mgbinspect Posted October 3, 2010 Report Share Posted October 3, 2010 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 85.72 KB Click to Enlarge 92.26 KB Click to Enlarge 29.6 KB Click to Enlarge 35.17 KB Of course, I know it needs impact protection and some other attention. Quote Link to comment Share on other sites More sharing options...
Marc Posted October 3, 2010 Report Share Posted October 3, 2010 Ducane MPGA series It's a upflow/downflow/horiz flow unit, can be modified in the field. First two pages. Marc Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted October 3, 2010 Author Report Share Posted October 3, 2010 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? Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 3, 2010 Report Share Posted October 3, 2010 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 Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted October 3, 2010 Author Report Share Posted October 3, 2010 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. Quote Link to comment Share on other sites More sharing options...
John Kogel Posted October 4, 2010 Report Share Posted October 4, 2010 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? Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted October 4, 2010 Author Report Share Posted October 4, 2010 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. Quote Link to comment Share on other sites More sharing options...
hausdok Posted October 4, 2010 Report Share Posted October 4, 2010 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 Quote Link to comment Share on other sites More sharing options...
Bill Kibbel Posted October 4, 2010 Report Share Posted October 4, 2010 The model number of that Ducane furnace starts with MPG... multi-position gas. That's the old numbering system. I have have their new one. I'll try to find it. Quote Link to comment Share on other sites More sharing options...
Greg Booth Posted October 4, 2010 Report Share Posted October 4, 2010 Posted - Oct 03 2010 : 6:36:47 PMThis 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 Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted October 4, 2010 Report Share Posted October 4, 2010 It would be really nice if manufacturers would figure out that the data plates for multi-position units should go on the covers, they're hard to read when you are laying on your back and the label is upside down under the inducer fan [:-banghea Quote Link to comment Share on other sites More sharing options...
Marc Posted October 4, 2010 Report Share Posted October 4, 2010 But the covers can be removed or interchanged. Perhaps install multiple copies of the data in various places. Marc Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted October 4, 2010 Report Share Posted October 4, 2010 Next to the view port with a single rivet in the center would work, then I could select whether I wanted to read it right side up or not[] Quote Link to comment Share on other sites More sharing options...
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