Trane Tstat T803...temp never moves?
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  1. #1
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    Trane Tstat T803...temp never moves?

    I have a quick question on my TStat (for Trane XV95/XL15i system).
    I had not focused on it because I have been distracted with static pressure and small duct issues.

    I watched the Tstat (T803) yesterday and it was set at 75. It never moved off 75 as the AC cycled on and off every 6-10 minutes. I thought the compresser was only signaled to come on if the Tstat temp reading changed and thus a call was made to bring it back to the set point?

    If I manually set it to 77 the compressor will go off and stay off until the room goes to 77 (even if it takes an hour or 2).

    If I manually set it to 73 it will come on immedialtely and stay on until the temp gets to 73....then stay at 73 as the unit cycles on and off.

    Can the unit be set less sensitive so that it only comes on if the temperature reading on the tstat goes above the set value a degree or 2?

    I have no confidence in my installer as he originally under-wired, then mis-wirerd the tstat. It has been corrected thanks to this site. When he corrected it with the info I provided from this site he admitted he does not know much about these Tstats.

    Thanks in advance.

    Key1

  2. #2
    Join Date
    Nov 2003
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    Rochester, New York
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    Some stats like honeywell controll within a degree, so they will never move from setpoint. EX 75.0-75.9*

  3. #3
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    Quote Originally Posted by key1cc View Post
    Can the unit be set less sensitive so that it only comes on if the temperature reading on the tstat goes above the set value a degree or 2?

    Key1
    You can I think using the installer's menu options, but doesn't that kind of defeat the purpose of having these types of AC's? I don't know if the XL15 has a multiple stage compressor or variable speed fan, but I know the XL16 does. So instead of wide swings of indoor temp, when the AC runs full speed to cool the house down to 1-2 below setpoint, then wait to 1-2° above setpot to come back on full speed, it runs more often in slower speeds maintaining a nice comfortable +/-1° of setpoint while providing very good energy efficiency.

  4. #4
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    Honeywell/Trane stats has a nice tight temp control, and you will not see the swing... Example. 75.1˚ to 75.9˚., Just set your temp you want and enjoy the new equipment.

    If you want the A/C to run longer the CPH (Cycle per Hour) can be set to a lower # like 2 vs 3 that the manual suggest.

  5. #5
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    There are 2 settings that can change that operation slightly.
    1 is to set the CPH to 2(or a number lower then the current setting).
    The other is to set the cooling to aggresive. It will tend to over shoot set point.

    Comfort stat, don't let the temp go up more then a few tenths of a degree before they bring the system on.
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  6. #6
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    Quote Originally Posted by mayguy View Post
    Honeywell/Trane stats has a nice tight temp control, and you will not see the swing... Example. 75.1˚ to 75.9˚., Just set your temp you want and enjoy the new equipment.

    If you want the A/C to run longer the CPH (Cycle per Hour) can be set to a lower # like 2 vs 3 that the manual suggest.
    Thanks...I'll give that a shot. I can't imagine the compressor is designed to keep turning on and off every five to 10 minutes.....I thought I read it is better if it ran all the time...
    Key1

  7. #7
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    Quote Originally Posted by beenthere View Post
    There are 2 settings that can change that operation slightly.
    1 is to set the CPH to 2(or a number lower then the current setting).
    The other is to set the cooling to aggresive. It will tend to over shoot set point.

    Comfort stat, don't let the temp go up more then a few tenths of a degree before they bring the system on.
    Thanks.

    I'll try both.

  8. #8
    Join Date
    Mar 2008
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    87
    Just curious if your AC is possibly oversized? I am having the same setup from Trane installed next week and 6-10 minutes on seems really short. They are putting in the XV95 60,000BTU and a 2 Ton xl15i AC for an older 1250SQ house in Northern NY.

    Teddy

  9. #9
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    Dec 2002
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    Teddy,

    I think you are OK with those size.

  10. #10
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    Quote Originally Posted by teddyc27 View Post
    Just curious if your AC is possibly oversized? I am having the same setup from Trane installed next week and 6-10 minutes on seems really short. They are putting in the XV95 60,000BTU and a 2 Ton xl15i AC for an older 1250SQ house in Northern NY.

    Teddy
    The house is 2800 sq. ft. in central NJ 4ton 15i and 100k btu XV95. No manual J ever done. System is set at 350CFM/ton and does a good job lowering humidity and cooling (even if I leave it off all mornig and cut it on at about noon). Problem is static pressure is high due to ductwork and that is being addressed.
    Key1

  11. #11
    Join Date
    May 2007
    Location
    Upstate SC
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    I wouldn't think the compressor should be turning on and off every five minutes. Doesn't the cycles per hour setting default setting and the "Wait" feature prevent this? What's the "Wait" time when the compressor can't come back on after shutting off... it's something like 7 minutes isn't it.. meaning if the compressor shuts off, it won't come back on for 7 minutes even if you adjust the tstat set temp down. Not sure why your system is cycling every 5 minutes.

    I frankly can't hear my system when it comes on, only when the blower goes to full speed and I'm near one of the returns can I the blower starting (or late at night when the house is dead silent, or next to the one window next to the outside unit). Maybe mine cycles more than I think, but I don't hear the relays in the tstat triggering that often, that's for sure.

  12. #12
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    Factory default wait time is 5 minutes.
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  13. #13
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    Mar 2008
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    Thanks for the comment mayguy. I did have a manual J done and it came to 51,000BTU heating and 19,000BTU cooling or so. I am a little concerned with the possiblility that in 10 years I could add an addition of another 500 or so SF. But I only currently have 8 inch insulation in my attic which I plan on icreasing in the next few years. I hope that will give me the headroom in case I add on. Of course the next size up Trane is 80,000BTU which seemed kinda large for my house. So I am going with the smaller one. Also the company will gurantee it.

    Key1cc sorry for stealing your thread. I am curious your outcome because I plan on having the same thermostat (Possibly the 802) installed. I am no expert, but I would think you would get some cycling when it is mildly warm outside (like 75-80) and long run times when it is (90-100). What is the outside temp when you notice this short cycling? Thanks

    Teddy

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