CPC used as interconnect on smoke detectors

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We all know this is wrong and breaches regulations and manufacturers instructions.

Good tread on this:
https://talk.electriciansforums.co....link-on-smoke-alarm-circuitwhat-would-you-do/

However the question is does it warrant a C2 over C3?
My recommendation is going to be radio link and reinstate CPC or rewire with 3-core. But what code to give?

GN4 recommends a lighting circuit supplying only class 2 as C3
 
if you give it a C3, then the customer gets a satisfactory report ........ and who's to say they will do anything.

Whether you can justify a C2 is somewhat debatable, except all fixed mains cables should have a CPC in them which is functional - so a C2 imho

EDIT: I think the GN4 advice alludes to lighting circuits without CPC's and your installation has clearly been done incorrectly so the C3 is not really an option.
 
debatable here. if the cpc is used as the interlink, then it's not carrying 240V. not right, but a C2 might be a little harsh.
 
as a non-electrician, I have a question...
if the cable used to interconnect is at mains voltage, shouldn't it have a cpc, even if the individual detectors don't need one?

If the detectors were non mains supplied, then any 3 core cable would do the job, but T&E presence might cause unnecessary confusion to someone opening up at a later date?

Radio interconnect is an option (a good one, imho) but not an option in rented housing...but in Scotland it will be soon, thankfully.

Hope i have explained that correctly...
 
There is a DIY fitted duel RCD board with all the circuits on one RCD and the second empty!!! Except for 2 lighting circuit non RCD protected.
Idiots!
I've got it down as C3.. Sup bond in place
 
It's not a separate cable the've used Pirate, it's T+E with the CPC over sleeved live and used as interconnect. Hence the problem, no CPC and no basic insulation for interconnection
 
Well every point on a low voltage circuit has to be provided with a cpc (reg?). So that's that surely code whats is face.
 
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A few years ago I did a periodic at a charity shop which had Part 6 detection. The shop was in darkness when I showed up because the manager was waiting for me to turn up to show me a trick. As she switched on the shop area modular fluorescents the detectors triggered. Turns out the interconnection was the cpcs which were also connected at some point to earth.
 
Interesting one here.

My initial reaction is a C2. Then when you think about it it is 8-12 volts DC that only has a single layer of insulation.

Would I C2 a speaker cable in the wall? No of course not.

If everything is also Class 2 then again I fail to see how to code this.
 
My initial reaction is a C2. Then when you think about it it is 8-12 volts DC that only has a single layer of insulation.
Click to expand...

But 12V with respect to what? A live conductor. If you connect one side of a PP3 to mains, the PP3 is still 9V but now it's potentially lethal (pun intended).
 
pirate said:
as a non-electrician, I have a question...
if the cable used to interconnect is at mains voltage, shouldn't it have a cpc, even if the individual detectors don't need one?

If the detectors were non mains supplied, then any 3 core cable would do the job, but T&E presence might cause unnecessary confusion to someone opening up at a later date?

Radio interconnect is an option (a good one, imho) but not an option in rented housing...but in Scotland it will be soon, thankfully.

Hope i have explained that correctly...
Click to expand...

Yes all cable installed shall have suitable cpc travelling with it. I'm not aware of battery alarms that ask for wire interconnect, so not thought about that one. It does annoy me that some folks steal it for some other purpose. Radio clearly the way forward for difficult situations :) .
 
The cpc in this case, has a distinct possibilty of making contact with one of the Live conductors in the detector and or the cable itself, if the cable become damaged, the cable is not being used as it should, so it should be replaced with a cable that is fit for purpose.
It's an inherently dangerous thing to do in my bok, would you use the cpc in respect of the strappers in a 2 way lighting circuit, well I know I wouldn't with that in mind you should code it as dangerous.
 
essex said:
Interesting one here.

My initial reaction is a C2. Then when you think about it it is 8-12 volts DC that only has a single layer of insulation.

Would I C2 a speaker cable in the wall? No of course not.

If everything is also Class 2 then again I fail to see how to code this.
Click to expand...
The cpc in question, does not have any insulation, the sleeving if used will only be an indicator.
 
essex said:
Interesting one here.

My initial reaction is a C2. Then when you think about it it is 8-12 volts DC that only has a single layer of insulation.

Would I C2 a speaker cable in the wall? No of course not.

If everything is also Class 2 then again I fail to see how to code this.
Click to expand...

Is it definitely 8-12V DC on the interconnect? And is that SELV or otherwise fully isolated from LV with no possibility of a fault making it live at 230V?
I have a feeling that manufacturers say the interconnect should use wiring to the same standard as the supply.
 
davesparks said:
Is it definitely 8-12V DC on the interconnect? And is that SELV or otherwise fully isolated from LV with no possibility of a fault making it live at 230V?
I have a feeling that manufacturers say the interconnect should use wiring to the same standard as the supply.
Click to expand...
An obviously correct answer Dave, quite what the problem is I'm not sure, does make you wonder though.
 
If the interconnect is ELV then the CPC isn't segregated or insulated to the highest voltage band, so C3.
I suppose you could say if the interconnect were 230v there is insufficient insulation since the outer sheath is intended for mechanical protection only, so C2?
 
pirate said:
as a non-electrician, I have a question...
if the cable used to interconnect is at mains voltage, shouldn't it have a cpc, even if the individual detectors don't need one?

If the detectors were non mains supplied, then any 3 core cable would do the job, but T&E presence might cause unnecessary confusion to someone opening up at a later date?

Radio interconnect is an option (a good one, imho) but not an option in rented housing...but in Scotland it will be soon, thankfully.

Hope i have explained that correctly...
Click to expand...

Where have you taken the above info from? Do you understand that 10 yr battery, radio linked will meet the revised Regs (ie not hard wired & radio linked)?
 
Yes, I do understand that Polo1...but although the scottish government have agreed that 10 year battery , radio interlinked will be allowed (and rightly so) it is not law yet. I have installed stuff where the first detector is mains and 10 year battery back-up, with radio interlink, the others are 10 year battery only, with radio interlink. In a small flat it makes sense as you can hear any one of them from anywhere in the flat. My question was whether there might be confusion if some T+E were present...in wired, interlinked installations.
I presume you meant ie not hard wired and radio linked only, and not mains powered at any point. That is certainly the outcome of the consultation, imho.
 
Yes, I do understand that Polo1...but although the scottish government have agreed that 10 year battery , radio interlinked will be allowed (and rightly so) it is not law yet. I have installed stuff where the first detector is mains and 10 year battery back-up, with radio interlink, the others are 10 year battery only, with radio interlink. In a small flat it makes sense as you can hear any one of them from anywhere in the flat. My question was whether there might be confusion if some T+E were present...in wired, interlinked installations.
I presume you meant ie not hard wired and radio linked only, and not mains powered at any point. That is certainly the outcome of the consultation, imho.
 
Murdoch, yes...the whole point about the consultation, on this matter anyway, was whether modern tech has brought us to a place where 10 year Lithium battery powered detectors can be used and relied upon. I have the government response on file somewhere, and will try to find it and send you a link. In essence, in Scotland you will be able to use 10 year battery modules, radio interlinked. It's a good step, because landlords will see it is cheaper than the old regs, so will be more likely to comply.
 
Murdoch said:
Are you 100% sure about the 10 year battery bit?
Click to expand...

No I’m not M, that’s why I posed the question.
The Scottish Gov recently announced that the standards which currently apply in new build and private rented (mains supplied and interlinked smokes in the main living area, hall and heat in kitchen) are to be applied to existing owned and public sector/HA property. The announcement made reference to detectors being no more than 10 yrs old but otherwise was light on detail about the spec and how the change is to be implemented.
Their review was prompted by the Grenfell Tower fire.
 
Hi - I understand that BS5839 already permits radio linking of mains powered alarms. There are a few conditions and reading the instructions from Aico on their Ei100MRF radio units, they meet those requirements when properly installed and commissioned.
 
Pirate,
Can you tell me exactly where you have read that 10yr battery only radio interlinked detectors will be acceptable when the Scottish legislation is changed?
Tia
 
“The following changes to this standard, all supported by the responses to the consultation, are also proposed:
  • to allow specified types of sealed long-life battery alarms as well as mains-wired alarms - reflecting the availability of appropriate technology and will encourage compliance;
  • to specify a maximum age of ten years for alarms; and
  • to require carbon monoxide detectors in all homes.”
The above taken from the Scottish Gov web site. Have to say I’m really surprised on the battery only detectors. It also says “proposed”, so I wonder if it will make the final cut.
 

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CPC used as interconnect on smoke detectors
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Periodic Inspection Reporting & Certification
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