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  1. #40
    Join Date
    Apr 2008
    Location
    Princeton, NJ
    Posts
    581
    Quote Originally Posted by beenthere View Post
    No, it does not.
    I kind of knew that....but I was hoping that since the non-programable version can do it....

    Key1
    In the land of the blind.....the man with one eye is king....

  2. #41
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    I'm not too familiar with that stat (TCONT803)
    But... even though it has a humidity sensor built in...
    it uses a concept I'm not too fond of to dehumidify....

    Dehumidification Droop Control
    The dehumidification control attempts to control to the
    user's humidity setpoint by turning on the air conditioner.
    In extremely high humidity conditions, the comfort control
    keeps the air conditioner running for up to 3°
    F below the
    temperature setpoint. It does this while trying to achieve
    the desired humidity setpoint and balancing that with the
    temperature setpoint
    IT would be really nice if there was an output from
    the stat that would 'turn on' when the humidity is above
    setpoint so the furnace would know its time to dehumidify
    and can run its blower at a slower speed.

    ITs a shame Trane does not have a programable stat that
    utilizes both the humidity sensor and BK terminal to
    get the most out of the variable speed blower.

    I must admit, Carrier does a fabulous job in that department
    with the Infinity system.
    (The company I work for sells both Trane and Carrier)


    For what it's worth, the Infinity is able to give you custom fan speeds
    during 'Fan On' operation.
    Don't know the percentages off the top of my head.
    All I remember at the moment is Low, Med, High settings

    I haven't messed with an infinity in a while, so I wouldn't be
    able to answer too much about that.... but I'm sure someone on
    here can.

    I did a little checking, the Honeywell IAQ does have a dehumidify
    signal that can be sent to the furnace.
    Basically, you set the humidity on the stat.
    If the humidity is too high in the summer,
    it will send the signal back to the furnace.
    The furnace will only allow the blower to run at most 80%
    so it can remove the max amount of humidity from the air
    during the run cycle.

    The furnace will still utilize the Comfort-R strategy...
    it just won't let it go over 80% when the time comes.
    So you'd have....
    1 minute @ about %50 airflow
    THen the rest of the cycle at 80% airflow
    as long as there is a high humidity in the house.
    Once it gets the humidity under control, it will allow the
    furnace to go up to 100% airflow.


    IF you also have a humidifier installed for winter moisture,
    the IAQ can bring it on as well if the humidity in the house drops too
    low.
    The IAQ is equiped with two seperate terminals.
    One is 'energized' when the humidity is too high(used in summer) the other is energized when
    the humidity is too low (used in winter)

    Side by side comparison:

    Tcont402
    Not programmable (has a setback feature.. hit dollar sign and temps setback to amount you want.. default is 5 degree heat/5 degree cool. I don't use it
    at home for that.... I hit it when my wife or I am fixing to jump in the shower... easy way to 'pause' the operation of the unit till we get out
    of the shower)

    IAQ and TCONT803
    Both are programmable
    and pretty much look the same as you can see (wonder who makes the 800 series stats for trane LOL)


    Tcont402
    Fan On: customizable fan speed
    Any other stat: Fan on 50% airflow (or is it 60%) A jumper can be added in the furnace to provide 100% airflow
    Comfort-R can be used with any stat (its just built into the tcont402)
    even if the fan is set to ON

    TCONT402 (without humidistat) vrs IAQ with built in humidistat
    The TCONT 402 has: Cooling Efficiency Booster - (Single Stage Compressor
    Only) - BK Enabled
    The indoor air flow is reduced to 80% at outdoor
    temperatures below 87°F in cooling mode. The outdoor
    temperature sensor must be installed and enabled
    This is Trane's way of trying to get away with not having a humidistat....
    THey figure the cooling is not going run as much at temps below 87, so
    the humidity will be higher at temps below that. Once you get above 87, the
    unit will run longer and in turn remove more humidity.
    If you actually have a humidistat control (like whats built into the IAQ)
    then the fan will run at 80% anytime it needs to based on "real world"
    conditions instead of a "calculated risk" method.

    TCONT803
    Has built in 'dehumidification' feature
    that runs the cooling up to 3 degree's colder than setpoint
    so the compressor gets extra runtime.
    Sounds a bit uncomfortable to me.
    Too much temp swing.
    This feature can be turned off at that stat and
    An ADDITIONAL humidistat CAN be added to the FURNACE to
    limit the fan speed to 80%, BUT.....
    If installed where it supposed to (right beside the thermostat) it makes things
    really stand out.
    It can be installed in the furnace, you'd have to set it and forget it...
    which most people do anyway.
    You can set it to 50% humidity, and leave it be.
    The furnace will then only allow the blower to go up to 80% just like if it had
    the IAQ stat since its using the same terminal.
    Grant it, if you have a humidifier, you'd have to add another humidistat to control it... but that one would be best to have by the indoor stat since it
    needs to be adjusted based on outdoor temp to keep the windows from sweating in the winter. The IAQ don't need the additional humidistat for heat, its built in.
    A compromise would be to install the humidistat(s) behind a filter grill.


    TCONT402
    the humidistat can be connected to terminals in the stat
    to allow for the same 80% limit
    When the thermostat reaches setpoint,
    it continues to run the compressor for 2 minutes longer
    then shuts the compressor and blower off (no 3 minutes of running
    the blower at 50%).
    This is less noticeable than the TCONT803 method of running
    the compressor till its 3 degrees cooler in the house


    There is one important thing to remember about all this.
    If you are expecting to have high humidity conditions.
    ie You live in Florida
    Then I'd recommend a two stage/speed compressor.
    This will do way more than the blower alone can.

    Under normal conditions....
    If the system is sized correctly and installed correctly,
    then the humidity in the house is typically within reason even
    with a standard blower.
    The variable speed blower with Comfort-R is going to make
    'good enough' into something better
    The TCONT402 is a really nice stat and does a wonderful
    job at controlling the temp as well as some nifty features for
    a variable speed unit. It does an absolute fantastic job with
    dual fuel heat pumps and with two stage heating units like the furnace
    you are interested in. It can also work with two stage cooling as well.
    With an additional humidistat, it makes
    the system even more better (But we reach a point where
    its hard to tell if its even worth it)
    If you're looking for the best control of humidity and want a programmable,
    then I'd suggest the IAQ. Although I haven't messed with the IAQ,
    I have installed a couple of the 803's and since the IAQ is a better
    stat than that, coupled with the high support of technicians that visit
    this site... I don't hesitate to recommend it myself.
    If you're in a high risk area for high humidity, then you'd benefit more
    from a two stage compressor.
    If you have an indoor pool, then you'd be better off having
    a dehumidifier from Desert Air
    Last edited by wormy; 03-22-2009 at 01:35 AM.

  3. #42
    Join Date
    Mar 2009
    Location
    Under the brilliant Midwestern Moon or Sun (depending on time of day).
    Posts
    135
    Some REALLY great info here. So kind of you guys, no doubt about it.

    So appreciate the Tstat comparisons, Wow.

    This will not only be helpful to me, as I figure this stuff out, but to many others who'll study these posts.

    Thank you beenthere for explaining the uniqueness of Tstat fan control to the Tcont402.

    Is that the only Trane Tstat with this feature? Sorry if that's too broad a question to ask.

    Would Tcont402 features work well with my present AmStd Allegiance 11 … Single Stage 2.5 ton ... Model # 2A7A1030A 1000AA, & my Evap Coil 2004 AmStd ... TXA-030C4HPCO?

    Also, I wonder if it would work with a new SingleStage Trane or AmStd A/C & Coil later when purchased down the road? I guess it depends on the model I use (not all models?)?
    Not sure I want to keep putting money into new Tstats every time I turn around, hopefully what I get now will satisfy needs later too.


    wormy,
    You said the following ...
    If you do get this stat and BK is enabled,
    then be sure not to turn on Comfort-R at the furnace.
    The stat will control fan timing and speed control.

    Does this indeed mean that Comfort-R is not compatible with any use of Constant-On Fan mode?

    And instead that I'm having to choose either Comfort-R, or Constant-On Fan mode (one over the other)?

    But, what would happen if I had Comfort-R on at furnace, but then turned constant fan on at Tstat? (If anyone cares to explain, Ha.)


    If that's the case about Comfort-R / Constant-On, maybe I should just use the 40% Constant-On Fan-speed wiring setup at furnace (referred to in this thread & Comfort-R Pocket Guide) instead of using Tcont402 for lower fan speed. And then have a different Tstat.

    Problem is, I mostly only want to use Constant-On during heating months, but then use Comfort-R for cooling months.
    Sounds like wiring change would be necessary per season to do this. Of which I would likely just choose one permanently though.
    I'm trying to grasp this & understand it. I'm a little
    naive with this.

    Also, I thought I read in a thread once that Dehumidify mode of Tstat can work in concert with, or in addition to, Comfort-R.
    Is this True?

    Thanks to all.

  4. #43
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by wormy View Post
    if you're looking for the best control of humidity and want a programmable t-stat then I'd suggest the IAQ.
    that is absolutely correct sir, also the IAQ can be set as a non-programmable if desired


    .

  5. #44
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,790
    Quote Originally Posted by SmackDabAOK View Post

    Thank you beenthere for explaining the uniqueness of Tstat fan control to the Tcont402.

    Is that the only Trane Tstat with this feature? Sorry if that's too broad a question to ask. As far as I know, yes.

    Would Tcont402 features work well with my present AmStd Allegiance 11 … Single Stage 2.5 ton ... Model # 2A7A1030A 1000AA, & my Evap Coil 2004 AmStd ... TXA-030C4HPCO?

    Not sure.

    Also, I wonder if it would work with a new SingleStage Trane or AmStd A/C & Coil later when purchased down the road? I guess it depends on the model I use (not all models?)?
    Not sure I want to keep putting money into new Tstats every time I turn around, hopefully what I get now will satisfy needs later too.

    Whats wrong with a new stat every couple years.
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  6. #45
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,642
    Why not sset-up the fan to the lowest amount of air flow possible short of freeze-up. This would max the amount of dehumidification. Seldom do have any over-dehumidification. Having times of 45%%RH gets the home dried out for all those evenings and rainy days of low cooling loads which even two-speed can not remove much moisture. I have yet to see anyone demonstrate <50%RH dehumidification with fresh air ventilation and occupants during wet cool weather. A whole house dehumidifier maintains <50%RH with no sweat. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  7. #46
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,790
    Because the lowest fan setting that won't freeze the coil.
    May be too low for the days when its near design conditions outside.

    A thermostat that can slow the blower when the indoor humidity gets high, will give the highest system efficiency when humidity is below set point and the blower can run at its higher speed. And still provide good moisture removal on days were humidity is high, and the blower needs to be ran at a lower speed.
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  8. #47
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    Comfort-R is basically a setting in the furnace to allow the blower to run for
    1 minute @ 50%
    7.5 minutes @ 80%
    Then ramp up to 100% till the end of the cycle (If humidistat OR IAQ's dehumidify terminal is connected to furnace, then if humidity is above setpoint then keep blower at 80%, if humidity is below setpoint, go ahead and ramp up to 100%)
    At end of cycle, it drops down to 50% for 3 minutes


    The TCONT402 with the BK terminal connected has the following options built into the thermostat.
    Variable speed turn-on profiles:

    1 minute @ 50%, 7.5 minutes @ 80%, then 100% (If humidistat connected to THERMOSTAT and sensing high humidity, then it will keep it at 80%. If humidistat senses low humidity, it will go ahead and advance to 100%

    1 minute @ 50%, 4 minutes @ 80%, then 100% (unless humistat is connected to stat)

    7.5 minutes @ 80%, then 100% (unless humidistat is connected to stat)

    4 minutes @ 80%, then 100% (unless humidistat is connected to stat)

    1 minutes @ 50%, then 100% (unless humidistat is connected)

    30 seconds with no blower on, then 100% (unless humidistat is connected)
    (Note: there is a setting separate from these in the stat for units without variable speed that can
    do the same delay of the fan for so many seconds to allow the cooling coil to 'pre-chill')

    FAN TURN-OFF PROFILES:

    NO Delay

    1.5 minutes @ 100%

    45 seconds @ 100%

    30 seconds @ 50%

    1.5 minutes @ 50%

    3 minutes @ 50%

    30 seconds @ 35%

    IF humidistat is connected to thermostat AND humidity is above setpoint
    Compressor and Blower will run for additional 3 minutes then both will
    shut off at the same time.


    If Comfort-R is turned on in the furnace,
    the thermostat no longer has control.
    The furnace board will take over and use its Profile


    I'm not sure how the system does the profiles if the fan is in the on position. If there is a humidistat connected (or IAQ dehumid connected)
    then it will still limit the blower to 80%

    I might have missed it somewhere... but why are you wanting to run
    the fan in continuous mode?

  9. #48
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,642
    Quote Originally Posted by beenthere View Post
    Because the lowest fan setting that won't freeze the coil.
    May be too low for the days when its near design conditions outside.

    A thermostat that can slow the blower when the indoor humidity gets high, will give the highest system efficiency when humidity is below set point and the blower can run at its higher speed. And still provide good moisture removal on days were humidity is high, and the blower needs to be ran at a lower speed.
    How many days a year is that? My data logging indicates no days in WI last year. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  10. #49
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,790
    You DATA logging is for one house.

    At one time you use to say your system was over sized. Shortly after it was installed

    And the most recent post say its sized right (The ones since you started posting the charts, or a liitle before you started posting your charts).

    You seem to prefer 74 or 75° as an indoor temp in the summer.
    Many people prefer 72°F at RH% levels of 50% or less.

    You can't use just your home and personal preferences to say that the nation would work the same.

    So, while your homes A/C had no problems keeping up at your prefered conditions, at what ever its current size is.
    You don't know how the rest of the homes in your county did, let alone the rest of the country.

    Just look at the number of post this board gets, of people saying there house gets X degrees above set point, when its what ever temp outside.
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  11. #50
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    My unit is particular is oversized for heating so capacity in cooling mode is not an issue.

    I was wondering what the impact of the reduced airflow (350CMF/ton instead of 400) would be on efficiency on a heat pump in heating mode.

    ON my XL16i, if I'm reading the tables right, I see about a 5% improvement in latent capacity at the lower airflow with a 2% drop in total capacity.

    In heating it's a 1-2% drop in capacity, but it doesn't look like there's any significant change in efficiency as the power consumption drops about the same.

    So it might be a useful if humidity becomes a problem. 350CMF/ton is only a 12.5% reduction so is icing really a concern?

    Obviously the best scenerio is for Trane to offer a non communicating thermostat with a the features of the 402 and XL900 to help out those that mistaken purchased a XL16i... instead of a XL15i

  12. #51
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,790
    35 a ton, is seldom a problem in average humidity climates areas.

    In Las Vegas, it would probably be a problem.
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  13. #52
    Join Date
    Apr 2008
    Location
    Princeton, NJ
    Posts
    581
    I run my Trane XL15i fulltime at 320CFM/ton without issue (so far ).
    I've only used it 1 full season as it was installed spring 2008.
    Key1
    In the land of the blind.....the man with one eye is king....

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