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Wiring a residential fire alarm - HELP!! #179118
06/27/08 12:51 AM
06/27/08 12:51 AM
bwise121  Offline OP
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
Last minute change order for a customer. The fire marshal is having him put in a fire alarm/sprinklers in his home. The sprinklers have been installed and now I learned they want me to wire for it. There is a flow switch outside and a bell that will be near it. When the flow switch is engaged the bell will ring. That is all good. Here is the part I'm confused with, the bell can't be heard at the other end of the house which is required. The marshal wants me to tie the bell into the smoke detector system. The smoke detectors are all new with 14-3 romex to each. How do I tie them into the bell? The issue I see is there is only 9 volts running on the red wire when they go off. The bell is 120 volts.

Waterflow switch:


I really appreciate any help.


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Re: Wiring a residential fire alarm - HELP!! [Re: bwise121] #179121
06/27/08 05:34 AM
06/27/08 05:34 AM
Trumpy  Offline

Joined: Jul 2002
Posts: 8,260
SI,New Zealand

Do FA systems in your area require a "qualified person" to do the installation?
I'm not being smart here, but some jurisdictions do require that a technician that is qualified in FA systems, period.
If you aren't, get someone that is.

Byron, by the sound of this thread, you are out of your depth, Life Safety systems like fire alarms are not something to be mucked around with.

I really can't give advice, as your understanding of relays and contactors seems to be lacking.
As simple as this would be to do, I'm not going to give advice as the execution could endanger lives.

One word- LIABILITY.

Re: Wiring a residential fire alarm - HELP!! [Re: Trumpy] #179123
06/27/08 09:06 AM
06/27/08 09:06 AM
bwise121  Offline OP
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
I agree Mike. It isn't in my contract and I didn't give a Change order yet.

I'll take your advice.


Re: Wiring a residential fire alarm - HELP!! [Re: bwise121] #179126
06/27/08 12:24 PM
06/27/08 12:24 PM
gfretwell  Offline

Joined: Jul 2004
Posts: 9,348
I believe interconnected smoke alarms are not really "fire alarm systems" (hence they don't qualify for the AFCI exception). A regular EC can connect them but modifying or adding something that is not in the manufacturer's instructions is a 110.3(B). I can think of a couple ways you might be able to trick them into going off from a 120v signal (relay, 9v wall wart etc) but it is probably a listing violation if you don't have guidance from the manufacturer.

Greg Fretwell
Re: Wiring a residential fire alarm - HELP!! [Re: gfretwell] #179134
06/27/08 05:52 PM
06/27/08 05:52 PM
luckyshadow  Offline
Joined: Jan 2005
Posts: 315
Maryland USA
I see a few things here.
1) Not in my contract - Homeowners problem to find someone to do this scope of work
2) Fire Marshall wants you to get the smoke detectors to do something that they're not designed to do
3) Are you covered by insurance for this type of liability?

Why not just add a 2nd bell at the other end of the house?
Feed both bells off the same flow switch as they have 2 sets of contacts. or locate the bell in the middle of the house - equal distance to both ends of the house.

Last edited by luckyshadow; 06/27/08 05:52 PM.
Re: Wiring a residential fire alarm - HELP!! [Re: luckyshadow] #179156
06/28/08 11:25 AM
06/28/08 11:25 AM
WireNuts29  Offline
Joined: Jul 2007
Posts: 85
Mass, U.S.A.
lucky has the right idea. But you should be able to wire both bells through the same contacts on the flow sw. Think of the flow as a sp. switch. c and n.o, hit the common with the feed and the n.o is the feed to the bells. Also if there is a burg alarm system on site, it's a smart idea to have that system monitor the second set of contacts. if no one is home for awhile and a sprinkler goes off the neighbors may not recognize the electric bell sound.and the homeowners may come home to a flooded house. as far as modifying 120 volt smokes and adding relays to trip them, don't do it! unless they are specifically listed for it. you can open a whole can of worms you don't want to.

Re: Wiring a residential fire alarm - HELP!! [Re: WireNuts29] #179158
06/28/08 02:57 PM
06/28/08 02:57 PM
leland  Offline
Joined: Aug 2007
Posts: 853
Lowell area, Ma. USA
10" bell! You'll hear it !!!

Re: Wiring a residential fire alarm - HELP!! [Re: leland] #179172
06/29/08 11:31 AM
06/29/08 11:31 AM
mikethebull  Offline
Joined: Mar 2007
Posts: 101
Rhode Island
I agree with leland any sprinkler bell I have installed could be heard 3 blocks AWAY

Re: Wiring a residential fire alarm - HELP!! [Re: mikethebull] #179181
06/29/08 05:53 PM
06/29/08 05:53 PM
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
Any bell or horn for use as a fire alarm - with the exception of the ones in your smoke alarms - are required by UL to be at least 105 decibels LOUD.

That said, I've had a few poorly operating bells .... the last one I am certain was 'saved' by the other guy just to annoy the sparky frown The flow switch used on the sprinkler may have a 30 second delay built into it. That is, water must flow for 30 seconds before the bell will sound.

Whoever made your smoke alarms ought to have some means, some accessory perhaps, for tying the alarms into a central station panel. The panel, in turn, would have whatever is needed to activate the alarm bell.

Yet - as a recent experience of mine illustrated all too well - you really need to obtain, and READ, every code that's being used by the various authorities. Fire Alarm code, Sprinkler code(s), local codes, etc. One thing I have noticed is that there are many - including the inspectors!!!! - who have never seen the actual codes, let alone read them. Their 'seminar training,' as a result, led to all manner of false assumptions on their parts.


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