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  1. #1
    Join Date
    May 2006
    Posts
    312
    relative of mine recently had a new trane xl16 system installed (I failed to convince them to install xl19i..sigh)

    while everything about the installation was smooth, they got all copies of manual J, D etc and are happy about the overall performance, there is one issue that is haunting them and since they don't have home pc, I'll ask for ideas on their behalf

    the system is able to cool their house to just about any temp and maintains humidity at well below 50% but there is an odd behaviour in that when thermo programmed setpoint (by time of day) switches to just one degree higher (nights=76F, days=77F) it sometimes causes a wide swing in inside temps.

    keep in mind as you read this that their thermo is always programmed to 76 starting at 6pm and changed to 77 at 9am so there are only two (2) set points for the thermo, any day, all 7 days of the week.

    for example it may cool the house at 5am to 74 while setpoint is 76 and keeps the house at about 74-75 until about 9am when setpoint changes to 77. when this happens, the house will very slowly climb all the way up to 77.7 which triggers the thermo (shows 78) to start cooling.

    the problem is that wide swing from a comfy 75 all the way up to 77.7

    the odd thing is that when it finally starts cooling (sometime it takes up to 2 hours for inside temps to climb from 75 to 77.7) it then keeps the house comfortable and later in the evening the programmed set point changes to 76 and it drops nicely down to about 75.4 and keeps it there until midnight (I stopped monitoring with my data logger)

    so, their question to me was how to adjust that one point in the morning where the temp climbs from 74-75 to 77.7 and since the change is rather large (it feels like 4 or 5 degrees). yet during this time the thermo is acting only upon a single (1F) change as it's adjusting to going from 76 to 77. here's where I wish there was a 0.5 adjustment but their thermo does not have that.

    I suggested trying for adjusting the set point for later. We then observed the house staying at 74-75.5 until 10am (we moved time up 1 hour) and then it slowly climbed up to 77.7 which happened at around 11:45am but the almost two hour time made the house feel a lot warmer (until system started running and the rest of the day was fine)

    since I have my Fluke instruments, I've checked the thermo and it's within 0.4 of accuracy

    all rooms in their house are at almost the same temp, within no more than 0.5 variation depending on time of day and sun exposure.


  2. #2
    Join Date
    Jun 2004
    Posts
    459

    what advantage?

    Originally posted by nina
    relative of mine recently had a new trane xl16 system installed (I failed to convince them to install xl19i..sigh)

    while everything about the installation was smooth, they got all copies of manual J, D etc and are happy about the overall performance, there is one issue that is haunting them and since they don't have home pc, I'll ask for ideas on their behalf

    the system is able to cool their house to just about any temp and maintains humidity at well below 50% but there is an odd behaviour in that when thermo programmed setpoint (by time of day) switches to just one degree higher (nights=76F, days=77F) it sometimes causes a wide swing in inside temps.

    keep in mind as you read this that their thermo is always programmed to 76 starting at 6pm and changed to 77 at 9am so there are only two (2) set points for the thermo, any day, all 7 days of the week.

    for example it may cool the house at 5am to 74 while setpoint is 76 and keeps the house at about 74-75 until about 9am when setpoint changes to 77. when this happens, the house will very slowly climb all the way up to 77.7 which triggers the thermo (shows 78) to start cooling.

    the problem is that wide swing from a comfy 75 all the way up to 77.7

    the odd thing is that when it finally starts cooling (sometime it takes up to 2 hours for inside temps to climb from 75 to 77.7) it then keeps the house comfortable and later in the evening the programmed set point changes to 76 and it drops nicely down to about 75.4 and keeps it there until midnight (I stopped monitoring with my data logger)

    so, their question to me was how to adjust that one point in the morning where the temp climbs from 74-75 to 77.7 and since the change is rather large (it feels like 4 or 5 degrees). yet during this time the thermo is acting only upon a single (1F) change as it's adjusting to going from 76 to 77. here's where I wish there was a 0.5 adjustment but their thermo does not have that.

    I suggested trying for adjusting the set point for later. We then observed the house staying at 74-75.5 until 10am (we moved time up 1 hour) and then it slowly climbed up to 77.7 which happened at around 11:45am but the almost two hour time made the house feel a lot warmer (until system started running and the rest of the day was fine)

    since I have my Fluke instruments, I've checked the thermo and it's within 0.4 of accuracy

    all rooms in their house are at almost the same temp, within no more than 0.5 variation depending on time of day and sun exposure.

    in my opinion, asking a progrmmable stat to setback 1ºF defeats the potential savings of a programmable. that 1º differential may be out of the operating range of the stat, try 2-3º differential and see if the stat performs better.

    the homeowners literature for the stat should list the minimum differential settings.

    [Edited by re2ell on 07-11-2006 at 05:26 PM]

  3. #3
    Join Date
    Mar 2004
    Posts
    1,042
    So... I hate to state the obvious, but.... just leave it on 76 all the time?

  4. #4
    Join Date
    Jun 2004
    Posts
    459

    fear of

    Originally posted by wyounger
    So... I hate to state the obvious, but.... just leave it on 76 all the time?
    you took the thoughts right out of my head! i just have a fear of expressing all i think

  5. #5
    My Trane rebadged Honeywell Vision Pro has a setting (I don't recall the menu number) but the manual says something like "more aggressive temp control" versus "less aggressive temp control".

    My much less expensive XL14i doesn't have temperature swings like that. If they had attached a less than desirable thermostat to the XL19i, they could have ended up with the same results as what they have now.

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