When I was coming up in the trade duct smoke detectors, they drove me nuts, because I could never figure things out and the contacts the normally open and the normally closed. They just never seemed to work right. I had such a hard time and then I figured something out and I figured it out by reading the manual today. I'm gon na try to break down these duck detectors and simplify them a little bit more and show a few tips and tricks that I have in my little book.

This video is brought to you by spore'ln quality, integrity and tradition. What we have here is a training board that I made, and this training board is is meant for originally for my own service technicians, but I started using it to show to classes and give presentations on because it really does simplify them. When you take a duck smoke detector - and you just look at how simple it is: okay, most duck detectors - are gon na have a 24 volt power source. In some instances, though, you can have higher voltages and you can have lower voltages.

You can even run them off a 12 volts DC with some particular types. Okay, this setup right here is a. I have a hundred and fifteen volt step-down transformer and we're dropping it down to 24 volts low voltage and we're powering the duct detector. We have a simple setup here with a double sensing head with a single circuit board.

We have a test and reset station and that's pretty much it currently right now. I have the system in a fire condition. I do have this wired up to simulate trouble conditions and to simulate alarm conditions and then also have the test and reset station fully wired into it. So I'm gon na try to break this down, and hopefully by the end of this, if you are confused on these things, it makes it a little bit easier for you.

I've got a basic duct detector right here, okay and in a duct detector. All that it is, is a smoke detector like you have in your home. Okay, we have a smoke detector right here. That's all that this guy is okay, but a duct detector is meant to be mounted in a supply or return.

Duct and air is actually forced from one side of the duct detector through the sensing head back out the other side, okay and then right inside here we have a series of contacts, normally open, normally closed, auxilary supervisory alarm contacts - you could do all sorts of things If you get creative within this detector, I could wire up flashing lights that set off the fire alarm. I can wire this up to an actual fire alarm panel. I can wire it up to shut down a fan or anything for that matter when this thing goes into a trouble condition or a fire alarm condition. We can also wire in annunciators that make audible, sounds or horns that you know set off the audible alarm and make everybody run out of the building.

Okay, duck detectors often will have tamper sensors on them like right here. So, basically, when you pull this cover off, this contact right here is opened, and it tells this thing and when it's programmed right it tells it to do a certain function. We can make an end-of-line resistor disappear. We can signal a trouble condition.

We can set off the duck detector, we can turn off the fin. You can do all sorts of things with a duck detector. All you have to do to figure it out is simply read the manual. The manual usually is three pages four pages at the most.

Nothing crazy and the manual actually breaks it down a duck. Detector works by having a sampling tube. This is a sampling tube right here. Usually these are meant to go the entire length of the ductwork from one side to the other oftentimes you'll.

Have it penetrate just the other side and you'll seal it up with silicone there'll, be a plug in 1 into this right. Here you put a usually a red cap in there. So that way, the air is forced to go in the holes which this would slide into here. Ok, so then this pushes all the way through the air is forced to go in the holes of the sampling tube and then it comes out is forced because of the way the cover is designed, it forces the air through the detector head and then out the Other side forcing it back into the ductwork.

Ok, there's really not that much to these things. They have different configurations; sometimes they can be in a square configuration. In fact, if I took this one apart, there's a screw actually there's a little clip right here and a little Jesus clip, and if I took this clip apart, you can set it up to sit on a duct like that. You could do all sorts of things.

You get into the fancier ones like I have on here this one's meant. This is an OEM duct detector that was designed, for. I think this was designed for a Linux or a York packaged unit, and this one could have to sampling heads with one circuit board, but it still serves the same function. So I can have meant this one's meant to have one in the supply and one in the return, and then they just basically communicate back, but you can also, if you just follow the instructions.

Why are two of these guys in and have them communicate back and forth to so it's really not that difficult! I'm gon na go ahead and go through some troubleshooting steps on this and hopefully break it down a little bit more for you guys, alright. So I have this system in a fire condition right now you can tell with the red illuminated light on the test and reset station. You have the red light on the detector circuit board itself, and then you have the red light on each one of the detectors. Okay, I can simply reset it by doing a couple different options here I have a test and reset station.

Okay, we use this for test and reset functions. This is a great thing. Fire marshals love these because when they do their annual inspections, often times depending depending on the municipality and what their rules are, they may come out once a year test, the fire alarm system and, if they're, actually doing their job right and being thorough, they go through Each individual duct detector and get the test and reset stations and trigger the fire alarm from there. So this is exactly what it is a test and reset station, so I can test the system or I can reset it.

So I'm going to go ahead, an get the reset button. Sometimes they may have a key. Sometimes they may have a magnet. Who knows this? One right here uses a magnet to initiate a test mode.

Okay, just like a detector uses a magnet to and it just uses a button push to do the test and reset or the reset situation. Okay, so this particular duct detector is ran off of 24 volts. You can see my my voltage right up here and I'll. Go ahead and jump on this and show you guys: okay, we have - or it's 25 volts right now in this situation - actually almost 26 volts.

Okay, all right, so that 26 volts brings power into the detector and powers the detector. There is all the contacts. Nothing is connected to those 20 or to the power contacts. Okay, there's no inner connection between any of the circuits, the relays, the the common terminals or anything all right, and the reason why they do that is because oftentimes, these dot detectors have multi volts.

So if you have inter connection, you can cause problems. So there's no connection. So if we want to use this auxiliary contact, we have a common and normally close and a normally open. We have two: if we wanted to power it somehow, we have to take power via jumpers and jump it over to the contact.

Okay. So in this situation, what I have here, I have a real, simple circuit: oxb contact is gon na, be my unit shut down. So that's gon na shut down my my indoor, blower motor or my rtu unit, okay, oftentimes we'll have it wired into an emergency, stop feature such as on a carrier or a Linux or a train unit. They have emergency, stop features built in other units.

You may have to power it down other ways by disconnecting the thermostat by breaking the 24 volt circuit coming out of the transformer all kinds of things. Okay, so this is my unit shut down, so I have a common terminal. Okay, the common terminal in my situation is actually coming up here, just for testing purposes, but you know I can basically shut down my unit. So if I went from common and I'm gon na go ahead and put my my meter on continuity and we'll go ahead and put it on tone, okay, and if I throw from common to normally open, I have a normally open circuit right.

If I go from common to normally closed, we have an audible tone. Okay, we have a closed circuit or a direct short across that contact from common to normally closed. So we could use that to power our unit. Some units require a 24 volt signal to not be an emergency stop and if you break the 24 volt signal it puts in an emergency, stop you know in some would go the opposite way, so you can do whatever you want with those contacts.

It's just a common and normally open a comm, a normally-closed, a really really important thing to understand on duck smoke detectors. If you read the installation manual or the instruction manual, you will find out that you have a supervisory circuit. The supervisory circuit is wired backwards. Is the best way to explain it versus where, as I have a common in a normally open circuit right and I have no direct short or no tone, but if I go from common to normally open on the supervisory circuit, I have a closed circuit.

The reason why is the supervisory circuit is actually used as a trouble contact. Some duck detectors will actually call that a trouble contact and what it's meant to do is to notify whoever, in most cases, the fire alarm company to say that there is a problem within the electrical circuit. That's potentially not going to set off the fire alarm. If something happens, another thing that we can do within the duck detector - and this is all in the installation manual - is we can set up the supervisory circuit or the trouble circuit to perform a certain function if we tamper with the duck detector.

So in this particular situation I have little dip switches up in this top right hand, corner and there's a couple different things and it says: do we want to turn it on and off on a trouble shutdown? Do we want one or two sensor heads? Do we want a time delay before it goes off on a tamper situation? Okay, so we can do all kinds of certain features with that now, if I go from common to normally open, we have a closed circuit again. Think about that common to normally open, but the way to understand it with a supervisory or a trouble condition is the normally open circuit is going to be in a trouble condition. So when something is wrong with the detector. Okay, so normally closed too common is open, but if we put it in a trouble, condition normally closed to common is going to close and if we put it in a trouble condition common to normally open is actually going to open.

So let's show this: I'm going to put this duct detector into a trouble condition by interrupting the tamper switch up here in the left-hand corner of this detector head. There is a tamper switch when I pull this cover off. We are going to open a circuit between these two and you notice. We got an amber, LED, that's not a red LED, that's an amber LED and we are now in a trouble condition.

So we can RI configure this duct detector to tell the alarm company that something is wrong if someone takes the cover off of the sensor head, why is that important? Well, if you take the cover off the sensor head, then the air is no longer forced through the sensor head and it's no longer looking for a fire condition. So what happens if we were doing service at this duct detector - and we forgot to put this back on there and we left well in the worst-case scenario: there's a fire or there smoke it wouldn't theoretically shut it down unless the concentration got super thick. So that's why we have a trouble circuit. I'm gon na cover.

Another reason why we have a trouble circuit in just a second, but I'm gon na show you the example. So again I have my meter set on tone and we're gon na go on the supervisory or the trouble contact and I'm gon na go between common and normally closed and there we go. We now have a direct short and we are now normally closed between common and normally closed. Now we're going to go common to normally open right and we are gon na - have a normally open circuit, so the Supervisory or the trouble condition the the labeling on that is meant to be looked at when it's in a trouble, condition or a supervisory condition.

Okay, so - and it explains that in the manual - but that's one of the things that confuse the most thing out of me - okay - and it tells me right here on this manual - so it actually tells us writing the instructions right here on note, 3 supervisory contacts shown In standby position, open contacts indicate a trouble condition to the panel. If we think about it like this, this shows us a superb, either a condition or a trouble condition. This alerts the fire alarm panel that something is wrong. Okay, now I said I was going to cover something else.

Another thing that I can do and I have this configured that way I'm gon na go ahead and reset this. Actually, I'm going to put the cover back on reset the tamper sensor notice that we went out of a trouble condition now that I put the cover back on and we went back into normal operation, okay, so here's what I want to do. I want to show you that my alarm system is monitoring. Let me see I am monitoring the red in the white wire, okay, so red and white, coming into the detector right up here, red and white.

That is my alarm panel. My alarm panel is looking at two wires and it is looking for two things within two wires and this is where it gets interesting. The alarm panel is looking for a direct short between the red and the white wire to say there is a fire condition. Okay, if we have a direct short between the red and the white, that means that our duct detector is telling you the alarm panel, that there is a fire or there a smoke if we have a direct short.

But you notice that we don't have a direct short right now, but when I switch my meter away from tone, look at what I see right now. I see 1415 K ohms. The reason why I see 15 K ohms again. This says this directly in the manual is that I have an end-of-line resistor right here, and this end-of-line resistor is wired from the alarm contact to the trouble, contact and notice, something if I put this duct detector into a trouble condition.

What is going to happen is the end-of-line resistor is going to disappear to the alarm panel. The alarm panel is no longer going to see the end-of-line resistor. Okay right now we have nothing. We do not have an end-of-line resistor that end-of-line resistor is simply there to prove a good electrical circuit to the alarm company.

So again, the alarm company is looking at two buyers coming to this detector and they're. Looking for two situations, they're looking for a direct short between those two wires and or they're looking for an end-of-line resistor that end-of-line resistor tells them that the electrical circuit is good. It proves that the circuit is intact. So how what happens if someone is working up in the attic and they sever the red and the white wire it no longer would have an electrical connection to this duct detector.

But how would the alarm company know that those wires are severed by putting an end-of-line resistor right there? We can prove to them that those lines aren't severed okay and then, furthermore, if we put the fire alarm into an alarm condition or the duct detector, it's actually not going to go when I have it in a trouble condition. So so now I'm gon na go ahead and reset the tamper contact and we're going to go ahead and put this into a fire condition. If we go across right now, we're in a fire condition. If we go across the red and the white, which again, is that what I'm simulating as the alarm contact, we have a direct short.

We have a direct short across the red and the white wire when there's a fire condition: okay notice that the end-of-line resistor is irrelevant because we have a direct short now. Okay, so we reset it. And now, if we go across the red and the white, we don't have anything and when I switch my meter back to K ohms, we will now see that end-of-line resistor again. So the fire alarm panel is capable of seeing that 15 km or whatever every panel designates what size the resistor needs to be.

I just happen to have a 15 K, ohm resistor, so I use that, but every different fire panel you know, is required to have a certain size, end-of-line resistor, and that fire panel is looking for that particular size. So you also can't just throw any resistor on there, because you could potentially cause a problem so because of the way that I have this one configured, what I did was I wired the alarm contact and the supervisory contact together using the end-of-line resistor. So that way, if the supervisory contact initiates, the end-of-line resistor disappears, it does not signal fire condition. It signals a trouble condition.

So I said that the alarm company is looking for two things on those two wires they're, either looking for a direct short or they're. Looking to see if they can see that resistor, if they can see that resistor, they know things are good if they get a direct short, they know there's a problem, there's a fire condition if they do not get a direct short, but that resistor disappears that 15k Ohm or whatever K ohm end-of-line resistor disappears. Then they know that something is wrong. Okay, another I told you you can do all kinds of things with these duck detectors if we wire this duck detector up to the r2 units, 24 volt power source.

Okay, now you have to be careful because certain municipalities have different fire codes. Some places do not allow you to but a lot of times our tu units. Okay, if we, if we're allowed to do this, I can wire the the fire alarm. I mean the duck detector if there's enough room within the the amp rating of the transformer, I can wire it up to the unit's transformer and we can essentially make a burglar alarm out of this duck: detector, okay, and what I mean for that is: let's say You get tweakers that go up there and try to steal the condenser and they're smart tweakers.

If they're smart, they shut off the power, so they don't get electrocuted when they start shutting stuff off right if they shut off the power in this situation, they're gon na cause a problem. So I'm going to show you something right now: okay, we're gon na! Look for the resistor. We see 15k ohms if I power down the rtu unit, I'm gon na simulate that by turning off power to this transformer, if I power down the r2 unit that end-of-line resistor disappears to the alarm company and I'll simulate that right now. Okay, I powered down the unit and I'm gon na show you guys right now.

We're gon na go across my power wires, which is blue and yellow, and we get nothing. We have no power from this transformer anymore. Okay, I go to my meter and I switch it and I go the end-of-line resistor and guess what the end-of-line resistor disappeared out of the circuit, because of the way that I have it wired between the alarm contact and the supervisory contact. If this duct detector loses power, I send a signal to the fire alarm company to say that there's a trouble condition.

It doesn't necessarily mean there's a fire condition, but something is wrong. So we could use that a bunch of different ways. We can use that to catch tweakers, smart, tweakers, right or maybe they're, not, I don't know whatever, but to catch people that shut off the unit. But we can also do it to see to verify that all of our equipment is on.

Ok, let's say you're doing a preventative maintenance and you go to leave and you forget to turn equipment on well, instead of the customer realizing a day later or something they'll know immediately, because the fire alarm company is going to see a trouble condition and, depending on The the procedures that the fire alarm company got deals with with a lot of the restaurants that I deal with. They immediately call the restaurant and say: hey, there's something wrong: we've got a trouble condition. Are you having anybody work on your equipment and if they say no, they just left and then the fire alarm company will say: well, you still have a trouble condition and then the customer knows before it becomes a big problem. Ok, I powered the unit back on now, not every single unit and every single municipality or every single customer is gon na.

Want the system wired up to a trouble, condition, ok or to simulate a trouble condition and make the end-of-line resistor disappear. To show that there's tampering or something ok, you can also simply in its flashing, amber because it's on its initial powerup right now it takes a minute for it to power up and then it'll go into normal operation. But you can also simply take that end-of-line resistor and just put them across the two alarm contacts. Okay, so the alarm company really only needs to see the common and normally open circuit and notice that this alarm contact doesn't have a normally closed.

It only has common and normally open, because again the fire alarm company is looking for a direct short across two wires to say: there's a potential fire something's wrong. We can still have an end-of-line resistor on that circuit. You literally go from one wire to the other, with the resistor and it'll still be there and it'll I'll prove that the circuit is intact. Okay, I noticed that that wire kind of moved so again to recap: if you do not have the trouble or the supervisory contact wired in, you can simply take the end-of-line resistor and run it from across the alarm contact.

It's not going to signal direct short or anything. Okay, it's just going to show the 15 K, ohms or whatever ohm resistance value that that resistor has to the alarm company to prove that the circuit is still there. The next thing that we have within this detector is we can wire up accessories now, if you follow the installation manual, the installation manual is going to tell you all the different types of accessories. Okay, it's also going to show you how to wire in the Supervisory contact right here on this schematic.

It actually tells you exactly how to wire the end-of-line resistor to the supervisory contact, so it basically just shows you everything, and then it tells you the different functions. Power goes here. 120 volts goes here. If it was set up for 120, this one actually isn't capable of handling to 120, but a lot of duct detectors are but yeah.

It tells you everything in the installation manual. It also tells you about the test and reset stations and how to wire in the test and reset stations. Now majority of the alarm, duct or the induct detectors - require that you use their test and reset stations. Okay, so you do have to be careful.

Sometimes you can make other brands work, but you got a little creative with the wiring. You can have test and reset stations also that have alarms built into them. Annunciators that squawk at you, you can have pilot LEDs. Sometimes it'll have a red and a green and it'll say green means.

Good red means bad. You can also have a key station that you turn a key okay. So let's talk about the the pilot light and the red LED alarm light. Okay, the pilot light could be used to indicate that there's not a trouble condition all is clear right.

So that way, the customer downstairs isn't necessarily, depending on the alarm company, to say that there's a trouble condition and they're just looking hey, my green LED went out what the heck there's something wrong and they know to call people. So, for instance, if we didn't have this wire damn at the end of resistor and the supervisory contacts you and all that, maybe we don't want the alarm company to call us and we just want to look for a green LED to disappear. But a red LED is not there, but we just know that if the Greens not there and the Reds, not there - maybe something's wrong, maybe there's no power again, you can do all sorts of things within the contacts on this detector. Okay, that's pretty much! It there's! Really not a whole lot to these detectors.

Okay, this one happens to have a dual head, but you can simply wire them up, like I said with two separate detectors, and you can wire them up a lot of times. They have like a parallel feature where they communicate back and forth, but this really is it guys, there's not too much with these things. Okay, if I didn't answer a question, throw it down in the comments or send me an email, HVAC, our videos at gmail.com, and we could talk more about it. I really really appreciate you guys watching this video.

I go live Monday evenings at 5:00 p.m. Pacific, where I always talk about these videos and I'll be sure to talk about this one, the next time. Okay, so please and thank you for watching all my videos and please leave me a comment. Let me know what you think: okay, you.