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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: Tom Sutton on May 26, 2015, 10:43:17 PM

Title: Does a 3 wired 24 VDC fire alarm system meet the present day standards.
Post by: Tom Sutton on May 26, 2015, 10:43:17 PM

I received the following enquiry but have no idea can anybody help.
 

Quote

I am sure this has been asked before, but I seem to be having trouble locating any info.

A long time ago everyone down my way and probably other places to, were installing panels that could be run of a 3 wire system. (both the sounders and the detection sharing the neutral).
 
I stopped doing this years ago but I have a client that I do a lot servicing for, yet another engineer does the installs and he is still using this 3 wire method.
I am pretty sure the regs changed with the introduction of EN54, but I cant find any text to back this up.
I would like to point this out to my client and if necessary ad it to my reports.
 
Would anybody have any knowledge on this.
 
Today I telephoned: FIA, BAFE, Elesca, FPA, TBFC, NICEIC and not one person could help.

I have seen the text somewhere but cant for the life of me remember where.

Title: Re: Does a 3 wired 24 VDC fire alarm system meet the present day standards.
Post by: colin todd on May 27, 2015, 12:37:05 AM

I expect they were all confused as to how you can have a neutral on a DC system.

Title: Re: Does a 3 wired 24 VDC fire alarm system meet the present day standards.
Post by: Owain on May 27, 2015, 08:57:10 PM

I don't see why it wouldn't comply.

There are 2-wire systems after all. And wireless.

Providing the system is designed, installed and maintained to applicable standards, and the design allows all the circuits to be appropriately monitored.

Title: Re: Does a 3 wired 24 VDC fire alarm system meet the present day standards.
Post by: John Webb on May 28, 2015, 09:38:46 AM

Some panels require the alarm circuits and sounder circuits to be separate because they are monitored in different ways. But if the fire alarm control panel allows the use of a common 0 volt line to both alarm point/detector circuits and the sounder circuits, I don't see any objection to using 3 wires.