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  1. #1
    Join Date
    Nov 2019
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    Furnace cycling every 6-10 minutes, normal?

    This is my first post and I'm a brand new homeowner, so I'm hoping your expertise can help me!

    I moved into my home in June and today was the first time using the heat. We used the AC all summer and had no issues;worked great!

    However, it seems that the furnace cycles every 6-10 minutes. As the system heats up to the desired temperature set at the thermostat, I will hear the furnace ignite, followed by the blower a few seconds later, the whole system will run 6-10mins, at which point the furnace turns off, followed by the blower about a minute later, and pretty much exactly 60 secs later, the whole cycle begins again.

    I spent about an hour timing the whole process with a stopwatch: the shortest cycle I timed it running was 6:32 and the longest was 9:10. It was off a consistent 52-57 seconds between turning off and the whole cycle starting again.

    It is definitely heating, reaches the desired temperature, and shuts off completely when achieving the set temperature, as it should.

    Sorry in advance as I donít know many technical details of the unit but itís a central hvac system with the AC condenser outdoors and the blower and GAS furnace in the tight attic crawl space. My home inspection documents noted that it was a 100k BTU furnace. It is a 1100 sq/ft single story home. The thermostat is a Honeywell TH6220D1028. I have verified that the thermostat seems to be setup as a 2 heat/1 cool conventional system and the Furnace Cycles Per Hour is set to 5. As it cycles, I do hear the typical "click" from the thermostat turning things on and off.

    Is this normal or is it short cycling? Some things Iím reading suggest that it can be normal for a furnace to cycle up to eight times an hour, but my previous residence didnít do this, though it was an older hvac system and a two story home. I've also read that if this is truly an 100k BTU furnace, that it is way more powerful than recommended and this could be causing this cycling issue. In the thermostat settings, I also noted that the Compressor Protection Function is set to 0 minutes instead of the default and recommended 5 minutes. Is this a concern?

    Any advice and input is greatly appreciated!

  2. #2
    Join Date
    Jun 2014
    Location
    Dover, DE
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    Sounds like horribly oversized equipment.
    Where in the world is this house that requires 100k BTUs for such a house?
    ďI havenít failed. Iíve just found 10,000 ways that wonít work.Ē - Thomas Edison

    ďItís not whether you get knocked down, itís whether you get up.Ē - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

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  3. #3
    Join Date
    Jan 2014
    Location
    New England
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    Possible one reason the thermostat cycles back on after only one minute is behind the thermostat where the wires hook up to the thermostat subbase the hole is large and it has cold air in that chase, cooling off the thermostat.

  4. #4
    Join Date
    Nov 2006
    Location
    Athens, Ohio
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    The furnace is oversized for your house. It cycles off because an inner safety is getting overheated from inadequate airflow. Either get a smaller furnace or enlarge the duct system to move the amount of air needed by the furnace.
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    Questions should end with a question mark "?" Statements end with a period "."

  5. #5
    Join Date
    Jan 2004
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    PA
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    5 CPH is too many, and the thermostat is doing as its set up to do. Reset the CPH to 3 or 2.
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    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Nov 2019
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    Thread Starter
    I've reset both Stage 1 and Stage 2 CPH to 3. It hasn't been very cold today, so I haven't had much change to test. However, I did run it under the previous 5 CPH and it did indeed seem to be doing just that, running about 8-12 minutes with 1 minute breaks in between as it reached the target temperature (which it did in under an hour, and then stopped completely as it should).

    I'm in the San Francisco Bay Area. 100k BTU is only based on what one inspector noted. I have no idea if it is, in fact, that big, as it's in a tight attic crawl space and I can't easily access the unit myself.

    I'm going to keep an eye on it, but it seems that there is not much I can do. It may be a combo of the CPH and overpowered unit and, from what I have researched throughout this forum, it sounds like I should just enjoy my home as there is no easy fix and I may just have a lower overall lifespan of the unit, but is not dangerous. Correct?

    Also, since Compressor Protection is currently set to 0, should I increase it at all or just leave it as is?

  7. #7
    Join Date
    Jul 2007
    Location
    Virginia
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    Quote Originally Posted by judino28 View Post
    In the thermostat settings, I also noted that the Compressor Protection Function is set to 0 minutes instead of the default and recommended 5 minutes. Is this a concern?
    Yes, change it to 5.
    Instead of learning the tricks of the trade, learn the trade.

  8. #8
    Join Date
    Nov 2019
    Posts
    8
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    Thread Starter
    Iíve received a recommendation to change the thermostat to a one stage heat system instead of two stage. Thoughts?

  9. #9
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Quote Originally Posted by judino28 View Post
    I’ve received a recommendation to change the thermostat to a one stage heat system instead of two stage. Thoughts?
    WHY???

  10. #10
    Join Date
    Jun 2014
    Location
    Dover, DE
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    Quote Originally Posted by judino28 View Post
    I’ve received a recommendation to change the thermostat to a one stage heat system instead of two stage. Thoughts?
    By whom?
    ďI havenít failed. Iíve just found 10,000 ways that wonít work.Ē - Thomas Edison

    ďItís not whether you get knocked down, itís whether you get up.Ē - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  11. #11
    Join Date
    Jul 2007
    Location
    Virginia
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    Quote Originally Posted by judino28 View Post
    Iíve received a recommendation to change the thermostat to a one stage heat system instead of two stage. Thoughts?
    Can you post the full model number of this furnace?

    Whoís recommendation was it? A neighbor, a friend, or a tech?

  12. #12
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
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    100K BTU unit in 1100 Sq Ft

    Im surprised it runs that long!

    Get a low level CO detector!

  13. #13
    Join Date
    Nov 2019
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    8
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    Thread Starter
    The recommendation to change from 2 stage to 1 was received in a posting I made to the HVAC Reddit page, which I had posted to before I found this awesome and more reputable forum. Judging from the reaction, I will not be changing that setting!

    I haven't been able to get to the unit itself yet as it is in a tight attic crawl space without much clearance/ease of access. And again, the 100k BTU is based solely on one report on one home inspection; I have no idea if that was an estimate or really is the size of the unit.

    Interestingly, this morning, I timed again. As it was reaching temperature, the shortest cycle was about 7 minutes, with almost exactly a minute between cycles, and the longest was the last cycle which about 15 minutes at which point the desired temperature was achieved and the system stopped cycling as it should. It almost seems that as the system is "learning" how long it takes to achieve temperature, the cycles are getting longer.

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