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  1. #1
    Join Date
    Nov 2019
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    S9V2C100U4 + Nest

    I did a search and couldn't find anything specific on this. I know from reading around that you guys don't like the Nest but please bear with me here:

    We just replaced our HVAC system but already have a 3rd gen Nest installed. I was told we could keep our nest thermostat, which we did. It saved us a little money plus I have found the Nest useful. From what I'm reading now, we may not be getting all the features from our new HVAC system using the Nest as our thermostat.
    Details:
    American Standard S9V2C100U4 2 stage furnace with variable speed blower
    American Standard 4A7A6048J1000AA 16SEER AC unit. I don't think there's anything special other than just a standard silver series unit
    right now we have it wired to the nest thermostat with the standard 5 wire setup for single stage heating and cooling: W1, R, G, Common, Y1 wires. BK Jumper is intact on the board. I have more wires available, brown, orange, black. Am I getting full use of this setup, the 2 stage and variable blower? I don't think so. Is there a way to wire the nest to properly take advantage of this setup? If not, can I at least improve upon it? I don't really want to buy a new thermostat, but if I have to I will. My understanding is that if left in this setup there is a time delay for the 2nd stage but the main board automatically kicks it in.

    Reading the manual on Tranes website (can't post link) it appears a jumper is needed between W1 and W2 on the main board when using a thermostat wired as single stage. This is not in place on my system.

    Can I just connect the W2 on the board to W2 on the thermostat for proper 2nd stage control? And then what about BK? One reference said to connect BK to * on the nest for dehumidify on demand. From reading the manual BK seems to be for the variable speed fan. If connecting BK to BK on a thermostat you cut the BK jumper according to the manual.

    As a side note, there is also a new humidifier but its using a separate control at the furnace itself and is not wired into the thermostat.

    Thank you for the help.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    40,574
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    Skip BK, hook up W2 for proper staging.

  3. #3
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    7,207
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    I not only "don't like" the Nest. I hate it!
    It can operate fine for months and then cause havoc for 5 minutes. Then it behaves normally for days. One caused us to first replace the refrigerant in a new heat pump and when the grinding noise still occurred sporadically, we replaced the heat pump. The noise still occurred. I removed the Nest and installed a Honeywell thermostat. Problem solved. That was last winter.
    I've encountered more Nest problems but people still think they're the bees knees.
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  4. #4
    Join Date
    Nov 2019
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    2
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    Thread Starter
    Quote Originally Posted by BaldLoonie View Post
    Skip BK, hook up W2 for proper staging.
    this was my first inclination. What happens to BK in this instance?

    Without the W1 to W2 jumper, am I getting any staging currently? Even the delayed 10 minute for 2nd stage?

  5. #5
    Join Date
    Sep 2008
    Location
    VA
    Posts
    3,723
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    The inter-stage delay is adjustable by the technician from 0 sec. to 15 mins in 5 min increments. They need to wire it properly and adjust the control panel in order for it to function as desired. Your installer should make a return trip if they didn't wire W2 on the control board. It's their job to ensure proper operation, I would allow them to do it.

    I believe the dehumidification function on your thermostat is reverse logic in comparison to the Trane/ AmStd furnace, so it will likely not work with BK without some creative wiring.

    The board has an auto blower ramping profile that can be adjusted for cooling mode/ dehumidification in several different configurations. This is likely your best bet. The Trane/ AmStd XL824 thermostat can actually communicate with the blower control in order to adjust the speed according to the desired dehumidification demand.
    "The only true wisdom is in knowing you know nothing" Socrates

  6. #6
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    10,217
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    As said you are missing true staging and the blower functions achieved through BK. I also believe the 824 is the best route to go.

  7. #7
    Join Date
    Jan 2012
    Location
    Missouri, USA
    Posts
    1,523
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    The American Standard 824 stat will give you the correct heat operation, bk dehumidification, and the ability to change blower speed when the fan only is on. And is WiFi compatible.

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