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Gas Furnace Heat Exchanger Clogged Problem- What it looks like and Burn Spots!
WEBVTT Kind: captions Language: en
00:00:00.000 [Music] 00:00:03.28000:00:03.290 hey guys this is AC service tech and 00:00:05.74900:00:05.759 today what we're looking at is heat 00:00:07.55000:00:07.560 exchanger failure all right we're gonna 00:00:09.98000:00:09.990 just talk about a few items here 00:00:11.74900:00:11.759 this is an older early 90s early 1990s 00:00:17.84000:00:17.850 ninety percent efficient furnace heat 00:00:20.17900:00:20.189 exchanger okay 00:00:21.71000:00:21.720 these are the early heat exchangers that 00:00:24.10900:00:24.119 were used and because of the way that 00:00:27.52900:00:27.539 the secondary heat exchanger was built 00:00:29.39000:00:29.400 which would be this one right here they 00:00:32.03000:00:32.040 tend to fail okay this is the primary 00:00:35.42000:00:35.430 heat exchanger and this is where the 00:00:38.27000:00:38.280 combustion gas mixed with the with the 00:00:43.10000:00:43.110 air alright and the ignition source and 00:00:45.47000:00:45.480 you'd have your flame and exhaust come 00:00:47.56900:00:47.579 right over to here and you're gonna get 00:00:49.61000:00:49.620 your exhaust being sucked through this 00:00:52.67000:00:52.680 heat exchanger and then it comes to the 00:00:54.86000:00:54.870 back right back here and then it comes 00:00:57.17000:00:57.180 over and meets the secondary heat 00:00:59.20900:00:59.219 exchanger over and here is where you're 00:01:02.63000:01:02.640 basically absorbing your heat from water 00:01:06.14000:01:06.150 that is created during the flame process 00:01:08.24000:01:08.250 so water is created during the flame 00:01:10.34000:01:10.350 process it is one of the byproducts is 00:01:12.28900:01:12.299 the chemical byproduct of the flame 00:01:16.13000:01:16.140 process so anyway water vapor is being 00:01:19.19000:01:19.200 carried in the exhaust and then you're 00:01:21.62000:01:21.630 cooling the exhaust and the water down 00:01:25.16000:01:25.170 so much that you you end up condensating 00:01:28.13000:01:28.140 the water in here and then it and then 00:01:29.87000:01:29.880 it's basically trickling and trickling 00:01:32.63000:01:32.640 out of the system so this side looks 00:01:36.28900:01:36.299 pretty good right this is where the 00:01:38.99000:01:39.000 inducer motor connects to and you have 00:01:41.06000:01:41.070 some gasketing material and everything 00:01:42.49900:01:42.509 and that all looks pretty good 00:01:44.51000:01:44.520 this area is pretty good there's no 00:01:46.60900:01:46.619 cracks in the heat exchanger over here 00:01:49.01000:01:49.020 in the primary heat exchanger alright 00:01:51.13900:01:51.149 but let me show you what happened here 00:01:52.71900:01:52.729 this the problem with these heat 00:01:54.83000:01:54.840 exchangers was the pressure switch would 00:01:58.96900:01:58.979 still close got the the pressure switch 00:02:02.33000:02:02.340 is supposed to prove that the inducer 00:02:04.28000:02:04.290 motor is running alright and that the 00:02:06.95000:02:06.960 condensate lines are not clogged alright 00:02:09.61900:02:09.629 so this right here is supposed to be 00:02:12.67900:02:12.689 protecting the furnace - no like say if 00:02:17.11900:02:17.129 there's a clog heat exchanger the 00:02:18.28900:02:18.299 problem with it is in a horizontal state 00:02:20.92900:02:20.939 you might have to okay that are working 00:02:24.08000:02:24.090 right and and the one could be cloth and 00:02:27.31900:02:27.329 that is what's going to create a fire 00:02:29.80900:02:29.819 alright so here is the combustion 00:02:34.91000:02:34.920 chamber right here so here's the 00:02:37.19000:02:37.200 combustion chamber and it connects right 00:02:39.55900:02:39.569 here right onto the here okay you have 00:02:42.31900:02:42.329 your one to three burner assemblies 00:02:47.36000:02:47.370 right there and you have on this side 00:02:49.94000:02:49.950 your flame rollout switch okay this is 00:02:52.52000:02:52.530 your flavor off switch on this one you 00:02:55.19000:02:55.200 can see that the problem occurred over 00:02:58.30900:02:58.319 on this side alright so there was no 00:03:01.84900:03:01.859 flame rollout switch over here and now 00:03:04.15900:03:04.169 that's why you see a lot of combustion 00:03:06.58900:03:06.599 areas have to sometimes even three flame 00:03:10.87900:03:10.889 rollout sensors that that do not 00:03:12.71000:03:12.720 automatically reset they have to be 00:03:14.11900:03:14.129 manually reset because if they do ever 00:03:16.64000:03:16.650 trip that means it is a fire in here and 00:03:18.53000:03:18.540 and there's more a bigger problem at 00:03:21.17000:03:21.180 hand okay they do not automatically 00:03:23.24000:03:23.250 reset so there was a problem here and 00:03:29.28900:03:29.299 you see that this PVC pipe actually 00:03:33.71000:03:33.720 started burning this right here 00:03:36.89000:03:36.900 plastic assembly started melting it 00:03:38.86900:03:38.879 started melting its way off of here and 00:03:40.99000:03:41.000 the fire started coming up towards the 00:03:44.05900:03:44.069 top alright you can see this alright and 00:03:46.43000:03:46.440 this assembly started getting very very 00:03:48.14000:03:48.150 hot alright and the homeowner luckily 00:03:52.39900:03:52.409 that's smelling some weird some weird 00:03:54.83000:03:54.840 smells in the house all right I believe 00:03:56.75000:03:56.760 this was right above his living area his 00:04:00.08000:04:00.090 living room okay so so anyway once again 00:04:05.78000:04:05.790 that you could have two of these working 00:04:07.81900:04:07.829 fine say say you know it's going through 00:04:09.97900:04:09.989 all the way over to here and it's fine 00:04:11.65900:04:11.669 finding its way back to here so so this 00:04:13.87900:04:13.889 pressure switch is finding negative 00:04:15.46900:04:15.479 pressure enough to close because there's 00:04:18.43900:04:18.449 a tube connected from here on to the 00:04:21.34900:04:21.359 inducer motor assembly all right 00:04:24.05000:04:24.060 but if 00:04:25.54000:04:25.550 on say say one path is clogged you you 00:04:29.23000:04:29.240 could then have a problem all right 00:04:30.93900:04:30.949 meaning that if one path is clogged 00:04:34.05900:04:34.069 then then basically the the flame is not 00:04:37.27000:04:37.280 getting sucked in here and the exhaust 00:04:38.92000:04:38.930 is not getting sucked in here it's not 00:04:40.77900:04:40.789 getting sucked in here it's just you 00:04:43.24000:04:43.250 know rising heat rises and it's just 00:04:44.89000:04:44.900 gonna come right here and it's gonna 00:04:45.93900:04:45.949 melt and burn everything all right so 00:04:48.82000:04:48.830 it's not good all right so now let's go 00:04:51.67000:04:51.680 ahead and take a look at the other side 00:04:54.27900:04:54.289 so here really over on this side is 00:04:56.58900:04:56.599 where the problem side is so I'm going 00:04:58.86900:04:58.879 to shift this around so that you can see 00:05:01.14900:05:01.159 what it looks like I'll also give you a 00:05:03.90900:05:03.919 quick shot from from top so that you can 00:05:06.90900:05:06.919 see what this looks like from overhead 00:05:08.70900:05:08.719 so let's do that person to give you a 00:05:10.62900:05:10.639 quick shot of what this looks like and 00:05:11.74000:05:11.750 then we'll go ahead to the back all 00:05:13.95900:05:13.969 right so this is where the flame 00:05:15.55000:05:15.560 originates right here and then you have 00:05:18.24900:05:18.259 the exhaust being pulled through this 00:05:20.64900:05:20.659 way all right then you have a little rid 00:05:23.14000:05:23.150 heat exchanger part of the primary right 00:05:25.62900:05:25.639 here comes to the back and then joins to 00:05:28.14900:05:28.159 the secondary and then it it comes right 00:05:30.79000:05:30.800 through here and any water condensation 00:05:33.70000:05:33.710 comes down towards the bottom and 00:05:35.20000:05:35.210 trickles out now here's here's an issue 00:05:38.76900:05:38.779 right okay 00:05:39.70000:05:39.710 so normal heat exchangers right made out 00:05:42.73000:05:42.740 of steel galvanized tin look here you 00:05:46.68900:05:46.699 have water condensating here all right 00:05:49.68900:05:49.699 and it's the same material it's it's 00:05:53.29000:05:53.300 it's not exactly the same material is 00:05:55.24000:05:55.250 this but it's still a material that a 00:05:58.11900:05:58.129 metal that's going to go ahead and rust 00:06:00.27900:06:00.289 regardless of what surface protection 00:06:02.86000:06:02.870 you know was put on it okay so that's a 00:06:06.45900:06:06.469 problem this is along the backside right 00:06:09.82000:06:09.830 here that was pulled off that plate was 00:06:12.49000:06:12.500 pulled off as well here is the other 00:06:17.11000:06:17.120 plate all right that holds all the 00:06:19.61900:06:19.629 exhausts you know to connect the primary 00:06:23.89000:06:23.900 to the secondary now I'm going to go 00:06:25.60000:06:25.610 ahead and switch this around so you can 00:06:26.76900:06:26.779 see what the back looks like so you have 00:06:29.80000:06:29.810 your plate right here on the inside and 00:06:33.51000:06:33.520 under this plate okay that holds 00:06:37.22000:06:37.230 all of the exhaust gas is in all right 00:06:40.52000:06:40.530 with with a gasket that runs around the 00:06:42.71000:06:42.720 perimeter now this is pretty pretty 00:06:48.23000:06:48.240 rusted but it's still you know in good 00:06:52.37000:06:52.380 enough shape all right to hold all the 00:06:54.89000:06:54.900 exhaust gases this over here is your 00:06:57.32000:06:57.330 problem area so if you look at this side 00:06:59.90000:06:59.910 right here you can see that this is 00:07:03.38000:07:03.390 still open enough to have the pressure 00:07:06.32000:07:06.330 switch read a negative vacuum when the 00:07:09.02000:07:09.030 inducer motor is pulling all right but 00:07:11.12000:07:11.130 you look over here and this is actually 00:07:12.95000:07:12.960 clogged solid let me get you a close-up 00:07:14.75000:07:14.760 shot of this okay here's a close-up shot 00:07:18.29000:07:18.300 of where the the one burner tube shoots 00:07:23.24000:07:23.250 into the primary heat exchanger and then 00:07:25.46000:07:25.470 into the secondary heat exchanger so 00:07:26.99000:07:27.000 this spot right here okay is where it 00:07:30.50000:07:30.510 was clogging to the point where the 00:07:33.11000:07:33.120 inducer motor was no longer able to suck 00:07:35.15000:07:35.160 the exhaust gas through which meant that 00:07:37.58000:07:37.590 the flame too started burning up right 00:07:39.17000:07:39.180 all right and then started burning part 00:07:42.77000:07:42.780 of the furnace and getting very very hot 00:07:45.49000:07:45.500 and the exhaust gasses we're not getting 00:07:48.08000:07:48.090 out of the house so so right here this 00:07:50.99000:07:51.000 is completely clogged solid you can see 00:07:52.82000:07:52.830 all the flakes and stuff like that right 00:07:55.28000:07:55.290 here this is a sandwich bag all right 00:07:59.66000:07:59.670 full of roughs that just fell right out 00:08:01.79000:08:01.800 of this as soon as this was opened all 00:08:04.43000:08:04.440 right no good all right some of the 00:08:07.85000:08:07.860 things that you want to look out for 00:08:09.17000:08:09.180 when doing preventive maintenance for 00:08:10.90000:08:10.910 gas furnaces especially these older 00:08:13.96000:08:13.970 early 90s furnaces you want to look 00:08:18.29000:08:18.300 right in this area right here 00:08:20.21000:08:20.220 you know anywheres around in here for 00:08:22.13000:08:22.140 any excess that buildup okay you want to 00:08:26.27000:08:26.280 make sure that you see a flame from this 00:08:29.36000:08:29.370 side you want to see that the flame on 00:08:32.93000:08:32.940 each of these three are all getting 00:08:35.08900:08:35.099 pulled up pulled in basically in the 00:08:39.68000:08:39.690 same manner okay so you don't see like 00:08:42.77000:08:42.780 one here and one here getting pulled in 00:08:44.93000:08:44.940 real nice and straight and then this one 00:08:46.49000:08:46.500 is off a little bit okay 00:08:49.19000:08:49.200 so if you could have the correct heat 00:08:52.13000:08:52.140 exchanger say a crack you know over in 00:08:54.26000:08:54.270 here somewheres and what that would do 00:08:56.36000:08:56.370 is is everything would look fine in the 00:08:58.52000:08:58.530 burner box right here everything would 00:09:00.35000:09:00.360 look fine as far as the flames go nice 00:09:01.85000:09:01.860 blue flame and then when the blower 00:09:03.62000:09:03.630 motor turns on the blower motor pushes 00:09:06.05000:09:06.060 air across this coil like say across it 00:09:08.90000:09:08.910 but while it does that it it goes in 00:09:12.29000:09:12.300 through the crack and and it blows back 00:09:14.93000:09:14.940 out this way and and that would make 00:09:17.78000:09:17.790 this flame rollout switch pop because 00:09:19.94000:09:19.950 you'd have a flame like popping a little 00:09:21.56000:09:21.570 bit like this you know it would actually 00:09:23.51000:09:23.520 pop out but in the case of a clog heat 00:09:26.75000:09:26.760 exchanger you want to make sure that you 00:09:28.43000:09:28.440 have a good path that the flame is going 00:09:30.94000:09:30.950 going in okay like the same amount in 00:09:33.35000:09:33.360 all three or all four or five okay you 00:09:35.93000:09:35.940 know all two as well you can check your 00:09:39.20000:09:39.210 combustion analysis you know these 00:09:41.42000:09:41.430 furnaces basically are basically preset 00:09:45.71000:09:45.720 the only thing that you can adjust on 00:09:47.21000:09:47.220 these furnaces is the actual amount of 00:09:50.57000:09:50.580 gas getting coming into these verses 00:09:55.79000:09:55.800 right here alright so you could adjust 00:09:58.01000:09:58.020 them with a combustion analysis reader 00:10:00.76000:10:00.770 and also in this case you could check 00:10:03.62000:10:03.630 that again once again just doing your 00:10:05.18000:10:05.190 preventive maintenance and making sure 00:10:07.28000:10:07.290 things are still you know within their 00:10:09.56000:10:09.570 acceptable levels now you could 00:10:11.45000:10:11.460 disconnect the tube off of your pressure 00:10:13.34000:10:13.350 switch and connect that to your digital 00:10:15.74000:10:15.750 manometer in order to get a water column 00:10:18.68000:10:18.690 reading off of your inducer motor 00:10:20.69000:10:20.700 basically verifying how much you're able 00:10:24.59000:10:24.600 to to suck through okay the problem with 00:10:28.37000:10:28.380 that is a lot of times manufacturers 00:10:30.11000:10:30.120 that it doesn't have what it should be 00:10:31.94000:10:31.950 otherwise this would be a great way to 00:10:34.81000:10:34.820 test to see if your heat exchanger is 00:10:37.61000:10:37.620 clogging over time now if you're on a 00:10:39.74000:10:39.750 preventative maintenance schedule you 00:10:41.15000:10:41.160 could catalog you know you could write 00:10:44.48000:10:44.490 down the reading that you're getting 00:10:45.95000:10:45.960 with your digital manometer and if you 00:10:47.87000:10:47.880 see a decreasing over time that could be 00:10:51.35000:10:51.360 an indication that this is clocking not 00:10:53.36000:10:53.370 firing so just keep that in mind as 00:10:54.89000:10:54.900 you're doing your preventative 00:10:56.24000:10:56.250 maintenance and you can always go back 00:10:58.37000:10:58.380 on your your 00:11:00.67000:11:00.680 your service invoices that you filling 00:11:02.74000:11:02.750 out during the preventative maintenance 00:11:04.13900:11:04.149 you can always use them those are a 00:11:06.73000:11:06.740 great tool you know just to test for to 00:11:09.79000:11:09.800 show degradation in a furnace alright so 00:11:13.06000:11:13.070 on some of these early 90s heat 00:11:14.98000:11:14.990 exchangers that typical warranties were 00:11:16.96000:11:16.970 running right around 20 year warranty on 00:11:19.81000:11:19.820 the heat exchanger and in it tends to 00:11:23.76900:11:23.779 take quite a while to replace a heat 00:11:25.51000:11:25.520 exchanger could take say 3-4 hours 00:11:27.13000:11:27.140 basically you have to take all of the 00:11:29.92000:11:29.930 items out that are in front of the heat 00:11:31.57000:11:31.580 exchanger in order to get to it and then 00:11:33.57900:11:33.589 reinstall it and Gascon it all up 00:11:35.35000:11:35.360 properly so a lot of customers tend to 00:11:38.50000:11:38.510 end up upgrading to a higher efficiency 00:11:42.16000:11:42.170 furnace it have a clog or a crack in the 00:11:44.07900:11:44.089 heat exchanger but in some cases labor 00:11:47.68000:11:47.690 is included from the manufacturer 00:11:50.13900:11:50.149 especially if there was some type of a 00:11:51.79000:11:51.800 suit that was wrong against the 00:11:53.62000:11:53.630 manufacturer of the equipment due to a 00:11:56.07900:11:56.089 failure a recognized failure you know 00:11:59.17000:11:59.180 within the time period about 20 years a 00:12:01.26000:12:01.270 lifespan but you have to take the model 00:12:05.29000:12:05.300 number of your furnace and then also 00:12:07.24000:12:07.250 find the installation date of the 00:12:09.51900:12:09.529 furnace and if you don't have say a 00:12:11.38000:12:11.390 initial proposal bill from the 00:12:14.01900:12:14.029 installation then you're gonna have to 00:12:15.91000:12:15.920 go by the serial number of the furnace 00:12:18.01000:12:18.020 in order to determine what the ages but 00:12:21.16000:12:21.170 you know in order to find out if you 00:12:23.11000:12:23.120 would fit within that time period but 00:12:25.39000:12:25.400 anyway I just wanted to give you a quick 00:12:26.65000:12:26.660 rundown of that in reference to the 00:12:28.69000:12:28.700 primary and secondary heat exchanger 00:12:30.37000:12:30.380 just so you are aware of that and I hope 00:12:32.86000:12:32.870 you enjoyed yourself we'll see you next 00:12:34.06000:12:34.070 time at easy service section
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