3 gang switch. Two Circuits

Doug Mc

Quick question Guys.

Doing some work following a bathroom refit.

Shower, Mirror, Extractor and some mood lighting. All new wiring. Only thing that remains is the original ceiling light.

This is switched via a three gang switch in the hall. The other two switches are for an external light and the hall light (2 way)

All lights are on the same circuit and protected by a 10A RCBO.

The 9kw shower will obviously have its own circuit with 40A RCBO protection. I plant to install a new circuit for the bathroom only for

Mirror, Extractor and mood lighting, with RCBO protection obviously.

My preference is to move the ceiling light to this circuit also, as it really should be on the dedicated bathroom circuit. The customer wants to leave the existing switch in place and wants no chasing / dust.

I can pull the wire SL to the light out of the existing switch and probably have place to run a new two core back down to the switch from the new circuit so that all bathroom lights are on the dedicated circuit but I'm not entirely happy that the different gangs of the switch are controlling lights on different circuits.

Can anyone confirm if this complies with regs?

Thanks in advance

2011

I am not aware of any in the rules that does not permit this. Please note domestic wiring is not really my area.

What I can say is that in industrial installations we would often have wiring from multiple circuits sharing the same bank of switches. They may even be on different phases.

So in my opinion your proposal is acceptable.

If anyone disagrees I would ask them to please point out where in the rules it states that this is not permitted.

standardg60

https://www.boards.ie/discussion/2058377552/3-gang-switch-two-circuits

Can you explain this a bit further? Does the customer still want to control the central light from the existing 3 gang and the rest on the new circuit? If so if it complied with then regs so doesn't have to be moved I would have thought.

17larsson

Bathroom lights don't need to be on a dedicated circuit anymore

Doug Mc

Thanks for the comments Guys. I need to double check that "Bathroom lights don't need to be on a dedicated circuit anymore" because if that is the case my preference is to leave the switch as is. I know its not uncommon in industrial / commercial to have multi-gang switches for example, controlling devices on different circuits but I'm a bit concerned about this in Domestic where someone might try and change a switch for example and fail to isolate all relevant circuits.

Anyway things have changes a little since. She wants the extractor to no longer be controlled from the light but to be able to turn it on and off independently so I need to swap the 3 gang for a 4 gang and add a deeper back box.

She has reluctantly agreed to allow me to add an isolation switch for the mirror & mood lighting above a doorway on a plasterboard section as both use some kind of TOF sensor / gesture control, with no other means of isolation.

The joys!

2011

https://www.boards.ie/discussion/comment/122761144#Comment_122761144

Regarding this bit "I'm a bit concerned about this in Domestic where someone might try and change a switch for example and fail to isolate all relevant circuits."

I understand your concern, but if you take this to it's logical conclusion, should you not be concerned that someone may try to replace the distribution board? Now maybe you could say I'm taking this to far. But I will ask you this: Have you confirmed that every other light switch in house is supplied from just one circuit? It would not be uncommon for some of the 2 way light switches for the stairs to be supplied from 2 circuits.

JL spark

by regs you have to put a label on the inside of the switch saying two circuits present

meercat

o.p

only a registered electrical contractor is legally permitted to carry out electrical work in a domestic bathroom (can you clarify if you are one)

the extractor fan requires all conductors to be isolated (live,switched live and neutral)the extractor fan will need both a switch and an isolator.

All switch heights and isolators need to be below 1200mm from finished floor level(can’t be over a door)

All new cables installed must be surged protected (IS10101:2020)

You can have 2 feeds at a switch once you label them(as JL spark said)

The shower isolator can be a pull cord but in my experience it’s really difficult to terminate 10mm t&e into them so my preference is a cooker switch mounted in a deep back box just outside the bathroom door (safe electric inspectors have no issues with this)

you say the customer requests so I’m assuming this is not your home

My advice is to leave the existing setup as is and run a new lighting circuit as you are already running a shower circuit back to the board

Disconnect the existing bathroom light and install a new one

That way all the new work is correctly installed, tested and certified and if there’s ever an issue on the lighting circuits in the house then it’s easily determined if it’s your responsibility or not. You must give the homeowner a certificate 2 and test records

2011

https://www.boards.ie/discussion/comment/122762866#Comment_122762866

Is there anything to suggest that the OP is not a REC? As the OP refers to a customer I assume the OP is a REC and will issue the required paperwork.

"All new cables installed must be surged protected (IS10101:2020)" - I don't see anything in the rules to suggest that this can retrospectively applied to an existing installation. Perhaps an argument can be made if the distribution board is being replaced. I would expect that most domestic installations that were wired before IS10101 would not meet many of the current rules.

I think the other points in your post are well made.

meercat

https://www.boards.ie/discussion/comment/122763205#Comment_122763205

no I haven’t seen anything to suggest he’s not a rec but I’d imagine he’d have known that bathrooms no longer require a separate circuit

If new cable is installed (for the shower or fan or mirrors or lights) then surge protection is required

I’m not talking about the existing installation

2011

https://www.boards.ie/discussion/comment/122763288#Comment_122763288

"no I haven’t seen anything to suggest he’s not a rec but I’d imagine he’d have known that bathrooms no longer require a separate circuit"

Not necessarily in my experience. Let's see what the OP says.

"If new cable is installed (for the shower or fan or mirrors or lights) then surge protection is required

I’m not talking about the existing installation"

I agree with you that SPD's are required for a new installation, but very clearly this is an existing installation.

I see nothing in the rules that states that SPD's must be installed in an existing installation if new circuits are added. I had just had a quick look through the latest version online, if I have missed something please point it out.

meercat

https://www.boards.ie/discussion/comment/122763348#Comment_122763348

from the frequently asked questions

https://safeelectric.ie/contractors/wp-content/uploads/sites/2/2021/03/MarchNewsletterSafeElecFinal-1.pdf

2011

fair enough! Thanks

Doug Mc

Thanks for the comments. Was away for weekend so only getting back now.

Few clarifications: Fan already has 3 pole iso. Extra gang switch is just so it can be switched independently of light.

It's already located just above door, which is why I was planning to put the one for mirror / mood lighting alongside alongside.

Surge protection is already installed.

I didn't check that all other switches control accessiories from only one circuit but I expect they do. House belongs to partners parents and I looked over the electrics before they bought it and moved west a couple of years ago. Checked DB, E & B, IR tested all circuits, only noticed two issues.

1. Ze was higher that expected, I think close to 1.5 from memory. I told them to make the guy who fitted the smart meter shortly afterwards aware and they said his answer was that can be the case " out in the sticks" ??
2. There was no earth rod visible, at least that I could see, so one was installed before they moved in.

drury..

https://www.boards.ie/discussion/comment/122759165#Comment_122759165

I always stuck to 1 circuit at an enclosure /switch etc for domestic work

Not sure if I was taught 2 circuits was bad practice or it was a regulation

Dom/Ind ya you'd have different circuits and phases at switch banks but competent persons (electricians ) carrying out works

Domestic ya have numptys carrying out minor works who will switch off 1 breaker and assume all is safe