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Topic Title: Smoke detectors in a domestic rewire
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Created On: 13 June 2013 08:52 PM
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 13 June 2013 08:52 PM
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chunk522

Posts: 126
Joined: 12 December 2010

I dont get many dreaded house rewires but I have one to quote for
Is it now needed to install smokes as standard to comply?

Thanks
 13 June 2013 08:56 PM
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perspicacious

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I'd quote to include with the amount shown to deduct if they then make the decision NOT to have them fitted. That way, they have a job taking you to task after the fire for not advising them it would be a good idea!

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BOD
 13 June 2013 08:58 PM
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OMS

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Approved Document B would suggest they are installed - depends on the definition of "refurbished".

As the BoD - offer a menu

Regards

OMS

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Failure is always an option
 13 June 2013 09:32 PM
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Grumpy

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Comply with what?
As I am in a similar boat I happen to have my Electrician's Guide to The Building Regs open at the relevant page. It says that the BR1991 require all new and refurbished dwellings to be fitted with mains operated smoke alarms . . . .
As BoD, include them in your quote and if they want to commit hari kari you can then deduct it!
 14 June 2013 07:48 AM
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SherlockOhms

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I'd put the argument to the home owner that "should, in the future, you be in a position where you need/want to let the property then you'll be required to put them in so you may as well do it now. Later will cost much more and make more mess"

It's surely no drama. Total material costs can't be more than £100.
Running the three core in whilst the floor boards are up is hardly a biggy?

Out of interest, how does BS5839-6 sit with Big Green on the subject of RCD's?
BS5839 suggests it would be better to supply detectors from a non RCD cct or one that doesn't feed sockets. Almost impossible under a 17th rewire/build?

S.
 14 June 2013 10:33 AM
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joepostle

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The idea of smoke detectors supplied from an RCD supplied circuit doesn't seem ideal to me though I appreciate all circuits being RCD protected for practical / regulatory reasons. Some of the detectors I've seen are battery backed-up, the only problem being is whether the detectors can charge rechargable batteries or whether its still up to the householder to forget(!) to change them when they deplete.
 14 June 2013 11:46 AM
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OMS

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Do you run the cables for smoke detectors in walls then ?

Not difficult to show they don't require 30mA RCD protection from a BS 7671 perspective.

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OMS

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 14 June 2013 12:59 PM
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SherlockOhms

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Not often buried but quite often through a wall or two.

Often the question is raised about external lights fed from a spur. Cable straight out of the back of the spur through the wall.
The light doesnt need an RCD but the cable through the wall does....or so the answer seems to be.

If the property is a TT then there will be a front end RCD.

S.
 14 June 2013 01:11 PM
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daveparry1

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A cable going straight through a wall doesn't require rcd protection, how could anyone put a drill or a nail through it!

Dave.
 14 June 2013 02:09 PM
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AJJewsbury

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BS5839 suggests it would be better to supply detectors from a non RCD cct or one that doesn't feed sockets. Almost impossible under a 17th rewire/build?

Only if you choose to use that botched marketing-driven rat's nest abortion of a solution of the dual-RCD board. An RCBO, even shared with a lighting circuit, would do fine (you can even get some nice MCB height RCBOs if you look far enough).
- Andy.
 14 June 2013 02:20 PM
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marclambert

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Originally posted by: AJJewsbury

BS5839 suggests it would be better to supply detectors from a non RCD cct or one that doesn't feed sockets. Almost impossible under a 17th rewire/build?



Only for grade E systems i.e. mains only. How many have those have you fitted??
Grade D which we all use is preferred to be supplied from local regularly used lighting circuit. The quote is part of the marketing spiel of the "17th Edition" consumer unit sales pitch.
Regards
Marc
 14 June 2013 09:45 PM
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ebee

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Originally posted by: OMS

Do you run the cables for smoke detectors in walls then ?



Not difficult to show they don't require 30mA RCD protection from a BS 7671 perspective.



Regards



OMS


3 core between detectors to include a common supply plus interlink would often be run in walls if detectors are on different floors surely?

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Ebee (M I S P N)

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 15 June 2013 09:19 AM
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JZN

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As Ebee says the interconnect between floor is often done up a wall. To keep it in an obvious sadfe zone I normally take it up next to a landing light switch box and run it up with the feed for the upstairs light circuit.

John
 15 June 2013 09:45 AM
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ebee

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I have no problems with it being RCD/RCBO on a local lighting circuit or RCBO/stand alone RCD if on it`s own circuit.

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Ebee (M I S P N)

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 15 June 2013 10:46 AM
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aligarjon

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Originally posted by: ebee

I have no problems with it being RCD/RCBO on a local lighting circuit or RCBO/stand alone RCD if on it`s own circuit.


agreed. i don't see an issue with an rcd, there is a back-up battery for a reason.

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 15 June 2013 08:26 PM
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mrl200

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When this came about I thought of this scenario:

Home owners go on holiday for two weeks, breaker trips on same day, batteries run down on all detectors after 6 days, home owners return home and think all is well as they don't hear any beeps, that night they have a fire and all die due to the detectors not working.

Then you think of this one:
Home owners go on holiday for two weeks, breaker trips on same day, batteries run down on all detectors after 6 days, home owners return home and the lights don't work, they have a look breaker/rcd has tripped, beeping starts in detectors(hopefully they don't take them all down), that night they have a fire and all survive due to the detectors working.

Which one is safer!!
 16 June 2013 10:14 AM
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aligarjon

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Originally posted by: mrl200

When this came about I thought of this scenario:



Home owners go on holiday for two weeks, breaker trips on same day, batteries run down on all detectors after 6 days, home owners return home and think all is well as they don't hear any beeps, that night they have a fire and all die due to the detectors not working.



Then you think of this one:

Home owners go on holiday for two weeks, breaker trips on same day, batteries run down on all detectors after 6 days, home owners return home and the lights don't work, they have a look breaker/rcd has tripped, beeping starts in detectors(hopefully they don't take them all down), that night they have a fire and all survive due to the detectors working.



Which one is safer!!


blimey, whats the chance of batteries in all detectors running down at the same time in such a short space of time. They work fine on battery only detectors and last years generally.
I rarely come across domestic systems that aren't wired off the lights, to be honest i could never understand the thinking behind a dedicated circuit, its nuts when frequently used lighting circuit is practically self monitoring the power.
i don't go around at home looking for little green lights and wouldn't expect many people to do so, even if it is the smart thing to do.
The only time i tend to notice them is in the middle of the night when i go for a little walk,although that seems to be getting a bit more frequent.

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 16 June 2013 06:10 PM
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Grumpy

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I have a situation where a two storey house is to be let. It has inter linked mains smoke alarms on the ground and first floor only. Do all the smoke alarms have to be fed from the same lighting circuit or can the additional one on the second floor be run off the second floor light circuit. The wording of the Building regs says "regularly used lighting circuit" singular. I can't see any particular issues with it and the inter linking would be RF. It would be buggeration indeed to get a supply from the ground floor lighting circuit to the second floor.
 17 June 2013 07:38 AM
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SherlockOhms

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I was under the impression that when one unit alarms then after a short period of time it sets off the others via the interlink?

If your third floor unit is seperate then this wont be the case.

S.
 17 June 2013 09:28 AM
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dickllewellyn

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You can use a wireless interlink Sherlock. That way they can be fed from different local circuits but still work together. Very usefull solution for retrofitting.

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Richard (Dick)

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