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#51694 05/08/05 10:22 AM
Joined: Nov 2002
Posts: 267
I was wondering if any of you have had a smoke installations over 40 line voltage smokes that had to be all interconnected? I suppose you would install some kind of relay?

#51695 05/08/05 10:39 AM
Joined: Jan 2003
Posts: 4,391
I have never seen an application that needed 40 interconnected line volt smoke alarms. (The UL name for these)

At that quantity it is usually low volt smoke detectors connected to a fire panel

Bob Badger
Construction & Maintenance Electrician
#51696 05/08/05 10:42 AM
Joined: Nov 2002
Posts: 267
YOur right IWIRE, that's what I would think. I guess this particular application has low voltage but the city wants them to install line voltage over and above. I told the electrician to check with the fire marshall in that town.

#51697 05/08/05 11:03 AM
Joined: Aug 2003
Posts: 1,374
First of all, we need to determine if you are talking residential or commercial.

If we are talking residential, I as the AHJ would require that the code required alarms be interconnected, and after that I wouldn't care. I can't fatham 40 code required smoke alarms in any house.

Ryan Jackson,
Salt Lake City
#51698 05/08/05 11:18 AM
Joined: Nov 2002
Posts: 267
It's a multi unit residential apartment building. They have battery smokes in the units now. 16 units that require 3 line voltage smokes each, and the city is requiring them to be all interconnected. So far this is the status, I don't have anymore info from the electrican. I understand there's a low voltage system in all the common areas.

#51699 05/08/05 11:54 AM
Joined: Jan 2002
Posts: 1,457
Here is what I found for Massachusetts. This appears to be in the R-2 use group.From the Mass Building code. " 918.4.7 Use group R-2: An automatic fire detection system shall be installed and maintained throught all occupancies in use group R-2 and in accordance with table 918.
Exceptions: 1. an automatic fire detection system is not required in buildings that do not have interior corridors serving guest rooms or dwelling units and where all guest rooms or dwelling units have a means of egress door opening directly to an exterior exit access which leads directly to the exits. 2. System smoke detectors are not required in guestrooms or dwelling units. 3. A system heat detector shall be required within each guest room or dwelling unit located not more than six feet from each door way that leads to an interioir corridor or exit. System heat detectors shall not be required where the guestroom or dwelling unit is equipped with residantial sprinklers that, when activated will activate the fire protective signaling system."

This is what I thought the rules were and looking it up confirmed. Sounds like the town is mixing up their multi unit dwelling code witht the single and two family code.
Even in a two family each apartments smokes are not interconnected with each other.

#51700 05/08/05 12:05 PM
Joined: Jan 2002
Posts: 1,457
Since I seem to have time on my hands here is a continuation. Only the parts pertaining to R-2 included.
919.3.2 Use groups R-2
Single and multiple station smoke detectors or household fire warining system shall be installed and maintained in all ocupancies in use group R-2 at the following locations: In the immediate vicinity of all bedrooms, in all bedrooms, and in each story within a dwelling unit including basements.

919.4 Interconnection
Where more than one detector is required to be innstalled within an individual dwelling unit in an occupancy in use group R-2 the detectors shall be wired in such a manner that the actuation of one allarm will actuate all of the alarms in the individual unit.

#51701 05/08/05 12:10 PM
Joined: Jan 2002
Posts: 1,457
In short, low voltage in the common areas. Heat detector in each unit connected to the LV system.
Smokes in each bedroom and outside of each bedroom interconnected within the unit only.
I am not even sure of the legality of the town requiring the building to be upgraded from battery to ac smokes. I know in existing one, two and three family buildings battery smokes in the units are acceptable untill a renovation.

[This message has been edited by Electricmanscott (edited 05-08-2005).]

#51702 05/08/05 03:33 PM
Joined: Feb 2003
Posts: 687
I would hate to try and figure a problem when you have 40 residential smokes connected together. If one was set off how would you know what unit to look in?

There are 2 limits to the number of interconected smokes:
1. Factory directions - Kidde is 24 smokes & accesories
2. NFPA 72 - no more than 18 initiating devices can be interconnected on a multiple station system, of these 18 alarms NO MORE THAN 12 CAN BE SMOKES

To interconect all of them 120v you would need relays. If you have to interconect all I would think your looking more at a supervised system.


#51703 05/08/05 05:37 PM
Joined: Feb 2005
Posts: 693
Don't forget to check the documentation supplied with the detectors. I recently did a large house with 14 setectors; the instructions specified a max of 20 interconnected.

Larry Fine
Fine Electric Co.
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