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  1. #1
    Join Date
    Nov 2012
    Posts
    39

    6 times per hour

    Quote Originally Posted by tedkidd View Post
    Wow, a properly sized piece of equipment! Hopefully we'll see more and more of this...
    Question for the pros here: I live in Northern NJ, and my new 110K BTU input furnace was still cycling even in single digits. It was cycling 6 times per hour, and likely never switched to the 2nd stage (unless it did it while I was asleep) Would it be worth changing the setting on my Honeywell CT-3500 to a system type of "3" so that it cycles 3 times per hour instead of 6? (even though temp would fluctuate more) In other words, would a setting of 3 cause less wear and tear on the igniters and Inducer Motor over time? (Or would 3 cycles per hour cause more wear and tear on the burners and heat exchanger over time?) Thanks.

    ADD: by the way, if you're curious, my thermostat is set to 67 during the day and 66 late at night.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Made this its own thread. You are not allowed to post in other peoples threads in the AOP forums. please read our site rules, thank.
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  3. #3
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Quote Originally Posted by Jreality View Post
    Question for the pros here: I live in Northern NJ, and my new 110K BTU input furnace was still cycling even in single digits. It was cycling 6 times per hour, and likely never switched to the 2nd stage (unless it did it while I was asleep) Would it be worth changing the setting on my Honeywell CT-3500 to a system type of "3" so that it cycles 3 times per hour instead of 6? (even though temp would fluctuate more) In other words, would a setting of 3 cause less wear and tear on the igniters and Inducer Motor over time? (Or would 3 cycles per hour cause more wear and tear on the burners and heat exchanger over time?) Thanks.

    ADD: by the way, if you're curious, my thermostat is set to 67 during the day and 66 late at night.
    Someone can correct me if I'm wrong, but after looking at the documentation on your thermostat, the "system type" in this case I believe directly controls the cycles per hour of the furnace. It would make sense that at type 6 (standard efficiency furnace) you get ~ 6 CPH and at type 3 (high efficiency furnace) you would get ~ 3 CPH. I'm not sure why Honeywell has used this CPH convention in previous and current models of thermostats (on The VisionPRO thermostats, the presets are similar -- 3 for 90+, 5 for 80%, 9 for electric furnaces). I would start there first. Better yet, upgrade to a 2-stage thermostat that can properly control the staging in your furnace.

    Yes, cutting your cycles in half (and extending them) will result in less wear/tear and better efficiency/longevity.

  4. #4
    Join Date
    Jan 2008
    Posts
    1,991
    What is the efficiency of the furnace?
    Who told you 110,000 btu was the right size?
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  5. #5
    Join Date
    Nov 2012
    Posts
    39
    The efficiency is 80%. Everyone who I got a quote from wanted to install a 110,000 BTU furnace. My previous furance was higher input than 110 (I think 125,500), but less than 80% efficiency. It could be that everyone is too afraid of undersizing, so they oversize by default.

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