Smoke-Heat-Carbon detectors

[driverman]

Hi Guys, Spoke in earlier threads about S/H/Co detectors ect. Listen to opinions and comments and decided to go for the Acio equipment. However home owner went and got the Kiddie type. No doubt they will do the job but, As far I can see the fittings are designed to fit onto plaster cavity wall type fixings. I was hoping to seal holes up where cables come through ceiling and fit directly onto the joist. What you Guys think of the kiddie fittings. The way I'm looking at it with the Kiddie ones is the ceiling fire rating has been broken.

 

[Octopus]

Ok, so in my case, at this point in time, i have wired the smoke/heat and carbon detectors on their own RCBO circuit. I don't like doing this but, to comply with regs, I could disconnect from existing RCBO and double up on another lighting RCBO. In other words, have 2 x radial circuits off 1 x RCBO.

Would that be compliant to BS7671?

In other words you would have 1 circuit off the MCB.

Putting smokes on their own circuit gives the resident the opportunity to turn the circuit off!

Matey you post a lot on here, what do you normally do?

 

[123]

He posts a lot? You have nearly 14k posts man! lol

 

[Octopus]

He posts a lot? You have nearly 14k posts man! lol

On one thread he says he doesn't do certs !!

The forum is a bit adictive, and as I ask questions and get answers I feel it appropriate to contribute in a constructive manner

 

[driverman]

In other words you would have 1 circuit off the MCB.

Putting smokes on their own circuit gives the resident the opportunity to turn the circuit off!

Matey you post a lot on here, what do you normally do?

Murdoch, spelt correctly ! I am an electrician, but been out of the game for decades. Doing electrics free for a new build. It's for family member to keep cost down. As you know, things have changed a great deal recently, so yes I'm out of touch .so need bringing up to speed. I come on here when time allows to gain bit more know how and possibly on the odd occasion give advice to others. That is on the very rare occasion lol

 

[driverman]

On one thread he says he doesn't do certs !!

The forum is a bit adictive, and as I ask questions and get answers I feel it appropriate to contribute in a constructive manner

Think I know where your coming from Murdoch..no I do not do certs, as I'm not doing electrical work anymore. Like I said in another reply, I've been out of the game for decades lol So, yes I'm very rusty.

 

[driverman]

In other words you would have 1 circuit off the MCB.

Putting smokes on their own circuit gives the resident the opportunity to turn the circuit off!

Matey you post a lot on here, what do you normally do?

I know this is an old subject re own circuit, or on with light circuit. I tended to go with own circuit with few jobs that I have done when doing complete rewires.
but this has come to light with using Kiddie which state must be 1.5mm. I now know thanks to the forum,that only light circuits can be wired in 1mm.

 

[andyb]

I think he is referring to the changes made to table 52.3 when the BGB came out. So if the smokes are on their own circuit they need to be 1.5mm but if they are on a lighting circuit they can be on 1mm

That's well spotted Murdoch, I have to admit I never knew that it had changed. It was 1mm for power & lighting.

However, I'm not too sure of the definition of a power circuit in so much as, is a circuit supplying only smoke alarms a power circuit? I would not class a circuit in a normal dwelling supplying 2 smoke alarms for example as a power circuit.

This is only my opinion & I know that a lot of people will disagree with me. What I will say though is this, if you are of the opinion that a circuit supplying smoke alarms is a power circuit so that the minimum csa is 1.5mm, then I would of said that the same circuit with some lights on it would still be a power circuit. So 1.5mm minimum csa.

 

[Octopus]

That's well spotted Murdoch, I have to admit I never knew that it had changed. It was 1mm for power & lighting.

However, I'm not too sure of the definition of a power circuit in so much as, is a circuit supplying only smoke alarms a power circuit? I would not class a circuit in a normal dwelling supplying 2 smoke alarms for example as a power circuit.

This is only my opinion & I know that a lot of people will disagree with me. What I will say though is this, if you are of the opinion that a circuit supplying smoke alarms is a power circuit so that the minimum csa is 1.5mm, then I would of said that the same circuit with some lights on it would still be a power circuit. So 1.5mm minimum csa.

The way I read it is 1mm for lights, minimum 1.5mm for anything else!

 

[andyb]

The way I read it is 1mm for lights, minimum 1.5mm for anything else!

That's defiantly how it reads, what I'm saying is if a circuit with smokes on it is deemed as a power circuit, then the fact that it has a few lights on it does not alter that and it must still be a power circuit and wired in 1.5mm minimum. So you can't really say that if the smokes are connected to a 'lighting circuit' then they can be wired in 1mm.

Just thinking aloud really.

 

[driverman]

That's defiantly how it reads, what I'm saying is if a circuit with smokes on it is deemed as a power circuit, then the fact that it has a few lights on it does not alter that and it must still be a power circuit and wired in 1.5mm minimum. So you can't really say that if the smokes are connected to a 'lighting circuit' then they can be wired in 1mm.

Just thinking aloud really.

Thats the beauty of this forum.....electricians all work from the same book, but have different opinions. I personally don't see anything wrong with the smokes on their own 1.0mm circuit. Like you say.....a lighting circuit will draw far more power than a typical smoke circuit. Possibly the reg was trying to address other issues ie 1.5mm minimum for central heating circuit with pump,Imm/Htr and or socket.

 

[Risteard]

So you can't really say that if the smokes are connected to a 'lighting circuit' then they can be wired in 1mm.

Why not? The term "lighting circuit" is not defined in BS 7671. Would you not consider a circuit with an extractor fan to be a lighting circuit?

But if the smokes are on a separate circuit it is difficult to see how it could possibly be classified as a "lighting circuit" even if such a circuit remains undefined.

 

[andyb]

Why not? The term "lighting circuit" is not defined in BS 7671. Would you not consider a circuit with an extractor fan to be a lighting circuit?

As you say there is no definition so I don't know. Is the term power circuit defined? I'm not sure that it is.

But if the smokes are on a separate circuit it is difficult to see how it could possibly be classified as a "lighting circuit" even if such a circuit remains undefined.

So a circuit supplying only smokes wired in 1mm does not comply,I wire a light in the loft from the last detector. Does it now comply?

 

[Risteard]

I wire a light in the loft from the last detector. Does it now comply?

If you want to claim that it does then who am I to argue? It is an opinion.

But it is a stretch too far to classify a circuit without any lighting as a lighting circuit. Your one light solution to this problem is an interesting concept though.

 

[Octopus]

That's defiantly how it reads, what I'm saying is if a circuit with smokes on it is deemed as a power circuit, then the fact that it has a few lights on it does not alter that and it must still be a power circuit and wired in 1.5mm minimum. So you can't really say that if the smokes are connected to a 'lighting circuit' then they can be wired in 1mm.

Just thinking aloud really.

Hum....interesting one that.

If I was adding smokes to an "existing" installation the cert would say "add smokes to lighting circuit" - so its not a power circuit.

If I was wiring a new build or new circuit I would say "add lighting circuit & ?? smoke alarms"

If I was adding a dedicated circuit for smokes I would say "add new circuit for smoke alarms"

I guess its down to the wording of the cert!

Brilliant. Another great success for BS 7671 - best we send a copy to the Plain English Society for review!

 

[davesparks]

If you forget the 'follow blindly like sheep' attitude for minute and consider the situation sensibly then a circuit with a known load of probably less than an amp is going to be quite fine in 1.0mm cable. So what if it's a departure from the regs, It's safe, sensible and justifiable ?