ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Split Bus Breaker Panel
by gfretwell - 01/25/21 12:35 AM
Ground fault remover :-)
by dsk - 01/24/21 04:35 AM
Questioning the electrical norms
by Trumpy - 01/24/21 03:16 AM
From an outsider- How does tipping work?
by gfretwell - 01/23/21 06:13 PM
Photo Editing Software?
by JoeTestingEngr - 01/23/21 12:47 PM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 15 guests, and 14 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
interconnecting smokes #51694 05/08/05 09:22 AM
Joined: Nov 2002
Posts: 267
Wirenuttt Offline OP
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?

Work Gear for Electricians and the Trades
Re: interconnecting smokes #51695 05/08/05 09:39 AM
Joined: Jan 2003
Posts: 4,391
iwire Offline
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
Re: interconnecting smokes #51696 05/08/05 09:42 AM
Joined: Nov 2002
Posts: 267
Wirenuttt Offline OP
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.

Re: interconnecting smokes #51697 05/08/05 10:03 AM
Joined: Aug 2003
Posts: 1,374
Ryan_J Offline
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
Re: interconnecting smokes #51698 05/08/05 10:18 AM
Joined: Nov 2002
Posts: 267
Wirenuttt Offline OP
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.

Re: interconnecting smokes #51699 05/08/05 10:54 AM
Joined: Jan 2002
Posts: 1,457
Electricmanscott Offline
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.

Re: interconnecting smokes #51700 05/08/05 11:05 AM
Joined: Jan 2002
Posts: 1,457
Electricmanscott Offline
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.

Re: interconnecting smokes #51701 05/08/05 11:10 AM
Joined: Jan 2002
Posts: 1,457
Electricmanscott Offline
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).]

Re: interconnecting smokes #51702 05/08/05 02:33 PM
Joined: Feb 2003
Posts: 687
Active 1 Offline
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.


Re: interconnecting smokes #51703 05/08/05 04:37 PM
Joined: Feb 2005
Posts: 693
Larry Fine Offline
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.
Page 1 of 2 1 2


2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Atomic City, ID USA
Posts: 803
Joined: October 2004
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 18
Popular Topics(Views)
274,154 Are you busy
207,958 Re: Forum
195,600 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3