This episode of the HVAC school podcast is made possible by some pretty good companies. Our sponsors and those are filled. Peace filled. Peace is going to be at the a HR conference and ask you to stop by their booth at c60, 359 at the a HR conference or HR Expo as it is properly called in Atlanta, I'm gon na be by the booth a couple different times.

So if you swing by there's a good chance, I might be there, we have been trying out their new JobLink probes, the jl 3 series of probes. We really like them. They are one of the best options for using measure quick out there because of the tremendous range they have listed on them. I think 300 foot range and as long as there aren't any, maybe thick concrete block floors or something in between you're gon na get all of that with the JobLink probes.

They really are great and you can use them to have some of your air probes on the inside and your refrigerant probes on the outside and pull those all in to measure quick. So if you haven't looked at field piece yet I would suggest that you do so and take a look at the products at ahr at booth, C. 63. 59.

Also, a big thanks to refrigeration technologies at refridge tech, comm, they're, going to be at B 44 17 and I'm gon na be at their booth on Monday at 3 p.m. so stop on behind this refrigeration technologies. They make Viper cleaners, and I log and all sorts of other things, also big thanks to navikev at global comm and then finally carrier and carrier comm. This is the guy who once said to have a bank evacuated because he tested the heat scripts during a maintenance.

Brian or today, on the podcast, so hey hey, this is Brian. This is the podcast that helps remember some things you might have forgot along the way as well as helps you remember some things you forgot to know in the first place. I know you never get sick of hearing that, so I don't want you to miss it, and today we've got Jason. A beaut on the podcast Jason is one of the finest young educators in the country neigh-neigh in the world.

If not the universe - and he is got a lot of stuff going on a lot of irons in the fire, but he took the time to come on the podcast and talk through furnace sequence of operation, which is always a popular one. He's got a nice little reminder, phrase that you can use, and I won't give it away here. We go Jason, ah beaut, talking about furnace sequence of operations, thanks for coming on Jason, thanks for having me that was kind of weird. I was thanks for coming on.

Jason today we're talking about the sequence of operation for gas furnaces, which is a topic that frankly, I stole from Zack and Andrews podcasts HVAC shop talk if you don't listen to that, podcast go over and take a listen. Jason had a great episode over there about diagnosis of smart valves, Honeywell, smart valves and he had a pretty good little. Would he call it a did? He is that what it's called yeah, he called it a did. Ii yeah, i did he.

Okay, yeah andrew's got the military jargon down and it was good and i thought i don't know that i've actually done a furnace sequence of operation. I mean I may have done one, but it's not my cup of tea. So I figured. Let's do it soup to nuts for a new technician, maybe who is still in school or maybe somebody who's in a market place like Florida, or we don't work on very many furnaces.

It's good to know what to expect when you walk up to a furnace. The first time yeah, if you don't use it, you lose it type thing we're in the summertime, you're running AC, calls left and right and then months later the temperature drops and all of a sudden the furnaces are back on and it's been months since you looked At a furnace, that's where it comes in handy all right so before we call off the ditty and start on the step-by-step. I want to give you a chance to talk about the book. Real quick, more people who are gon na be able to find it when it is out.

I don't want anybody to miss that. Thank you. I work for ESCO as a Content developer, so this is the project we did with them. The title of the book is gas heating and it's an overview of everything from combustion to opponents to wiring diagram sequence of operation, installation, it's one of their longer books that they'll have published.

It took a year-and-a-half to write. We had a real good team people looking it over telling me how you should have this or have that teachers have looked at it. I've taken input from technicians, students, teachers, manufacturers - I mean it was a very long process to get it together, we're hoping that it's gon na be real useful to not just students but also teachers and technicians as well. It will be available on s co, group org.

After the first of the year, I believe we got all of the copyright is beyond all that information setup, so it should be on the website very soon great. So yes, ESCOs website, that's where you can find it. Esco has put out a lot of different books over the years of an educational type books and a lot of technicians miss out on books that are kind of designed for the classroom, but have really good information for the field. And this is going to be no exception to that.

So what we're going to be talking about today is stuff that you can find in there if you want to reference it later. If you are a contractor or service manager and you've got technicians who make you struggle with gas furnaces - and this is gon na be the book you want to get there's a lot of great books out there like, for example, the rack manual, which Jason also contributes To and is gon na be on the cover of the new rack manual, which is pretty cool, but it's a small segment of that manual covers gas, where this kind of takes a deep dive into gas, which is what a lot of technicians need. More of ESCO will they do a lot of that they put out a lot of titles that are short sweetened to the point. It's not this 600 page volume.

A lot of their titles are one to two hundred pages and they're primarily focused on one aspect of either a large text book or a piece of the trade, something like that yeah, which for technicians, I think, is good because it's a little less overwhelming. It's also gon na be used in classrooms, but I think Tech's miss out on some of this type of content - that's maybe written in books that they would not think of buying and keeping on the van. But I think this is one that you're definitely gon na. Want to go out and get so, let's go ahead and dive into it.

So, let's start with what is the ditty? I've broken it down into and there's a lot of subsections and little things, but there's six steps and then there's a lot of filler material. That goes in between the steps with the six steps I break it down to our thermostat inducer motor safety switch igniter gas valve blower motor, so it's thermostat, inducer motor safety switch igniter gas, whoa blower motor and to remember that its take it slow. It's gon na blow. Okay, take it slow! It's! The first letter is it's a anything orders that just a filler igniter igniter.

Okay, all right! I couldn't write fast enough, so thermostat inducer take it slow, igniter! It's gon na gas valve blow is blower right now. The safety switch is a generic name for the pressure switch because we in the industry can't decide on common terminology from one manufacturer to the next. It's a negative pressure switch. It's a pressure differential switch, it's a combustion vents which I just gave it to generic name.

Safety switch, but that's the switch were referring to the pressure switch yeah. I think when I first came into the trade, the guy, who I rode with called it. The air proving switch. Was the term he's like so many different aims, all right.

So, let's start at the top and walk through it, so you walk up to a gas furnace. You power the thing up and we're gon na walk through the steps that you expect to see happen. So we're not talking faults here. Initially we're just talking what a gas furnace should do when it's working properly and before we even do that is this fairly universal? Does this work for really high efficiency, furnaces all the way down to standard 80 percent, or is there some variability there anything that uses a circuit board basically induced draft miles? It can work for high efficiency.

Eighty percent, I mean it'll even work on the smart valve furnace. It's just that! There's two circuit boards that are doing it. Instead of one I mean if you can apply two intermittent ignition direct ignition spark ignition hot surface ignition, any type of ignition system. As long as it's induced draft uses a circuit board, so if he's using an old fan type control, where it's got no inducer and very very simple, then this wouldn't apply.

I mean it still kind of does I mean some of it applies just not the whole thing right. All the steps aren't there in the standing pilots, the natural draft. As soon as you turn the thermostat on instantly that gas valve fires up, there's nothing in between there, I mean it's instantaneous, you put the red-and-white thermostat together and the gas valve is on. There should be, let's start with room instead, so we walk up to a gas furnace, obviously disconnects on.

We start with a thermostat right. The thermostat has to send the signal to the circuit board that we need heat has to initiate to call for heat when a 24 volt signal to the W terminal. We don't want, because this came up years ago on some Lennox furnaces that we had down here. In Central Florida you don't want a G call simultaneously.

We had some thermostats that were set up for electric heat and they were sending a G call along with a white call and that's not desired. No certain furnaces may lock out. In that condition, some will just turn the blower on instantly and you'll be circulating, cold air because the furnace hasn't had time to warm up. It may affect your venting if the blowers already on when the furnace is trying to warm up, there's quite a few issues.

You can have with that. I mean when we say call for heat gas, furnaces weren't designed to have the blower energized immediately right and for those who are working on older electric fan coils, where you needed to have a G call in order to bring the blower on and even then that's Really abnormal I mean in most cases you're gon na have some sort of fan interlock in general and heat. You don't need a G call. You just go with the W call, and that's just enormous that signal.

So 24 volt signal usually using the white wire to the W terminal and then the next we have the inducer right. Well, the board works in a series of inputs and outputs for every input. There'll be an output for every action. There will be a reaction so when the Board sees 24 go into W.

The next step is gon na, be a 120 signal out of the board to the inducer motor and that's gon na start, the draft inducer combustion blow or power vent or whatever you want to call it all right. So, let's pause there, real, quick and, let's just nail down, protects you really unfamiliar with furnaces. What is the point of that inducer and most furnaces? It's used to pull the gas combustion air flue gasses through the heat exchangers to deposit them into the exhaust on category four furnaces on high efficiencies. It actually pressurizes the flue pipe to aid in the venting and your category 1 furnaces.

It just dumps the flue gases and the temperature. The flue gas is what creates the venting action. So we needed to pull in the gas, the combustion air, to establish the fuel to air mixture and the burners and pull the combustion gases through the serpentine heat exchangers. Because they won't rise through that on their own, so in an old traditional non induced natural vented type furnace, you were just simply relying on the free draw of air being brought in with the flame, the primary air being brought in with the flame primary secondary air And then just the heat rising up the flue or chimney is what would then additional air in.

But that was when you had a very simple type of burner design where you would look in, and you would see the flames essentially going straight up, which wasn't a very efficient design from the standpoint of heat transfer, or nowadays we have these, like you mentioned, serpentine Heat exchangers, where it's much more complex, and so you need to have that additional force provided to help draw that air in right. The older furnaces used to straight up and down heat exchanger, where the flue gases rose really fast actually, and it would draw in a lot of the air needed. So the amount of time the flue gas spent in the heat exchanger was real low. As the flue gas.

It just went straight up and then straight out, whereas the modern furnaces use, tubular or clamshell, serpentine heat exchangers and even in high efficiency, we had a secondary heat exchanger. The gases won't naturally walk through there and come out into the combustion or to the vent pipe. We have to kind of pull them through there got it, and so a key thing here is is that when we think of this inducer - and you mentioned it - we can think of it as always being positive pressure, but in the older furnaces like the ones, we See here in Florida, 80 % standard efficiency furnaces, it's still going to have a negative pressure on the flue. If you were to measure it with a draught gage, you would still see under atmospheric pressure, whereas with the higher efficiency systems, you're gon na tend to see an actual positive pressure and the venting correct.

Yeah you'll see larger flue pipes on the 80 percenters and then the smaller to 3 inch PVC on the higher efficiency it has that effect. If you take a whole ways of water hose and you just let the water start running out, and then you take your thumb and you put it over the hose and you get this force when you have a larger pipe like that, it's there's no pressure that Builds up or anything like that, whereas in the high efficiency, when we take these 2 or 3 inch pipes and squeeze it, we do get some pressure buildup perfect, so that is the inducer and then, after the inducer we're looking for safety, and we mentioned this - is The word that maybe could be a little confusing, but how does that switch work now in most models? It's a negative pressure. Switch it'll have a hose connected to either the inducer housing or to the heat exchangers, and it takes that negative pressure that suction that's created by the inducer motor and the heat exchangers. To close.

So it's a normally open switch and the negative pressure generated by the inducer will pull that switch closed and the reason for that is if we have a block in the flue pipe or something along those lines, and we run the furnace. We're gon na have some serious issues with flue gas and flames shooting out of the furnace, with this motor added to it this inducer motor. So if we do have any kind of restriction in the flue, we won't generate that negative pressure needed to close the switch. The switch will prevent the furnace from operating.

Yes, that goes back to that way. That Dave barefoot taught me the name of the thing he called it. An air proofing switch that is kind of its job. Is it's there to prove to make sure that you have air that's able to draw through, which is not just the inducer fan, because that's what a lot of guys think they think! Well, if it's not pulling enough air through, it's got ta be the inducer fan or it's got to be the switch, maybe not making, because it's not working right, but anything within that assembly, in the heat exchanger or in the flue or venting that's restricting the flow Of air, so you have a bird stuck in your flue pipe or whatever that's going to cause you to not have enough air moving through and then it's that safety switch is supposed to not allow it to turn on the actually apply gas to it and turn On the furnace, so you don't have danger right.

We won't make it to the next step exactly, and so, when we think about furnaces, we have these two things that we've got ta prove we've got to prove that you have air, because if you don't have air you're gon na have problems, and you also have To prove and that you have flames so that way you don't keep putting unspent gas into it, and those are two proving functions that we have to do before. We can allow a furnace to keep operating. One of the things that always comes up is a cracked heat exchanger and if there is a crack in the heat exchanger depending on the size, the pressure switch may not close. That I mean these pressure switches work on really really low pressure.

Point five point: three point: two inches of water column: some can get into the one and two range but think of it as a straw in a soda when you put the straw in a soda and you take a drink, the soda comes up through the straw, But if you cut a hole in the side, you don't get a whole lot of soda up through the straw cause you're sucking air in through the side, you've lost your suction, so, depending on the size of the crack and the heat exchanger, you won't generate enough Suction to pull that switch closed, there's things where we run into issues with the gasket between the inducer motor and the furnace. Where we're drawing air in through the side, we don't have enough suction. To close it so there's a variety of issues that can get into why the pressure switch, didn't close, simply diagnosing it as okay, it didn't close. It's a bad switch.

Is improper. You'd have to find out first, why you'd have to hook up a manometer and see? Okay, what kind of suction am I looking at yeah anytime? You have any safety, that's not closing! I mean, if you think about it in the air-conditioning side, it would be like saying well, my thermal overload inside my compressor is failed. It's a bad thermal overload. It's like no is something caused that problem.

You always want to figure out the why behind a safety failure, because in order for it to not be closing, there's some kind of core reason that that's going on, not to say that you can't have a failed switch because it can happen. But I've seen it everything from like. We mentioned an animal, some sort and the venting to another common one that we saw for a while is cracks in the tubing. We see this a lot and gas pool heaters where we work.

If you have cracks in the tubing that feed the switch well, then that's obviously gon na cause it not to make as well, and sometimes those cracks can be very hard to see visually. So a lot of little things to look for another thing you get in cooler. Climates is a little bit of moisture condensation in that hose in the tubing that connects the switch to the inducer to wherever it's taking its suction from just one or two drops of moisture in that little hose and the switch won't close. So that's a common thing too, alright, so step one thermostat.

So it's remind me the duty again before I forget, I'm already forgetting it take it slow it's gon na blow. Take it slow, it's gon na blow, okay, so the thermostat is first, that's your W call. 24 volt W call now your inducer is spinning and it's moving the proper amount of air. So now your safety switch.

It's proven that there is enough air and it closes so what's next, once the switch closes, it's gon na send another signal back to the board. Remember its input/output 24 into W 120 out to the inducer, the pressure switch closes. It says 24 back into the board, so the board's gon na respond it's going to send out a voltage to the igniter, whatever the igniter may be a spark igniter or a hot surface igniter, and this is what we're gon na get our first time delay. There's gon na be a delay built into the board to allow the igniter.

If it's hot surface, to reach temperature, we may have a 30 or a 45 second delay or a minute the way for the igniter to come on. Some of these newer furnaces, the higher efficiency to stage 96 97 percent. They do a little test with the igniter. They start off with the first time you light it up.

It does a 60 second warm-up time and then each ignition sequence, after that it cuts 10 seconds off for five seconds off. What it's doing is looking for the least amount of time that it can stay energized and still achieve ignition, then once it finds that it sticks at that, and what's the reason for that, the life of the McKnight er? Is it energy, the usage? It goes down to the life of the igniter and them quickens up the process. If I have to wait 60 seconds for the igniter to warm up before the gas comes on versus 30, we get the burners on 30 seconds quicker and there's a couple different types of em, and I know that's not what this podcast is about. But I think it's worth calling out the most common types of igniter technology that we see now I think most commonly would be so.

Can I try it? Is that right so it can. I tried it hot surface ignition, yeah, there's two of them. You got the silicon carbide and the silicon nitride now new models and everything today you'd find the silicon nitride on all your existing models. You'll find the silicon carbide right.

Those are the real fragile ones, all right, the ones that you're always seeing cracking the silicon nitride tends to just be, like a very simple looks like a straight up. Little rectangle little stick and the silicon carbide tends to be look more almost like a coil kind of thing. Some of them do yeah, yeah, varying designs. Obviously, weird shapes right.

Yeah tend to be more so and with silicon nitride for a while there - and I don't know that they're still doing this, but they were using a pulse width, modulated signal to the igniter in order to reduce the heat of the igniter to as low as they Possibly couldn't still achieve ignition, it's been so long since I've messed with many of these, but the first models did that yeah. Now they all work on the standard voltage, but back when they came out. If you wanted to put a nitride igniter into a furnace that had a carbide igniter, that was a little adapter, a little box that you had to put in between the igniter and the board to kind of regulate the voltage to the igniter to temper it down. But today they've got it set up to where you just hook it up to the board and it's a go, there's nothing kind of in between there anymore and they are way more durable.

They don't crack nearly as often yeah makes a lot more sense. I remember when Trane first started using a silicon nitride, there was all sorts of training on that because it wasn't very easy to test because it wasn't necessarily just strictly 120 volts mic Pro cup. He was the one who I was listening to about that. He did some classes on that and I remember blowing my mind.

I was 19 or 20, whatever yeah the original models, I believe, were working on 90 or 95 volts at sometimes different frequencies, depending on who made it and the little box that was, there was, and they had settings. If you read the manual it was okay set. It to a if it's an American standard, if it's a train, you said it to be. If it's a Goodman Amana, you set it to C, so they had different settings for all the different manufacturers.

I wan na take a quick second. I thank one of our sponsors, and specifically today, I want to thank Aero Asus air Oasis has been with HVAC school for a while. They make really nice indoor air quality products, really three primary indoor air quality products for the air conditioning, refrigeration industry. They make the bi-polar product.

That's an induct air purifier uses bipolar ionization very easy to install no parts to replace a real great kind of entry-level indoor air quality product helps kind of bond together particles and it deals with both living and nonliving particulate matter. They also make another version of the bipolar: they call it the bipolar ice, it's easier for use on refrigeration units specifically designed for ice machines. It can also be used in ductless, where the little brush is separate from the head unit. It really works great in restaurant applications, where you have a lot of crud that wants to build up on the plates of your ice machine.

It was specifically designed for that and it especially helps deal with yeast, and a lot of people have talked about sub shops. How the ice machines get so filthy in sub shops because of all the bread that's being handled, and these greatly reduce the amount of growth on the plates. If you haven't taken a look at those, I would suggest that and then also the Nano the Nano is sort of their flagship product. They've made it for years are really well made made in the USA.

Part sourced in the USA, made by John Bennett is the guy who's come in on the podcast one of the owners of air Oasis. And if you look back in the archives, look up. John Bennett's name, you'll, learn more about bipolar and the nano how they work. But they're really good products.

We use them in caelo, so we don't have any warranty issues with them at all, they've been very reliable and I would suggest that you check them out. You can do that by going to air oasis.com /go, that's air, oasis.com, /go! There's a form there fill it out, let them know where you are and they can instruct you on what the next steps are to find out more about these products and your contracting business all right here we go back to Jason. Sorry for taking everybody on a stroll down memory lane there and then, in addition to hot surface ignition, then we also have intermittent expert ignition, which will often be described as ISI as how it'll be listed. So if it's hot surface ignition, it was a lot of times, they'll say HSI and ISI is intermittent spark.

Would you mind just giving a quick description of the difference or you could have direct spark as well? Oh direct spark. I've been trying to think of what uses direct spark: Rheem, rimi. Okay, all right all their residential indoor models are still direct spark they're. The only manufacturer that I know of using it on residential indoor furnaces so do a quick overview of the differences between those two intermittent spark.

Indirect spark all right. Direct spark functions. Just like the hot surface igniter, we use the ten thousand volt spark to light the main burners. There's no pilot, there's.

No. Nothing will use the flame sensor to sense that the main burners are on intermittent spark uses the same spark to light a pilot, and then the pilot is used to light the main burners. We see spark ignition outdoors a lot rooftop units gas packs things like that, because when it comes to the wind, cold weather things like that, obviously the older standing pilots wouldn't work they blow out and the hot surface igniter x', don't last as long outside. When there's such a wide temperature range, it's ten below zero out, and then you warm the igniter up to 2500 degrees, and then it cools back down to ten below they don't last as long they tend to crack a lot sooner so spark ignition is was for The longest time reserved to mostly outdoor type units but Rheem, does put them in all of their units.

Indoor and outdoor, so intermittent spark lights, a pilot and then the pilot lights. The main burners direct spark uses the spark to light the burners right away. There's no pilot step, all right got it, so that is the igniter part, so that is the it's in the ticket slow, it's gon na blow, and now we get to gas valve so once our igniter has been on as as hot service, it's been on long Enough then, the gas valve opens right. We get 24 volts from the board to the gas valve and this is going to initiate the flow of gas it'll hit the spark igniter or the pilot or the hot surface igniter, and we get ignition.

Now the flame sensor is in there. Okay, that's always gon na add right. I mean it's not part of the steps, because the flame sensor can fall in in a few different places, depending on if it's intermittent ignition, where the flame sensor is picking up. Only the pilot flame and not the main burners or direct ignition, where the flame sensor is picking up the main burners themselves, an intermittent ignition.

The flame sensor is used to test a pilot, so the system doesn't know if the main burners lit or not the flame sensor is picking up the pilot flame. Now there are some systems where you can incorporate a secondary flame sensor to pick up the main burners, but by design and intermittent ignition. The flame sensor picks up the pilot and not the main burners, which that goes back all the way to old standing pilot systems. Where you had a thermocouple, that's buried in the pilot flame, that's the old-school way, where you're, essentially relying on the fact that if you have an open gas valve that your pilot is going to light that primary gas that's coming through which to me, as always, seems A little scary - and I guess you're just relying on the fact that it's going to hit that eventually at some time right all right at some point.

It's gon na cross over and hit that point, even if you had a restricted heat exchange or something it's always a little scary. To me, of course, being that I haven't been doing gas for my entire career, it's less gas in general is a little bit intimidating, but you do have to have some way of proving flame, whether that flame, that you're proving is the pilot or whether that flame, That you're proving is the main burner. You have to use some method and nowadays it seems like most commonly or using flame rectification or some form of an eye. That's actually looking at the flame itself right, the CAD.

So is there anything else that I'm missing over there any other common ways of proving flame there's a variety of different thermocouples, as you mentioned, standard thermocouple with a thermo-pile or the mercury filled and then flame rectification. Those are the main ones. Besides the eye that we use a lot in oil, yes, I used in anything else commonly I'm trying to think. I don't know that I've ever seen it not residentially yeah I've run into it a few times and, like you said, a larger stuff, commercial, but not residential, okay and then it's time for the blower, and so the blower hasn't been on this entire time.

It's been off because, again we don't have a G call. It's waiting for the furnace board to the integrated circuit board, to tell it that it's time for it to come on right. Once we get 24 to the gas valve, a timer is started 30-second, 60-second, whatever it happens to be for the furnace to warm up and after that, timer has expired. The blower motor will come on 120 out, which is interesting.

Cuz you had the old fan limit controls that would actually bring the blower on based on temperature, which we don't do anymore right. I mean that's kind of a funny thing is in some ways that almost seems like a better way of doing it, but nowadays we're always just using a timer. It is in my opinion, but to their credit, they have made it with dip switches. The circuit board adjustable so that technicians can go on and set the delay for the blower to come on, and then the delay after the blower has turned off.

We can't leave the blower on too long after the heat is turned off. We're gon na start, circulating cold air and initiate a call for heat again, so they put dip switches on the board, so you can adjust. Okay, wait. 15.

34. Whatever how many seconds you wanted to wait before the blower turns on and then once the blower turns off, there's a set of dip switches for you to say right. How long does it have to stay on the cooler furnace down? That's one thing: I think it's good for texts to know if they're, primarily electric or heat pumps, that this blower coming on after everything else is something that you should expect when guys see the furnace come on in. Oh, my gosh, why isn't my blower running? Well? There's something to know, but next thing is, is that if you can visually see the flame which obviously on higher efficiency units, it's not the same as with the 80 % gun burners that were used to.

But if you can, if you're, working on 80 % and that blower comes on, it's really good to have the blower compartment sealed. Obviously, that needs to be all closed off and then watch those flames when that blower comes on, because that's a really good visual indication of maybe there being a problem with the heat exchange or some other communication between space air and the burner compartment. I can't stress that enough. If you're gon na be staring at the flames we're service in the furnace, we have the door panels off.

You have to put that door panel back on. If you see the flames moving, when the blower turns on, and the panels off, you're not really checking anything you're, creating all kinds of air movement in the room where you're at and that flame movement might be considered normal. If you really want to see the blower's effect than the flame, you have to have that door panel on and you have to think about other straws that could exist as well. So if you've got a Aperta coil on top and there's an overlap and maybe there's a gap there, that could be affecting the pressurization of the space rater on the furnace or even if, let's say you have a furnace, that's in a conditioned room and you've got A vent that's blowing on and you got to think about all this stuff, anything that could be disrupting the flame from the outside.

You have to kind of eliminate all of those possibilities, but once you get all that eliminated and the panels on nice and snug and there's no straws where somebody drilled a hole in the side of the cabinet, with a Unibet to run a thermostat wire through or Something and didn't seal it up once all. That's all sealed, then, looking at the flame for flame disruption is a valid test. In fact, I want to ask you this. Is that something still teach yes watching the flames reaction to the blower motor is one of the most accurate ways, a side of heaven and combustion analyzer to see if there is an effect.

As you said, the air that's being circulated through the conditioned space should in no way touch or affect the combustion process and the flames themselves. So when you watch that blower turn on, you should see no difference in the flames at all yeah and obviously we're talking standard efficiency, 80 % type equipment, because you don't have this luxury. Of course. Also, when you get to higher efficiency equipment, then we should have sealed combustion where you're bringing in all of the air from the outside anyway.

If it drives me crazy, when I see guys put in really high end furnaces and then still pull in their combustion air from the space, it's like one of the best advantages of having a high-efficiency furnace is the fact that you're not pulling combustion air from the Space right you redefine confined space, you can throw it in a closet, there's no issues yep and in Florida we really don't care about the efficiency standpoint because we don't run the heat enough. But from a safety standpoint, bringing in your air from the outside has a lot of additional benefits. Besides the fact that now you don't have to worry about having combustion air in the summer when you don't want to have a giant hole into your attic or to the outside of the space which can cause problems if your furnace is inside. So a lot of factors there - another issue is returns.

You had mentioned the furnace being in the conditioned space. Well, if there's a return anywhere near where the furnace may be, the return may be pulling away all your combustion air all right so moving that pipe to the outside is a big benefit right exactly now, you got to make sure that it's done properly and that's A whole nother ball of wax there. Obviously, if any of that's not done right or it's accessible to creatures that can get into it and cause additional problems. Now you've got another piece of venting to worry about which some guys don't love, but I think it's something that I think we're gon na go to all across the country, not just in the northern states that have traditionally used those systems.

That does cause an issue. Not all properties, not all buildings or structures, are set up to have a high efficiency flue pipe. When you come out the side of the house, there has to be X amount of feet from the end of the pipe to the nearest building or structure and in the city. These homes are all built on top of each other.

You might have three feet of space or two feet of space between the homes on both sides, so your only option is to cut out the walls and go all the way up through the roof. If it's not too high, I mean it becomes a larger job. So you're going to have all these existing structures, there's a in the cities where the houses are on top of one another condos places like that, where you don't have close access to an outside wall where there isn't some kind of obstruction or restriction on the other End of it right, yeah, sometimes you're, just limited by what is and there's not anything you can do about it, which is a challenge right. As when you're doing a furnace install you the homeowner says all right.

I want a 90 percent all right, I'll, sell you. One you got to go there and check it out. Is there a drain, because we know the high efficiencies make a lot of water? You have to have a drain nearby. Where can I vent this thing? You have to scout around and say all right.

I have to find a place to terminate this and it's not Universal. Each different manufacturer prints a chart in the install manual for how many feet of pipe. How many elbows you can use. There's a lot that goes into that the inducer motor.

How well it can pull through and the temperature the flue gas is coming out. So it's not! Oh! You got 60 feet on this. Well, some you may have 60 some you may have 80. You might have to step it up to 3-inch some.

You only have 40, depending on how many elbows there's some calculations that need to be made it back. In the day when you were selling 80s, you just alright. We connected to the flue pipe and that's that, but with these you have to bring them to the outside wall and you're. Gon na have to go on the site, investigating plan for a high-efficiency, install and obviously when you're, not gon na, have as easy access to see flame disruption and all that this is where combustion analysis comes in, because it's the same sort of process.

But instead of looking at the flame with your eyes, you're watching your combustion analyzer what it is before the blower comes on and what happens to it after the blower comes on. That's a really good indication when you can't necessarily use your eyes for the diagnosis right you're, watching your o2 levels, your co2 levels rise and fall with the blower that shouldn't happen, yep and again. Just even with that, though, you got to keep in mind that there may be some tiny changes that occur just because nothing is ever perfectly sealed. So there's sometimes you're gon na see some small changes, but you shouldn't see anything significant.

I was gon na bring up one more thing, notice that when we went through the whole sequence of operations, thermostat inducer motor safety switch ignited gas valve, take it so it's gon na blow. We went through all the components you didn't hear. Anything about limit switch rollout switch any of the safety switches in that sequence of operations. There's a reason for that: in most systems, those are being monitored.

24/7, whether the heat is on whether the air is on whether nothing is on so they're, not necessarily a part of the heating sequence. There's a constant 24 volts running through the limit switch and sometimes the rollout switches are in series with the gas valve and I get into that later. But when the limit opens most boards respond. The same way, they're going to turn the blower motor on and sometimes the inducer motor and stay that way until when it closes, you don't get your sequence of operations, you won't start with thermostat and it does nothing.

It turns the motor on and stays that way. That's a clear sign that we have a safety issue when you come up to a furnace and you see the blower and the inducer are running and we got nothing else going on. You probably have an open limit, switch or Roth switch. They use a safety loop for that right versus maybe the old-school way when we would think of a standing pilot system with the thermocouple or thermo-pile, where we thought of it all is a single loop that went in and out of each safety and then back to The gas valve nowadays you've got this integrated circuit board, that's essentially watching its own set of circuits, and it's going to throw a fault of some sort, whether it's flashing lights or a code, or something on the controller and unmodern communicating equipment.

It's watching these circuits individually. Just like you said, you have a high limit that what are the systems out on high limit? It's gon na at the very minimum, bring the blower to full speed and almost always bring on the inducer too, and it's just gon na sit there flashing. Whatever code, your high limit code is, and that's what you want to look for for new technicians if you're going to a system that has some sort of a Fault in it, you don't want to walk up to the thing and immediately just start pullin panels off You want to walk up to it and look to see if there's any existing codes or anything that the system is telling you before. You start pulling it apart because sometimes in certain brands, you'll actually clear the codes as soon as you pull that door off and trip the door switch.

That's big, and the other thing I would say is after you've seen the code and it says, let's say open pressure switch or overheated for whatever it happens, to shoot the furnace off as long as it doesn't say, even flames rolled out or something along those lines Shut it off turn it back on and observe it for yourself, for example, it may say flame not detected well, that can be a million different things. It could be that the pressure switch didn't close. It could be that the igniter was cracked. It could be, the gas valve was bad.

The flame sensor could have been bad. You know that a flame wasn't detected, but it doesn't necessarily point you to ok, replace this part, there's still investigative work. That needs to be done. On your end, I always tell technicians when I'm teaching the troubleshooting, that you need to listen to the customer and they're gon na have some positive information for you.

But you need to see it for yourself. You need to observe the sequence of operations for yourself and see: where does it stop when we're troubleshooting and take it slow, it's gon na blow to reset the furnace and follow it through the steps and wherever it stops. That's where you start it drives me crazy. Whenever technicians - and maybe I gave you the wrong idea there when I said that whenever technicians think that the equipment can diagnose itself, there's almost no case in which the equipment will tell you exactly what part needs to be replaced, it's almost always going to point you In the direction right, but it is helpful right, it's very helpful to look up those codes before you go resetting, but it's not gon na, say.

Okay here, replace your inducer fan or place your ik nighter. It's almost never that simple right, one of the tips I'll give is back. In the day the furnace manufacturers used to make one loop of safety switches, and it would have your main limit. You roll out switches and the auxilary limit switches in one big loop and if any one of those switches opened, it would turn the blower on the inducer on and it wouldn't do anything.

So if it was a rollout switch, which is a manual reset, switch. The blower would stay on indefinitely until someone came out to reset it you're talking, maybe a day or two, depending on how long it takes the technician to get there. Some manufacturers decided that they didn't want to blower motor running for days and then like that, and they moved the rollout switches to the line and the gas valve. So when the 24 volts comes out of the board, it goes through the rollout switches and then to the gas valve, and what happens then is if the rollout were to trip we'd get no gas, so it would go through three trials for ignition trial.

One trial two trial three and then it would go into a hard lockout where it wouldn't do anything. So there's no blower running, but it's in lockout nothing's happening. So you can have an open rollout switch on one furnace, where it's running the blower in the inducer motor constantly and on another furnace. The same issue open, rollout, switch and the furnace just puts itself in the lockout after three trials for ignition, but they both have.

The same problem, the furnaces are behaving differently, a huge part of furnaces or any piece of equipment. Is that they're all trying to accomplish ultimately the same thing, but they do it in different ways with different manufacturers so reading through the manufacturers, sequence of operation, understanding what types of safeties you have in the circuit and what the different responses are. That's something you definitely want to take the time to do. One thing we're gon na do on hvac school.

I just talked to one of my text about this. Is i'm going to start going through if ik pieces of equipments installation and service manuals not reading them verbatim, but just kind of walking through them in the podcast? So that way, you can get a feeling of how different manufacturers do things ultimately they're all trying to accomplish generally the same thing, because I get lost it's been so long since I've worked on certain types of equipment. Like you mentioned a Rheem furnace, I don't think I've probably worked on a Ruud, Rheem furnace and who knows maybe fifteen years maybe, and so now I don't know exactly what to expect. But if we had a manual that we could kind of walk through, I think that'll be helpful, so we're gon na do more of that.

This schematic is your best friend. It's your number one tool. When you're troubleshooting to gas furnace for sequence of operations, it would show you that the roll-out switches are in series with the valve and not on the safety loop, and that could cause the lockout understanding and following the schematic, will always help you in determining the sequence Of operations on esko's, I did a presentation on this at the conference in Vegas and I did a whole PowerPoint to go along with it. It's all an animated PowerPoint and it's available for free download on ESCOs website.

It walks you through, take it slow. It's going to blow and the different steps that are in there how to teach it and stuff in its own ESCOs website in the conference archive section, anyone can download it and have it in the 2017 archive is where they'll find that PowerPoint. If they want to look for it, ok, great yeah, so look up the conference archives. You need to go to the ESCO site anyway, because you need to be looking for the new book that Jason helped to write.

I'm very thankful to Jason to ESCO that they allowed me to come out to Vegas this year, 2019 and March to speak, which I'm excited about it's a great conference. I am everyone. If you can be there, be there. Brian is doing a session and it's gon na be great.

You need to come, see him well, if you're an educator, because if you're not an educator, then I don't even know actually know how I snuck in. I must have her doing some people, but you do a lot of Education, believe it or not. You do. I appreciate that.

I really appreciate you taking the time to go through all this with us Jason. It's invaluable information for technicians out there. Obviously this is it. Whenever we're talking about gas, especially, this is something that's for tax.

We say that in our tagline is for text by text. People have been properly trained. This is not for homeowners. This is not for people who are not properly trained and licensed to do this work.

If you don't have that training, then please don't try to practice this at home. But if you do have that training that I'm going to encourage you to always work safely and make sure that you read through minified, there's literature when you start working on particular pieces of equipment that you're not familiar with and then also go out and go to The ESCO website find the new gas furnace book and purchase that as well, so that way you'll be up-to-date with some of the best training out there. I appreciate that I do look forward to the release of the book and the industry's reception of that book. You can send me comments feedback at je, o BR zu t @ s, co, group org.

I look forward to any a feedback, positive and negative from anyone that does go on and get this book. I appreciate it alright. Thank you. Jason I'll see you soon at ahr, all right, yeah I'll, see you then thanks for listening to the podcast, thanks to Jason, for contributing to this podcast as well as others he's a great resource for the industry, and I really appreciate him.

He's gon na be at ahr we're also gon na get a chance to hang out with the educators conference in March, and if you have a chance to make it to either of those events, I would highly suggest that educators conference is only for educators, so technicians Are not allowed unless you can find some sort of sneaky way of making it there, but anyway yeah Jason's, good guy. If you meet him, let him know that you heard him on the podcast. Also. I want to take quick story.

There were two goldfish and they were in a tank and one goldfish looks over the other and says: how do we drive this thing? Okay, if you haven't downloaded the HVC school app yet go to either Android or your iPhone store, App Store and download that, but until next time - or I should say we'll talk to you next time on the HVAC school podcast, thanks for listening to the hvac school Podcast, you can find more great HVAC our education material and subscribe to our short daily tech tips by going to HVAC our school comm. If you enjoy the podcast, would you mind hopping on iTunes or the podcast app and leave us a review? We would really appreciate it see you next week on the HVAC school podcast.