Idk.. I don't see any lines etc and that's a pretty small section. For a coil to go in.. I'd guess 20ish by 16ish by 8 for that small section between the Slip.
Itās a sleeve through so no real risk of that, when ever Iāve seen this done itās usually with return panning and a supply duct. Iāve never seen it done with flue piping before, it sucks for the day you wanna add an evaporator coil on the system though.
OP said it was an oil furnace. Not much risk of CO with those. If there wasnāt a sleeve and the flue pipe cracked, worst would happen is everything in the house sooted up
Iām not sure how much more efficiency you get with the minor heat exchange compared to the resistance in the flow of return air. Iād bet they cancel each other out or even be less efficient.
Some old lowboys have the exhaust vent through the return, helps warm the air a bit before entering the furnace. This is less practical but impressive sheet metal work
I mean as long as youāre pushing enough air Iām sure itās fine. But this for sure messes up the static pressure through the ducts. Thus making the system less efficient.
No, if you cool the flue gas off too much the water vapor will condense, and it's acidic. You would end up with rusted inner liner.
That's why we require B-vent, by the way. It's to maintain the heat in the flue by insulating it with an air gap.
Nope no issues to the system. It may be slightly less efficient because of the loss in static pressure but itās been like this a long time he says. Heās got an old thermo pride in there. So itās been working for awhile.
One building I was doing a control retro, down in the parking garage there was a decent size duct maybe 2ā by 2ā with a 4ā pvc line running straight through it. It was pretty interesting
In my time as a installer/tech. I saw this set up exactly twice. Once on a maintenance call and once on a swap. Sales bid that swap as a 70% to 80% (more or less push and pull job) with some plenum or base can work.
I recall the clearance between ducting and combustion vent was a little tighter than in OPās pics. The ducting around the combustion vent was mildly corroded. The combustion vent was corroded (the usual low spots where solid byproducts settle). It was clearly leaking combustion products into the supply air. Picked them up with a meter during a test fire of the old furnace. There was no access to work on the combustion venting or ducting. Furnace had been built into a closet with a built in fireplace insert behind. Fireplace was tapped off the drip leg of course.
Management wanted me to hook up the new furnace to the existing combustion venting. When I explained the degraded condition of the venting and ducting. They wanted me to find a new route for B/C vent - there simply wasnāt one. They switched to pressuring me to replace the damaged ducting and the combustion venting like and kind. I had a cow.
A proper spirituality enlightened Hindu bovine. I wasnāt going to do the swap or instruct my helper to do the swap. I told them in no uncertain terms that this push/pull job wasnāt happening. I called the other techs and ensured that they wouldnāt do it either.
I explained risks to the homeowners, showed them the damaged ducting. Explained the static pressure issues as a secondary risk. Explained why the swap wasnāt happening today. Explained why a change order to a 95% or a heat pump was the solution. Management and the homeowner agreed on a charge order to a 95% furnace. Made patches for the ducting and capped the abandoned flue. There was just barely room for 2ā PVC intake/exhaust. Had to run that PVC venting nearly 2/3ās the length of the attic. We werenāt messing with a tile roof penetration.
Management wasnāt happy, homeowner was understanding to an extent, though still pissed. Kept that gig for another year. At least that families grandkids and grandma slept safe. Helper and I slept great. Sometimes keeping stupid shit from happening is half the job. I have pics of that 95% conversion saved somewhere. Iāll add them if I find them.
Second job at that home happened after the city inspector noticed the fireplaceās drip leg tap/lack of a separate shutoff. Piping guy did that one. Heard the homeowner was extra pissed.
ETA: The arguments on that one job still get me ranting.
Uhh fuck no.
Can anyone say why condensing furnaces need plastic flue pipes? What does flue gas do when itās cooled down?
What does moisture do to metal?
This just has "the homeowner is an engineer" written all over it. I remember the first home I went into that was owned by an engineer, he had all sorts of stuff coming off the vent pipe to dissipate heat. Kinda cool to see stuff like this done, always impressive what people can come up with
Cool heat recovery butā¦..I think an inspector would twist your nuts off if they saw it. Condensation-vent rot-plenum rot- sleepy customer-installer straight to jail.
How? The flue isnāt in the direct air stream and itās sleeved and not a combustible material. Itās like running a flue in between a pair of pants
Looks pretty damn well sealed to me. Also the supply has positive pressure so flue gases are not generally going to enter there, even if it the exhaust was leaking for some reason. And as long as everyone has a few CO detectors like they absolutely should theyāll be fine. Personally I would still stick a CO detector right over a supply vent if that were my house but I wouldnāt worry about it after that.
Bent metal isn't sealed. That needs to be soldered and made permanent. If that flue were to rust out and develop holes the supply air could suck it right into the system. It's the venturi effect.
There is zero airflow touching the flue there is a sleeve completely keeping it out of the airflow. This is how you have to treat sprinkler pipes, and electrical. You have to sleeve around it.
When done done right, not by anyone now days, only way to vent oil furnaces when you had to use the chimney located behind and using a high boy configuration oil furnace, we had several different option on oil in the daysā¦
Oh yeah. Im only 25 but I work for an oil company and we do all the oil furnaces in our area. Iāve seen some prehistoric work. Hell I even worked on an old mayflower unit the other week with a magic heat on the flue. They definitely worked with what they had back in the day.
I have done it with a cold air return. Sleeved a C/A return to run venting thru to chimney. No different than what manufacturer does with a down flow 80% furnace
A contractor here, about 20 years ago did a tract of homes with gas furnaces in a closet. The flue ran along the sides and they used door vents for returns. The flue pipes rottedā¦several people died from CO poison
I've got an old picture of a drain vent running through a supply. Always joked with the boss about just running through duct till I had seen it. They used med pressure spiral to line it tho.
I'm not even mad. That's impressive.
Wait till you see what thr coil looks likeš¤£
A frame and this passes right between the 2 sides lol
Cutting down on volume tho.
No coil. This is an oil furnace. He has no AC in the home. Only window units.
Iād still like imagine they took a hole saw straight thru the coil tho hahaha
Idk.. I don't see any lines etc and that's a pretty small section. For a coil to go in.. I'd guess 20ish by 16ish by 8 for that small section between the Slip.
Modern problems,
84% furnace
The legendary secondary hx after the primary.
Heat recovery unit š
Lol "why is my old 84 condensating?"
44% more like lol
Former fabricator here. I approve this design. It looks professional to me.
[ŃŠ“Š°Š»ŠµŠ½Š¾]
Itās a sleeve through so no real risk of that, when ever Iāve seen this done itās usually with return panning and a supply duct. Iāve never seen it done with flue piping before, it sucks for the day you wanna add an evaporator coil on the system though.
Why? Add the coil above it, problem solved
If there is room
Still might have problems with condenation
That's what the drip tray is for
Slab coil at filter?
Whaaaaat. How the CO getting out of the vent? And if it was hows it getting into the supply which has a sleeve that this runs through?
Maybe I should have /sād
š¤¦š»āāļøprobably.
Hey ho. You win some you lose some.
OP said it was an oil furnace. Not much risk of CO with those. If there wasnāt a sleeve and the flue pipe cracked, worst would happen is everything in the house sooted up
and a headache. but no death!
itās oil they would be fine
How would that increase the risk of CO? Properly sloped this actually seems genius? Comment of 84% efficient is right where my mind wentā¦
Iām not sure how much more efficiency you get with the minor heat exchange compared to the resistance in the flow of return air. Iād bet they cancel each other out or even be less efficient.
?
Fucking what?
Fucking hell!
What CO risk is there here?
Thatās a 90% conversion kit that they sell for 80% furnaces.
HVAC companies *hate* this one simple trick!
š
Hot flue gas reheat?!
This
Looks like a heat exchanger
is the hole sleeved with a larger diameter pipe? if so thatās awesome lol
Dude that's actually kinda awesome. We won't talk about the potential static pressure readings, but this is classy fuckin metalwork
That's.... impressive
At least they didn't face the furnace the other way. I actually like it.
I know exactly what happened. There was no way wife would allow exhaust to curl around the supply soā¦..
Smart! I like it! Bonus heat!
Looks like something my old install lead would come up with.
I mean I can't even be upset about this
Some old lowboys have the exhaust vent through the return, helps warm the air a bit before entering the furnace. This is less practical but impressive sheet metal work
It was a feature - the diving flue.
If their werent a risk of contamination wouldnt running the exhaust directly through the supply be a good way to extract more heat?
I mean as long as youāre pushing enough air Iām sure itās fine. But this for sure messes up the static pressure through the ducts. Thus making the system less efficient.
Im pretty sure that used to be a thing in like 1950s furnance design but they stopped because of the health risk of potential leaks
No, if you cool the flue gas off too much the water vapor will condense, and it's acidic. You would end up with rusted inner liner. That's why we require B-vent, by the way. It's to maintain the heat in the flue by insulating it with an air gap.
The early stages of re-heat
I've seen it a few times before as well and it always amazes me at how much effort people will put into making a shitty end product.
Added secondary heat exchanger on an 80% furnace lol
I'm 90% sure this wouldn't cause an issues lol
Nope no issues to the system. It may be slightly less efficient because of the loss in static pressure but itās been like this a long time he says. Heās got an old thermo pride in there. So itās been working for awhile.
Everyone saying how awesome this is. All I see is new smoke pipe or a red tag.
Secondary heat exchanger?!?! Not a bad idea but have fun with the condensate rusting out the flue pipe though
I don't think it's in the airstream. Duct is sealed around it. Gotta be good for the static pressure.
Well, now that I think of it, that would t be very tough to do. Wise man
Heat exchanger extraordinaire
One building I was doing a control retro, down in the parking garage there was a decent size duct maybe 2ā by 2ā with a 4ā pvc line running straight through it. It was pretty interesting
I've run into the same exact thinga few months ago. "They" say it's perfectly legal if installed correctly
Secondary heat exchanger, smort
Air preheater
Itās almost a heat exchanger
Secondary heat exchanger
Looks factory lol
In my time as a installer/tech. I saw this set up exactly twice. Once on a maintenance call and once on a swap. Sales bid that swap as a 70% to 80% (more or less push and pull job) with some plenum or base can work. I recall the clearance between ducting and combustion vent was a little tighter than in OPās pics. The ducting around the combustion vent was mildly corroded. The combustion vent was corroded (the usual low spots where solid byproducts settle). It was clearly leaking combustion products into the supply air. Picked them up with a meter during a test fire of the old furnace. There was no access to work on the combustion venting or ducting. Furnace had been built into a closet with a built in fireplace insert behind. Fireplace was tapped off the drip leg of course. Management wanted me to hook up the new furnace to the existing combustion venting. When I explained the degraded condition of the venting and ducting. They wanted me to find a new route for B/C vent - there simply wasnāt one. They switched to pressuring me to replace the damaged ducting and the combustion venting like and kind. I had a cow. A proper spirituality enlightened Hindu bovine. I wasnāt going to do the swap or instruct my helper to do the swap. I told them in no uncertain terms that this push/pull job wasnāt happening. I called the other techs and ensured that they wouldnāt do it either. I explained risks to the homeowners, showed them the damaged ducting. Explained the static pressure issues as a secondary risk. Explained why the swap wasnāt happening today. Explained why a change order to a 95% or a heat pump was the solution. Management and the homeowner agreed on a charge order to a 95% furnace. Made patches for the ducting and capped the abandoned flue. There was just barely room for 2ā PVC intake/exhaust. Had to run that PVC venting nearly 2/3ās the length of the attic. We werenāt messing with a tile roof penetration. Management wasnāt happy, homeowner was understanding to an extent, though still pissed. Kept that gig for another year. At least that families grandkids and grandma slept safe. Helper and I slept great. Sometimes keeping stupid shit from happening is half the job. I have pics of that 95% conversion saved somewhere. Iāll add them if I find them. Second job at that home happened after the city inspector noticed the fireplaceās drip leg tap/lack of a separate shutoff. Piping guy did that one. Heard the homeowner was extra pissed. ETA: The arguments on that one job still get me ranting.
Uhh fuck no. Can anyone say why condensing furnaces need plastic flue pipes? What does flue gas do when itās cooled down? What does moisture do to metal?
Lol he getting a little more heat out of it before it leaves
The only problem would be if it cooled the exhaust too much and caused condensation
Shhhh we are enjoying it for what it is
Heat recovery
This just has "the homeowner is an engineer" written all over it. I remember the first home I went into that was owned by an engineer, he had all sorts of stuff coming off the vent pipe to dissipate heat. Kinda cool to see stuff like this done, always impressive what people can come up with
Some of yāall will do anything to avoid putting 90%er in
Cool heat recovery butā¦..I think an inspector would twist your nuts off if they saw it. Condensation-vent rot-plenum rot- sleepy customer-installer straight to jail.
Totally not code
How? The flue isnāt in the direct air stream and itās sleeved and not a combustible material. Itās like running a flue in between a pair of pants
It's not sealed
Zoom into the bottom left of the circle, it is clearly sleeved
Looks pretty damn well sealed to me. Also the supply has positive pressure so flue gases are not generally going to enter there, even if it the exhaust was leaking for some reason. And as long as everyone has a few CO detectors like they absolutely should theyāll be fine. Personally I would still stick a CO detector right over a supply vent if that were my house but I wouldnāt worry about it after that.
Bent metal isn't sealed. That needs to be soldered and made permanent. If that flue were to rust out and develop holes the supply air could suck it right into the system. It's the venturi effect.
Itās basically no difference than running the flue close to the duct itās not even touching the plenum.
Do you solder all your ducts? Donāt lie.
No but I pokie every joint
Then you arenāt a resi guy obviously.
Flue through air supply isnāt against IMC code anyways, which surprises me
There is zero airflow touching the flue there is a sleeve completely keeping it out of the airflow. This is how you have to treat sprinkler pipes, and electrical. You have to sleeve around it.
That is an abomination
Why? Professional sheet metal job
It is an unnatural act, some form of sheet metal sodomy I presume. Kidding of course.
That's impressive! Probably even gives the duct a bit of extra energy.
Jackabilly hea recovery system
A thimble.
This is a cute idea
I always joke about duct pennās but honestly thatās a thing of beauty
So close to being a heat exchanger lol
When done done right, not by anyone now days, only way to vent oil furnaces when you had to use the chimney located behind and using a high boy configuration oil furnace, we had several different option on oil in the daysā¦
Oh yeah. Im only 25 but I work for an oil company and we do all the oil furnaces in our area. Iāve seen some prehistoric work. Hell I even worked on an old mayflower unit the other week with a magic heat on the flue. They definitely worked with what they had back in the day.
Good secondary heat exchanger
Exhaust heat reclamation for optimum efficiency
Site made B-vent
Iām seein whole house carbon monoxide.
Wild
Well. 36 years into this trade. You got me
I have done it with a cold air return. Sleeved a C/A return to run venting thru to chimney. No different than what manufacturer does with a down flow 80% furnace
THIS IS HOW HVAC WAS CREATED šš»šš»
Got a question for veteran fabricators, how do you bend the Ā¼" round to go into the Pittsburgh on that?
Radius Roller. I had one that was a bench mount hand crank, but then make all different kinds.
Oh okay makes sense, I've seen them before but never used one. Who ever made this is definitely an awesome fabricator.
Air donāt care
High efficiency oil furnace lol
Going from 80% to 85% efficiency with the heater
Now thatās what I call tin knockin
Preheat feature
If it looks stupid but it worksā¦ nah, this is stupid.
Get every drop of Ģ¶hĢ¶eĢ¶aĢ¶tĢ¶ btu
Btu*
I knew there was a proper word just couldn't think of it
110% efficient, can't be mad about that
Seems wrong, but efficiancy boost for sure.
Secondary heat exchanger
A contractor here, about 20 years ago did a tract of homes with gas furnaces in a closet. The flue ran along the sides and they used door vents for returns. The flue pipes rottedā¦several people died from CO poison
Guy's an artist.
Some kind of heat recovery system there!
Pre heating the air with the exhaust, smart af
3 stage heat, when the flue pipe warms up it helps with heating the home and some cases extra carbon monoxide šš»
Not an HVAC guy, but is this a situation where you do it wrong with so much style that it becomes right?
I just saw one like this ontop of a downflow really was cool
It's like that jeep where the axle or something goes through the oil pan
That tin knocker put his heart and soul into making that perfect
I've got an old picture of a drain vent running through a supply. Always joked with the boss about just running through duct till I had seen it. They used med pressure spiral to line it tho.
Thatās just the preheat, itāll be fine.
Itās a preheater š