Tips on Inspecting Furnaces with CPI Lon Henderson

I'm lon Henderson today we're in it or not chi headquarters in Boulder Colorado to discuss furnaces we're going to be doing some basic examination of the basic types of furnaces we're going to be talking about mostly class 1 and class 4 type furnaces because that's the most common ones that we see in general and we have some representative samples of those here today we're gonna be talking about looking at these from a home inspectors point of view so we're gonna be following the internachi standards of practice and looking at these so it's not an invasive take it apart in depth exhaustive inspection of these so talking about our basic types here we have the three basic types the old natural draft units that are going away quickly just because they're old we have an 80% version with a metal flew on it and over here we have an example of a 92% high efficiency furnace so we'll just start a discussion with the natural draft unit here which is very typical of natural draft units a natural draft unit does not have any active collection like we see with a 80 percenter or certainly a higher efficiency unit doesn't have an active collection of the combustion gases forming in the heat exchanger this passively warm air in the heat exchanger rises gets drawn into the diffuser box here and air from the room is drawn into this because warm air is rising here these temperatures here are going to be around 600 degrees on this so it's going to be very hot hot we're gonna have a metal flue coming up here and it's drawing in room air into here to lower the dew point of the combustion gases here to reduce the opportunity for condensation in our flue here these units have been basically outlawed for quite a few years and so probably the youngest of these is going to be in that hmm 35 38 year range which is well beyond their normal working life but for us as a home inspector we're going to be looking for the obvious evidence of problems with it we're going to be checking across the face of it for back drafting with whether you use a smoke test a candle or most of us are going to be using some sort of carbon monoxide combustion gas detector and then we're going to be just looking for physical signs of a problem with it on this one we see rust along the bottom here that rust doesn't come from the outside and go in its from the inside coming out so that is a ding-ding-ding clue that we have a problem here probably excessive condensation on the inside forming and coming through right there we have reason to call for an HVAC tech to do a further evaluation on this thing and you know the term that a lot of real estate agents love is certified safe and that's a good term we can pull this guard off here if we want to and look inside the burner compartment you can use mirrors and a flashlight if you like look around up there see if you see evidence of cracking but that's about as invasive as we go as home inspectors look at the quality of the flame one of the little tricks watching the flame is you do your startup on it the blower comes on if we see any movement in the flames when that blower comes on that's a good indication that there's a problem with the heat exchanger a crack in it and it air movement through that crack in the heat exchanger caused the flames to change the pattern ever so slightly I got to say not something I see very often even with ones that furnaces that later prove that they have a cracked heat exchanger but it is one of those little clues that we look for as its operating also on these units we all will always have the service switch somewhere out here on the wall and maybe mounted to the furnace or something flip that off and make sure the burners go off at the same time the blower does these older natural draft units we want the burners to go off at exactly the same time as the blower if it does anything different that's going to be a defect that we're going to report in our in our inspection we don't typically see blower door safety switches on these the filter systems are it can be you know similar to anything else we see or they can be something kind of goofy with a basket filter in there or something on the older units all these furnaces are beyond what we consider the typical life expectancy of a furnace you know it varies from region to region humidity environmental factors can influence the average age of a furnace regionally but in general that 2530 years is about the max we expect to get for a typical furnace and all these are beyond that age at this point just because they quit making them that long ago you are not in a wrong place if you say this needs to be evaluated and certified safe by a licensed HVAC technician in my opinion moving on to yet another version of a category 1 furnace is the 80 percenters so on an 80% furnace we have an induction fan here that acts as a collector of the the combustion gases in the heat exchanger we're going to have a metal flue now sometimes you'll see an actual flex piece sitting here but usually it's going to be a smooth tube single wall vent connector is the technical name for it minimum 8 inches except obviously if you got a ceiling here too low you're not going to have room for it under ideal circumstances an 18 inch flue connector going up here and then connecting with the rest of the flue running out on that flue we don't want more than two 90-degree turns on it the reason we can have a metal flew here on an 80 percenter is our temperatures of our flue gases coming out are still around 400 degrees so very hot warm enough to keep that condensate or the humidity in the flue gasses in a gas form in the warmth of the flue gases carried them out the induction fan here does not force the gasses out so this is still under a negative or net zero pressure here though in the induction fan only introduces the flue gases into the flue and then the warmth of the flue gasses carry them on out so if we see evidence of condensation forming in that flue and caught in running back through or worst rusting the flue out that is a defect that we want to point out in our inspection another place to see that and on this particular furnace we don't see a lot of it but you have a little bit of staining underneath the induction fan right here and that is condensate that has run down the flue and it through the induction fan and leaked out and some furnaces will see a lot of that a lot is a concern a little maybe not so much because think about how warm air rises out of a flue on a cold night you can have thermal capping in the flue so you get this cold air slug sitting in the flue in the attic or above the roof for instance and it takes a good push of warm air to get that cold air slug out of the flue so that this warm air hits that cold air slug immediately get some condensation from that and that condensate runs back down now if the hot air goes ahead and gets the rest of that that cold air slug out and starts flowing out of the house the warm air can really lock on night might still run down and trickle out if it only happens occasionally we don't get too too concerned about that but if it's happening regularly you'll see big staining here often big staining in the flue or rusting and now we have an issue that should be addressed and corrected and we let the expect tech decide on the correction but we want that Condon any condensate in our flus control this is not a condensing furnace it is not designed to have condensation or at least excessive condensation running through the flue so we also have ported burners here we see a little bit of rust on the burners here you see a little touch of color there in general this is not considered a defect so this isn't something that we're going to call out for a correction or evaluation heavy rust flaking rust that's a different story but a little bit of color there not a concern under normal circumstances you might well want to put into your report a photo of it in observation that you saw it but not something that requires some sort of further evaluation by an HVAC tech we have a much more efficient system set up here we have a different heat exchanger in it then we'll see in this is a tubular heat exchanger here more efficient than the clamshell heat exchanger that a natural draft typically has that's how we get to that 80% efficiency and our temperatures here in the flue are going to be less than our natural draft system but still high enough to get the flue gases out without being under positive pressure that we see with the cat for furnace which is a typical high-efficiency unit and then so on these remove the cover which is you know so the two things that we do is home inspectors typically remove the covers look inside in this case we see a missing blower door safety switch so oops that would be a defect for us and then we're going to take a look at the blower try to get an angle whether you use a mere or however you can get an angle on the blower and look at the fins inside and see how dirty they are dirty fins can affect the performance of the unit and the efficiency of the air movement out of it a very dirty blower can reduce air flow by 20% but how do you know it's really dirty I look for texture in the dirt a little light coating of dust on the blower fins that's kind of normal probably not maybe could use a cleaning but it's not desperate but if you see texture in that buildup of dirt lint hair whatever it is on the fins now we need a furnace cleaning and one of those things that we would recommend as a home inspector we may also note the efficiency of the system whether it's a high-efficiency unit or an 80% efficient unit and by the way natural draft units are typically going to be 70% or less so over here we have a 92% and this one's going to be our category for example here because the flue gases are under positive pressure on a high-efficiency furnace the reason is a high efficiency furnace is trying to collect every bit of heat it can from the combustion gases so unlike our natural draft unit over here and our 80% unit over here where the flue gases are running four to six hundred degrees over here typically under a hundred degrees these flue gases are just warm and don't have sufficient heat in them to keep humidity in the flue gasses in a gaseous form and so we get condensation here the system is designed for condensation and designed to control that condensation even in a low humidity environment like we have here in Boulder Colorado will have tremendous amounts of humidity and our flue gases because the two main products byproducts of even complete combustion of fuels is water vapor and carbon dioxide and so water vapor being one of those big byproducts you're always going to have a lot of water vapor in the flue gases and trying to condense on the cooler surfaces of the flue if it can because they're already at around 100 degrees as they come in here or less even you're going to get condensation period whether it's a cold day or warm day you're gonna get condensation so it's very typical to see a PV C sometimes an ABS so flue on these the manufacturers in America allow either one in Canada they do not allow abs for you Canadian inspectors but in America PVC and abs which is black are still allowed we know an incident immediately as soon as we see the furnace that we're dealing with a high efficiency unit because we see the plastic flue on it whether again ABS or PVC so ding-ding-ding we know immediately so the things we're looking at with our high efficiency unit and this is kind of some of the basics that we do with any furnace we take the cover off so as you know and our SOP we're doing visual inspections but there is still some limited opening up of things obviously we take a dead front covers off of electric panels typically to look at those and on furnaces we take covers off to look in those so these are a little places where we kind of go slightly beyond the SOP just to see what's going on so we're looking at the basic components here of this unit that's being a brand new unit we're not going to see many defects in it we're also going to cover pulled the blower door cover off while we're doing this and we pull it off and we see some of our basic features here the two terms used to describe these furnaces are condensing furnace or high-efficiency furnace the two terms are interchangeable so since many of the features here are similar to what we see on an eighty-percent unit let's discuss some of the features we see here this is our induction fan except on a 90 percent unit or high efficiency unit the induction fan is collecting the combustion gases from the heat exchanger because we have a secondary heat exchanger in here we have flue gases at far lower temperatures than our other two furnaces so because of that our induction fan here has a different purpose than we see in the 80 percenter it's doing more than just introducing the flue gasses into the flue it's actually pushing them out so that's what makes this a category 4 positive pressure appliance it's pushing the flue gasses out and sending them out of the house the purpose of this fan is far more active than what we see in an eighty-percent unit with pushing the gasses out then we have our burner here on this one so some of the other features are pressure switches here we have the regulator over here on it and then down here we have the AFC integrated furnace control unit it's always a little circuit board looking thing it's a mini-computer type and then the course it's in this case it's sitting on the blower and then these rubber hoses over here which is something different from the other units these are for controlling and collecting our condensate which we expect to have in this unit and it's normal to have the rubber hoses collect that kind say direct it through this collector here down and then out of the furnace into whether a floor drain sometimes to the outside of the house sometimes a condensate pump any of those things but we always want that condensate controlled as far as some defects that we'd be looking for one of the big ones is again condensation not being controlled ever look in here see excessive rust see water buildup that's a defect that we're gonna call out because all condensation should always be controlled one more word about condensation in furnaces it's not distilled water it's acidic it's like diluted vinegar but inquiring minds ask why is it acidic one of the Tres products in fossil fuels and we're talking natural gas propane heating oil is sulfur and the refining processes for making our fuels just it's just not cost-effective to get all the sulfur out of those so we have trace amounts of sulfur as sulfur in our water vapor and our flue gases causes them to be slightly acidic so that slightness acidity can accelerate rusting on any steel components and so we won't condensate controlled because of that and one of the reasons why we often will see fairly aggressive rusting and in any furnace where the condensate isn't being controlled it's slightly acidic so one of the things about the high efficiency category for furnace from the others is the secondary heat exchanger and so the great thing about here at the school and the house of horrors is we can look inside the furnace and so here we see the primary heat exchanger on this unit and this is going to be similar with other high efficiency furnaces so we got the hot the primary heat exchanger here that what separates this from the 80 percenter is down in here that radiator looking thing at the bottom and the bottom of this one is a secondary heat exchanger that is collecting the last of the GAT warmth from the combustion gases that it can that makes this jump from an 80 percenter to a 90 plus percent furnace and that is the difference between this one in the 80 percenter we were looking over here is that secondary heat exchanger down there and it can be configured differently and different manufacturers and stuff may have it configured differently but in this particular furnace here that's what it looks like and that's a something that well normally we'll never see on an inspection because the stuff should never be open but it's nice for you to see what this looks like when you have those clients who are asking you what the difference is this is it and you can see how it's set up right here so one more thing that I want to show you while we're here is we have another high efficiency furnace that was defective and let's walk over here for a second and here we can see some defects and so while this furnace has a cracked heat exchanger here when we look in we see this rust down here at the bottom now if this was an active furnace and we showed up at this house on an inspection we might be seeing water sitting there condensate sitting there on that rust spot that would be a big defect we want condensate controlled now it may not be a defect that makes this furnace bad we can't judge that but we know that we won't condensate controlled so we're gonna point this out take our photos of it put it in our report condensate not being adequately controlled in the furnace needs to be corrected by an HVAC technician so this is a defect that would jump out at us immediately on this particular unit if we found it in a house during an inch affection so here we are in the utility room of the house of horrors if you walk into a furnace room with all the things wrong here you got a lot of stuff to write up so we're gonna kind of blow through some of the big stuff jumping out at us here some of the good some of it bad but here as we look up our flue we see our transition to our be vent which we want to see where it goes into the ceiling we want to see be vent up there never single wall but oops we have our condensate discharge hose here draping across the flue that would be a defect of course also we have our even our B vent here our double walled in within an inch of combustible materials both on the framing in the paper of the sheetrock or drywall up there chipboard and then we have an electrical line some nm wire here running across to our service outlet on the furnace again should be in conduit can't drape across the flue that would be a defect that we would note also the way the wiring goes into the junction box here would be a defect also on this unit here we see some foil tape most parts of the country do not want to see foil tape here even if it happens to be a high temperature tape rated for a flue we don't want to see it or most jurisdictions don't want to see it because it hides the quality of the connection here so that for most of us around the country that's a defect that we would be making a note of even if it's not a major one let us take a closer look at our furnace so we typically arrived with the covers on it even if it's operating you might take off the cover just to see what's going on the quality of our flame that flame should be blue we don't want to see a lot of yellow a little yellow flicking and flaking in the flame is acceptable but it should be predominantly blue with the yellow streaking or any laziness in the flame that's a defect the unit should be tuned among our other things here we have our gas flex connector coming directly through the cabinet that is never allowed it must be hard pipe so typically we're looking at black hard pipe coming through however the furnace guy that HVAC tech can do it configuring it hard pipe on the outside then our flex connector here gas effect flex connector connects to the end of the hard pipe so we're looking at what else is going on here here's our induction fan this is a metal fan we had a bakelite fan plastic fan cover on the other units here it's a metal one it's still an induction fan we know by our metal flue that this is an eighty-percent unit so this fan is just collecting the gases combustion gases and introducing them into our flue where they're going to rise naturally out of the furnace so we're looking at this oops we see the filter sticking out like that so we know instantly it's the wrong size filter and then as we look at it we see oops they have it in backwards how do we know it's backwards there's the arrow on the frame of the filter pointing away from the furnace that arrow on the filter frame must always point toward the blower of the furnace done don't flip the Fernet the filter around and put it in correctly because oops what would you have you would have all this blowing through the house now so not something that would be good to do but we often point out to our clients because part of our job is educating our clients and many of them don't understand this sort of thing until we tell them but when they replace the filter arrow points toward the blower and also of course getting the correct sized filter so now we can take the blower door off and if this was operating it would shut off because the blower door safety switch here would pop out and kill the furnace now if the unit is off when we arrived here one way we can easily check to see if our blower door safety switch is working properly is push the button and you'll typically hear a click in the IFC down here they integrated furnace control and we'll probably see an LED light come on telling us that this is working right so we don't always have to have the furnace operating to check the blower door safety switch so loose wires hanging out well that can't be good right so that's something that we'd be looking at and making a note in our report on again we try to see our blower at the inside of our blower as best we can sometimes it's difficult to see sometimes you can see it through the filter slot ones furnaces like this and this is a very typical furnace it's pretty tight sometimes you have to get a mirror in there sometimes stick a camera up in there and take your photo or something but try to see the condition of the blower our overall do we see water stains one more thing as we're looking up here we see we have wiring coming in from our service switch over here coming in directly through the cabinet there should be a bushing there where that wiring goes through the cabinet so that would be another defect we would call out on this particular furnace we have taken our visual look of it we'd probably close it back up go find the thermostat somewhere turn it on get back here as fast as we can and watch the sequence as it fires comes on listen for noises look for vibration that sort of thing among the other features that we're looking at on this furnace is when we look up on our plenum up here above it we're missing a a vibration collar or sometimes called an expansion collar we have one over here on this plenum but we do not have one here that's something we would call out any parts of the ductwork that directly connects with the furnace should have an expansion collar it does two things for us it cuts down on noise from the furnace getting transmitted through the house but also the normal vibrations of the furnace are absorbed with our vibration collar and of course if you live in a earthquake area then this helps keep the furnace in place during a mild earthquake so it's one of these things we definitely want to see and oops we're missing it here on our furnace among the good things we have here at the house of horrors and not everything is an example of bad stuff here we do have examples of things done properly here we have combustion air so we have this is the high source of combustion air up here within a foot of the ceiling which is where we like to see it coming in from the outside bring introducing outside air into our utility room for our furnace and water heater in this case to have adequate air to burn without having to draw air from the house and then we have another combustion air intake within a foot of the floor and these are adequately sized for the appliance BTUs that these appliances are using and so we have a high and a low which we want to see and the purpose of a high and a low one is to create a passive convection cycle or our airflow between the two so that we're getting active combustion air coming in for these appliances to have so they're not relying on house air inside the home and can get what they need from the outside look this affects the overall energy efficiency of a home but it's a trade-off that we're willing to make so that we have adequate combustion air for these appliances so one more thing that is wrong in our house here is a return air is sitting here not only in the same room with the furnace which we don't like if we can avoid it but also it's within 10 feet of the furnace a returned air source must be minimum 10 feet away with the idea that it reduces the opportunity to create a negative air pressure in the room and possibly cause back drafting so this would be a fairly in my experience fairly rare occurrence to see but it's one of these things that we're always looking for to make sure that things are put together correctly and we would want the combustion air ideally in another room if it has to be in the same room more than 10 feet away so that concludes our mini discussion on furnaces and HVAC systems here at the house of horrors thank you very much for watching our video and hopefully we'll catch you on the next one thank you very much

Channel: International Association of Certified Home Inspectors (InterNACHI)

Views: 17,657

Keywords: International association of certified home inspectors, InterNACHI, NACHI, become a home inspector, home inspection training, home inspection education, gromicko, inspection tips

Id: uvfnABki1mU

Length: 32min 3sec (1923 seconds)

Published: Mon Nov 11 2019