This episode of the HVAC school podcast is made possible by our great sponsors carrier carrier, comm makers of everything from big old industrial systems, chillers all the way down to ductless systems. In fact, they have a new ductless dealer program where you can experience their new ductless systems find out everything that carrier has to offer. If you are a carrier, dealer get some exclusive benefits by being a ductless dealer, you can look into that by going to carrier comm or talking to your local territory manager for your carrier, distributor near you for us, that's carrier enterprise, and we like working with those Guys really good guys, Greg Schmidt Bauer is our territory manager and Greg takes good care of us. I also want to thank Aero Asus Aero Asus comm.

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Finally, I'm gon na thank nav. Ak makers have some pretty fancy vacuum pumps, recovery machines and a lot of other tools make a switching tool. They make a cordless, meaning battery-powered flaring tool that we've really liked and that's what we're using right now for all of our ductless installs and it just spits out perfect flares every single time, which i think is just Nandi and their vacuum pumps are great. They just solid heavy duty vacuum pumps.

They have actually built in vacuum, gauges which is nice to help confirm your gauge against, and that way you can just kind of start them up and see how deep the pump will pool before you connect it sort of saves. You a step there so anyway, you can find out more about nav act by going to two tech tools, calm and typing in a vac there, and you can see everything in their product line. I don't you're curious and anything you buy from true tech tools. You can get a great discount by using our special handy dandy, offer code get schooled, that is, offer code get schooled, and now the man who tries to explain make up air and ventilation to his kids whenever they eat out Brian or testing one two: three: oh Hey hey, this is the HVAC school podcast and to make sure you were there I'm Brian.

In case you didn't know. This is the podcast that you come to to remember the things that you forgot along the way as well as help you remember some things. They forgot to know in the first place about the HV EC, our trade and today we're talking about the hh4 heating and, specifically combustion analysis with Jim Bergman. This is an episode that we've been trying to get together for a long time.

We talked about Kaz testing. Last podcast, but this is the full combustion analysis, podcast and I know you're gon na enjoy it. So here we go Jim Bergman, alright, so we're back and your time I should say, may have been a week or two in our time. It was about five minutes.

So last time we talked about worst-case Draft and pressure, testing combustion, air zone testing draft so on and so forth, in the space, and so now, let's move on to the process for a proper combustion analysis, one of the very first things being on page 2 of The guide there I put down the proper steps to combustion analysis and the guide started with a cast testing, simply because I needed a big place to put all that information on the front there, and I wanted a house in the front of it because I thought It looked cool one of the very first things you actually want to do. When you walk into homes, you want to check the CL level. I don't know if you've ever watched his stuff for Geary Reacher, but Gary's been carrying a CEO arm personally for years and he's had to go off several times on there and again we talked about the fact that you just don't know what you're gon na walk Into and in fact several years ago I had a friend of mine call me at church, she said her furnace wasn't working quite right and the gas company been out and shut it off what was spilling yeah and they go over to the home, and I do An ambient Co test, because one of the first things you should always do when you going into home is doing an ambient Co test. I'm still picking up like 25 30 parts per million SCO in the house after the fire department had left so that nobody had ventilated the house which they should have done.

But can we get down there and I'm looking at the furnace and I measure and draft there's no draft at all on the appliance. So I go ahead and I pull the chimney apart and I'm look inside there and there's a raccoon had made a nest inside the rec was dead at that point, but it made a nest inside the chimney in the early fall and blocked the chimney up completely Thing was completely filled full of branches and stick in there, but had I walked into that basement just on a regular service call and not really paid attention to everyone walk in an area that was just laden with CO, and you want to be aware of that. It doesn't take a lot of gas to make a huge amount of carbon monoxide. It's just got to be burning improperly.

So one of the things that you should consider doing again, a combustion analyzer has an ambient Co meter on it or carry a personal Co meter or carry a low-level Co meter, just like when you'd use in the house that displays in parts-per-million. But you should have something that displays: has a resolution of one part per million, so it'll read down that one part per million range and typically we have different calls to action. So zero to nine ppm is considered. Okay in a home.

I actually never want to see it above zero to be quite honest with myself, but if you have smokers in the home or you have an oven running so many baking cookies, consistently you're doing something. You'll get a small amount of CO from the oven, but that should be always less than nine personal million Co and then it up to 35 person or million, is safe to occupy for a short period and a 75 person. Typically, when we stop work, is you can walk in a home in at 75 person or higher? You need to get people out of there call the fire department get the people checked, because you don't know how high the co has gotten over time. That's when things become dangerous but verify safe levels, ambient CO first and you want to record those and then the next step is going to be start.

The appliance and check for spillage - and we talked about you - guys - have a lot of 80 % efficient appliances in your neck of the woods that are connected to hot water tanks. And so you got to remember that if you have an atmospheric draft appliance, you have a pathway for Co to come back in the home. It's a wide open opening and it's necessary. That's what keeps the draft hood is.

What disconnects the full pipe from the draft, but it is a necessary thing, but you got to make sure you're not spilling the flue gases from the chimney in there. So we want to make sure that we're checking for spillage at the anything connected to an atmospheric draft appliance. So then we want to set the fuel pressure to the manufacturer's specifications and what I would do a lot of times like even on my own furnace. I just because you're you'll pressure as an allowable range for input, that's typically plus or minus 10 %, and what people don't realize is input on a furnace is probably the most important aspect of commissioning a furnace aside from the temperature rise.

The input is what is going to determine how well that appliance operates, because it's engineered to have a certain amount of fuel and air in excess air, and if you do not have that input correct, it compromises the entire operation and equipment. So what we're going to do here in this case in this steps, the proper combustion analysis, is more like setting up a brand new appliance, so we're going to set that fuel pressure to let's say this: calls for three and a half inches. What kind of sled, exactly they three and a half inches, then we're going to go outside we're going to the meter and and a meter is simply verifying the correct input. The correct amount of gas is going into the appliance, and for that we need our heat content of gas and we need the amount of time that it takes to do one revolution now back in that combustion guide.

I did put in a gas meter clocking chart and it's the gas meter clocking chart is designed for gas that has a heat content of one thousand BTUs per cubic foot, depending on your area that can be as high as 10, 50, 10, 70 or as low As I've seen as low as 900, there is a heat content of gas by state chart available and it actually is updated every month and tells de content by month. But what we want to look at on that chart is, what's called the average heat content of the fuel over the course of the year, and the reason we want to do that is because the heat content of the gas is constantly changing from the gas company. So it's almost like you go to the gas pump and you buy 88 octane gas and some days you get 86. Some days you get 88.

Some days you get 92, it's a crapshoot, because that's why we want to look at average. I think it's called a wobble point of gas and what that means is that it's average heat content over the course of a year is, let's say, 1050, but the heat content can go up or down a little bit depending on the gas, are delivering and what They do is, they add in a lot of times, they'll add on a little bit of propane into the nach gasps. Just keep the heat content leveled out, depending on what the heat content is in your area. But that's typically are constantly trimming the natural gas to keep the heat content consistent.

So the key thing is here is we're going to the average heat content of gas and we're going to clock the meter and we're going to figure out how many seconds it just took to make a revolution of the one foot dial, typically, is what I would Use if the large appliance I might even let it go around two or three times and then divide my average by three, because gas meters have your watch the gas meter. They don't consistently move around like a clock like a real smooth movement, they'll actually jerk a little bit, and so you want to make sure you're getting a good average time there, because what you want to be able to determine is the input of the natural gas. So when you're doing that timing, you obviously a larger than me to dial the longer it takes to go around the longer you take to do that, the better, because it's going to give you a more accurate input on there. So at that point, what we want to do is we haven't set it three point: five.

We determined that if the input is correct or not and then what we're going to do is we're going to raise or lower the fuel pressure slightly between the range of three point, two to three point: eight plus or minus 10 % to get the input of The appliance correct if we've got to go above three point: eight inch as a water column, the orifices are under sized. If we go below three point, two inches of water column, the orifices are undersized. You either have to upsize or downsize those few offices on there and depending on your area, and how close it is because many manufacturers ship the orbiters, the shipping, the appliances are actually for the highest heat content of gas in the country. They don't know where the appliance is going to end up at so they put it in the highest econ ten, the country which is like in at ten seventy range and if you're, in a place where the deliveries 950, your orifices, are definitely under sized and that's Gon na result in a high excess air and fuel quenching and all kinds of things that are going to cause a host of different problems like your condensing appliance, not condensing or even high levels of CO, because the amount of excess air we have going into the Flame and it cools the flame off so that input is absolutely critical to get that input correct on there, and this chart will allow you to do that and we're actually building this whole thing into measure.

Quick for you. So it'll do the calculations and then, when you put in your heat content of gas, it'll automatically output, the correct input and then we'll probably even work off your geolocation. So we know what state you're in and put in the correct heat content for the state. So you don't even have to think about it, but that kind of stuff is available.

So now we got the input correct. So in a sense, what we've done here when we walked in a home? First of all, we made there's no seal in the house. If we started the appliance, we're made sure it's not spilling so we're not gon na put ourselves in any harm's way. As the appliance is running, we set the fuel pressure, so we got a baseline fuel pressure to go on and now we set the baseline fuel pressure.

So now we have a baseline to go on and now we're talking to meet or making sure that it's correct and then we can adjust that with a new album limits and we get that input correct. And at that point, like I said, you may have to stop and change your orifices out, we'll get that input correct and now we're to the point we're actually going to combustion test. There's no need to combustion test. Until we make sure we have the input correct in the appliance right, it's not the first thing.

We do. It's done after a couple steps there to make sure that it's running the way that it's going to run, because if I can bust and test first and then turn around and change the fuel pressure, I just changed everything I just changed. The amount of gas going in I changed a lot of fuel pressure. I change the temperature rise, the appliance.

I changed the draft. I changed everything so there's certain steps you want to do in order and that's what line in a combustion guide. So now that we've got the correct fuel and air now we want to verify. We have adequate draft because again think about what's happening.

If I increase the amount of gas or decrease the amount of gas, the volume of flue products is changing, and so, as I'm filling that stack up with high temperature exhaust gas and a volume of it, I want to make sure that I can adequately exhaust it Out so now I'm gon na check my draft make sure I can draft properly. Then I'm gon na set my temperature rise and get my temperature rise across my appliance right and then last I'm going to verify that Mike a zone is still in the allowable limits. So what I'm doing there now is, because I got all those things the temperature rights cuz think about what's happening here when I set that blower speed. If I increase or decrease it - and I have any duct leakage - is all I've increased or decreased my amount of duct leakage right because it's directly proportional to the amount of air the blowers moving.

So, as I'm going through and doing all this work, what I want make sure as I'm following a very regimented process, so that when I'm done at the end of the day, I know the appliance is burning safely. I have adequate drafting and get the exhaust gases out. I know that the temperature rises in the right range, and I know that my combustion air zone doesn't have a high chance of being overcome and that's all we talked about the steps now we're good in the combustion testing and just a minimum way to talk about The steps - those are the steps that we want to take to make sure that it's all working properly again. One of the last things we do is set the blower speed because raising or lowering the fuel pressure is going to directly impact the heat produced by the gas and the temperature eyes of the appliance.

So we want to make sure that we're doing that all correctly. One of the things that we have to remember when we're doing all those types of testing is that, although there's not a lot, we can adjust on a gas furnace, I mean, if you think, about what can you adjust? You can adjust the gas pressure and you can adjust the blower speed. That is pretty much. If you think about everything on a gas furnace, there's not anything else you can adjust.

Everything else is a function of the installation and the reason we test a non-adjustable for the most part appliance is because it's installed in a dynamic environment. We have doors, opening and closing. We have fans turning off and on dryers, going. We have all kinds of things happening inside that home the homes is dynamic, the building is constantly changing, it's a living breathing thing and we got to make sure those furnace can operate safely within that structure and we have to make sure the furnace can operate safely.

As a function of its installation, in other words you're gon na install one, that's gon na have three or four foot of exhaust pipe you're gon na install another one. That's going to have 50 or 60 foot of exhaust pipe. Those two furnaces sitting side by side will operate a little bit differently because the friction created of the air moving through the plastic exhaust pipe so that all those things play into effect and you've got to make sure that you're testing that appliance and make sure as Installed as operating, hopefully it's installed to code, but whether it's code or not, doesn't mean it's gon na work right. It could be a hundred percent up to code, but because of other factors and at home, it's not operating safely, and this is again why we always have to properly Commission in combustion tests gas appliances a few things here that are jumping to mind.

The heat content of the fuel is a big impact factor which then impacts whether or not you have the correct, orifices or not. I mean it's obviously there's a potential that the incorrect orifices could be in from the very beginning, but that would be pretty rare. I would think, but it's more a matter of matching it to the heat content of the fuel you've got fan. Speed relates to the ductwork and everything else, and you also have the exhaust installation the length like you mentioned, and then you have the actual pressurization or depressurization of the combustion zone.

Those to me are the areas that I'm automatically kind of looking at when I show up on a site, so not just using my test instruments, but also using some common sense analysis to try to pick out some possible areas to focus on. I actually thought about the same as use that earthís has almost never need changed on appliances until I went to CSA labs that which happens to be right here in Ohio, and when I was a teacher I took my students on a field trip there and watching Them bringing all these furnaces in I'm asking the guy Sue's on boxing these things, they're literally taking him apart. Why aren't you testing them as they're designed? He goes, oh well, because they don't have the right orifices on him. I said what do you mean? I was right because well her heat content and here's a 1050 BTUs or whatever they actually had a calorimeter running right in the CSA labs, and he goes the first thing we do.

Is we pull the orifices out? We put the correct orifices in so we can get the correct input on the appliance at the rated manifold pressure, because it's absolutely critical that you have that setup right. Otherwise, we're not testing the appliance with this rated input, so it didn't come down to the appliance. Having what components it had with CSA Labs, what it came down to was having the correct input of fuel. That was a real eye-opener for me and I started clocking meters.

Then I started noticing that every manufacturers as well, you should clock the meter, and I wasn't doing that on a consistent basis and I found out after I started caulking meters that most appliances that I tested in my region needed the orifice has changed. I talked to some other contractors at that point and they found exactly the same thing that when they started clocking the meters, the appliances didn't have the correct input on them that actually quite a bit more common than you might ever care to adjust. Now some of the manufacturers will tell you you: don't really have to change the orifices up to say 2,000 feet, you'll, see that we have to de-rate a furnace when we get into higher elevations and that's because the air density changes it goes down and we have To do rate, the appliance but operating satisfactorily, in other words operating safely and operating at its optimal, is completely two different things. So I'm a big believer because I've seen the efficiency gains by getting the appliance operating correctly and I've seen it in my own house, where I've increased it three or four percent efficiency, because I had literally over a hundred percent excess air.

When I started my appliance - and I got it down to about 50 percent excess air by the time, I got the input correct, I'm at excess air dilutes the flue gasses, and it causes a condensing appliance to not condense, because it the air dries out. The flue gasses that's unused air going through the combustion process. It dries those flue gasses out and so then we're not getting. If we have a condensing appliance, you know how do we get from ninety to ninety seven percent? Well, we lower the stack temperature slightly, but the primary reason we do that is we get the moisture out of the flue gasses we're condensing every bit of moisture.

That's left in those flue gases out that we can get out. That's where we pick up all that latent heat energy, and so we got to make sure that that is set up properly and that's I can't say enough about how important that is to do that correctly. So those are kind of some of the key things that we're at least looking at and obviously you're really big into getting the input right. You also one of the more controversial things.

That's come up a lot and I think it's worth just saying again. We've said in previous episodes is that you are not a fan of increasing your gas pressure over the manufacturers recommended levels because of some potential and liability issues and things that can be associated with that. So it's not just liability issues. I'm going to ask you a question, a baited question because I know you have but have you ever used a torch? I have yes when you, you know, there's a knob on the side of the torch and you can actually increase or decrease the fuel pressure right.

Yep, what happens to the characteristic of the flame when you change the fuel pressure changes? It changes the flame right. What typically changes is the length of the flame you ever notice that the length of the flame goes up and down and if you ever looked at a heat exchanger, what happens is it starts the neck down once it gets out of the combustion chamber, it actually Starts the neck down in size, because now what it's trying to do is slow those full gases down it's working by convection to scrub along the sidewalls as much as we can. So you want to tighten that flue pass to jump as tight as you can and you want to get as much surface area as you can around that flue gas to extract everybody, heat energy. We can without getting it too cold and ignite condensing appliance and not condensing in our primary heat exchanger on a condensing appliance.

But the key thing is here is that when we change the fuel pressure, we change the length of the flame. We change the length of the flame, we could be getting into the area now where the flame starts to impinge, and it doesn't have to impinge because here's the other thing, if you remember when you cut the distance of a flame, the distance between the flame and Adjoining wall in half, how much does the radiant heat energy increased by drummer know four times four times more heat energy? When you cut the distance in half okay, when we increase the size of a flame and we have the distance of the flame to the wall, we just put four times more heat energy against that back wall that furnace than it was designed to have by changing The orifice size we change the diameter of the flame in the combustion chamber, but we're not extending it into the combustion chamber further than it should go. So that is the reason that I'm not a big fan of I'm telling you straight up. Don't ever adjust fuel pressure outside of the manufacturers recommendation to correct input.

The correct way of doing it is to put the correct or faces in the appliance. That's gon na get you the correct volume of gas at the correct fuel pressure and that's going to keep you from getting in trouble and that's going to keep you from premature heat, exchanger failure, and that is what the manufacturer calls for and that's what the equipment Is designed for so that's the way that it needs to be done. There's no reason, except for laziness to not do it the right way, period and I'll stand by that all day, long all day, long and all night, long and all night, maybe even for the next 20 years. Yes, yes, all right, so I don't know where to go from here next, I will say that again, this guide from per Mackay tools that Jim wrote is really good and it goes through each different type of equipment.

Or do you want to go next? You want to go into carbon dioxide thresholds. Where do you want to go so yeah? Everybody typically picks up and talks about carbon monoxide thresholds, which are really something we all need to know quite a bit about, but I want to take it a little bit a different direction. Let's just talk about combustion analysis in general because we tend to fixate on the same part of it, which is can't be understated, but I also think there's a lot of importance, understanding just in general, what we're looking at when we do a combustion analysis. One of the places I'd almost like to start is just talking a little bit in general about what combustion analysis is because a lot of people just don't understand in general.

What we're doing you know? A combustion analyzer for the most part is not a appliance efficiency. Analyzer, in other words, we're not measuring the AFUE of the appliance, we say it's a 70 or an 80 or 90 percent efficient and we see on the energy label. That's like ninety four point: two percent AFUE. That is not what the combustion analyzer is actually measuring, and I will say it's very close when we get into condensing to the AFUE the appliance it just happens to be that way.

But what a combustion analyzer is actually doing is measuring the efficiency of the combustion process. Nords we're mixing up fuel carbon hydrogen together with our oxygen and it's producing Heat, carbon dioxide, water, vapor and there's some excess air that goes through there. And so what we're trying to do is make sure that all the carbon in the fuel is converted to carbon dioxide and so we're trying to also it's a modified equation. So it's very interesting with these analyzers because it's not just also measuring the efficiency of combustion, but it also takes into account how much heat goes up to the stack.

So it's also looking at how well it was burned, but then how much energy goes up? The stack so those are considered, what's called stack losses and the higher the flue gas temperature is going out. Well, that's going to make the combustion analyzers read a little differently and there was just a standard actually made on combustion and efficiency calculations and it's a naturally standard off tasks phone. What it is. I don't know if top my head, what it is, but what it did was it actually normalized all of the combustion analysis calculations between the manufacturers years ago, if you don't put a test, Oh Bacharach came a blue flame.

All on the same stack. You get all these different results and today now there's a standard written for how those are going to work. All those analyzers should produce very, very similar if exactly the same results on there and that goes back to each manufacturer has their own little proprietary, calculation and equations, and now those are become standardized, we're getting consistency on the output of the appliances. That part, I think, is very important to remember, but we're talking about a combustion analyzer we're talking about again the efficiency, the combustion process.

So here's what I think this is very important to understand if you were to take an old atmospheric craft about 70 %, what we consider 70 % efficient, appliance and hook up your combustion analyzer to it and right next to it, was a brand new 80 % Furnace, the odds of them reading almost identical combustion efficiencies are extremely high and you're going wow. This old appliance isn't operating too bad well. Yeah you're correct in the fact that it's not operating too bad as far as its combustion efficiency goes because it's burning the fuel very well and it's got enough heat going up the stack that it's not going to get that from the stack. I mean talk about a an old furnace, an old 70 % or the stack temperature was somewhere between 325 and 500.

If you're talking about an 80, it was between 325 and 450, so a slight drop in the temperature of the flue gas. But what made a 70 % and 80 % efficient appliance different? What did they do that made it more efficient? Well, what it came down to is what's called standby losses, and if we're going to look at an appliance and look at its efficiency, its annual fuel utilization efficiency, we also have to look at losses that are associated with old 70. It had a standing pilot and that standing pilot burned year round 365 days a year and it used gas right for that standing pilot, so that is considered a standby loss and that it was about a 10 % standby loss. It had a draft hood on there and when do appliances, draft year-round right so we're taking warm air from her house and pulling it up and out the flue and replacing it with cool air from outside and again that's another standby loss.

So we lose 10 % for the standing pilot, 10 % for the flue damper right. We get into really old furnaces, they had no circulation water in there and that would take another 10 % off. So you take that 80 % efficient appliance because it just mattered. 80 % combustion efficiency and you can subtract 10 % for the draft hood.

You can subtract another 10 % for the standing pilot, so now that 80 % combustion efficiencies down to 60 % AFUE. So when we say a lot of guys get this really confused into thinking well, it's combustion analyzer says it's 80 % efficient and the way you got a word that is the combustion analyzer says that combustion efficiency is 80 %. So what that means is that 80 % of the usable energy net flue gas is available for heating, the home right 20 %. His stack losses, 20 % going up the stack that doesn't account for the standby losses of the pilot or the uninsulated ductwork in the crawl space or the uninsulated cabinet of the furnace in the crawl space or the draft hood on there.

That's continually venting and that's an important thing to remember when we look at appliances and their features, so in the guide there we also have a whole section on a general guide, AFUE and appliance features. It just tells you if it's a low efficiency in that 60 % range. It's gon na have a standing pilot. A draft diverter, probably gon na, have either gravity or a belt drive type blower in it.

It's gon na have a single up shot cast iron burner. Probably in a cast iron heat exchange or single wall, flue, pipe and bottom temperature is probably 180 degrees, which means it's. They produce a lot of nice. Warm air coming out of those hole appliances, but they do it at this cost of efficiency.

When you get into that standard efficiency is 70 75 percent. Well, what do we change? We got rid of the pilot. We went to intermittent pilot or hot surface ignition. We have an hour draft diverter with or without a flue damper.

That came to a point where they were putting flue dampers in to shut the draft off and when we weren't burning gas went to a direct-drive blower, which is a little bit more efficient of a blower multi-cell construction ribbon slotted burners. So now we got a little bit better of a burner where we've actually changed, Believe It or Not, from a carbon luminous flame to a blue flame. At that point, it's really cool carbon luminous means that, instead of having enough oxygen right at the primary air to burn all the fuel that it gets, this oxygen when the carbon atoms get to the edge of the flame and the carbon flashes Orange and when it Hits the air in the combustion chamber and that type of a flame carbon luminous flame transfers about six to eight times more heat energy by radiation than a blue flame does and those old furnaces. They had a big burner pot, so they're primarily transferred heat through radiation.

If you think about an old furnace, it's got a very simplistic heat. Exchanger design looks like a 55-gallon drum in there and it's got a tube coming off the top of it or off the side of it, and all of its heat transfer was done by radiation. So that carbon luminous flame radiated heat to the exterior walls key to those exterior walls up with blue air around it - and that was pretty much it - I mean they're very, very simple. I've always started getting into the standard efficiency.

Then we started nekkid down the heat. Exchanger and we had the Lenox wave design and we had all these little modifications to give more surface area so that more he could transfer by convection, because we changed the color of the flame. We made a better burning flame and what happened there now is: we've gone from heat transfer by primarily by radiation to heat transfer by convection, so we did all those little improvements to get the 70 to 75 % range. Now we get to the mid of fishin C and again it's got the intermittent pilot or hot surface, but now we've gone to induce draught because our furnace has gotten such a complex heat exchanger, designed that the flue gases will no longer naturally flow through it all Right because now we've restricted it way down.

We have a ton of area that the flue gas has got a scrub and we now require a small blower to create the draft on the heat exchanger that we used to get by natural draft and now we're doing. Maybe multi stages variable speed. We've got again an increase in efficiency, the burner design, and now we might have gone to a single wall or double wall chimney and if we got a masonary chimney had to be lined right because now we've dropped the temperature, the flue gases down. So now we've gone where the 82, maybe 82 percent efficient range, and you won't see a lot of appliances between 85 and 90 %, because it's at that stage where the flue gases are a little bit too hot, to vent with plastic but they're, also not condensing.

So it really, it makes a big jump from 80 to 90 %. Let me go to that condensing appliance and you used to see a few of those mid-range appliances and they used to vent them with like stainless steel tubing or they had a high-temperature plastic pipe at one time. A lot of that stuff's gone now. I only ever see high efficiency appliances that operates with a condensing range in 85 to 90 percent range.

So now we've gone. We consider the ultra high efficiency, which is 19 and 98.5 AFUE. This stands to reason that if you have a system, that's designed to condense than it needs to condense, and if it's designed to not condense, then under no circumstances should you be in the condensing range yeah. That's primarily because there's a lot of we use air for combustion and because we use air for combustion, it also carries with it all kinds of chemicals that are in your house.

So things like dryer sheets, hairspray, water, softening chemicals, chlorine, you name it that might be in your home air floating around in there get bowled in a combustion chamber and then they make acids, and so what we want to do is we don't want those acids to Condense and end up as water in the flue pipe or in the heat exchanger or in the liner, because what happens is if they condenses and they start to attack the metal services. So it's really appliances that they're either designed primarily to condense or not condense like we don't see that middle-of-the-road thing, because those appoints just just the end up, probably being more problematic than you get benefit from them. So that's why we've seen this big jump to the higher efficiency appliance and now we've introduced that secondary heat exchanger inside of that secondary heat, exchanger xions, what's called turbulator, which are just like a twisted stainless steel spiral to make the flue gases scrub around as much As possible, so what we've done realistically, if you want to really think about, what's happened in furnace design, we've gone from this primarily heat transfer by radiation, all the way to really high-end convection, meaning that those flue gases are contacting as much surface area of the heat. Exchanger as possible and we're liberating every little bit of heat that we can and then we're cooling that flue gas down so far that we actually start condensing the water out of the flue gas and we get that secondary heat, exchanger, crankin and basically, what happens now Is we get latent heat energy that we extract out of that and now the do the flue gas temperature so low below 120 degrees that we can vent that in PVC plastic pipe right? That's ultimately, what we've gone to now is so we've got that stack temperature down 120 and we've got all the moisture.

We can extract it out of the flue gas so now we're getting into that 98.5. Even AFUE range condensing, I'm looking through this guide here, and it really does give you a lot of acceptable ranges for all of the different types of appliances when it comes to doing the combustion analysis. Now are there any best practices things that you want to think about when actually doing the test, placing the probe itself that that vary from furnace to furnace? Or is it all basically the same? It's not at all the same, and this is again I went out just a couple weeks ago went out with a customer, and I asked them how many you guys have done combustion analysis. Everybody raises their hand.

I said: okay, well, how many you guys actually know what all the readings mean and they're all raising their hand and they said well, then, why is nobody drilled, a hole in the right spot in the hood to actually do the combustion analysis and they're all looking At me, like, oh geez, so if you look at some of these old appliances like the 70's or hot water tanks, right here's, a couple of important things - combustion analyzers need to measure undiluted flue gas. So that means they need to measure the flue gas before it goes into the draft hood, because a draft hood it introduces all that dilution air. So it's gon na take those combustion byproducts that are coming out of that appliance. I'm just gon na dilute them like crazy because it's going to pull in 15 cubic foot of air per cubic foot of gas of dilution air into that draft hood.

So it's pulling a ton of air in there. It's gon na dilute the sample. So when we're testing in an older, like 70 percent efficient appliance, we need to actually test each cell individually, so it doesn't require like if you have three or four cells and a furnace. It's extra requires three or four combustion tests, because each cell has to be tested individually.

When you get to an 80 % of fish an appliance, then we have to test typically I'd, say at least 12 to 14 inches away from the induced draught motor. You need to be up in the flue little ways, and the reason for that is, there is coming off the end of that blower there's, what's called a little bit of static regain, so the draft inducer motor actually is exhausting the byproducts of combustion into the flue. It has a little velocity coming off the end and it will actually affect your draft reading. So you need to be far enough away from that from that induced draft motor that it's not going to affect your draft reading and we really won't affect the combustion readings.

As much as it will the draft reading on there and we're talking a little atmosphere, compliance you're going to have to measure draft in a different place than you measure, the combustion test. You measure the combustion test in each cell all right at the outlet of the cell right where it's going into the dilution, error, hood or the draft hood, and then you measure the draft in the stack itself in the vent connector itself right to different places. We've got it measured, and so that's a really important part to doing a combustion analysis is placed in a probe in the right position. You also need to make sure that you're out on line of sight like on some older boilers, they had the cells and, what's called a canopy that goes on top of the cells on top of the cast iron and it canopy.

Sometimes you can look down in there. You can actually see the flame in there and you don't want to have your combustion analyzer right over top of the flame, because that's going to give you a higher than normal stack temperature due to the fact that it's seeing the flame you'll get a lot rate Of heat transfer so again things to consider it you're doing the testing. You need to make sure that your auto- sited in the flame and your an undiluted flue gas, when you're doing that otherwise you're gon na get some wonky readings out of the combustion analyzer. I want to take a quick second here in the center of this podcast and just remind you of the support that we get from our sponsors, because I think some of you, you just kind of fast forward through the sponsors, and I understand that I do that.

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So obviously you got to make sure that you're taking your measurements in the right place, which this shows you the correct place like you just mentioned, but let's go through each one. So fuel pressure that's fairly easy. You should all know how to measure fuel pressure. If you don't know how to do that, then that's kind of a different thing, but let's talk about excess air.

So what is excess air and how is that different than o2, so excess air and fuel pressure actually go sort of hand-in-hand. We might want to even talk a little bit about both of those, but excess air is air that goes through the combustion process. That is not used in the combustion process. If you think about we have these carbon and hydrogen molecules in the fuel, and in order for those to burn, we actually need to have them contact an oxygen molecule.

We need to mix the fuel in the air together in order to make it burnable fuel on its own. It does not burn without oxygen and oxygen does not burn without fuel, so we have to have a correct ratio of fuel to air in order to get burn. Well, when we look at that fuel, what we want to do is we want to provide enough excess air that we assure that all the fuel is turn from carbon to carbon dioxide, because we don't want to get that an intermediate step, which is carbon monoxide, carbon Monoxide is formed when we have unburned fuel or personally burned. Fuel will go through the combustion process without fully being so, we provide excess air to the appliance to make sure that all the fuel is consumed and all the carbon converts to carbon dioxide.

A lot of people, in fact I just got a call. The other day somebody bought a blue flame analyzer, said: hey this thing's reading zero parts per million co-heir free. Is that even possible? I'm like absolutely yeah, that's exactly what you should be doing. That means all your carbon and fuel is converted into carbon dioxide.

Now one of the things we were talking about there was he was using an old analyzer that did not have a NOx filter and NOx. You know X is a oxides of nitrogen which are cross interfering with Co sensors, so his old co meter would read Co. Even when there was no Co present. He had never just seen a properly designed analyzer providing a filtering, not the NOx than the flue gas.

So that's another story on there, but that excess air is required and so because he had excess air and he had the right amount of fuel. We got zero parts per million, co, air free, here's, the key thing there remember we're, not appliance this 90-plus doesn't have air shutters on it. It doesn't have a way to adjust the draft on it. It's actual draft is a function of the vent pipe length.

So there is no provisions in here to adjust the we can't adjust the pot or anything on the induced draft speed motor to speed it up or slow it down. The only thing that we can adjust the whole'pliance is the fuel pressure and the polar speed. So the fuel pressure actually becomes critical importance because, as we raise or lower the fuel pressure, we're gon na increase or decrease the amount of excess air. We raise the fuel pressure up.

Excess air is gon na go down because remember a fan moves a constant CFM, independent of the air density. So it's always going to be pulling the same amount of air through that burner and at this point it's the air & fuel mixture. So as we increase the amount of fuel the air drops proportionally if we decrease the amount of fuel, the air increases proportionally so you'll see a direct relationship. When you adjust your fuel up and down your excess air will go up or down then lower.

The excess air reading is the higher the combustion efficiency will be because you're taking away the air, that's cooling down the flue gases and preventing them from condensing. Now. That said, you need to have excess air to assure a complete conversion of carbon to carbon dioxide, so excess air is a necessary evil, but we need trim it down. In fact, the appliances designed for a certain amount of Exeter's I've seen some of these new appliances.

Like I just put a 97 % efficient appliance in from one of my kids, he was running 25 percent, excess air and mine at my house is a 94 %. It runs about 50 percent excess air. So what happens? Is the lower the excess air is? The more the furnace will tend to condense. So when you get into these 98 percent efficient appliances - and I need a half percent efficient, so their excess air is trimmed down to that 20 to 25 percent range.

Typically, really, I haven't seen a lot of furnaces operate below 25 percent excess air. When you get down much below that, you take a little bit of a risk if that appliance, isn't serviced regularly of creating carbon dioxide, because if you get dirt and stuff in the burners in there, it could impact the amount of primary air going in and obviously That would affect the combustion in there, so excess air and fuel pressure run hand-in-hand, which also means that your o2 reading, when I look at a furnace, there's only really, if I fixate on two readings, I mean, if there's two things that I always really fixate on. It's carbon monoxide, air, free and excess air, and then the next two would probably be temperature rise in stack temperature right because the carbon dioxide air free you know an x-ray on a combustion guy - tells me how effectively we're converting the carbon to carbon dioxide right. We want to make sure well burning appliance, can produce zero parts per million co.

Air free, we're allowed up to 400 ppm in the stack. That's the ANSI BPI standard. 1200. 2017.

It's on that table one and a guide. You are allowed up to 400 ppm and that's considered safe. However, we know by good practice. Under 100 parts per million is easily achievable and zero parts per million is quite typical.

Unless you have a combustion analyzer, it's got a NOx filter in there to fill sorts of oxides of nitrogen. You won't see that, but like the blue flame analyzer test, though analyzers some of the higher and Bacharach analyzers, they all have NOx filters in them and that can give you a co reading of zero. So what we're trying to make sure there is that the appliance is safe. The reason we focus on carbon monoxide, air, free and not just raw carbon monoxide is because the excess air, the Lutz, the carbon monoxide in the stack.

So what we're doing is is we're just basically doing a ratio we're taking out the amount of dilution in the excess air to normalize the carbon monoxide, because, if you think about it, this way, if you had two manufacturers furnaces sitting side by side and they're, both Producing the same amount of carbon monoxide and one guy says well just increase the excess air and dilute the carbon monoxide. So it looks better well, then, that would sort of undermine the safety of the appliance, because, if they're both spilling in the same space, the percentage of carbon monoxide is identical. It's just once diluted a little bit more than the other in the flue gases, but when they both end in a space, it's going to have the same impact on the space, so we always want to make sure we're looking at co air free. The only reason we ever pay attention to Co on an analyzer is to protect the sensors.

The sensors are good anywhere from four thousand ten thousand two thousand parts-per-million, and if you over expose the sensor to Co for a long period of time, you will damage the sensor. But co. Air free is a reading that we need to fixate on for safety of the appliance and that's what all the standards are written on. Unless you live in Canada and they still have some hot standards, it's still reference straight up, ce o -- or unless you're testing like a stove burner.

That is an ambient air. And then we don't need to look at an undiluted reading because it's going right into the space anyway, so we looked at the straight raw Co reading. I want to add real, quick, a lot of technicians, and this is just basic science, but they get the idea of oxygen and air confused as if they're the same thing. But air is only made up of about 21 % oxygen, and so our Oh to reading is going to show how much oxygen is in the flue still so unconsumed or not.

That oxygen is consumed but uncombined oxygen, and so that number is obviously going to be less than that 21 %, because that's what it would be going in and that's where that range comes in correct consumed is a good word. I mean it is consumed. It's burned up. It's turned to carbon dioxide, water vapor on water vapor I mean it is consumed.

If you think about like a candle snuffer like in your kid, you put the candle snuffer over the candle, I know you're, probably an altar boy Church.