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  1. #14
    Join Date
    Jan 2020
    Location
    Colorado
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    10
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    Thread Starter
    Thank you for all your time and thoughts rundawg.

  2. #15
    Join Date
    Jan 2020
    Location
    Colorado
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    10
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    Thread Starter
    Goodman does not require a restrictor plate. I have installed Carrier and Bryant, and the small Btu furnaces did ( to your point).

  3. #16
    Join Date
    Aug 2002
    Location
    Cincinnati, Ohio
    Posts
    3,048
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    Is your flue 2-pipe? It sounds like it might be too restrictive. With the O2 low and the temperature low it sounds more like the inducer isn't doing its job.
    captain CO

  4. #17
    Join Date
    Jan 2020
    Location
    Colorado
    Posts
    10
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    Thread Starter
    Thank you for your input Jim. The furnace is a 40kbtu and the length of pvc pipe is about 20-25' with about 5- 90s. I am well within the specs on that, but I will do some more investigation on that. I did double check for obvious blocking, but I will have to look further into it. I will keep you posted.

  5. #18
    Join Date
    Jan 2020
    Location
    Colorado
    Posts
    10
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    Thread Starter
    Hello Jim. I did not see any blockage. Originally the furnace ran the same weather the burner compartment door was on or not ( with high CO and manifold pressure set at 3.5 IWC) The furnace burned way cleaner at a 2.8 IWC but the BTU produced was too low and the factory specs are 3.2-3.8 IWC. I think that one of the problems is that Goodman just does not do enough testing on their furnaces at altitude. The only orifices they offer are .45 for 2000'-7000', .49 for above 7000' and nothing in between. Not a huge deal, I just like a furnace to burn as clean as possible.

  6. #19
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    11,842
    Post Likes
    Quote Originally Posted by hvasee6 View Post
    Not a huge deal, I just like a furnace to burn as clean as possible.
    I would stop worrying about clean air, and focus on output of the furnace.

    As Jim stated back in post #8, even at 100 ppm, “you are burning 99.99% of the fuel”…….

    I wont argue that Goodman doesn’t do enough testing at high altitudes, but neither do any of the manufactures. Most of their info, for altitude other than sea level, is computer generated.

    As long as the CO levels are less than 100 ppm and STABLE during the run cycle, I would not have a problem with increasing the manifold pressure above the manufactures stated "max", in order to obtain the flue temp and supply air temp required to meet the manufactures rated output.

    The next time "National Comfort Institute" (NCI) is in the Denver area, you should take their "Combustion Performance and CO Safety" class. It is an eye opener on this subject.

    https://www.nationalcomfortinstitute...x.cfm?pid=1042
    Instead of learning the tricks of the trade, learn the trade.

  7. #20
    Join Date
    Aug 2002
    Location
    Cincinnati, Ohio
    Posts
    3,048
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    #45 orifices are 17,072 btus with 1030 btus per cubic foot gas.. You might be a little over concerned about the CO. Starting your vehicle in the morning one time may produce more CO than your furnace does all winter.

    We teach CO under 100 ppm and anything close is good. If you want heat and efficiency you sometimes have to accept higher CO. Just for the record, if a burner is misaligned 1/16" it can cause slightly higher CO and looks are deceiving
    captain CO

  8. #21
    Join Date
    Jan 2020
    Location
    Colorado
    Posts
    10
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    Thread Starter
    Rundawg. Just wanted to get back to you. I tested static pressure and it was pretty high .8 the furnaces lowest fan speed for a 40,000 Btu furnace was 990 CFM The motor is a variable speed so I had the ability to trim it down by -10% not exactly sure of the CFM with that high of static pressure. The temperature rise was between 37-40 Degrees name plate was 20-50. Stack temperature was still a bit low 78 deg. The Btu output with the smaller orifices is still low and under firing a little bit, the furnace is burning really clean though. I think I will put the bigger orifices back in and accept the dirtier burn.

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