What would you say about this vent placement?

Besides needing a 90 on the air intake is there anything else wrong here ?

fast picture.jpg

For where you live, the furnace intake is too close to the exhaust. You may get a snowball in the intake and shut things down (when they are needed the most, very cold weather).

Needs a 90 and an extension.

What is min you have?
I am getting 6" so is that correct?

No issue with the bath exhaust? Just looks strange to me never see that many jammed together of one unit.

Depends on orientation. Get below the rising exhaust and you should be fine.

I see nothing wrong with the bath vent unless it sucks in when “off”. Negative building pressure from HVAC leaks to the exterior, dryer, mech vents etc.

Guess the double whammy of HWH and Furnace bothers me the most .OK thanks.

Forgot to mention lack of pest screen.

Why would you need a 90 deg on the combustion air intake? I can see needing a downward extension on it to prevent crossflow/intake from the exhaust… or having a 90 + short horizontal extension on the exhausts to blow exhaust gases away from the intake.

Here’s a home made video of a Lennox direct vent system. I inspected a house with this system on Tuesday.


Have a PDF that makes it required, will check links.

Nice to see you posting again Dave.

I checked the PDF out and it lacks detail.
Here is part of mine from Nordyne (sorry no link)

  1. Insure the combustion air inlet pipe (for a 2
    pipe installation) has a 90 degree termination
    elbow as shown in Figures 21 and 22.
    Figure 21. Alternate Horizontal
    Vent Installation
    Note: A combustion air intake must be provided
    with an elbow opening downward. The screen
    provided with the furnace must be installed in the
    elbow to prevent entry of debris or creatures.
    When the vent pipe must exit an exterior wall
    close to the grade or expected snow level, a riser
    should be provided as shown in Figure 20.
    Table 6 describes the maximum length of fl ue pipe
    that can travel through an unconditioned space
    or an exterior space. The total vent length must
    not exceed the lengths noted on Table 5.
    Vertical Venting
    Figure 23 shows the proper installation and
    clearances for vertical vent termination. The
    roof penetration must be properly fl ashed and
    waterproofed with a plumbing roof boot or equivalent
    fl ashing. Termination spacing requirements
    from the roof and from each other must be per
    Figure 23.

If I read your diagram correctly Bob, your vents should be seperated by min. 18 inches o.c.

Good (thank you) glad you saw that because I am confused here.
I have another that seems to state 6 inches in the same PDF.



Does anyone have something more definitive or different on minimum gap between intake and exhaust on cat 4 units?
Am I reading this wrong?

Also 18 inches makes more sense because it sucks fumes back in but remember they also use concentric vents (right).

One reason is you dont want (wind driven) rain to get inside the furnace intake.

There are usually provisions for draining moisture/condensate on the exhaust, but not on the intake

Very true and a good point.

That table/diagram indicates clearances to elements other than the furnace intake. So its 6" clear to the combustion air intake of any other appliance at 10,000 BTU or less (and 12" for > 50,000 BTU)

Typical spacing between the intake and exhaust pipes for the same furnace (90%+) are usually between 3" (e.g. Goodman) and 9" (e.g Trane) … your mileage might vary … :wink:

The diagram you posted earlier showing the wall termination was the correct one to get the spacing between the intake and exhaust of that furnace … BUT it looks like an older version of the Nordyne instructions that has a typo (or they changed it). It probably should read “8 to 36” spacing of the Nordyne furnace intake and exhaust per their current (90%+) furnace installation instructions.

Way beyond an inspection to get into the Mfr’s install instructions, but you seemed confused by the mfr info (it can get sticky).

I would just look for some separation between the furnace intake/exhaust (could be very minimal depending on Mfr), and an elbow pointing down for the intake (more important in my mind).

Nordyne SC-SL Furnace Venting Termination Diagram.jpg

Nordyne SC-SL Furnace Venting Termination Diagram.jpg

I find it amazing that only inches is needed when the intake is like a vacuum.Must be me.

P.S. Another reason that spacing of the intake/exhaust for the same furnace is less important in my mind (from an HI’s point of view) is that many manufacturers typically sell concentric/flush wall vent termination kits to improve the appearance … which have very little separation between the intake and exhaust for that furnace.

JMO & 2-Nickels … :wink:

Its a closed system, so it really not a big deal to draw in some exhaust thru the intake … they are designed that way … :wink:

I know and inspected one 2 weeks ago on cat 4.
Do not like that either but I do not make the rules.

All that acidic goodness back at metal.Ymmmm.

And in fact the manufacturer’s give Maximum separation distances between the intake/exhaust for the same furnace (in addition to ensuring they are under the same atmospheric pressure) … :wink:

Hope I am not interrupting your private conversation:)

Having maximum is pointless IMO (my take on it)(or intake:)) since they also allow there to be no outside pipe for it at all in the first place.:shock:

Off to the next one.