Interconnection of Smoke Detectors

[ELAR]

NFPA 72 states that only 12 detectors can be interconnected. I have a house with 15 detectors - 8 upstairs and (with the basemet finish) 7 in basement. I was thinking of interconnecting all upstairs with one interconnected in the basement and the rest interconnected to basement. Any suggestions would be appreciated. I was planning on serving all on the same circuit for power. I am in Colorado.

Thank you,

[j_erickson]

NFPA 72 states that only 12 detectors can be interconnected. I have a house with 15 detectors - 8 upstairs and (with the basemet finish) 7 in basement. I was thinking of interconnecting all upstairs with one interconnected in the basement and the rest interconnected to basement. Any suggestions would be appreciated. I was planning on serving all on the same circuit for power. I am in Colorado.

Thank you,

So 8 upstairs interconnected with one in the basement and then the other 6 in the basement interconnected with just each other?

I don't believe that will be compliant either.


Also, most manufacturers instructions only permit up to 12 interconnected. I'd say you need to use system detectors with a panel. The easiest way is to use a residential burg/ fire panel. If it is a remodel/ addition, there are approved wireless smokes for the application in conjunction with the burg/ fire system. They are referred to as low power wireless transmission by nfpa.

[iwire]

NFPA 72 states that only 12 detectors can be interconnected.

Just a word here, if NFPA is talking about smoke detectors it is not talking about the line voltage smoke alarms we use is houses.

A smoke detector only works when connected to a fire alarm panel.

A smoke alarm is the device that can be stand alone or interconnected.

[wbalsam1]

Hi: Iwire's correct when he points out the difference between detector and alarm. At first blush one would think a detector "detects" and an alarm "annunciates", but it's more complicated. A single-station smoke alarm is an assembly that incorporates a detector, the control equipment and the alarm-sounding device all within one unit. It often can be operated from commercial power and / or battery. A multiple-station smoke alarm is two or more of the single-station smoke alarms. In NYS, new installations are commercial power with battery back-up. Check the manufacturer's listing and labeling to assertain how many alarms may be interconnected. This number can sometimes be in excess of 12 depending on the manufacturer, etc.

[goldstar]

Depending on the manufacturer you may be able to use an interface relay to wire in additional single station smoke alarms. The problem with these units (I believe) is that the signal sent over the red wire to activate the additional units on the run is not strong enough to activate (or was not tested to activate) more than 12 units.

As far as wiring a maximum of 20 system smoke detectors on one circuit, I don't believe that's an NFPA issue but a design issue. Many of the microprocessor based control panels (on the lower end of the spectrum) today are capable of having 198 devices on 1 pair of wires. Some of the larger systems can accept more addressible devices. The design problem arises when the circuit is cut or interrupted somewhere, say after the 10'th device. In Bob Iwire's design you would only lose the 10 detectors that were wired in after the break. In my scenario you would lose as many as there were wired after the 10th unit.

[j_erickson]

Hi: Iwire's correct when he points out the difference between detector and alarm. At first blush one would think a detector "detects" and an alarm "annunciates", but it's more complicated. A single-station smoke alarm is an assembly that incorporates a detector, the control equipment and the alarm-sounding device all within one unit. It often can be operated from commercial power and / or battery. A multiple-station smoke alarm is two or more of the single-station smoke alarms. In NYS, new installations are commercial power with battery back-up. Check the manufacturer's listing and labeling to assertain how many alarms may be interconnected. This number can sometimes be in excess of 12 depending on the manufacturer, etc.

Thanks, but I realize all this. I do a lot of homes that get multiple station smoke alarms and a lot of others that get detectors wired into a combination burglar/ fire alarm panel. And I do commercial fire alarm systems.

Not sure why you put my name in the title of your post.:)

[bstoin]

Just a word here, if NFPA is talking about smoke detectors it is not talking about the line voltage smoke alarms we use is houses.

A smoke detector only works when connected to a fire alarm panel.

A smoke alarm is the device that can be stand alone or interconnected.
This is true and a very important point because depending on where you live a fire alarm panel with detectors may not satisfy the AHJ for the requirements of NFPA 72. I have run into this on occasion on residential applications. Not quite sure if I agree with this. If a fire alarm panel is good for the NFPA 72 on commercial applications why not residential applications?

[bstoin]

My previouse post doesn't really address your problem, however.
My suggestion would be to contact the AHJ and/or the manufacturer of the smoke detex (certainly you aren't the first to run into this).

[bjp_ne_elec]

ELAR - the question I have, is why seven (7) smokes in the basement?

Thanks

[satcom]

This is true and a very important point because depending on where you live a fire alarm panel with detectors may not satisfy the AHJ for the requirements of NFPA 72. I have run into this on occasion on residential applications. Not quite sure if I agree with this. If a fire alarm panel is good for the NFPA 72 on commercial applications why not residential applications?

Some AHJ's want the alarms even if you have detectors and a control panel, and with good reason, the control and detectors, can easly be disabled, or disconnected, very common thing with monitored systems, the owner decides to discontinue service and the the first thing to go is the battery back-up, then with the sounder ringing from a dead battery they pull the AC plug, and bingo no more protection, this is why some AHJ's require the hard wired alarms, even if there is a control with detectors.

We have a lot of commercial properties, that have both detectors, and alarms, both were required by the AHJ.

[goldstar]

Some AHJ's want the alarms even if you have detectors and a control panel, and with good reason, the control and detectors, can easly be disabled, or disconnected, very common thing with monitored systems,
I've run into this before but I can't buy into the reasonig. No matter what type smoke alarm or system you have installed, if a homeowner wants it disconnected they'll find a way to disconnect it. There are advantages and disadvantages to both types of installations. I would say, however, that if an individual smoke alarm was getting annoying with unwanted or nusiance trips and a homeowner removed that device, they would still have some protection throughout the house with the others plugged in. In your scenario, if they shut off their entire alarm system they're completely out of business

[Mike03a3]

NFPA 72 states that only 12 detectors can be interconnected. I have a house with 15 detectors - 8 upstairs and (with the basemet finish) 7 in basement. I was thinking of interconnecting all upstairs with one interconnected in the basement and the rest interconnected to basement.
Assuming you mean smoke alarms, I wonder if you could put one wireless alarm on the upstairs circuit and a second on the basement circuit, with the two wireless alarms serving as a bridge to inteconnect the two sets of alarms.

[ELAR]

The reason for 7 detectors in the basement:
4 bedrooms.
1 outside bedrooms.
2 different locations where ceiling height changes by more than 24".

Thanks for taking time to address this issue.

[satcom]

I've run into this before but I can't buy into the reasonig. No matter what type smoke alarm or system you have installed, if a homeowner wants it disconnected they'll find a way to disconnect it. There are advantages and disadvantages to both types of installations. I would say, however, that if an individual smoke alarm was getting annoying with unwanted or nusiance trips and a homeowner removed that device, they would still have some protection throughout the house with the others plugged in. In your scenario, if they shut off their entire alarm system they're completely out of business

A homeowner will unplug a control panel, It's not as common for them to shut off an interconnected hardwired system, if they shut the breaker off they may loose some area lighting, and call for service, if they unplug a control panel they most likely notice nothing changed, something we see a lot of is unpluged controls with dead batteries, it's rare to find interconnectd alarms, disconnected by a homeowner. In commercial if they have sprinklers all that may be required is, monitoring of water flow and tamper, smokes may not be required, we see a lot of installations, where smokes have been installed and not required.

The hardwired interconnectd alarms are required, the control, and detectors are not.