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  1. #1
    Join Date
    Mar 2009
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    Default raise exhaust pipe from furnace?

    I've got a high efficiency Carrier 9200 furnace with two PVC pipes (intake and exhaust). The system works fine. The problem is the exhaust pipe elbow sits at about 3' off the ground and points directly at my car in the driveway. In cold weather this results in a fair bit of condensation forming on the side of the vehicle.

    So I'm wondering if it's possible to raise the exhaust a few feet? Don't need a lot more, probably just another 2' higher. That'd be enough to let the warm air to blow over the vehicle instead of directly at it.

    I'm wondering whether that would have any adverse impact on the exhaust operation of the furnace. Right now, inside the house the pipes extend up 5' from the side of the furnace, to the joists and over about 4' through the exterior wall. Once outside they extend up about 2.5' for the intake and 3' for the exhaust. The intake has an inverted U fitting and there's a 90 elbow on the exhaust. It looks like it'd be fairly simple to trim off the elbow, use a coupler and add a 2 feet more pipe with a new elbow. And maybe another bracket to secure it to the wall.

    Are there limits on how high this exposed portion of the exhaust pipe can rise?

  2. #2
    Join Date
    Jul 2009
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    Default Re: raise exhaust pipe from furnace?

    I don't believe there are limits to the height of the exhaust as long as the minimum height is met, there is a code for this but I don't know if it varies from state to state( don't think it does).
    There is a maximum length that these can be and it should say what that is in your install manual. You should take into consideration how many 90's and 45's are included cause you will lose length for both. 6' per 90, 3' per 45. The total length may also be increased by going from 2" to 3" dia. on these, that should also be in your Install Manual.

    PLEASE READ THIS BEFORE YOU ALTER ANYTHING
    The owner of a company told me a story of a guy that wanted him to sell him a 90+ furnace and said he (homeowner) would do the install himself. The owner of the co. did not sell him the Furnace because the guy wasn't trained or knew what he was doing.
    Well the Homeowner bought one from Craigslist and did the install himself. Unfortunately three people lives were lost because the Homeowner didn't know what he was doing and ran the exhaust improperly, his girlfriend, him and her 16 year old daughter all died.
    IF YOU DON'T KNOW WHAT YOUR DOING CALL AN HVAC CONTRACTOR, IT'S NOT AS SIMPLE AS YOU THINK
    Last edited by Sten; 02-27-2011 at 12:47 PM.

  3. #3
    Join Date
    Mar 2009
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    Default Re: raise exhaust pipe from furnace?

    Quote Originally Posted by Sten View Post
    I don't believe there are limits to the height of the exhaust as long as the minimum height is met, there is a code for this but I don't know if it varies from state to state( don't think it does).
    There is a maximum length that these can be and it should say what that is in your install manual. You should take into consideration how many 90's and 45's are included cause you will lose length for both. 6' per 90, 3' per 45. The total length may also be increased by going from 2" to 3" dia. on these, that should also be in your Install Manual.

    IF YOU DON'T KNOW WHAT YOUR DOING CALL AN HVAC CONTRACTOR, IT'S NOT AS SIMPLE AS YOU THINK
    Agreed. Fire and carbon monoxide poisoning kills far too many people each year. Were I looking to make bigger changes I'd certainly hire an HVAC pro.

    The change I'd make would probably make things safer anyway. The exhaust would stop being vented at the level people breathe. It would end up being higher than a nearby window. Which makes me wonder about where they put it in the first place! Granted, you're not likely to be running the furnace while the windows are open. Fortunately we have CO detectors nearby anyway.

    By rough estimate the total length of the pipes (including your elbow adjustments) is 27', with about 4' of it being outside up the side of house. A 2' higher position would still be alongside the brick wall and still protected from the wind.

    I want to make sure there won't be some dramatic disruption in the operation of the system by raising it a few feet. I'd be changing the amount of vertical pipe exposed to the outside by two more vertical feet. I could see where making longer runs could cause problems by letting the exhaust cool too much. But would 2' higher, here in the DC area, be a problem for this?

    I may well have an HVAC professional do the work. I'm probably due for an inspection anyway. I just want to get a feel for what is or isn't appropriate for this sort of setup. I don't want some idiot contractor to either gouge me for something that ought to be simple, or do something that'd make things worse out of ignorance.

  4. #4
    Join Date
    May 2010
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    49

    Default Re: raise exhaust pipe from furnace?

    i am not a qualified HVAC guy, but i have a suggestion.
    would it be possible to cut off the elbow at the top & just install a new one at 90 degrees to the original (parallel to the house as opposed to perpendicular). that wouldn't change any of the original characteristics.
    sten (or anyone else with experience), please advise if this is feasible

  5. #5
    Join Date
    Mar 2009
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    Default Re: raise exhaust pipe from furnace?

    I don't think it'd be wise to change the direction. Going one way would point it toward an adjacent chimney. The other would be toward an open-able window and a wall-mounted hose winder. My goal here to it get the exhaust up and away from being able to damage surfaces. Changing it's direction would likely cause new trouble.

  6. #6
    Join Date
    Jul 2009
    Location
    Northeast
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    Default Re: raise exhaust pipe from furnace?

    To be honest with you I've never had to reposition the exhaust perpindicular to the house so I wouldn't know. I've never seen one installed that way and have always done the installs per Manufacturer Specs, best way to keep everyone safe. I would suggest maybe having a Concentric installed which would eliminate two pipes exiting your house and you would have one 5" protruding about 6". Or you can follow the link below to a termination kit I came across, make sure that the code for your area allows for these. Good Luck

    http://www.myhvacparts.com/Catalogue...tion%20Kit.htm

  7. #7
    Join Date
    Mar 2009
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    13

    Default Re: raise exhaust pipe from furnace?

    Given that's a brick-on-block wall using a vent setup like that would be way too much hassle to install. If it were just a vinyl sided wall, sure.

    But I don't need to move the vent 'bad enough' to go through that much hassle.

  8. #8
    Join Date
    Jul 2009
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    Northeast
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    Default Re: raise exhaust pipe from furnace?

    Sorry, didn't know what building mat. was used, can you move you car?

  9. #9
    Join Date
    Aug 2008
    Location
    Midwest
    Posts
    179

    Default Re: raise exhaust pipe from furnace?

    Get the model number for the furnace, then get the manufacturers specs for the installation. There are also some mechanical codes regarding distances to windows, doors, air intakes, etc. They will be included in the Carrier specs. Use this link and scroll down to the "Installation" pdf . Read pages 31-42 for all the information for on vent pipe installation on this model. This is a good example, but you would want to use the one specifically for your model.
    http://www.commercial.carrier.com/co...t-Installation
    "Lead by Example"

  10. #10
    Join Date
    Mar 2009
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    13

    Default Re: raise exhaust pipe from furnace?

    Quote Originally Posted by ZZZ View Post
    This is a good example, but you would want to use the one specifically for your model.
    http://www.commercial.carrier.com/co...t-Installation
    Thanks for the link. For that model it appears an external length of up to 28' of uninsultated PVC is possible. Right now I've got under 4' exposed to the outdoors. Adding another 2 looks like it wouldn't be a big deal.

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