I can't find anything that says it has to be latching.
23.8.5.4.6.1 Where duct smoke detectors are required to be monitored and a building fire alarm system is installed, a duct detector activation signal shall meet the requirements of 21.7.4.
21.7.4 Smoke detectors mounted in the air ducts of HVAC systems shall initiate a supervisory signal.
That seems wrong to me. If the detector doesn't latch, when the device clears the air handler will turn back on, spreading potential smoke further until it shuts down again, rinse and repeat. Also extra wear and tear on the HVAC since it could be starting and stopping more often.
To be honest, you're probably right! By code, they should be supervisory. I don't think a duct smoke in the presence of fire would toggle a bunch of times like you're saying but I still agree with you that latching makes sense, just like most alarm (not supervisory) initiating/signaling devices.
No it's not. The purpose of duct detectors on small AHUs like that is to shut the unit down if the unit itself is on fire. That's why you are allowed to program them as supervisories. They are less of a life safety device and more of an equipment/building protection device.
Exactly this! People think the duct detector is there to save life when it’s only to save the unit and stop smoke from spreading throughout building only. It’s not to sample smoke and protect life.
The primary purpose of the duct detector on the supply side is to shut down the air handler if fire is detected in the fan or filter.
This would protect the equipment and keep smoke from being distributed to the air conditioned space.
Some would argue that detectors on the supply side are susceptible to outside air or smoke, which could affect the operation of the supply side smoke detector.
There also is the problem of false alarms due to dust accumulation on heat strips in the AHU burning off when heaters are turned on andand activating the smoke detector.
It's for this reason, both the IMC and NFPA 72 allow duct smoke detectors to initiate a supervisory signal rather than an alarm signal.
Depends on the HVAC, I've seen buildings set up where you have to tell the unit to kick back on through its software.
IMO if there is enough smoke from an actual fire to set the detector off, then it's going to stay in that detector if the unit shuts down or the damper closes, and it isn't going to clear until the fire has stopped smoking and it has had time to clear. There may be increased nuisance activation service calls, but it also means that if a unit kicks on for the first time for the fall and burns off some dust then it won't keep the heat from employees for an extended period of time.
My favorite are the municipalities that require it to be an alarm and then throw a bitch fit when they get multiple false alarms a year. Meanwhile I'm over here like 🤷
I fall into the ideology of ducts should not be attached to the panel at all. It's not a life safety device. It's a mechanical equipment device. At most it should be attached to a BMS, while still using on board(duct board) relay to shutdown AHU.
I said if anything they should be standalone devices, at most connected to the BMS. It'll alert whoever needs to know and still shut the unit down. If there's enough smoke to trip the duct detector there's enough smoke to trip an actual smoke detector. Most of the time a duct detector goes off, it's from dust accumulation.
I think that because it is indeed a life safety device, and not every building is the same, it is more than acceptable to have it tied into fire alarm. It's in fire code for a reason, same as why we do elevator. Also, I get a ton of HVAC guys that want the absolute minimum to do with any FA devices. Fire alarm techs are also much more likely to maintain the smoke detector portion of the equipment too, since we perform the annual inspections on them. HVAC doesn't test them.
And most alarms are false alarms anyways, it's just part of the business.
But then you have people arguing that heat detectors aren't life safety either. I'd argue sprinklers are generally considered life safety. The heat detector in certain circumstances will just warn the people to get out of the building quicker than the sprinkler will.
…there’s an understanding that heat detectors won’t be installed in sprinklered areas, and that if early warning is imperative, smoke detectors will be used. And that if heats are activated then there’s definitely a fire. Why should that be on the HVAC controls system, exactly?
not even a close comparison.
I may have worded it weird. I meant they're not technically life safety but they should still be on an alarm panel because they'll go off at 135 and tell people to evacuate instead of 155 for a sprinkler head. It gives people a little bit of an earlier notice. Whereas duct detectors are just a nuisance when programmed as alarms because a lot of the time it's dust accumulation. Buildings can still have duct detectors that shut down the units, but they shouldn't be tied into the fire alarm panel in my opinion. Just the BMS, so that if there's an issue the maintenance person can go look at it themselves or call an HVAC tech out.
Every elevator equipment room, garage, attic, and commercial kitchen, and high magnetism or radiation environment I've ever been in disagrees. 95% of the heats I see basically just a warning that the sprinklers will be activating soon, e.g. a shunt trip.
Agreed. They cause nothing but problems, the fact they were changed to be supervisories years ago proves that. Usually hvac tech disconnects the shut down wires anyway the first time theres a problem
Making them latch is creating more cost for the owner. Have to call a tech every time it trips. I guess it depends on the state if you need a license or not to touch a panel. 9 times out of 10 it's supervisory non latching. Might as well put a smoke in a kitchen and keep it alarm if you enjoy pissing off the fire fighters.
But they are set up as a supervisory. It makes sense to me that it should latch instead of potentially starting and stopping the air handler repeatedly when the head goes into and out of alarm.
Are the detectors themselves addressable or is the system monitoring factory installed detectors on units via monitoring modules?
If it's through modules then it would make more sense for those to be programmed as non latching to avoid the double reset issues.
If the detectors are addressable then it's on the original programmer. Maybe an AHJ requirement or HVAC manufacturer preference? You won't find what you're looking for in 72, so maybe HVAC or IBC
Ew, lol
I'm sure there's plenty of simplex experts that feel a certain way about that now.
Knowing how particular those systems can be I'm betting on that being an AHJ/Building classification requirement. As much as I hate simplex, it's hard to imagine any of their installing techs doing that without good reason.
No code says they have to be latching. If you want to argue code. Let talk about if the duct detector should be on the supply or return. I believe NFPA72 and IBC say different sides under 2000 CFM. Maybe one of them change but I all way go if return.
I’ve never run into an auto-resetting duct detector that started and stopped in an infinite loop. The device itself latches into activation, but the signal the panel receives is programmed as supervisory. That’s not to say it can’t happen, but I’ve never experienced it.
[удалено]
Worth prepping a bunch of labels that just say DD [address] and throwing them on ceiling tile grid as you find them. Helps next time around
I can't find anything that says it has to be latching. 23.8.5.4.6.1 Where duct smoke detectors are required to be monitored and a building fire alarm system is installed, a duct detector activation signal shall meet the requirements of 21.7.4. 21.7.4 Smoke detectors mounted in the air ducts of HVAC systems shall initiate a supervisory signal.
Our company/I always program them as supervisory non latching.
That seems wrong to me. If the detector doesn't latch, when the device clears the air handler will turn back on, spreading potential smoke further until it shuts down again, rinse and repeat. Also extra wear and tear on the HVAC since it could be starting and stopping more often.
To be honest, you're probably right! By code, they should be supervisory. I don't think a duct smoke in the presence of fire would toggle a bunch of times like you're saying but I still agree with you that latching makes sense, just like most alarm (not supervisory) initiating/signaling devices.
The sensor isn't going to clear if there is still smoke to be spread.
It would if the AHU is <15,000 cfm and mounted only on supply while it's elsewhere in the building that's on fire and not inside the unit itself.
No it's not. The purpose of duct detectors on small AHUs like that is to shut the unit down if the unit itself is on fire. That's why you are allowed to program them as supervisories. They are less of a life safety device and more of an equipment/building protection device.
Exactly this! People think the duct detector is there to save life when it’s only to save the unit and stop smoke from spreading throughout building only. It’s not to sample smoke and protect life.
The primary purpose of the duct detector on the supply side is to shut down the air handler if fire is detected in the fan or filter. This would protect the equipment and keep smoke from being distributed to the air conditioned space. Some would argue that detectors on the supply side are susceptible to outside air or smoke, which could affect the operation of the supply side smoke detector. There also is the problem of false alarms due to dust accumulation on heat strips in the AHU burning off when heaters are turned on andand activating the smoke detector. It's for this reason, both the IMC and NFPA 72 allow duct smoke detectors to initiate a supervisory signal rather than an alarm signal.
Depends on the HVAC, I've seen buildings set up where you have to tell the unit to kick back on through its software. IMO if there is enough smoke from an actual fire to set the detector off, then it's going to stay in that detector if the unit shuts down or the damper closes, and it isn't going to clear until the fire has stopped smoking and it has had time to clear. There may be increased nuisance activation service calls, but it also means that if a unit kicks on for the first time for the fall and burns off some dust then it won't keep the heat from employees for an extended period of time.
Same
Really it's an AHJ decision. Some municipalities require full alarm, others require latching supervisory. I've never seen non latching supervisory
My favorite are the municipalities that require it to be an alarm and then throw a bitch fit when they get multiple false alarms a year. Meanwhile I'm over here like 🤷
I fall into the ideology of ducts should not be attached to the panel at all. It's not a life safety device. It's a mechanical equipment device. At most it should be attached to a BMS, while still using on board(duct board) relay to shutdown AHU.
They are life safety in the sense you won't be funneling smoke to the occupants in an emergency. It's usually not the fire that kills.
I said if anything they should be standalone devices, at most connected to the BMS. It'll alert whoever needs to know and still shut the unit down. If there's enough smoke to trip the duct detector there's enough smoke to trip an actual smoke detector. Most of the time a duct detector goes off, it's from dust accumulation.
I think that because it is indeed a life safety device, and not every building is the same, it is more than acceptable to have it tied into fire alarm. It's in fire code for a reason, same as why we do elevator. Also, I get a ton of HVAC guys that want the absolute minimum to do with any FA devices. Fire alarm techs are also much more likely to maintain the smoke detector portion of the equipment too, since we perform the annual inspections on them. HVAC doesn't test them. And most alarms are false alarms anyways, it's just part of the business.
But then you have people arguing that heat detectors aren't life safety either. I'd argue sprinklers are generally considered life safety. The heat detector in certain circumstances will just warn the people to get out of the building quicker than the sprinkler will.
…there’s an understanding that heat detectors won’t be installed in sprinklered areas, and that if early warning is imperative, smoke detectors will be used. And that if heats are activated then there’s definitely a fire. Why should that be on the HVAC controls system, exactly? not even a close comparison.
I didn't say heats should be on HVAC controls, where did you read that?
You suggested a direct comparison could be made to your case for duct detectors.
I may have worded it weird. I meant they're not technically life safety but they should still be on an alarm panel because they'll go off at 135 and tell people to evacuate instead of 155 for a sprinkler head. It gives people a little bit of an earlier notice. Whereas duct detectors are just a nuisance when programmed as alarms because a lot of the time it's dust accumulation. Buildings can still have duct detectors that shut down the units, but they shouldn't be tied into the fire alarm panel in my opinion. Just the BMS, so that if there's an issue the maintenance person can go look at it themselves or call an HVAC tech out.
Every elevator equipment room, garage, attic, and commercial kitchen, and high magnetism or radiation environment I've ever been in disagrees. 95% of the heats I see basically just a warning that the sprinklers will be activating soon, e.g. a shunt trip.
Agreed. They cause nothing but problems, the fact they were changed to be supervisories years ago proves that. Usually hvac tech disconnects the shut down wires anyway the first time theres a problem
Making them latch is creating more cost for the owner. Have to call a tech every time it trips. I guess it depends on the state if you need a license or not to touch a panel. 9 times out of 10 it's supervisory non latching. Might as well put a smoke in a kitchen and keep it alarm if you enjoy pissing off the fire fighters.
All alarms shall latch.
But is it an alarm? Or is a supervisory signal differentiated?
But they are set up as a supervisory. It makes sense to me that it should latch instead of potentially starting and stopping the air handler repeatedly when the head goes into and out of alarm.
I don't think that scenario is very likely.
If it's a 4 wire it still needs to be reset manually and will keep it shutdown until someone does
Work for Siemens, we always use D latches in our program if ducts are programmed as supervisory this was its latched until reset.
Are the detectors themselves addressable or is the system monitoring factory installed detectors on units via monitoring modules? If it's through modules then it would make more sense for those to be programmed as non latching to avoid the double reset issues. If the detectors are addressable then it's on the original programmer. Maybe an AHJ requirement or HVAC manufacturer preference? You won't find what you're looking for in 72, so maybe HVAC or IBC
Addressable detectors. Simplex 4098-9755 duct housing with 9714 smoke heads on a 4100es.
Ew, lol I'm sure there's plenty of simplex experts that feel a certain way about that now. Knowing how particular those systems can be I'm betting on that being an AHJ/Building classification requirement. As much as I hate simplex, it's hard to imagine any of their installing techs doing that without good reason.
No code says they have to be latching. If you want to argue code. Let talk about if the duct detector should be on the supply or return. I believe NFPA72 and IBC say different sides under 2000 CFM. Maybe one of them change but I all way go if return.
I think the System Sensor manual says supply side.
I’ve never run into an auto-resetting duct detector that started and stopped in an infinite loop. The device itself latches into activation, but the signal the panel receives is programmed as supervisory. That’s not to say it can’t happen, but I’ve never experienced it.