Jump to content

Downdraft or Upside down?


mgbinspect
 Share

Recommended Posts

OK, Here's one for the brain-trust.

The home I inspected Friday had a furnace installed (as a replacement) in 1999. This Ducane furnace is upside down. I understand that it has a draft inducing blower and should work, but is this OK, or is this the wrong setup for downdraft? I guess what has me wondering is that I don't fully understand why the burner HAS to be over the heat exchanger even if the distribution airflow has to be downward.

It just seems illogical to have the burners over the heat exchanger unless it's just unavoidable. Of course, with a unit laid on its side, there's really no option with an induced draft unit.

So, if this is an acceptable application, I'd still like to understand why it had to be setup exactly like this.

Thanks in advance.

Click to Enlarge
tn_2010103185133_DSCN0719.jpg

85.72 KB

Click to Enlarge
tn_2010103185233_DSCN0720.jpg

92.26 KB

Click to Enlarge
tn_201010318545_DSCN0721.jpg

29.6 KB

Click to Enlarge
tn_2010103185458_DSCN0722.jpg

35.17 KB

Of course, I know it needs impact protection and some other attention.

Link to comment
Share on other sites

Thanks Marc!

So, now there only remains the question: Why can't the furnace orientation remain up, so the draft is rising up through the heat exchanger, which would appear more efficient, even if the distribution airflow needs to be downward? Any takers?

Sure. This arrangement is better for this house because the return air is coming down from the ceiling and the supply air is going down below the floor. If you oriented it the other way, you'd need more ductwork next to the furnace.

Also, in this case, you want the air conditioner evaporator coil to be below the furnace. This way, when the blower is running, you won't get a spray of condensate all over your heat exchanger, which could cause it to rust & decay. The fact that the evaporator is downstream of the heat exchanger is also good because, if there's a refrigerant leak during the heating season, the leaking refrigerant won't hit the hot heat exchanger and turn into a toxic gas.

- Jim Katen, Oregon

Link to comment
Share on other sites

Thanks Marc!

So, now there only remains the question: Why can't the furnace orientation remain up, so the draft is rising up through the heat exchanger, which would appear more efficient, even if the distribution airflow needs to be downward? Any takers?

Sure. This arrangement is better for this house because the return air is coming down from the ceiling and the supply air is going down below the floor. If you oriented it the other way, you'd need more ductwork next to the furnace.

Also, in this case, you want the air conditioner evaporator coil to be below the furnace. This way, when the blower is running, you won't get a spray of condensate all over your heat exchanger, which could cause it to rust & decay. The fact that the evaporator is downstream of the heat exchanger is also good because, if there's a refrigerant leak during the heating season, the leaking refrigerant won't hit the hot heat exchanger and turn into a toxic gas.

- Jim Katen, Oregon

Thanks, Jim.

It's funny, I am familiar with your explanation regarding the location of the evaporator coil, but It's so rare for me to see a setup like this that I'd not given much thought to the cooling side because I was so hung up on the heating side. I gather that, even though it's probably not very significant, this setup is slightly less efficient on the heating side of the equation. Yes?

And, prior to draft inducing blowers, they would have merely dealt with the additional ductwork and kept the furnace right side up.

Link to comment
Share on other sites

This place I'm in now had a downdraft propane furnace in it. (It's gone now, I got $150 for it).There were no return air ducts, just heating ducts in the crawlspace. It was open to the hallway and just pulled return air from the surrounding area and blew down thru the heat exchanger into the ductwork below. I've seen similar setups, where a large grill is installed in the wall of the furnace room to provide return air from the living space. It is simple, but the furnace needs to be near the center of the house. The return air will always be relatively warm and dry, so maybe the heat exchanger lasts longer?

Link to comment
Share on other sites

This house was nothing to write home about, but it DID have individual returns for each room, which was pretty rare for such a low end house.

LOL,

Regional differences. Individual returns in homes after the 60's around here are scarce as hen's teeth. The biggest most expensive homes around don't even have them.

ONE TEAM - ONE FIGHT!!!

Mike

Link to comment
Share on other sites

Posted - Oct 03 2010 : 6:36:47 PM

This place I'm in now had a downdraft propane furnace in it. (It's gone now, I got $150 for it).There were no return air ducts, just heating ducts in the crawlspace. It was open to the hallway and just pulled return air from the surrounding area and blew down thru the heat exchanger into the ductwork below. I've seen similar setups, where a large grill is installed in the wall of the furnace room to provide return air from the living space. It is simple, but the furnace needs to be near the center of the house. The return air will always be relatively warm and dry, so maybe the heat exchanger lasts longer?

99 out of 100 HUD code homes are set up in this manner.

Greg

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...