Uh, so we're gon na talk about gas furnaces. This is a very florida uh gas furnace class because we're gon na work on an eighty percent, and i'm not gon na teach this the way that you would learn from nci or jim bergman or folks who work on a lot of furnaces um. This is a very practical class for the way that we do it at kalos and um. The way we need to do it at kalos.

Maybe some of you aren't following all this, but these are. These are all pretty simple practices: we're going to cover it from the top, so flame rapid oxidation produces heat as a byproduct. What do we need for flame? What's the flame triangle, fuel fuel, air, oxygen? Lose you lose oxygen, not air. You know we wouldn't need any air, you wouldn't need any nitrogen, although nitrogen is very explosive good times, and then you need some sort of heat source.

You need something that's going to actually initiate combustion. Really you know with certain types of fuel gases you wouldn't necessarily even need any abnormal uh heat source all right. So that's what we're that's, what we're doing and in terms of uh, one of the things that i'm going to talk to you a lot about is the idea of combustion air controlling this oxygen part of it, because that's where it starts to get dangerous. If we don't provide enough oxygen for flame or we don't have proper mixing of oxygen with flame, then we start to get carbon monoxide, which is no bueno.

This class, i'm not going to focus a lot on um things that we're not that we don't do here. Like clocking meters and gas input levels and all that kind of thing, because it's just not something that we care about that. Much because here we're not working with efficiencies uh, where tweaking at one percent is going to make a big difference. We don't have a very long heating season, so we're just going to focus on some things.

You need to know for our market, like i've already mentioned, but there's a lot more to this in terms of the math and science of combustion and so on and so forth. All right, we use two different types of gases, typically um. Actually, it is more than two, but we call them two different types of gases and what are those two different types of gases? We work with natural and you said, propane, propane, okay, so lp lp stands for what we can stand for low pressure. What does it stand for, in this case, liquefied petroleum, liquid, petroleum right and it's not just propane? We kind of use them interchangeably, um, but lp can actually be a mixture of butane or propane or just propane or just butane, and it can and it can kind of be either or now they have very similar properties, um and uh.

You can see here that both propane and butane, which are what make up lp, are heavier than dry air and natural gas is lighter than dry air. So that means that when you have a natural gas leak that natural gas is going to travel up and escape where, when you have an lp leak, that's going to sink down now either way we're burning a gas. I think some people get confused because they hear liquefied petroleum or liquid petroleum and they imagine that it's a liquid going into the furnace and it's not it's a gas either way it's a gas. But if you're burning, lp or propane uh, then it is heavier than air which does make it a little bit more dangerous.

Why? Why does it make it more dangerous when you're dealing with lp, based on what i just said? What's that well, this place is oxygen. Yeah so i mean it could actually suffocate you, but it would be really dangerous before it got to that point, because it's flammable and it fills the room up from the bottom up. So when natural gas leaks, it tends to dissipate and escape uh the space, whereas with lp it's going to kind of sit at the floor and it's going to fill from the floor up now. It's still going to kind of mix around and all that, but that does tend to make it a little bit more a little bit more dangerous with every fuel mixture.

You can have it be too rich or too lean to the extent that it won't burn. So when you get above 15 of natural gas in the air, it'll actually get so rich that it will stop burning now. Does that mean that it ceases to be dangerous? Obviously, not because, as soon as it dilutes down to below that 15 level, then you're in the combustible space again, if you have 4.3 or less than it's too lean and it won't burn. So everything has these everything.

That's a fuel. Has these levels of concentration that are required for for combustion, and so when we talk about things like um, then some of you may not even know a lot about this, but like a2l refrigerants that are coming out like r32, where you're going to hear a lot About combustible refrigerants moving forward, there's a big difference between r32, which is an a2l combustible, refrigerant and r290, which is propane. They have much different levels of concentrations that are required for combustion, so whereas uh r32, you could actually even have a spark and it's not going to ignite you'd, actually have to have an open flame. You have a spark with r290 and see what happens.

Answer fire fire is what happens yes, which what is fire again? What is flame, rapid oxidation of fuel resulting in a release of heat, obviously come on. It's rusting, the air. It is actually rusting the air yes, so oxidation does mean that there's a bonding with oxygen, which is why oxygen is necessary. So it's not again.

Air is a constituent part. That oxygen is a constituent part of air, but it is not air. It's not the same. You know about what percentage of air is equals oxygen? How much of the air that you breathe is oxygen.

Anyone know you got a 5 anyone else under 50 percent under 50. Okay, all right good 69 nathan says 69 uh, no uh yeah 69, nitrogen, which is also very explosive uh. One time nathan said nitrogen was explosive and that's just my favorite thing. Uh no oxygen is about 20 percent uh.

Nitrogen is about about 70, just under 70 percent, so 90 of our air is made up of oxygen and nitrogen, and then we have water, vapor and a bunch of other stuff. So now we're going to talk about the sequence of operations, so we're kind of jumping a little bit ahead here. But i do want to get right to this, because the point of this class is to make you much more comfortable working on gas furnaces and the sequence of operation, regardless of the type of furnace, is actually pretty pretty consistent. So the first thing the furnace receives a w call when i say a w call.

What do i mean by that? What's another way of saying that call for heat 24 volts applied to the w terminal, the white wire whatever right, and that that 24 volts ends up on the furnace board on the furnace board? W now do we need a g call as well with the gas furnace and heat. No any other opinions got a no here. Nathan says it depends on what i don't know. Okay, no you do not.

There is no furnace that i'm aware of that requires a g-call in heat. Some electric uh fan coils. So if you electric only do require it especially older ones, but nowadays in heat, which is actually why, if you remember the old thermostats, it would have a selector. That would say you would select the heat source, whether it was electric heat or gas, and that was the main reason for that was.

It would switch between whether you had a g call or not. In fact, we had a set of linux furnaces that we had a set of thermostats that were that were creating a g-call in cooling and they would just lock out right off the bat, and so we had to go in and do something to them. I don't remember what we did, but you don't want a g-call in heat. Why don't you want a g-call in heat? Anybody know why? Don't you want 24 volts on g at the furnace board in heat on a gas furnace? The first part of it is correct.

The second part, not quite the first part, what's that? No, not really it's it's that you don't want it a couple reasons. The main reason for the customer is that you don't want it circulating cold air before the furnace lights, that's kind of the main and old-school reason for it. You know you say you live in a really cold climate. The ducks are, you know, really cold and you're.

Just moving a bunch of air through these just cold air blowing on people makes them uncomfortable, but there's actually another reason, and that is that we want to be able to observe this is actually kind of a servicer's reason. We want to be able to observe that flame before the blower starts and then observe it after the blower starts. So just as a quick, really important thing to know when you're testing a gas furnace, you see, we have this external panel, that's already off right. This outside panel - that's off, but do we leave this panel off when we're testing it this inside blower panel? The answer is no.

This must be on when we're testing the furnace, because if it's not, then we're not separating the air airstream from the combustion air zone. So imagine two different zones: we have the combustion zone where the flames go through and we can see right into it, because this is open combustion right. We have this area and then we have the area where the air is circulating into the home. If those two aren't separated from each other, then you're going to be drawing potentially unspent gas, carbon monoxide, carbon dioxide, whatever into the home, which is not a good idea right, so that has to be closed.

But what we do is we start it up at first, the blower's not on right. We see the flame we're watching it and then all of a sudden the blower comes on. What are we watching for anybody know? You said: roll out what'd, you say wiggly flame you're watching for wiggly flame yep. That's what you're watching for you're watching for a change in the flame, really any change! You can see all of a sudden.

You know it changed to some orange. It starts to starts to move more and the reason why what would be the possible reason why, when the blower is off, the flame would be nice and straight and normal, and then, when the blower goes on, you'd get a wiggly flame, cracker, cracked heat exchanger right And it would be a pretty significant crack right and truthfully again this. This is a florida thing versus another market thing in other markets. They spend a lot of time focusing on cracked heat exchangers, because in other markets they have a much longer season and there's much more opportunity, many much more cycling, and so the the metal is stressed more and then it cracks more in florida, cracked exchangers on furnaces That are under 20 years old yeah, pretty abnormal i mean i have honestly never seen it.

Actually, there was a commercial unit. I saw it on, but even then i think was like a condensation issue. So it's not it's not a real common thing. It's not something.

We need to do this like excessive testing on, but if you watch the flame before the blower comes on and it's nice and straight and then the blower comes on and the flame stays nice and straight then we're gon na say it's okay to move on to The next step now what would happen? What's the first thing you should do if you're watching it and you do notice the blow the flame start wiggling. What's that kill it shut it off? Okay, what's another reason why the flame could start wiggling other than a heat exchanger leak, good music inducer motor, no, not inducer motor. It would be some other sort of air leakage, so if there was because again um we've got this panel really close to this thing. Imagine that there's a big leak right here, where that panel is right, underneath the right underneath the burner, and now, when that blower comes on, it's sucking a bunch of air in there.

That could also result in a wiggly flame. Now, that's something you should still solve! That's a that's a problem that you need to solve, but it's not a crack heat exchanger right, so you'd want to figure out. Is it a cracked heat exchanger or is it something else? Some other air leak? That's exchanging air between the combustion air zone, where you're burning the flame and the air and the home again useful thing to have diagnosed and to resolve. Does that make sense make sense all right.

So, let's keep going through the sequence we kind of jumped ahead step. One furnace receives a w call step. Two inducer fan starts now before the inducer fan even starts the circuit board checks and when we say checks i mean it's not like it has a brilliant look. Let me check it's just all part of the circuitry, but it checks to see is that inducer fan starting open.

So if, if it, if you receive a w call and the inducer fan, is uh or the sorry, the the switch, the pressure switch is closed before the inducer fan even starts, the board will lock out because the purpose of the pressure switch. That's this guy right here right here is to prove that we have inducer air that we're moving air, that we are inducing a draft right, and so, if we're not inducing a draft, if this little guy isn't isn't measuring a negative pressure, then it shuts the system Off that's the design, but on the other side imagine that that switch got stuck closed or somebody jumpered it out. You wouldn't want the board to think well, it's always got inducer fan just because somebody put a jumper across it. So when that thing starts up it checks first to see, is it? Does it start open? Because if it doesn't start open, it won't even let it start that makes sense.

The switch has to start open before this fan starts spinning. This is this. Is our inducer fan that draws air into the burners? If this starts closed locks out how it should work is this starts open? Then it starts the inducer fan. Then this closes and now the furnace knows that you have proven inducer air go ahead.

Is that only a carrier thing no checks for that nope, because i've jumped out pressure switches on systems so see if the pressures will be issued. Well again, you can jump it out once it's already past that part of the sequence. So once it's already passed the open check now to start it up with it jumped out. I don't know of anyone that should work that way: um, maybe yeah, maybe if it's really old, uh possible.

I've done it on like brand new goodman's 90 because they have two to three pressure: switches on them. Um and like one goes bad and i've like jumpered one out to test the system and then replace it. You know daylight or whatever. It is some start off.

Close a bra there's, a brand that starts off close and then goes open, yeah not for i'm not familiar with it, and i haven't worked on many 90s. So regardless it's always going to prove one position. It's going to check for one position and then it's going to notice that it goes the other position with multiple switches if some of them are secondary, maybe not but again for a standard 80 that you're going to work on in florida. That's that's the normal thing.

Now again, it's not it's not going to come up much other than if you try to jump it, and i guess for you having not seen that before you wouldn't want to jump it right off the bat and then start it because it still won't work. Even if the switch is working the right way to test a pressure switch is to actually hook up a manometer to the port and then look at the actual reading and see first, if that switch or if the, if the inducer is actually producing that negative pressure. That you're supposed to produce and then put it back on the switch and see if the switch is closing or opening it's easy to prove whether a switch is closing or opening you just take the the leads off and and ohm it out. If you suck on it, that's what a lot of people do, but you can actually a damage.

The switch doing that and you're also producing far more pressure than that inducer actually produces. So just the fact that it closes when you suck on it doesn't mean it's going to close with a proper draft and again, one of the main reasons why pressure switches, don't close, isn't because there's a problem with the pressure switch. It's because there's a problem with something in the flue assembly or some you know a bird stuck in the inducer or whatever so you're. Only the only way that that switch is going to close is, if there's sufficient negative pressure in order to close the switch, and so when one isn't closing, it could be the switch, but it also could be the assembly and that's how you can tell the difference.

You just take your manometer hook it up and see how much negative pressure are you getting compared to that to the switch if it's less than it should be or on the low end, go ahead and figure out what's blocking the flue or what's going on with The inducer so deucer fan starts pressure, switch, ensures a proper draft and it does that generally with a negative pressure. So it's just measuring a negative pressure on the negative side. Now again, it's kind of an interesting thing: it's not going to come up much, but if you're working on an 80 furnace - and you were to measure the pressure in the flue pipe, what kind of pressure do you think you would get just guess, positive pressure, sure That makes sense anyone else go ahead. It's just been a point of intention.

It's been a point of contention, yes, but you actually measure a negative pressure in the flue in reference to the outside, okay, and there becomes a point where it does become positive. This is a really short one so, but on a standard flue that you would have where it's going out through the roof, if you measure it by the appliance by the furnace you're, actually going to measure a negative pressure and that's because the force of those gases Traveling up through the stack through the flue are actually creating a negative pressure below and a positive pressure above, it's like it's. You know jim berman always says it's like you know, trying to blow into a into a shop vac hose trying to blow into a vacuum. Hose you can create a positive pressure in one sense because you are drawing air in, but there's actually more force associated with those hot gases.

Traveling up, that's creating a negative pressure down there at the bottom, where we measure. So that's why we call it an inducer. That's why we don't call it like a draft booster or something, because it's not creating positive pressure in the flue. It's just inducing air in it's it's used in order to draw air in through these more complicated uh heat exchangers.

There was a time when heat exchangers were super simple, we'll look at that, but they were pretty much just straight up and down, and everything could just move really easily well now, they're much more complicated, a lot of different types of designs, and so that inducer fan Is there to suck air in in order to overcome that pressure, so that we can provide the right amount of air and oxygen to the flame make sense? Now if it was a 90, it would be positive because they actually are um. It's that much pressure, and by the time it gets up to the by the time it gets to the flue. It's such a low temperature that it doesn't want to go out. You actually have to push it out, um and that's why we can go sideways with it and all that other stuff, because you're not actually at that point you're just using you're you're, just using your uh draft blower to push it out all right.

So once we've insured the proper amount of air, now we go into the ignition sequence and the ignition sequence starts with what anybody know igniter right now the igniter can be a couple different types of igniters and we're going to talk about that. But there's going to be something: that's there to ignite the gas once the igniter has had sufficient time to either heat up or start sparking or whatever it is. Then the gas valve opens gas valve opens and it's going to uh in the case of intermittent spark. Ignition, it's first going to light a pilot and then the main gas valve's going to open but either way you're going to start flowing flame.

It's going to prove that you have gas, and it's going to do that with some type of a flame rod, an eye something there is going to prove that the flame is burning, and why does it do that? Why do we need to make sure that that flame is burning? Otherwise it's just putting out gas, otherwise, unspent gas is just filling the thing and you're creating a bomb. So there's a there's two major risks even more than that, but the two most common risks associated with the gas furnace are unspent gas building up which creates explosions right. So that's one obvious one and the other is carbon monoxide and then generally just fire hazards right. If you've got a flu, that's getting flaming hot and it's sitting up next to a trust or something it could cause a fire hazard to roll out could cause a fire.

You know there's lots of things like that, so we need to make sure that if we are pushing gas through this furnace we're pushing gas into the burner that that gas is lit and the most common way that we do. That is with something called a flame rod or flame rectifier. We'll talk more about how that works in a minute, but that's just there to make sure that we've got flame on older gas furnaces or on water heaters. Does anybody know what they call the flame proving device in those flame sensors? Some people call it a flame sensor.

It's got an old school name, though it's called a thermocouple or a thermopile, and in a thermocouple or thermopile, those are traditionally for millivolt systems. It actually generates a voltage when or generates a current when there is a flame on it. So it's a much more old-school analog way of doing it without having to use modern digital controls. So you just basically when there's a flame on this little rod.

It generates a voltage that then can be used to actually energize the um uh to well your the gas valve's already energized, because that's because you have a intermittent spark or some other method - um, not sorry, not intermittent spark, backup, standing pilot standing pilot is there and Then it lights the main burner yep, once we've proven flame, so we've proven air we've proven flame. Now we keep that gas valve locked in. So until all of this happens, this thing's going to just keep trying to restart until it locks itself out. We've got to prove airflow, we got to prove flame, then the blower is going to start after sufficient time has passed 30 seconds 60 seconds 90 seconds.

Whatever, then the blower is going to start up and now we're moving heat through the house and so for us. We can actually observe that entire sequence of operations after that time, if anything, changes if all of a sudden the system is no longer proving flame. All of a sudden, the flame rod isn't sensing flame anymore. It's going to shut it off it's going to start over.

If all of a sudden, our our pressure switch drops out so we're not proving air it's going to shut off, but then we also have a series of other safeties as well that can shut off the system. We're going to talk more about that. So here are our standard types of ignition, and really this pretty much sums it up. You have standing pilot standing pilot.

You light the pilot light if you've ever had one of these on a water heater. Wherever you turn the thing you push it in it sparks, it runs a little bit of gas through here it lights, the pilot light. The thermocouple proves that you have flame on the pilot light and the assumption is, if you got flame on the pilot light your pilot, then, when you open the gas valve it will always it will always ignite. I mean it's a pretty good assumption.

There are some things that could happen. You could have like a serious amount of rust or a plate or something that falls down that gets in the way of it, and then it still doesn't ignite and that's super dangerous. But, generally speaking, do you got an open flame? Has anybody ever done this, where you light your grill by just lighting one of the burners and you just close the top open the others until it lights all the way across i do it all the time you're. Not supposed to do it, but it's like you light it and then it just kind of sits and goes all the way through when you know when all your little spark igniters are are broken.

So if you were to have an excess, because that's going to be on the first burner right, that's where the gas is coming in, you would have an excess of rust buildup on your burners with that, where it's not yeah, it would just eventually. So it would then this is what i'm saying this is kind of the example. It's not safe or a good idea, but eventually what would happen is it would light the first one. The other ones would keep having unspent gas go in and then eventually enough of, that concentration would build up there to go boom and then it would all light and you may, if you were standing right in front of it, you may get a little roll out.

Whatever it's like, not a good thing, but that's you know, that's one of the challenges with this design is that there is the assumption that if the pilot is lit, that the main burners are just safe to open because there's nothing monitoring the main burner. The other thing about pilot lights and this old kind of thermocouple design is that you're just running gas 24 hours a day, seven days a week, all the time, you're always burning a little flame, which just is a stupid waste of energy. If you don't have to do it, the other thing is: is that because they work on a millivolt type system, it's kind of unreliable too any poor connections, any corrosion are going to lead to problems with it. So, there's still a lot of pool heaters out there that work on this type of system, you're going to walk up to the pool heater and there's not any there's no wires leading to it.

What was the one that happened with tyler recently? What was that? Oh? That's right he's like he's. That was what it was. He said i came into this furnace and it just had a fire going all the time. So i shut it off.

I was unsafe they're still out there i mean you'll you'll still see them, yeah that tyler uh right. Did you actually do that once in summer yeah i mean you know it's not, and that's actually, why and a lot of places they do that on purpose. They will shut it off and then every season you got ta light. The pilot light you'll still get some old-timers you'll.

Ask that, like you, got ta, come light, the pilot light and if you had 75 yeah, if you guys yeah, if you had the right, you buy a lot of gas for that um. But you know that's the design, that's how it used to be, and so you had to light it every time and you'll still like i said, you'll still see them. Next is direct spark. Now this isn't.

I mean this is a form of direct spark, but when you light your grill and you push that button to light the main burner, that is a form of direct spark you're using a spark. You know, click click click and it's directly lighting. The main burner. That is not common in furnaces, but ream roo does use that design.

So it's just a it's a spark ignition and it just opens the main burner and the spark sparks and it lights the main burner. So you will see that it doesn't look like this, but this is just an easy way for you to kind of get your head around how it works. The next is intermittent spark. Isi intermittent spark ignition.

So if you ever see isi anywhere that's what that means, and that is where you have a pilot, but it's not lit all the time. You light the pilot with a spark and you light the main burner with the pilot. That's why it looks very similar to this, but this is acting as both a flame sensing rod and a spark ignition. In most cases.

Sometimes there is a separate flame sensing, but typically that electrode does both of those purposes. So what will happen is it'll. The gas valve will send a little bit of gas to the pilot. Then it will spark lights.

The pilot senses, the flame of the pilot and then allows the main burner to open again. This design is also relying on the fact that this pilot is going to light the main burner and then, by far the most common nowadays is hot surface ignition. Now this is a silicon carbide, um hot surface igniter you're going to notice most of them nowadays. Don't look like this most of them nowadays just look like a single little rod.

That's it that's silicon nitride and that's far more common. Nowadays, they work basically the same way. There was a period where trane used this like voltage modulating system going to keep dropping down the voltage and all that but um hot surface igniters are a common fail item in gas furnaces um. So if you go to one that's you know seven, eight.

Nine. Ten years old - and it's not working, it's a good chance that it could be the hot surface igniter, and sometimes it's because you know the flame is maybe too hot or something like that. But a lot of cases, it's just the cycle times, just eventually they fail. Um also, if they, if there is short, cycling uh that can also increase the likelihood that they will fail, your gas valve is what actually opens and puts gas into your main burner the place you do.

Your testing on your gas valve is in these little ports. Right here and then you're going to have some larger, looking screw that you take off and you adjust your your gas pressure now, if you have a multi-stage valve, you may have multiple points that you adjust. It's all actually quite simple, but the first time you do it, especially for florida boys is like oh, my gosh. This is super complicated.

This is so scary, so this is what we're going to focus on today is testing gas pressure and just kind of running through the sequence of operation and all that hands-on things you don't want to find in your pocket correct these things right here. If you find them in your pocket, when you get home, i don't know what you should do. Just move to another state keep driving um yeah and it is actually i mean it's not. It is a pretty small amount of gas um, so you should just drive straight back and you know plug it back up again.

Look i left my tools in your unit yeah. Some of you may not have seen these types, though there's a type of gas valve called a gemini valve, and it has a port that looks something like this and on gemini valves. You actually shut it off. You just crack open the port, and then you put your adapter right over it, so you're not actually taking anything out, and that's actually, my understanding is that's the reason why they designed this.

This way is because it is much less likely that you're going to do what we just talked about, because, literally, when you pull the thing off, it's you know it's still open. All you got to do is just all you got to do is just close. It down it's less like you're, going to lose them or forget them or whatever, and then also the flow rates are going to be really low coming out of those as well. I have a video just specifically on gemini valves.

This is your pressure, switch inducer air approving switch whatever you want to call it. It's just proving that you have air and there will be uh somewhere on it. You're going to find a location, that's going to tell you what the negative pressure will be that activates the switch, and so you can use that to test it there. Actually, a field piece makes a, and i don't know if you have that one in here, but field piece makes immunometer.

I think it's the sdm6 yeah this guy right here is this the no. This is the more basic one uh. No, this is the one yeah. It has a pump on it, so we can actually do this, that's cool, so it has a pump on it, and so you can actually use that to test your pressure switch to see if it opens and closes at the right design pressure.

It's actually a really nice feature kind of a special thing about that particular uh. Manometer everybody say manometer, i want to say inducer, blower um, pretty basic. It's just a fan, a motor, it's a shaded pole, motor um doesn't have a capacitor. I mean i guess there are some that do.

I think i have actually seen some inducers that do, but generally it's just a shaded pole motor. It looks like this when you're working on pool heaters, the blades corrode out all the time and that's a big cause of not proving air, but when you're working on a gas furnace, the most common reason why they don't work is because something's blocking them. Another thing that can happen sometimes is just the tube that's leading in there could be blocked with something too. I've actually seen that sometimes it happens because water is getting in to the flu, and so it's causing a little bit of like build up in there, and so that's another problem to solve uh.

I think i we especially saw that like during some high winds and stuff, if they didn't, have proper roof caps um. But if you have a pressure switch, just not closing just don't assume it's the pressure switch and replace the pressure switch. That's the you have to make sure is the pressure switch, not closing when it's supposed to? If it's not okay, then replace it. But don't just say it's not closing.

So it's the pressure switch because it could be a bird stuck in here. There could be a bird stuck in the flue anything like that is going to cause that problem. Oh there's, some nice pictures, we've got roll out switches. Roll out switches are going to be in an obvious position so that way they trip.

If the flame rolls out. These are just thermodiscs, it's a bi-metallic disc. They get too hot. They open up very, very simple to test literally, are they open, then they're tripped? Are they closed, then they're not, and so that would be a matter.

Pull the wires off. Take an ohm meter go across it see if they're, open or closed high limit switch same thing when a furnace is going out on rollout. There's a reason: switches don't fail in the open position without having tripped. So if it is rolling out, then figure out why why it's rolling out modern furnaces, rarely roll out? That's not a super common problem for modern furnaces you're.

Looking at me like, have you had them roll out on you? No older older furnaces where you didn't have an induced draft and you didn't have draft proving that was actually quite common, because you were literally just relying on gravity or you were literally just relying on the buoyancy of hot air in order to draw everything up through. So it's pretty common transformers, transformers roll out. Okay, i get it okay, i get it now wow um, but in the case of both in the case of both high limits and roll outs, if they are tripped figure out, why? Because there's going to be a reason for high limits, the main reason why a high limit trips is what what do you think so high limit is furnace is getting too hot. Why do you think the furnace would get too hot airflow airflow low airflow? That's the most common reason right so check all the normal things you would check for low airflow if it was a freezing, evaporator, coil, dirty air filters, dirty evaporator coils a lot of times, people think well.

How can a dirty evaporator cause the because anything that blocks the air stream is going to result in low airflow? It's going to result in high furnace temperature an easy way to test that on a furnace. Is you do you do what's called a temperature rise test and it's just it's just the same as a air temperature split and cooling return supply check the difference, because inside the furnace there is a number posted of what that should be if you're, not inside. That range, if it's or it's on the high side of that range, then just increase your heating air flow in order to get that where it should be or figure out, the cause obviously figure out the cause first, but that's a pretty good indication of of what's Causing it all right, we're gon na go through our different furnace types. This is the kind that you're not going to see much of they're a lot of fun.

If you get to work on them, they have this thing called a unit. If you think um a standing pilot is crazy, wait till you see a fan limit, switch a fan limit switch uh is this device that actually uh is looking at the box temperature and it's the temperature of the uh of the inside of the furnace of the Heat exchanger that causes it to turn via bi-metal until it brings on the blower, so literally the blower, rather than being brought on by because there is no electronics in them rather than being brought on by an electronic board or a relay is being brought on by This gigantic wrap of metal that, as it changes temperature, it expands at different rates and then finally trips and brings the blower on it's crazy. Craziest thing we had a bunch of them. Actually, in uh there was a bunch of furnaces in greater hills, uh that that were had that, probably still some are so.

This is a under 80 efficiency, you're, going to notice, there's no inducer draft. A lot of them had no electronics at all in them and in some cases that's where you would have standing pilot. You might not even have any electricity going to the furnace. That's how crazy this is.

Sometimes the actual furnace part itself may not really have any electricity other. Obviously you got a blower motor, so that would be weird if you didn't have electricity going to that, but the actual furnace part um was really just electromechanical at that time or mostly mechanical. So when you see burners like this, that's your natural draft. These are what are called upshot.

Burners the flames just go straight up. You would have little shutters that you could adjust the air mixture going in and they were much more volatile and that's where you would get a lot more roll out and that sort of thing you'd have high high exhaust vent temperatures coming out, but very simple design. This is our standard 80 non-condensing, open combustion induced draft furnace. So it's induced draft because we are inducing a draft.

We are pulling air into the heat, exchanger we're actually drawing air. In now on an 80 open combustion where's that air coming from on our typical furnaces. We work on here in florida where's the air coming from for combustion just around the furnace, wherever the furnace happens, to be there's louvers in the front panel and wherever it happens to be it's just drawn air in which produces creates a very big problem and that Problem is: do we have enough air? We can't jam these things in closets and just expect that they're gon na work because you've got to be bringing in combustion air from around the furnace. So when we say open combustion, that's what we mean it's just pulling air in from what we call the combustion air zone.

It's the same thing is true of water heaters same thing. When that water heater heats up that that flue gas is going out, we know it is right, where's, the air coming from that, replaces it just wherever right, so it negatively pressurizes the area it's in and it better have enough oxygen. Otherwise, as that oxygen level keeps decreasing, we get to a point where we have incomplete combustion. We start producing carbon monoxide and it can actually get to the point where, on some devices you can get.

You can get roll out now on an induced draft furnace, very unlikely, you're going to get rolled out because you've got this inducer fan. But let's say that there's a water heater in this same space. Do we ever see that a water heater in the same place as the gas furnace all the time right? So if that space is starving for air, this guy here is sucking air in that space is going under negative pressure more and more. What ends up happening to the water heater? It ends up back drafting right, so it ends up where air is going, the wrong direction and it starts trying to grab air from inside the space.

And that's where you'll see if you ever looked at the top of a water heater and you see like like rust and like like it's been burned on top of the water heater under the draft hood, that's what's had been happening, is it's been back drafting and It back drafts generally, not because of its fault. It's generally the other things that are in the room with it, and those are things to look for as a service technician pay attention to that. The water heater in our market tends to be more dangerous than the furnace itself. This is what we call a um uh in in shot burner or a gun burner is what some of the guys used to call.

When i first started, i don't know why they called it that but um you tend to have more complicated heat exchangers. You have your induced draft fan. You have your pressure, switch. That proves it and still, while it's still negative pressure at the top there, you are still moving air in for combustion, and then you have high efficiency condensing.

So it's not only condensing well, first off what is it condensing? What's? What's condensing in a 90 condensing gas furnace, anybody know what's that air vapor, it's actually, so it is condensing stuff out of the air, but it's condensing the products of combustion themselves, so you're actually cooling it so much that the products of combustion are condensing out and You're actually getting water, it's an acidic water, and so you got to do something with that, which is why you can't go. You can't really go above 80 or much above 80 efficiency with an 80 furnace. Otherwise you start creating water, and now it starts rusting everything out. So when you work with a 90 you're going to notice, almost everything in here is plastic.

You know the exhaust vent, the due strap fan the collector box. All that's going to be plastics, sometimes stainless. Steels but they're going to be much just a corrosive environment and you've got water involved. You also have the burners up top, and the reason is: is that now we're actually drawing air in we're going down the other direction and then we're going into a secondary heat.

Exchanger, which looks like a big kind of almost like a condenser sort of there's a big fin box where it squeezes out that last little bit and then that's where it condenses and then it goes outside. But now it has to be under positive pressure because it's so low temperature - it's you can put it in pvc, so you vent high efficiency furnaces through pvc and it's melting because it's sealed combustion good question. Thank you. I didn't.

I didn't cover that. So you've got, you see, you have two ports, so one would be your outlet and one would be your intake, and here it shows it. This is showing you just going out the side, but they're generally both going to go at the top. So you have outdoor air that's being drawn in into sealed combustion, and that's actually my favorite part of a 90 furnace.

This is the part that i wish we would have in. Florida makes a lot of sense rather than burning the air from just the space and having to have uh combustion air grills, going up into the attic or wherever, which is really annoying right. Why? We want a giant grill going up into the attic so that all summer it can just you know, cause condensation issues and all kinds of all kinds of issues. So, with this you're drawing in outdoor air you're using that air for combustion and then you're exhausting your products at combustion makes sense much better design.

The condensing part is the part i don't really care for, because that's the part that creates other issues, because now you have to have a separate drain on the furnace. You have to deal with the fact that it's acidic in some places you got to treat it before it goes back into the sewer system. So it's just kind of a kind of an issue. Secondary heat exchangers tend to block up and fail on certain models.

So it's just a it's a whole another thing, but the sealed combustion part is nice all right. So what are our biggest dangers? I already talked about them number one gas leaks. So let's talk about that. How do you check for gas leaks? What's the right way? Hey check for gas leaks sam.

What's the right way to check for gas leaks, sam hold a lighter around huh bubbles, maybe but again you're dealing with a very low pressure assembly, so you can use bubbles, but bubbles aren't always gon na. It's not like refrigerant, where you're dealing with hundreds of psi you're dealing with inches of water column rather than hundreds of psi. So huh do they make a device they make a device. It's called a combustible gas leak, detector, yeah yeah, that's the right thing to use! Now a lot of old-timers will use a lighter and you may think.

Oh that's, horribly dangerous right because in our heads we imagine that this flame is going to burn back into the pipe or something like that. But that's really not how that works. Why? Why isn't that? How it works that it just burns back into the pipe, because there's no oxygen, there's no oxygen in the pipe right, so old-timers will just take their lighter and they'll flick it around and those you'll see a little flame shoot out and that's how they know. Now.

I'm not telling you to do that, but that is a very normal way that it's been done in our trade for a long time. Bubbles are your other option. One of the best options, though, is just your nose right. If you show up and inverted that video, if you show up to his face and you smell that methyl mercaptan smell, you smell that garlicky, i just had to say the fancy name for it.

You smell that garlicky smell. That's an indication that you need to find. What's causing it, don't just do the whole well yeah! Well, it's a furnace! So it's burning it! No! No! If it's burning it, then you don't smell it. So if you're smelling, it find the leak figure out where it is so, yes, bubbles can sometimes find it, but really a combustible gas leak.

Detector is the right tool to use a lot of guys get confused and they and they confuse combustible gas with carbon monoxide. Those are two totally different things: combustible gas is unspent gas, it hasn't burned. Yet carbon monoxide is what happens when you burn gas and you don't have enough oxygen and that's very dangerous because you don't smell it, you just get dead right. You just get enough of it.

You just get dead, so we don't want any level of carbon monoxide in or around the customer's home um, which brings us to the point of like when you're, when you're working with customers who have furnaces the thing that i wish. We would do and we still haven't gotten to it being a standard practice, but this is really really what i want. You go to a customer. They have a furnace, you do all the right tests, but then, at the end you look to see if they have a low level carbon monoxide detector.

If they do not have a low level carbon monoxide detector, you offer them one literally in your hand, i can give this to you right now. It's x number of dollars. This protects against low levels of carbon monoxide. They may not kill you instantaneously, but can still make you sick and it acts as an early detection device.

Beyond what you have already in your house, i thought the level up to point: zero, zero, seven on a carbon dioxide right here was safe, zero, zero, seven on a carbon monoxide rate, so it'd be. We generally read carbon monoxide in parts per million, yes and anything up to so so what they'll tell you is when you measure inside the flue um, the more extreme folks will say over 300, you have to deal with under 300. You don't i'm in the home right. So if you oh inside the home the whole, if you were to measure the carbon monoxide into the home 0.007 is what inside the home, it should be zero.

If it's not zero, then there needs to be a reason why it's not zero. Do they smoke in the home? Is it not zero outdoors, you know. So maybe they live in new york city. They live in a big city where there's carbon monoxide present everywhere, but if it's not zero inside the home, i want to know why - maybe maybe they are using the stove a lot.

There are studies that show even levels as low as three parts per million carbon monoxide regularly can cause some respiratory ailments and mental impairment. So you don't want it, you just don't want it in your house, the issue with - and i don't remember what the actual ul rating is, but on standard carbon monoxide detectors before they alarm it's pretty high, it's like 100 parts per million or 50. It's a high number before they start alarming um, and it could be bad enough that, like they could actually die, it's good that they have those in there. But if we put a low-level carbon monoxide detector in the home, like i think defender is the name of the common one that we use.

I think um. It really just eliminates that risk that that big risk, because something went wrong with the furnace and uh kind of eliminates, not only our liability, but just again, it's just one of those really like simple things that anybody who has a furnace. If i had a furnace in my house, i would have one no doubt and i'm not a worrywart um. So it's something it's just easy.

It should be pretty easy for us to offer and even if they decline, that's good because they declined, then you know so much of the gas furnace market in other places is about optimizing for efficiency of the gas furnace. For us. I don't really care that much about that. I care about making sure that it's safe, they care about making sure it's safe too, but a lot of the reasons why they become unsafe is because they're getting really fine-tuning with it, whereas with us i don't care.

If you have a bunch of excess air, i don't care if you're not burning fuel at the optimum efficiency. I just care if it's safe and so, if you're measuring your carbon monoxide in the combustion air zones or around the furnace with your car with your low level, carbon monoxide, detector, um and you're doing it inside the space, maybe just set it on the counter, while You're there, that alone is is enough for me. I don't need you to do a combustion analysis on every service, caller every maintenance. We do a combustion analysis when we set up a new piece of equipment.

That's my that's my policy for max to go and do that because now we're responsible for the whole thing. But if you go in and you're doing, a maintenance and things run for several years and there's no uh ambient carbon monoxide and there's no carbon monoxide spillage around the unit and you're doing all your other tests that you're supposed to do watching for flame displacement. All this i'm feeling pretty good about it and at that point we're already doing better than every single contractor in the state of florida, so other than maybe joel becker joel becker would be an exception. That guy am i right, a joel becker.

What a fancy boy! All right so big things to look for. First, improper venting, you'll, see people do all kinds of crazy stuff. You'll see people use t-fin to vent gas furnaces uh at times you know like it'll, you know t everybody knows some t-fan is right: thermofan, it's what they use for venting, um, bat fans. So that's not designed for gas furnaces, um you'll, see single wall uh venting.

That's right up against the truss right up against a combustible material which it's not supposed to be so things like that. Just pay attention anything anything, that's obviously a problem if it's disconnected, obviously that's a problem just things like that: poor gas line installation, so that would be gas lines that are installed with obviously the wrong size, especially when they're using these gas connectors. Those are the most likely to leak because with vibration they leak or they can rub up against something so make sure your gas line isn't rubbing up against something make sure that it's not clearly the wrong size. That sort of thing on gas furnaces size isn't usually a huge issue where we run into size.

Issues is on pool heaters, especially on 400 000 btu pool heaters, because just your regular old three quarter, inch connector just is not going to move enough gas for those and they're going to. They start burning, really uh poorly and can actually produce a lot of carbon monoxide really quick, um and that's still dangerous, because it can still get re. You can still get picked up into the home, especially if the homes are under negative pressure and it's underneath the soffit that can get drawn into the home and can still be very dangerous, so poor gas line installation to include you know gas connectors that are looped. All over the place and rubbing against things and also improper gas size line, size back, drafting or orphaned water heaters, so we're going to run into orphaned water heaters, mostly when we, because in our market, we're not replacing 80 with high efficiency.

We're replacing a lot of 80 furnaces with heat pumps and what that means is, if you have a common vent, a common flue for your water heater and for your gas furnace. And then you get rid of your gas furnace and you leave your water heater. Just on that big old flue pipe that can cause draft issues for that water heater and often it will so don't just assume that you can just leave that. Basically, at that point just ask somebody who knows for most of you um, but if you notice that if you go to a house and clearly a heat pump was put in and you see this orphaned water heater pay attention to that, because that is a risk.