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  1. #1
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    Default Furnace air intake/exhaust location

    Hello,

    I was watching Holmes Inspection on Netflix the other day and came across episode where they are venting furnace into A/C unit outside, which they said was illegal. Reason being if furnace exhaust contains any flammable gas and if there is short in electrical, it would ignite. I take look outside and mine is exact same way, so i got concerned. I know they are in Canada and I'm in Michigan, but still, if it's concern there, it should be concern here.

    Furnace is 100,000BTU, 95.5% efficiency. Home is new construction and we just moved in, in Sep 2014

    Can someone tell me if what you see in the attached pictures is per code? Also additional question, water heater exhaust is less than 3 ft from furnace intake, is that per code?

    Distance exhaust to a/c 16"


    Intake to a/c 16"


    Furnace intake to water heater exhaust 33"


    Exhaust to window 12" (my understanding is ok, but borderline, for 100,000btu furnace)


    Water heater exhaust and furnace intake are both at 15" off the ground, which i think is too low considering we get sometimes 10-15" of snow, but code doesnt seam clear 12" off the ground or expected snow height

    http://s692.photobucket.com/user/djo...gxgze.jpg.html



    Thank you all for help in advance

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  2. #2
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    Default Re: Furnace air intake/exhaust location

    I would be concerned about the height above the ground. Here in NJ, the intake/exhaust must be 18 inches above the ground or roof. That's 12 inches above the anticipated snow level which is 6 inches here. I'm sure the snow level in Michigan is more than that of New Jersey.

    Darren www.aboutthehouseinspections.com
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  3. #3
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    Default Re: Furnace air intake/exhaust location

    I don't see the connection between a/c and raw natural gas being pushed out the exhaust from the furnace. There are built in safety features which would shut the furnace down or not allow it to operate if there is no ignition. Also furnace cannot run while a/c is on and vice versa.

    Sometimes Mike says things for affect.

    Refer to installation manual for furnace and a/c for clearance requirements.

    Also these are generally accepted clearances in the dia.

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  4. #4
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Darren Miller View Post
    I would be concerned about the height above the ground. Here in NJ, the intake/exhaust must be 18 inches above the ground or roof. That's 12 inches above the anticipated snow level which is 6 inches here. I'm sure the snow level in Michigan is more than that of New Jersey.

    how do you find out what the anticipated snow levels are for the area, is there a number specified by code? There are days when we get 15" of snow here, not very often, but still sometimes.


  5. #5
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    Default Re: Furnace air intake/exhaust location

    I would say that there is a slight potential for more corrosion of the AC unit then if the vent was higher or somewhere else.

    Regarding the leakage of gas and explosion, I'd worry about the sky falling before worrying about that.


  6. #6
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    Default Re: Furnace air intake/exhaust location

    thank you all for your help


  7. #7
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    Default Re: Furnace air intake/exhaust location

    No one mentioned that the disconnect is blocked by the condenser unit ...

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  8. #8
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Jerry Peck View Post
    No one mentioned that the disconnect is blocked by the condenser unit ...
    Can you please elaborate, im not sure what is disconnect? Thanks


  9. #9
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    Default Re: Furnace air intake/exhaust location

    The disconnect is off to the edge of the condenser, looks accessible to me.

    The condenser is the unit outside, and the evaporator is the A frame coil which is located in the supply plenum of the furnace.

    See schematic.

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    Last edited by Raymond Wand; 06-01-2015 at 04:43 AM.

  10. #10
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Raymond Wand View Post
    The disconnect is off to the edge of the condenser, looks accessible to me.
    Not entirely off the edge of the condenser unit, at least does not look it to me, thus the required working space in front of the disconnect is not provided.

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  11. #11
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Jerry Peck View Post
    Not entirely off the edge of the condenser unit, at least does not look it to me, thus the required working space in front of the disconnect is not provided.
    I'm not sure I have ever seen one with the required working space (a slight exaggeration, but not by much).


  12. #12
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Mark Reinmiller View Post
    I'm not sure I have ever seen one with the required working space (a slight exaggeration, but not by much).
    On a side note ...

    Anyone writing up missing locking caps on the refrigerant ports?

    Anyone trying the locking caps to see if they resist removal? Many more will simply unscrew than you would think - either defective design or defective installation ... or both.

    Jerry Peck, Construction / Litigation Consultant
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  13. #13
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Djordje P View Post
    how do you find out what the anticipated snow levels are for the area, is there a number specified by code? There are days when we get 15" of snow here, not very often, but still sometimes.
    I sent a letter to the DCA (state board on building codes) and attached is their response.

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    Darren www.aboutthehouseinspections.com
    'Whizzing & pasting & pooting through the day (Ronnie helping Kenny helping burn his poots away!) (FZ)

  14. #14
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Djordje P View Post
    Can you please elaborate, im not sure what is disconnect? Thanks
    It's the gray enclosure on the wall I am measuring to in the annotated photo I posted.

    That is where you "disconnect" power from the unit so it can be serviced safely. The disconnect is required to have a safe working space (level, nothing intruding into it, such as those refrigerant lines, etc) in front of the disconnect. The minimum size of the safe working space is 30" wide by 36" in front of the disconnect. The 30" width measurement can slide side-to-side or be centered in front of the disconnect, but side-to-side would mean measuring from one side of the disconnect (the right side in the photo) and out 36" in front of the disconnect with nothing in it ... but your condenser unit looks to be within the working space where I have it marked.

    No one has said this yet, but you mentioned "I was watching Holmes Inspection ... ", don't base anything on what you see on TV, it is, after all, just a "TV show". It may be based on real life situations, but don't take it as good work, building practices, or codes ... it is a TV show and Mike Holmes manages to take a lot of money to the bank from it, just like actors do from their TV shows.

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  15. #15
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    Default Re: Furnace air intake/exhaust location

    I don't see an issue with the furnace exhaust but I really don't think the water heater exhaust is going to help that condenser cool down the refrigerant during the summer when someone is taking a nice hot shower. Dumb location for either the exhausts or the condenser. At least the dryer vent isn't back there also! I would have a plumber extend the water heater exhaust where it won't get drawn into the condenser.


  16. #16
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    Default Re: Furnace air intake/exhaust location

    On a side note, never seen brick installed below ground level and parted over. Would this not attract moisture to bricks and when freezes they crack.

    - - - Updated - - -

    On a side note, never seen brick installed below ground level and parted over. Would this not attract moisture to bricks and when freezes they crack.


  17. #17
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    Default Re: Furnace air intake/exhaust location

    Honestly i dont know, ill look at other houses in the sub to see if its the same


  18. #18
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Ermanno D'Angelo View Post
    On a side note, never seen brick installed below ground level and parted over. Would this not attract moisture to bricks and when freezes they crack.
    Looks like thin brick adhered to the edge of the slab as the ground level drops.

    Starts out showing the edge of the slab, then one row of that brick below the through-wall flashing, then two rows, then ...

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  19. #19
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    Default Re: Furnace air intake/exhaust location

    Quote Originally Posted by Ermanno D'Angelo View Post
    On a side note, never seen brick installed below ground level and parted over. Would this not attract moisture to bricks and when freezes they crack.

    - - - Updated - - -

    On a side note, never seen brick installed below ground level and parted over. Would this not attract moisture to bricks and when freezes they crack.

    Around here where it gets cold and most houses have basements it is common for brick to extend below grade. I'm not saying its a good practice, but I can't ever recall seeing deterioration or damage near grade grade or below (when I have dug adjacent to FWs) with any modern brick houses.


  20. #20
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    Default Re: Furnace air intake/exhaust location

    Codes dictate there has to be a clearance from bottom of brick to grade. Six inches is usually required. Clay brick below grade will suffer the consequences.


  21. #21
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    Default Re: Furnace air intake/exhaust location

    One point to mention:

    I do know that many of the condensing units have specific language on their locations stating that they should be certain distances from any exhausts from combustible gases. the reason is that the exhaust contains certain compounds that accelerate deterioration of the fins on the unit.
    Although it is a recommendation, I do not know if I would call it a defect, as this was probably written for older furnaces that burned less efficiently and had more corrosive exhaust. The same reason that high efficiency exhausts can now be located closer to window openings (1 foot versus 4 foot) = cleaner exhaust.


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