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Topic Title: 2 wire fire alarm v conventional system.
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Created On: 26 December 2012 07:26 PM
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 26 December 2012 07:26 PM
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hertzal123

Posts: 302
Joined: 26 August 2007

Been asked to fit a system in 2 storey outdoor centre comprising bedrooms with smokes and sounders and other rooms with same or detector only.I know that a 2 wire system would be easier to wire,but wondered what others on the forum would do.If I installed a conventional system,I,d thought of using 4 core,2 for the sounders,2 for the smokes.
Does anybody else use this method?
Thanx for any help
 26 December 2012 07:31 PM
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Rulland

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Iirc it wouldn't comply to regs- sure someone else on here would confirm one way or the other.

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 26 December 2012 08:12 PM
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jamieblatant

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It has been possable to do this and comply as we have used it in student flats to keep costs low , I would have to check with our engineet to see if its still allowed I can't see why not

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 26 December 2012 08:33 PM
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hertzal123

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Thanx for replies so far,
Has anyone used the 2 wire system and do they prefere it to conventional?I have concerns about not obtaining compatible spares if the manufacturer goes t@ts up.
Regards,Hz
 26 December 2012 09:19 PM
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slittle

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The two wire systems are pretty good. We've used them in various small offices on farms.

It seems that most of the panels are generic and therefore spares don't appear to be a problem. The only issue you may have is that you can't always do the "clever" things with the simple panels. but for what you are describing I would have expected it to be ok.

Stu
 26 December 2012 09:29 PM
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Fm

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I see no reason why a 4 core system wouldnt comply? Assuming its fp200 or similar.


Rulland, can you advise of the fire reg that prohibits this?
 27 December 2012 01:44 AM
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Dave69

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What does the Fire Risk Assessment say about the type of Fire Alarm and Detection system? L1, L2,,,, etc.

Bi wire, Twin flex etc. (2 wire systems) are OK but they do cost more so it all depends on how many detectors, sounders, strobes and call points you need and how much cable you need as obviously a conventional system uses around twice as much cable. Also remember conventional series 65 heads are so easy to get hold of, I always keep 5 twinflex and biwire heads in my van and replace them as quick as I can as they often have a delivery time of a couple of days

how many zones do you need?

problems using 4 core on a conventional system occur when trying to spread the sounders over 2 circuits. Its ok running a 4 core out to one area and then splitting the cores, using a proper junction box, 2 cores for detection and 2 for the sounder circuit, but remember ideally sounders on a conventional system in each area should be spread across 2 sounder circuits unless you can prove that if one sounder circuit fails the sound level generated by the other circuit will be at 65dB and at least 5dB above any background noise in ALL areas and in any case if you have more that 2 zones you'll be snookered as most small conventional panels only have 2 sounder circuits so you will still end up having to run a 2 core from the last sounders in one zone to extend the sounder circuit onto the next zone. From experience it is far easier to run invidual 2 core cables for everything, i.e. 2 core for each zone and then 2 core cables for the sounder circuits and if it is a new installation I would always go for a conventional 4 wire system

I hope that makes some sense.
 27 December 2012 01:47 AM
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Dave69

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Originally posted by: Fm

I see no reason why a 4 core system wouldnt comply? Assuming its fp200 or similar.





Rulland, can you advise of the fire reg that prohibits this?


Talking about FP200 cable dont forget that even the mains supply must be wired in FP or similar cable, you cant just spur off the nearest socket with a bit of T&E its FP back to the CU and its own MCB, its amazing how many supplies to fire alarm panels are wired in T&E
 27 December 2012 09:26 AM
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lyledunn

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Two wire is fine and complies if properly installed. Ctec make a panel compatible with Apollo detectors which I often specify and which,so far, has not caused any serious problems.I am sure that there are many other manufacturers who have acknowledged the benefits of the two wire system. I find sparks generally prefer it. As previously suggested a FRA is necessary as a first off. Unless it throws up any unusual concerns, there is no need to duplicate circuits for sounders other than to provide a separate one at the panel.
Detectors with sounder bases are a neat way of providing alarm signals.

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Lyle Dunn
 27 December 2012 12:21 PM
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perspicacious

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" there is no need to duplicate circuits for sounders other than to provide a separate one at the panel."

So when the sounder circuit in the building fails, the remaining circuit with one sounder by the panel to be heard by the occupants the other side of, say 4 doors, is compliant?

Regards

BOD
 27 December 2012 04:05 PM
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Dave69

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Originally posted by: perspicacious

" there is no need to duplicate circuits for sounders other than to provide a separate one at the panel."



So when the sounder circuit in the building fails, the remaining circuit with one sounder by the panel to be heard by the occupants the other side of, say 4 doors, is compliant


well it would be hard to get 65dB all over a building from just one sounder at the panel and remember its more in a bedroom and fire doors cut down sound aswell as stopping smoke and heat.

A fault on any circuit should lose the EOL device and bring up a fault anyway so losing a sounder circuit should not cause a problem so long as the responsable person in charge of the fire alarm reacts to the fault
 27 December 2012 07:11 PM
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lyledunn

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Perspicacious,
Yes, can be compliant (see 12.1 commentary 5839-1 2002) but as I have already said, detailed risk analysis would need to be undertaken. all I am saying is that given the brief description of the premise provided by the op, it is possible that duplication of circuits for fire alarm devices will not be necessary.

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Regards,

Lyle Dunn
 28 December 2012 09:42 AM
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TeesdaleSpark

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There are a conventional systems on the market that can have sounders and detectors on the same cable.

E.g.:

http://www.c-tec.co.uk/Products/twowire.htm
 28 December 2012 12:44 PM
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hertzal123

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Thanx for all the advice.Have decided to go for the c-tec 2 wire panel.The proposed system will have 230v door closers.Have noted that the c-tec has no 230v rated voltage free contacts,only 35vdc I believe.Is this common to most panels,as it just means extra components are required?
Regards,Hz.
 28 December 2012 03:21 PM
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DOUGIE1000

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Yeah look for relay modules we only use JSB cooper

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 28 December 2012 03:46 PM
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Fm

Posts: 667
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are you competent to design a fire alarm system?
has a fire risk assessment been done?

2 questions i would answer first
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