This here Chris! Hvac guys in my area won't even try to do anything with ducts. We can't even get meet ups with most. Usually we have to mark where they need to hookup shutdown and wait. Thanks for helping others understand the operation.
The supervisory contacts are "backwards" so that it will go into trouble should the unit lose power. A powered-off detector won't detect smoke after all.
hahaha the roofing sealant everywhere. reminds me of the fire sealant guys here in england, they spread fire mastic all over absolutely everything. it's not possible to be on site when they are there and not come home covered in it myself
Sounds like drywall installers. Mud everywhere, even on everything that's not supposed to have it. I've also seen concrete guys scrape their trowels (and boots) on anything rigid that's handy and destroy equipment because they don't clean up after themselves.
Like Chris pointed out as in USA and UK the people that go round putting the mastic on and fire doors are not trained enough. I am usual as have been in the fire world and then moved into HVAC so well understand this topic and seen so many horror commited. Like the guys going round doing the fire doors and seals gaffer taping the smokes (detector) to stop dust while they chip away at the doors to fit and leaving. Best bit to not have dust in the flats they work in the plant rooms the one place you do not want a smoke to work! I wish I could post pictures of them at work here!
Those supervisory connections always get me because they are technically backwards, as you mentioned. I have to remember the internal supervisory relay is continuously POWERED in NORMAL operation. This is why the trouble monitored sites require a call to the alarm company BEFORE turning OFF the equipment DISCONNECT. When the 24v (or whatever is powering the SD) is lost, you will trigger a TROUBLE alarm for that unit. BTW, all SD used today are non-radioactive, they are optical smoke sensors. There is an internal test done periodically for each sensor to make sure the light emitter and detectors are working and unobstructed. If the sensor gets dirty, the system will also trigger a TROUBLE alarm condition. Thanks for the video
If you see two resistors on the wire, you are probably looking at Double-EOL wiring. This lets you detect four states: normal, alarm, open circuit and short circuit.
That "signaling device" is what's usually called a "monitor module"(some brands like to use different names, I don't recognize this one). They connect to a modern addressable loop, and provide a circuit that you can connect to a set of dry contacts like a duct detector, or waterflow switch etc.
Just FYI, there's a second reason the fire mode goes 'full air sucking out of the mall': If there's a fire somewhere, then unless it's already roasting you, it's pretty harmless on its own. In a closed building, the smoke is way more deadly than the fire. Thus, getting the smoke out of the mall by all means possible will allow the people within to have a greater chance of survival and escape. And if they let fresh air in - so what? Yes, the fire will get more oxygen, but so will the people still trying to get out. All the building, burnable material an all that, it's not THAT important compared to a single human life. So, getting rid of as much smoke as possible is a very good thing, and trying to starve the fire by pulling out air is a nice side-effect.
Fun fact hi-rise stairwells have fans that do the exact opposite and bring large amounts of air into the stairwell. This creates a positive pressure in the stairwell to keep smoke from other parts of the building from entering the stairwells. There is a duct detector in the duct work of these fans that will shut them down, however, if it detects that it's actually bringing smoke in.
@@kg4mrv I think an important detail to keep in mind here, there is usually separate smoke exhaust or stairwell pressurizing equipment from the regular HVAC stuff. With those HVAC units on the roof, depending on the ductwork, they usually get shut down to prevent them conveying smoke from one part of the building to a different part. Or depending on the heat they may take in, setting other parts on fire. Most parts of fire prevention in modern buildings are less about blocking fire from burning through (although often material are chosen to slow that down) but you got doors, curtains etc. that automatically close to contain smoke within limited areas. Within those areas then there are smoke exhaust systems to clear up the air and, by ventilation, possibly cool down the air to keep escape routes accessible. That is although why modern elevator controls are connected to fire alarm systems, to prevent an elevator car from stopping on a smoke filled floor and afterwards the smoke preventing the door from closing again (by blocking the photoelectric barrier that should prevent the door closing while someone is in between the doors.)
the other reason is that the heat can go somewhere than cooking everyone inside. I'm a firefighter, it's the reason we do vertical ventilation so that the smoke will get out because we're not worried about the smoke, we're worried of the heat that's in the smoke because if that smoke is hot enough it will burst into flames and cook everyone inside, this is called a flashover, if you can find a way for heat to escape you take that chance.
Lol I just went to a Smokey bones today on a water leak. Met up with a roofer. Lol my lord. He was so convinced that bc one of the units was missing a screw on the filter door that ran was being blown into the screw hole and causing the roof leak.
I used to have a mock fire alarm board with a addressable panel, horn strobe, pull station and a few field smokes with a sperate board with a duct smoke detector.. I wired in supervisory as a trouble as well. I actually thought they looked difficult to wire but it's really not rocket science to install I could install these all day lol.. great video as always!!
I love how thorough your explanations are on everything you do. A great review for seasoned techs and important learning technique for someone that may not know or remember this particular issue.
So, maybe the roofer had a 5 gallon bucket of mastic, and didn't want to carry it back down? "A little bit here, a little bit there... My bucket is empty a lot lighter now!"
Some fire sensors do use radioactive material that decays over time, so this could just be an age related replacement to ensure that the detector has the correct sensitivity.
Yes, amerecium-241, with a half-life of 432 years. Works out that it loses about 1.6% of its initial output in 10 years, which is the nominal life for ionization type smoke detectors.
@@elco_os9355 dust is the main issue. the smoke chamber is actually a light trap that should prevent light from the outside and a defined light source being reflected onto the actual sensor. Smoke in the chamber will reflect light onto the sensor. dust accumulating over time sadly will do as well. Or it just covers the light source or the sensor to make it go blind. I think usually they say they are good under normal operating conditions up to ten years. By now, although there sure still will be a lot of those around, I think most new smoke detectors used in the last 15 to 20 years are optical. Not sure if the ionization type models still exist, at least I could not find anything about them being banned for new installations. Looking around here in Germany, I obvisoulsy don´t find any of them to buy anymore
Exhaust fans remove the heat. Same thing when they cut a hole in the roof of a burning house. Giving the heat an escape route helps keep it from igniting new material. Also if anyone is inside it helps clear the smoke.
The two problems are flashover and backdraft. Exhaust fans remove the oxygen, which reduces the ability of the fire to burn. But, that can contribute to a backdraft, where incompletely burnt gases can ignite when oxygen is introduced. Introducing oxygen carefully can reduce the possibility of a backdraft. But, that's why they cut holes in the roof eventually, to allow the fire to breathe, to prevent fire from injuring the firefighters from either a backdraft or flashover. A trained firefighter would be able to explain this better than me.
Technician types tend to be hands-on/visual learners. We had training boards just like yours for motor controls, fluid power, and PLCs when i went to school for industrial maintenance.
Those fire exhaust fans are used because they extract smoke. Smoke is usually the most dangerous thing during a fire, since it contains toxic gasses like carbon monoxide. So when a fire occurs in a crowded shopping mall, you want to get the smoke out as soon as possible, because it takes a lot of time before everyone has left the building.
exactly. kill the HVAC that would recirculate the smoke. Turn on exhaust fans to get rid of smoke. not to smother fire. To get rid of the smoke that kills people.
Chris, you’re not in any way dumb for not immediately understanding how something works from technical manuals. Those things are incredibly information-dense, and none of it is actually “how it works” - it’s all “what it is.” It *should* take time and effort to understand what you’re reading. Anyone who really could understand how things work from those manuals isn’t someone you should compare yourself to. Being able to take what you learn and teach it to someone else is more than enough smarts for anyone. Look up the Feynman Technique sometime.
The keyword is: big picture. Before diving into all the details, make sure you get a overview of all the things that are there. At least, that is how i learn things. If i don't get the big picture, then i wouldn't understand the details either. However, most manuals start right away with all the detailed stuff.
This video is brought to you by Spor-craft by Fieldpiece instruments in conjunction with United refrigeration at Johnstone Supply 😆 🤣 😂. Just messing around
My personal opinion is the old detector had reached end-of-life, or was getting close to it, and they wanted it replaced. I love every time you go to the training board to explain duct detectors even though, as a child helping my father install Simplex fire alarms, I "get" how it all works.
It's not the most uncommon thing to just fire off the parts shotgun at fire alarm problems once you've narrowed an issue down to a single unit. The FA tech should have done something about that monitor module just swinging in the breeze where it can get wet, whether it's putting it in a J box or inside the terminal box side of the detector, but if the issue was having the duct shut down the unit randomly and setting off the alarms then a new detector would be most likely to resolve it. They could also have taken care of that crumbling prefilter foam, cleaned the inside of the smoke chamber that was probably dirty enough to be hovering near it's alarm threshold, and made sure the sampling tubes weren't nasty, but that's not as easy as saying "we don't service duct detectors, get your hvac dude to change it." Like he said at the end of the video, duct detectors always live in a weird gray area of who's responsibility they are, and it changes depending on the design of unit, local AHJ rules, and even what one contractor or another is willing to work on.
Good call on liability. Make sure you leave that on the fire alarm company. Always schedule a vendor meet between you and the fire alarm company to cover you ass. Im sure i could figure out the alarm system but lawyers....
When thares a broken line the alarm company calls you when thares a trouble at my sister old job they used to get a lots of troubles with an old fire alarm intill thare was smoke was spotted we called 911 and pulled the alarm we knew the old system wasn’t ganna call them a ful days later they come to replace the old system with a new one
Sir I want to know one thing plz guide me... I have 10Ton package unit of carrier its breaker will be trip after two days three days I already clean Condencer and I already changed the breaker But still have same issue
16:50 More worse case scenario: What if one of those wires broke because a fire melted the wire? (If it did that before setting off the alarm/detector.) You'd want to know. 🙂
firefighter here: we respond to multiple fires with the fire alarm system still sounding. the wires have a fire resistance rating to how many minutes it takes to melt it and at what temperature
How it's possible to 2 detector in alam if you only put in your set/reset station in alarm. Here in the Netherlands it's not allowed, and if one going only that alarm will be visible (to be specific where the alarm is). Maybe in the USA this is normal but for me its strange.
It depends on the manufacturer. On some smoke detectors, the test switch actually puts the detector into a "test" mode, where the detector will actually turn on a small LED inside the sensing chamber in an effort to get the sensor to trigger an alarm. Usually detectors that employ this more-realistic test method take a few moments to activate. On other detectors, the test switch simply triggers the same alarm input as the sensing chamber does, which tests whether the logic board can close the alarm relay, but does not test if the sensing chamber can actually respond to smoke. Either way, many AHJs view "smoke in the chamber" (usually canned smoke sprayed into the detector using a special tool) as the only test that actually proves that the smoke detector can detect smoke, but when a building with 20 RTUs has one tripped in false alarm, or you just want to verify a fix to the building wiring, that test/reset switch is much faster than climbing onto the roof and opening every unit until you find the problematic one.
Some places/inspectors are happy enough with just hitting the remote test, and just rely on the fire alarm contractor having certified everything is working correctly, with their on-site inspection being little more than a spot-check that strobes are where the plan says and that the fire department gets a dispatch call. Many will require full-on smoke-bomb testing to prove shutdown happens and to verify that the entire assembly of sampling tubes, detector, shutdown, alarms, etc... all work in a real-world actual smoke-in-the-ducts situation.
@@boginator55 Should the fire inspection guys actual do a REAL smoke test? They do sell cans of simulated smoke that should set off a detector. Not something an HVAC guy should worry/care about, just an interesting tid bit. 😀 edit: Whoops, TheWomble already mentioned smoke bomb test.
That foam prefilter breaking down to dust might have been building up in the smoke chamber and setting off the false alarms that were why they wanted the detector replaced anyway.
Well it's not really E stop but fire alarm signal. Fire alarms always use normally open contacts, you don't want it to trigger due to a loose wire. Instead they require regular testing for functionality and the resistors for supervision. It is not likely the short wire inside the AC from the duct detector to the control board gets loose/damaged between testing periods.
The link between smoke detector and HVAC controller should also be a resistor terminated bus, so it can know if it's a trouble condition with the wire, or an actual alarm. (In a world where things are perfectly engineered.)
Omg what did you do to the Fluke? You know you coulda just use a panel meter. Very cool video though everything makes sense. My curiosity would be does the sensor head ever get coated with grease?
It may not matter on your Training Board but the HVAC and ALARM guys in our area do not use Telephone cabling for signaling & Control. ALL Alarm stuff is RED. And HVAC is BROWN and a heavier Gauge . I ran into an issue earlier on in My carrier about 30 some years ago where an Alarm Co. spliced into a Telephone cable. I was trouble shooting an Issue of open conductors in said cable only to find Alarm Ckts on it. Thanks. Mike M.
Here we use regular white "telephone wire" for burglar alarms, if they are damaged the alarm will just go to trouble mode. Fire alarms use bright red fire proof cable.
Depends on what local AHJ says, but yeah, by code you have to run fire alarm in FPLP or FPLR cable, and while color isn't dictated by code to *HAVE* to be red, it's best practice anyway. We recently have had a hard time getting red cable and had to switch to blue for a few installs because that was the only FPLP we could get ahold of. There's some municipalities and AHJs that require explicitly fire alarm be run in red, masked off from fog painting when that's done, and all that, but in my experience most don't.
@@nnyboy320 - I guess I can check and see if I left it in the ceiling. For that matter, there's probably two or three others that I didn't pull out because they weren't in the way. Building went up in 78, and was rewired at least four times just for alarms, and all sorts of trash for network.
I also collect fire alarms. I'm into all sorts of electronics and I will be 21 next year. I plan to get into the fire alarm or HVAC trade, just have to wait for logistics to line up. But I'm very knowledgeable in this equipment. I mostly collect old Simplex equipment, made by Simplex Time Recorder Co. Fire alarm panels, signals, pull stations, etc. There's some content on my channel. I love Chris's hard work and great videos :)
