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Thread: rheem furnace short cycle

  1. #1
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    rheem furnace short cycle

    Hello techs , I had a home owner call saying a company installed his furnace & had to redue the flue pipes after it failed inspection from the bldg department, know his furnace short cycles after the new flue pipes installed ,i want to share few pictures & get some opinion on what could be wrong with the piping. Am not sure if i want to get involved with someone's problem,but figured to share the job.plz update

    rheem M# R92PA0601317MSA


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  2. #2
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    What exactly do you mean by short cycle. Is the furnace inducer running and then shutting down before ignition takes place?

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  3. #3
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    not sure, I havent seen the job yet ,trying not to get involved with job, but the main reason I posted is to share pictures on how the flue pipe install looks.

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  4. #4
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    I mean it looks absolutely horrible in every way. I don't know if there's much more to say than that if you don't want to get the details or get involved...and honestly I don't blame you for passing it up.

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  5. #5
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    i appreciate your comment , even though am not getting involved in the job , I still would like to learn from the job pictures, to me it looks like the termination pipe on the outside wall I believe is the intake pipe. is ran 2ft vertical then needed & the flue piping by the furnace not only looks ugly but the intake pipe is pitched way to much, if possible i would like to hear some details from your end ?

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  6. #6
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    It's hard for me to make a judgment from these pictures....
    But it looks like one run has a bit of a reverse pitch to it.
    And I also see both intake and exaust have downspouts on them.
    If in fact one of the pipes has a reverse slope in one area then that will effectively make a trap and you'll be dealing with a blockage and short cycling or not running at all.
    It's also not a good idea to have a downspout on the exaust of the furnace as it will be recycling the exaust and starving for oxygen among other problems.....
    However this is only based on what I can see. And I'm making the assumption that these two downspouts are from the same unit.
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  7. #7
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    Quote Originally Posted by Restaurant mech View Post
    It's hard for me to make a judgment from these pictures....
    But it looks like one run has a bit of a reverse pitch to it.
    And I also see both intake and exaust have downspouts on them.
    If in fact one of the pipes has a reverse slope in one area then that will effectively make a trap and you'll be dealing with a blockage and short cycling or not running at all.
    It's also not a good idea to have a downspout on the exaust of the furnace as it will be recycling the exaust and starving for oxygen among other problems.....
    However this is only based on what I can see. And I'm making the assumption that these two downspouts are from the same unit.
    X2. Hard to make out the intake or exhaust from those pictures but if the exhaust is on top it will have real problems real quick. Rheem should have pictures in their installation manual as to what is acceptable. Guarantee what is pictured is not in there.

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  8. #8
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    Hard to say without seeing full venting application, and info on length of run/ size and specs of furnace it is served... all limitations and sizes are different to each specific piece of equipment.

  9. #9
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    No mfg recommends close sweep 90's for an install. The outfit that put this in obviously used the install manual for a pad to lay down to put their knees on. Is that electrical pvc conduit used for flue material. Ya I bet this is having pressure switch issues. By the way who decided the best place to take this out was directly at some kind of fence?

  10. #10
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    I would say the company that originally installed it.

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  11. #11
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    Quote Originally Posted by theoldscroll View Post
    No mfg recommends close sweep 90's for an install. The outfit that put this in obviously used the install manual for a pad to lay down to put their knees on. Is that electrical pvc conduit used for flue material. Ya I bet this is having pressure switch issues. By the way who decided the best place to take this out was directly at some kind of fence?
    I see stickers on every fitting. cant read the warning but can see the arrows. Never have I seen that on Sch 80 conduit. That has to be some new exhaust piping!

  12. #12
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    yes there from the same unit ,anyways I never heard back from the owner, thanks again

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  13. #13
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    Quote Originally Posted by nytech28 View Post
    Hello techs , I had a home owner call saying a company installed his furnace & had to redue the flue pipes after it failed inspection from the bldg department, know his furnace short cycles after the new flue pipes installed ,i want to share few pictures & get some opinion on what could be wrong with the piping. Am not sure if i want to get involved with someone's problem,but figured to share the job.plz update

    rheem M# R92PA0601317MSA

    If you put an email address in your profile, or email me (address is in my profile), I can get the installation manual off to you for review.

    From the middle picture you posted, the left PVC pipe (the vertical one) should be the exhaust pipe, and the horizontal pipe in that same picture, should be the combustion air pipe.
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  14. #14
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    I have the installation manual , I was able to find & download ,the illustration for the flow pipe is not near to what's installed on the job, I didnt get involved with job ,but sure did learn how to deal with similar situations in future, am happy to share more future missup jobs ,thanks for taking the time to look into this.

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  15. #15
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    Seeing that fence my first thought was duplex. From what I have seen you can use short 90's but they add about double the equivalent footage of a long sweep. If that is PVC conduit is it even rated for use as a flue? I know you have to watch as there are 2 different types of the white PVC the one I believe they refer to as cellcore is not rated for venting as it will sag as it gets warm.

  16. #16
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    https://www.centrotherm.us.com/InnoF...t-Lengths.aspx

    Looks the product is for Flue Venting....first time I have seen it...
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  17. #17
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    Quote Originally Posted by nytech28 View Post
    Hello techs , I had a home owner call saying a company installed his furnace & had to redue the flue pipes after it failed inspection from the bldg department, know his furnace short cycles after the new flue pipes installed ,i want to share few pictures & get some opinion on what could be wrong with the piping. Am not sure if i want to get involved with someone's problem,but figured to share the job.plz update

    rheem M# R92PA0601317MSA


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    This is what the code enforcement passed?

    Shame on them.

    The flue gas clearly will recirculate.

    Both point downwards, and terminate next to a fence.


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  18. #18
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    The inspection failed the 1st time & I believe the flue piping was repiped according to home owner, I didnt get involved with job, I only shared the job pictures.

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