Furnace stuff

There is plenty to go wrong here, but you can repair it
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Oil use

Post by kevm14 »

kevm14 wrote:I also need to pull the flue stack off the furnace and check for soot buildup. I believe my furnace runs quite cleanly but I haven't checked this area yet.
I checked. Quite clean really. I don't know how many hot air furnace designs there are but this one looks very robust against buildup. There are really no small passages to clog. I am sure if the burner was adjusted poorly soot would cover all of the heat exchanger area but again, no small passages that would be easy to clog.

I have the LB168, biggest "low boy" in this series. Fun fact: divide output BTU by input BTU to get rated efficiency. Mine is 80% which is quite standard for oil hot air.
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So I pulled the big 8" flue pipe off. I am not sure the guy who serviced this 3 years ago even did this. If not that it's been something over 3 years since this was cleaned. It's not bad at all. That big hanging plate I think serves to slow down the heat and transfer to the heat exchanger (and air) before rushing up out of the fire box. Junk sitting on top of it may even increase the efficiency of the unit. I vacuumed it out anyway.
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10 minutes later, clean. Looking at these again, this stuff mostly didn't even look like soot. Almost seemed like the inside of the heat exchanger was painted or coated and this was the coating having peeled off. If that is the case, it has probably been a LOT longer than 3 years since the upper part of the heat exchanger was cleaned.
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I'm going to say the heat exchanger actually looks quite good.

Now, for the SECOND half of this....of which I have no pics, see that long tube that goes away from the camera in each shot? Best I can figure that is some kind of a soot trap. That pipe is a dead end but is part of the fire box area in that it probably gets quite warm when the burner is on. Right below that pipe is the return area with the filters, blower and so on. So some heat actually pre-warms the return air before getting blown up around the sides of the fire box area. I removed the access cover and vacuumed it out. It wasn't terrible but there was still probably 1/8-1/4" of crap at the bottom of it. Worse though, the very end of the pipe is actually rusting, providing a direct suction path from the flame area into the return air that eventually comes out of the vents. This is likely why I smell diesel byproducts sometimes.

I tried a few different things like cutting out a patch from an old, unused 6" flue pipe. I ended up losing one of my self tapping screws and gave up on the patch. I just shoved some pink fiberglass insulation in there to try stopping the majority of the air flow. I think what I'll do is patch it from the other side next time I change my filters.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Furnace stuff

Post by kevm14 »

My air filters were overdue by the looks of them so I changed them. I was going to patch this heat exchanger pipe thing but then I realized it just bolts in. I will see if I can track down a replacement. I left the insulation in there that I stuffed in.
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kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Thanks to my uncle I managed to order a new extension pipe and ceramic fiber insert for the firebox.

Removal of the extension pipe was pretty easy really.

Steps:
- Remove air filter access panel
- Remove air filters (mine uses 2 16x25x1 filters)
- Remove 4 sheet metal screws on the side of the panel with the big extension pipe hole. This is critical as it allows the panel to move outward to get the pipe out later.
- Remove 4 mounting bolts on the outside and remove the access cover
- Remove the 4 mounting bolts on the inside which was tricky to get access but my cordless impact and some extensions worked.
- Bend the upper panel outward making room for the extension pipe to slip below and out.

The rest is just cleaning up gasket surfaces, vacuuming crud and that kind of thing. I installed the new one so the seam is up rather than down. I thought it would be better for any moisture to sit on a solid metal surface rather than in that seam like the original one.

While the pipe came with new gaskets, it used large metal screws into some drilled holes, despite there being 4 larger round holes. The original pipe used these nut inserts. The holes were square on the original so I couldn't reuse them. So I had to use the big metal screws. On the inside, I used the original hardware as those nut inserts were still there.
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Overdue for replacement.
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Inner bolts.
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The side cover sheet metal screws.
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Old pipe out. Couldn't have taken more than 45 minutes to get to this point and that was taking my time, studying the job.
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Look ma', no pipe (has different meanings depending on where you are from)
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Old and new. They look the same other than 8 new drilled holes. I guess they didn't feel like broaching the square holes that the original had, so I could reuse the old bolts. Lame. Both gaskets are stacked on the end and were screwed in since this is a single P/N.
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Looking through the upper heat exchanger area. By the way, the point of this pipe is so the furnace can be vented on either the front or the back. Mine is vented on the front.
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Close up of the new pipe with the extra holes.
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All buttoned up using the new metal screws. I wire wheeled this cover off where the gasket goes. I also tweaked it on my vice to be flat, for best sealing.
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Ahh, look at that. Satisfying. And the family will appreciate less diesel smell.
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Shot from the inside before I tightened the screws all the way. I ended up just going full tilt on the cordless impact. That seemed about right.
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Probably had an hour or maybe an hour 15 into it at this point. Saved big bucks. I think most HVAC guys would have sold a different home owner a brand new furnace. I will need one at some point, perhaps when I do central A/C. This pipe, including freight was about $200.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Then I moved to the other side to replace the ceramic fiber insert. This would also give me a chance to clean the lower heat exchanger area for the first time in years. I'm not even sure it got cleaned when I had it serviced as part of the inspection. I knew I knocked a bunch of crap down there when I cleaned out the upper heat exchanger anyway. And there sure was some crap in there.


Steps:
- Shut off oil valves at tank and at burner
- Remove line from valve, push a little out of the way
- Remove 2 9/16" nuts holding burner to plate. Pull burner off and set aside
- Remove, uh, 14-ish 1/2" bolts holding plate to furnace, remove plate.
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It was pretty loaded with crap. This stuff decreases the efficiency of the unit obviously.
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So I cleaned it all out. Lots of junk. The contraption that holds the ceramic fiber insert just slides out.
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Old insert.
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New insert. The whole reason I did this is because I thought it had a hole in it. It did, but that is because there is a center thing that I guess it is supposed to kind of hang on so it doesn't fall over. I'm not sure I had to replace this but it DID need to be cleaned out.
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This part of the job probably took only 40 minutes. The ceramic fiber insert was $13 shipped. It is important because it is what the flame shoots at. If it became damaged, the flame would probably melt a hole in the metal heat exchanger pretty quickly. Again I think my old one was doing its job.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Total cost for all parts used: $214 including freight.

I will say again that a hot air furnace is a pretty simple device and working on it is really not a big deal.

I did test it and of course it fired right up. I detected almost no diesel smell coming out of the upstairs vents. What is left is probably soot deposits on the old filters, which I need to change before the next heating season. Or today so I don't forget...
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Decided to try the heat after running the stove the last 2 days. Came on perfectly and had no smell at all. I think we just entered heating season....
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Decided to service the furnace.

No pictures. Highlights:
- Remove flue pipe from furnace and chimney pipe, vacuum/dump out
- Vacuum upper area of heat exchanger. This is fairly easy. Make sure to run the wand all the way into the heat exchanger extension pipe (the one I replaced last time).
- Close valve at oil tank
- Close valve at furnace burner
- Disconnect oil line from filter inlet
- Loosen ignitor screws and fold open on hinge
- Loosen line going into the oil injector tube and the retaining nut
- Remove injector/ignitor apparatus, inspect. Looks fine. Still haven't changed the nozzle from somewhere in the late 2014/early 2015 timeframe.
- Remove two nuts holding the burner onto the plate, pull burner out and set aside. Inspect/clean. Not much to do there.
- Remove flange plate from furnace. An impact makes this quick. There are something like 12 bolts.
- Remove plate.
- Remove the fire stop thingy with the ceramic that I replaced last time.
- Clean lower heat exchanger. This takes a while to sweep all the tubes and vacuum the debris.

At this point I installed the plate but forgot to install the fire stop thingy. One of the bolts may have gotten cross threaded and got stuck. The cage nut spun in the furnace and I was stuck. Had to cut off the bolt with a reciprocating saw. The cage nut was not accessible so I just left it in. I ran to Ace to get a new 5/16-18 3/4" bolt and cage nut which they had but I was unable to install. I would have had to remove the entire front panel of the furnace and while I tried, I couldn't figure it out and didn't want to keep prying on it. So I gave up and just left that bolt out.

Continue reassembly in the reverse order of disassembly.

I did have another issue due to sort of not paying attention. The retaining nut that holds the injector assembly into the burner was on the wrong way. It is dished to accept the flare nut. So at first, the flat side faced out and I could not seat the flange nut. I didn't realize this at first and flipping the switch on and it sprayed a nice jet of oil sideways out of that fitting. Sweet. I tried tightening it before realizing that nut was flipped around. Once I flipped it back it was fine.

Fired it up, bled, and it was good to go. Made heat, shut it down. I didn't even replace the filter as I had previously went years between filter changes with no apparent issue. The water heater filter is due though. That will be next on my list to service.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Did another service. It was quite clean inside, especially at the top, but I still got some stuff out. Also did an oil burner service, nozzle and strainer (both first time for me, as well). Everything went fine. Another $10 in parts and a couple hours. It is simple work.

Bled, kicked heat on, let it shut off, and then I did the filters. Good to go for another season.

This takes a 1.25 80A nozzle. I did not downsize. Still a little nervous to do that without a gas analyzer to make sure the air dampers are adjusted right.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Thinking much more seriously about downsizing my nozzle to a 1.0. Now I have two reasons. First the house has been insulated and it has made a very noticeable difference. Second, I installed the great room mini split which will definitely take some load off of the furnace. I may also close down the duct dampers going to the great room which would also mean I need a smaller nozzle. It's possible that an even smaller one than 1.0 is needed but I think that's a big enough change and it's a nice round number I guess.

In order to do this safely I'd feel most comfortable with a gas analyzer. I COULD use smoke tabs but I think the instrumentation will make me feel better even though it's expensive. If I ever replace my water heater I could use the gas analyzer to setup my burner on the new water heater so and doing that DIY all by itself will pay for the instrument a few times over so that's cool.

Ended up ordering a Testo 310 from Value Testers. https://www.valuetesters.com/testo-310- ... lyzer.html

Definitely not the cheapest way to do this but it seems to be a trusted unit. Ended up getting a slightly better price than Amazon. $597.06. I probably could have gotten a different brand and a used example on eBay for half the price. Sometimes that's what I would do. In this case I just want a new, quality unit so I am not guessing about the calibration and stuff like that.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Furnace stuff

Post by kevm14 »

Got my fancy analyzer. I do think this will pay for itself when I do the water heater and paying a tech to come out, downfire my burner and adjust would probably push $300, which is half the cost of this.
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As for the 1.00 GPH nozzle, Lowes actually had the closer selection. I like to use the Delavan ones which Home Depot carries. But they do not carry the type I need. Lowes carries Durst and SEEMED to have a compatible 1.00 GPH with 80 degree hollow spray. But they called it 80D instead of 80A which I find odd.
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https://www.lowes.com/pd/Durst-Oil-Nozzle/3526164

So I probably could have just picked one of those up. But I'll wait until Monday and go to a real plumbing supply place to get the nozzle I want plus I need a filter for my oil tank and neither Home Depot nor Lowes carried the right one. This will be my first time attempting to tune an oil burner so I am not going to add variables to this process.
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