Heat exchanger location

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Tjcole50

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Kind of hard to describe and will try to get another pic up later. The area below whats marked in red looks perfrect but the back side is curved and narrows toward the main split or T off the plenum. This makes an install seem harder to me and also cuts down on the size of hx i can use. So i was thinking of useing the area marked in red to put the exchanger. My concern was how to support the sides of the hx when installing since the split angles out ward. I am also wondering if air passing around the heat exchanger will effect the performance if that makes any sense. I guess maybe all of the air wouldnt pass through the hx and leak around it
b0b1edd6f0367715743e3ff19c559e52.jpg


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I had the furnace installer put mine in so not sure how they supported it or how much space there is around it. With a gap there will be performance loss, but I doubt it would be enough to make much difference. I like the fan to run and get the air circulated anyway and a slower heat is more even.

Maybe others who are better experts will chime in.
 
Hey TJ, is that a Lennox High Efficiency? If so, you're in for a lifetime of cracked heat exchangers, I have almost the same furnace and the service technician told me that the Lennox is known for this problem, mine cracked less than a year after being replaced for the 2nd time. I use wood to heat and the fan on the furnace to circulate, also! Best of Luck!


Dave6390 in WI
 
You got the right idea. I'd try to put it a little lower if possible though. Personally, I would cut a window in one side the height of the heat exchanger and then I would pop river some 90* aluminum angle to the inside. Then I would slide the heat exchanger in. I'd use some tape foam on the edges of the heat exchanger to make a seal to the aluminum angle and the back of the duct. Get some flat sheet metal and fab a door covering for the hole you just cut and make it so the HTX connections come though. Probably use some self tappers and more foam. I would try to minimize any bypass because it will make it less efficient and you will end of running the fan longer to get the living space to temperature. Running the fan costs money. Not sure if the HTX needs any type of hold down pressure or not...
 
Why would the heat exchanger crack? Furnacr has been here for many years before i moved in. Not problems knock on wood. Here is a picturr of the sloped back side. I csnt slide my hx in from thr front like in first pictue becaue thr lineset is in the way having a very hard time finding a proper sized hx. The front where line is is actually 17.5" wide. Front to back sloped side at 3.5" tall is 18". I was debating on doing a 18x18 hx would have a 1/2" hanging outdide the duxt work cause any problems if i foil taped thr hell out of it?
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Or theres this idea furnace is configured so stupid no way to turn a trunk and do a return air
2f345d30e372b211b0347759941b0467.jpg


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Or theres this idea furnace is configured so stupid no way to turn a trunk and do a return air
2f345d30e372b211b0347759941b0467.jpg


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Tjcole50,

I hope you're not planning on installing the heat exchanger on the return air side of the furnace (due to over heating the blower motor itself). I had come across two jobs because of this problem happening. You can metal fab. above the A/C coil case by boxing it out like instead.

Henry
 
Gotcha yeah i just got done reading about that. I noticed from my first pic showing that slanted transition duct is not a weihht supporting piece indont think... so i was thinking about just cutting thay section out and building a nice little frame with no gaps for hx. Then just buy sheets of sheet metal and cut square pieces and just box it in useing foil tape on the corners to hold it together or is that to rigged?? Would sure be easy that way. I have no tools to make good bends in sheet metal is the reason and im grtting crunched on time then longer i delay. Also is a 100k btu hx plenty or does it need to be larger?
 
Tjcole50,

I hope you're not planning on installing the heat exchanger on the return air side of the furnace (due to over heating the blower motor itself). I had come across two jobs because of this problem happening. You can metal fab. above the A/C coil case by boxing it out like instead.

Henry
He could get a high temp motor, no?
Simplest solution would be to just have a HVAC/tin knocker mod that transition area to fit the HX in there proper like, shouldn't cost that much. I had a metal shop price out a whole new plenum for me a few years back...$200.
I suppose you could cob it together with some tin n tape but from what you describe it sounds like only part of the HX would see good air flow
 
I'd buy some sheet metal and build a new plenum for the heat exchanger myself. Only need some tin snips a marker a tape measure some boards to help bend the metal and a pop rivet gun. Harbor freight has all of those things and even probably the material. It would be plenty ridged if you bend the metal and not cut individual panels and tape them together. You can practice on some cardboard first to make a template.
 
Hey TJ, is that a Lennox High Efficiency? If so, you're in for a lifetime of cracked heat exchangers, I have almost the same furnace and the service technician told me that the Lennox is known for this problem, mine cracked less than a year after being replaced for the 2nd time. I use wood to heat and the fan on the furnace to circulate, also! Best of Luck!


Dave6390 in WI
Are you propane? Lennox heat exchanger shouldn't crack within a year or ANY manufacturer! Your furnace guy sucks, if it's a propane g26 they fire at 7.5 "wc NOT the industry standard 10"wc. I've seen that happen but it boils down to bad service guy not product[emoji6]


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I hear ya, I basically use wood to heat and use the fan to circulate, but when it's-30/-40*F outside the furnace does occasionally kick on, but I've had 2 different guys come in to check it out and they both say it's the model of furnace, they get called out on all the time.


Dave6390 in WI
 
You got the right idea. I'd try to put it a little lower if possible though. Personally, I would cut a window in one side the height of the heat exchanger and then I would pop river some 90* aluminum angle to the inside. Then I would slide the heat exchanger in. I'd use some tape foam on the edges of the heat exchanger to make a seal to the aluminum angle and the back of the duct. Get some flat sheet metal and fab a door covering for the hole you just cut and make it so the HTX connections come though. Probably use some self tappers and more foam. I would try to minimize any bypass because it will make it less efficient and you will end of running the fan longer to get the living space to temperature. Running the fan costs money. Not sure if the HTX needs any type of hold down pressure or not...

Almost exactly how I set mine up last year...minus the rivets. All self tappers for me. Used some heavy gauge aluminum to make a tray for it to sit on. Foam tape to reduce any vibration and to seal any gaps.

I though I had more pictures, but this is all I can find. It's mounted right above the A coil, similar to the placement in your first pic.

e5b403bbaf9200526d518a0da5863759.jpg



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You got the right idea. I'd try to put it a little lower if possible though. Personally, I would cut a window in one side the height of the heat exchanger and then I would pop river some 90* aluminum angle to the inside. Then I would slide the heat exchanger in. I'd use some tape foam on the edges of the heat exchanger to make a seal to the aluminum angle and the back of the duct. Get some flat sheet metal and fab a door covering for the hole you just cut and make it so the HTX connections come though. Probably use some self tappers and more foam. I would try to minimize any bypass because it will make it less efficient and you will end of running the fan longer to get the living space to temperature. Running the fan costs money. Not sure if the HTX needs any type of hold down pressure or not...
This
 
I hear ya, I basically use wood to heat and use the fan to circulate, but when it's-30/-40*F outside the furnace does occasionally kick on, but I've had 2 different guys come in to check it out and they both say it's the model of furnace, they get called out on all the time.


Dave6390 in WI
Get a third guy! No furnace set up properly should do that! Something is wrong with burners, firing rate or airflow. give me the model and serial . Been a heating guy for 25 years


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Had the pros out... he asked how long the return air has pulled off the basement i said since it was built... he asked any problem heating or cooling i said no... he said spend the money if you want but really not needed sure it will boost efficiency. Think he was beingprettu real n straight forward with me. Any way he said 200$ he would build a return air box and a slot for the hx and air filter.. he walked out the door i said screw that and framed up a 2x4. 3.5 inch space for hx slide right in extend one more 2x4 and i have a filter slot. Now whicu direction does thr hx prefer or does it not matter? Also i figured wood was safe for this seeing as the hx only hits 180-200 degrees on high side. Any input or cautions greatly appreciated
9d57845a4c2ea80952bbf0b1db9e9b8e.jpg


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Which ever is more conveient to plumb or looks the best. I don't think it matters. Ideally it should be on the discharge of the fan. You might change it if the flow and pressure drop too far from installing it on the inlet side or after you burn up your first fan motor.
 
Had the pros out... he asked how long the return air has pulled off the basement i said since it was built... he asked any problem heating or cooling i said no... he said spend the money if you want but really not needed sure it will boost efficiency. Think he was beingprettu real n straight forward with me. Any way he said 200$ he would build a return air box and a slot for the hx and air filter.. he walked out the door i said screw that and framed up a 2x4. 3.5 inch space for hx slide right in extend one more 2x4 and i have a filter slot. Now whicu direction does thr hx prefer or does it not matter? Also i figured wood was safe for this seeing as the hx only hits 180-200 degrees on high side. Any input or cautions greatly appreciated
9d57845a4c2ea80952bbf0b1db9e9b8e.jpg


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Tjcole50,

I hope this furnace doesn't had high limit manual reset switch type located in the blower compartment (just in case you tried to run the gas furnace again and will not fired up), you'll have to remove the lower panel and push the red reset button (if this have this type), and I have been on service call due to of this happening. Are you going to leave this air filter setup like you had now, your heat exchanger will eventually get all loaded up and start slowing down your air flow and will take out your blower motor like I had seen twice (over heated and bearing grease running out on both end of the motor,burnt winding, ect..). I'm just trying to give you a head up for what I have come across in this type of work I see happening.

Henry,
 
I would make a filter slot for incoming air ahead of the hx. Should be easy to get to and clean if need be
 
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