 does not define 'supply' (or 'electrical supply'), but 514.15 seems to imply that it is using the word to relate to the source of generation - in which case holmslaw may well be correct.

Kind Regards, John.

 

[holmslaw]

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[JohnW2]

I can't see the illusion What are you guys seeing that I'm not? The pictures seem to make sense.

Try concentrating on the vertical junction between the light wall and the darker cupboard door, which passes just to the right of the switch plate. However, as others have said, once one has seen it 'right', it's very difficult to get one's brain to see the illusory 'wrong'!

Kind Regards, John.