This can't be right

[Alan C Grubb]

Sorry origninal post was not what I wanted to know. Posted at two in morning after long day not good thing to do. My appologies for wasting your time. Looked up manual on line and verified information.

[Michael Thomas]

Found this in home I inspected today. The pipe that is exposed to the interior of the home looks to me to be the exhaust pipe. It is the Carrier xr90series which is high efficiency. But still can't be exhausted into the interior can it?


I believe that would be a Trane xr90.

The center pipe is the inlet.

Trane recommends (reduced HE corrosion, for one thing) but does not require that combustion air be drawn from the exterior:


TRANE XR90 SINGLE-STAGE FURNACE (http://site.mypointnow.com/documents/trane-indoorHVAC/sellSheetTDX1.pdf)

When air is drawn for the interior, some manufacturers recommend or require a 90 degree bend in the intake to reduce the likelihood of accidental obstruction or that debris will fall or be drawn into the intake.

________________

Likely, that is the manual for the furnace sitting between the pipes - if so you can consult the manual for immediate answers to such questions.

[neal lewis]

Alan, did you actually operate the furnace to see if the pipe was the intake or exhaust? If air was being discharged out of the pipe, that would've been a pretty good clue right there.

Yikes

[Michael Thomas]

I think it's a bit confusing because the sight-glass for the burners is below and in line with the intake, and it seems "logical" that the flue would be above the burners (seemed that way to me at first glance, the first time I saw one), but if you pull the access panel it's clear which is the intake and which the exhaust:

http://www.butcherdistributors.com/Images/Interior/xr90_uf_cut.jpg

[Alan C Grubb]

Alan, did you actually operate the furnace to see if the pipe was the intake or exhaust? If air was being discharged out of the pipe, that would've been a pretty good clue right there.

Yikes

No Neal, it was a forclosure and the gas was off.:(

[Alan C Grubb]

I think it's a bit confusing because the sight-glass for the burners is below and in line with the intake, and it seems "logical" that the flue would be above the burners (seemed that way to me at first glance, the first time I saw one), but if you pull the access panel it's clear which is the intake and which the exhaust:

http://www.butcherdistributors.com/Images/Interior/xr90_uf_cut.jpg
Thanks Micheal your info was helpful.

[Bob Harper]

one thing to keep in mind with two pipe CAT IV furnaces is the flow and pressure gradients. The combustion chamber is under negative pressure from the combustion blower so it inhales air from the intake pipe and from gaps and cracks in the burner housing. They are not air tight in most cases. The combustion gases travel through the primary heat exchanger Down to the secondary Hx where condensate is extracted and drained. The remaining warm moist fumes then enter the blower to be exhausted out the pipe to the right under positive pressure.

Since the burner box is under negative pressure and not atmospheric pressure, they have to put a hose port referencing burner pressure to the gas combination valve's manifold pressure regulator. When I set up furnaces, I have to conduct an tedious evolution that includes tapping into this tubing with a tee to get my true manifold pressure for proper adjustment. You don't have this situation with your typical boiler, water heater or gas fireplace.


BTW, those sight glasses on Tranes are plastic that snap in rather loosely.
HTH,

[David Bell]

The most important question in this install is whether or not there is sufficient combustion air available in this basement and, if there are other appliances requiring combustion air.