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S636 CPVC vent pipe clearance to combustibles

robjmc1 Member Posts: 7
Anyone use PVC or CPCV vent pipe on a mod/con and have it in contact with wood or combustibles. I had System 636 CPVC installed following manufacturers manual when by house was under construction but did not have gas yet. I used this because it is classified as Type BH Class IIB vent, suitable for use on appliances with flue gas temperatures up to and including 90ºC (194ºF) and has a 0” clearance to combustibles. Now that I am looking at different boilers I find they all have different clearances to combustibles for the vent. Some have 0” some have 1/2” and others have 1” clearance around combustibles also some say do not insulate as the temperature will damage the pipe and some say to insulate if it passes through a unheated space others say only leave the first 3ft exposed and must be CPVC. In my installation it is ran in a chase from the basement to the roof there is clearance around the pipe except in two places between the 1st and 2nd floor it touches wood a there is insulation around it at the attic floor. Has any had an installation where the vent is in a chase or touching combustibles any problems with over heating pipe or different manufacturers having different stack temps. I would think if they can be used with PVC rated at 140f than CPVC with a 190f rating should not be a problem especially if the pipe manufacturers approve it with 0” clearance to combustibles .


    EBEBRATT-Ed Member Posts: 15,635
    Steam pipes run at 212 minimum and are in contact with wood all over the place.

    Running lower water temperature will keep the flue pipe cooler as well as save money on fuel and promote condensing....if you can

    A lot of installers never give this stuff a second thought. It's good that you do