Smoke detectors

[contactm]

Hi!!!!! anyone have an idea!!! i'm installing smoke detectors that work on 24 volts, am i required to install 120 volt smoke detectors too ??????

 

[peter d]

It depends on what, if any, fire code is enforced in your area. Most jurisdictions around me require 120 volt stand alone smoke detec...err....I mean alarms in addition to the 24 volt system detector.

 

[wbalsam1]

Hi!!!!! anyone have an idea!!! i'm installing smoke detectors that work on 24 volts, am i required to install 120 volt smoke detectors too ??????

You must check with the building official in the community where you are contemplating doing this work. The installation of a smoke alarm or a smoke detector will require a building permit and a compliance inspection.

 

[radiopet]

Check your IRC. It states that in NEW installations the building wiring has to power the required smoke detectors and must have battery backup. If you choose to also put in 24V smoke detectors as well....thats your choice.

Check out IRC - R313.3 - Power Source

 

[brantmacga]

Check your IRC. It states that in NEW installations the building wiring has to power the required smoke detectors and must have battery backup. If you choose to also put in 24V smoke detectors as well....thats your choice.

Check out IRC - R313.3 - Power Source

does it list a specific voltage? i don't ever remember the article saying it had to be 120v, or any voltage for that matter.

it has always been my understanding that low-voltage smoke detectors w/ a battery backup in the control panel meet the requirements because technically they are hard-wired, just to a low voltage transformer.

 

[peter d]

It depends on what, if any, fire code is enforced in your area. Most jurisdictions around me require 120 volt stand alone smoke detec...err....I mean alarms in addition to the 24 volt system detector.

I should clarify that my original answer is based on motel, hotel rooms, guest rooms, nursing homes, and similar rooms. That is the only place that I can think of where a system 24 volt heat or smoke detector will be present in the same room as a 120 volt line voltage smoke alarm.

 

[wireman3736]

If you install a listed 24 volt fire alarm system why would any jurisdiction require additional 120 volt alarms?

 

[peter d]

If you install a listed 24 volt fire alarm system why would any jurisdiction require additional 120 volt alarms?

Yeah, those silly fire codes. :roll:

 

[acrwc10]

It is common to see 24volt smoke alarms in a residential job ( in place of 120volt ) I forget where I read it ,it's late and I'm tired, but 12 or less you can use 120 volt inner connected, after that they need to go to a fire alarm panel at that point you may as well be using 24 volt as it is a lot easier to run them.

 

[wireman3736]

Read the paper work with the 120volt smoke detectors, that will limit the number of smokes to 12 although it will allow up to 15 total devices, also nfpa 72 limits the total number of unsupervised smoke detectors to 12, after that they are required to have supervision.

 

[gadfly56]

does it list a specific voltage? i don't ever remember the article saying it had to be 120v, or any voltage for that matter.

it has always been my understanding that low-voltage smoke detectors w/ a battery backup in the control panel meet the requirements because technically they are hard-wired, just to a low voltage transformer.

Ahhh, the joys of living in New Jersey, where our very own special edition of the IBC requires the detectors to perform the alarm function even if you rip the FACP off the wall. Hence, 120VAC interconnected smoke/heat/CO alarms even if you have a full blown FACP as well.

 

[wireman3736]

Ahhh, the joys of living in New Jersey, where our very own special edition of the IBC requires the detectors to perform the alarm function even if you rip the FACP off the wall. Hence, 120VAC interconnected smoke/heat/CO alarms even if you have a full blown FACP as well.

I'm just curious how you meet the supervision rule if there are over 12 connected, even if the supervision rule has been modified my understanding is that there isn't a manufacturer that makes a 120 volt smoke alarm that is listed over 12, at least thats what a rep from BRK told me.

 

[acrwc10]

Ahhh, the joys of living in New Jersey, where our very own special edition of the IBC requires the detectors to perform the alarm function even if you rip the FACP off the wall. Hence, 120VAC interconnected smoke/heat/CO alarms even if you have a full blown FACP as well.

The good old "What if" clause.

 

[gadfly56]

I'm just curious how you meet the supervision rule if there are over 12 connected, even if the supervision rule has been modified my understanding is that there isn't a manufacturer that makes a 120 volt smoke alarm that is listed over 12, at least thats what a rep from BRK told me.

There is, indeed, a deafening silence regarding "supervision" of these devices. Also, I believe the BRK rep is a teensy bit wrong in his assertion. What the directions with the detector say is identical to NFPA 72; the limitation is in the code, not the product.

You could do up to 64 devices, 42 of them smoke detectors if you could supervise them. Possibly as follows: Carefully install the devices as a Class B circuit, NO T-TAPPING! At the end of the circuit install a relay, such as a System Sensor PR-1 or throw up a 24VDC transformer and use an EOLR-1 and connect to a listed communicator such as a Silent Knight 5104B. If power on the circuit fails, the relay changes state and trips the communicator calling the central station and/or maybe ringing a local notification appliance. Cumbersome, but I think it meets the intent.

 

[wireman3736]

There is, indeed, a deafening silence regarding "supervision" of these devices. Also, I believe the BRK rep is a teensy bit wrong in his assertion. What the directions with the detector say is identical to NFPA 72; the limitation is in the code, not the product.

You could do up to 64 devices, 42 of them smoke detectors if you could supervise them. Possibly as follows: Carefully install the devices as a Class B circuit, NO T-TAPPING! At the end of the circuit install a relay, such as a System Sensor PR-1 or throw up a 24VDC transformer and use an EOLR-1 and connect to a listed communicator such as a Silent Knight 5104B. If power on the circuit fails, the relay changes state and trips the communicator calling the central station and/or maybe ringing a local notification appliance. Cumbersome, but I think it meets the intent.

You obviously know your products but I would be surprised to see an inspector or a state review board approve a setup like you just described. I don't see how you wold be able to supervise a 120 volt smoke alarm without T- Tapping, the detector plug alone would be enough to call it a t-tap. I don't think the central station would appreciate a signal every time the power failed. I also believe getting a listing on such a contraption would be a losing battle.

 

[wireman3736]

There is, indeed, a deafening silence regarding "supervision" of these devices. Also, I believe the BRK rep is a teensy bit wrong in his assertion. What the directions with the detector say is identical to NFPA 72; the limitation is in the code, not the product.

You could do up to 64 devices, 42 of them smoke detectors if you could supervise them. Possibly as follows: Carefully install the devices as a Class B circuit, NO T-TAPPING! At the end of the circuit install a relay, such as a System Sensor PR-1 or throw up a 24VDC transformer and use an EOLR-1 and connect to a listed communicator such as a Silent Knight 5104B. If power on the circuit fails, the relay changes state and trips the communicator calling the central station and/or maybe ringing a local notification appliance. Cumbersome, but I think it meets the intent.

So are your saying that there is a mfg out there that makes a LISTED smoke alarm that has been approved for 42 but because of the code it isn't allowed. What mfg. would that be?

 

[gadfly56]

So are your saying that there is a mfg out there that makes a LISTED smoke alarm that has been approved for 42 but because of the code it isn't allowed. What mfg. would that be?

Alas, I do not have a copy of UL 217 so I don't know if it directly addresses the issue of how many detectors can be hooked up on a single loop. If anyone can provide assistance on this, inquiring minds want to know. A careful reading of the Kidde manual http://www.kiddeus.com/utcfs/ws-384/Assets/Manual_820-1183_Rev_B.pdf again seems to suggest that the limitation is indeed NFPA, not UL.

 

[gadfly56]

... the detector plug alone would be enough to call it a t-tap...

If you remove a hard wired detector from its base and don't disconnect the module plug from the loop wire, the remaining detectors will continue to function. Hence, not T-tapped.

 

[gadfly56]

If you remove a hard wired detector from its base and don't disconnect the module plug from the loop wire, the remaining detectors will continue to function. Hence, not T-tapped.

OK, I take it back. From a supervision standpoint, it could be viewed as T-tapped. I suppose you could remove all the detectors and have no coverage and you wouldn't know it. The set up I've described only monitors for loss of power.

More generally, I know that in New Jersey there is an inclination to work with the homeowner on this. If you have a truly impressive spread that simply can't be covered under the NFPA limitation, my understanding is that the AHJ's will approve a variance for a full blown system. We don't do resi work (we're too expensive) so I can't attest to this on a personal level, but it's what I've heard.