Junction Box & Linked Mains Smoke Detectors

[DIYWell]

Wiring run for two linked mains powered smoke detectors goes like this:
Consumer unit -(T&E)- detector 1 -(3 core & earth)- 20A 4 terminal junction box -(3 core & earth)- detector 2

My question is is there any regulation that prohibits the use of a junction box in a linked smoke detector circuit?

 

[holmslaw]

..

 

[Taylortwocities]

In most domestic situations smoke alrams DO NOT HAVE to be linked.
It is better that they are though.

There's no problem with there being a JB in the interlink wiring as long as has been properly installed (eg accessible, screwed to a fixture, cables clipped, etc etc)

Not sure if Holmslaw has a smoke alarm in his jungle hut?

 

[holmslaw]

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[Taylortwocities]

So why do the fire brigade run around the countryside installing battery smoke alarms without interlinking them. They must be in contravention of BS 5839-6:2004.

In fact, it must be illegal to sell smoke alarms that cannot be interlinked. I'd better sell my shares in Kidde.

 

[flameport]

My question is is there any regulation that prohibits the use of a junction box in a linked smoke detector circuit?

No, provided that the usual rules regarding junction boxes are met (must be accessible etc.).
If not, replace the JB with crimps or soldered joints.

Why is the JB there anyway - was there a third detector which was removed?

 

[holmslaw]

..

 

[sparkiemike]

In most domestic situations smoke alrams DO NOT HAVE to be linked.

See BS 5839-6:2004, they have to be interlinked in ALL domestic situations.

Part B of building regs only asks for interlinked alarms in new dwellings or where there are material alterations

 

[DIYWell]

No, provided that the usual rules regarding junction boxes are met (must be accessible etc.).
If not, replace the JB with crimps or soldered joints.

Why is the JB there anyway - was there a third detector which was removed?

Doing a bit of forensic detective work I'm hazarding a guess that before the detectors were on a separate breaker they were patched into the permanent live on the lighting circuit.

The junction box is screwed vertically to a floor joist and "accessible" if the floorboard above it is unscrewed. Most of the boards in that area can be unscrewed since there's a veritable spagetti of pipes under there. Several creds to the plumber who stuck it all together, but minus a few hundred creds for being too lazy to clear out all the crap he left behind in the ceiling void.

 

[ban-all-sheds]

Part B of building regs only asks for interlinked alarms in new dwellings or where there are material alterations

PART B FIRE SAFETY

Means of warning and escape

B1 The building shall be designed and
constructed so that there are appropriate
provisions for the early warning of fire, and
appropriate means of escape in case of fire
from the building to a place of safety outside
the building capable of being safely and
effectively used at all material times.

And

 

[sparkiemike]

Part B of building regs only asks for interlinked alarms in new dwellings or where there are material alterations

PART B FIRE SAFETY

Means of warning and escape

B1 The building shall be designed and
constructed so that there are appropriate
provisions for the early warning of fire, and
appropriate means of escape in case of fire
from the building to a place of safety outside
the building capable of being safely and
effectively used at all material times.

And

From the aproved document (pg 16)

1.14 Where more than one alarm is installed they should be linked so that the detection of smoke or heat by one unit operates the alarm signal in all of them. The manufacturers’ instructions about the maximum number of units that can be linked should be observed.

 

[Taylortwocities]

Hmm. It says "should". It does not say "must".

 

[sparkiemike]

its a brave man that would defy the local building officer on semantics

and I am sure somebody will remind me that the approved document is a guidance document, the buildings regs are not prescriptive (by that I mean they don't tell you how to comply). For mere mortals like myself we have to rely on the approved documents, British standards and the guides that help interpret the BS to comply with the law.

 

[holmslaw]

..

 

[ban-all-sheds]

Part B of building regs

From the aproved document

Make your mind up.

its a brave man that would defy the local building officer on semantics

The difference between "should" and "must" is hardly a semantic subtlety.

and I am sure somebody will remind me that the approved document is a guidance document,

The Approved Document is a guidance document.

the buildings regs are not prescriptive

The Building Regulations are not prescriptive.

For mere mortals like myself we have to rely on the approved documents, British standards and the guides that help interpret the BS to comply with the law.

Fine, then say that "For me the easiest/most practical/most sensible way to comply with the Building Regulations is to install interlinked alarms".

Do not say "Part B of building regs only asks for interlinked alarms in new dwellings or where there are material alterations".