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  1. #14
    Join Date
    Aug 2008
    Posts
    416

    Video vs. His Install

    Just to help the OP understand. Your video shows a duel fuel setup where the heat pump coil is on the bottom (upflow) and you can see the p-trap that was installed. The upper drain connection (that uses the tee fitting) is for condensate from the high efficiency furnace which has its own internal trap. From his description its sounds like he has an ac coil on top of furnace and that the AC coil drain uses a 'tee' fitting. Just guessing.

  2. #15
    Join Date
    Jul 2011
    Location
    Northern VA
    Posts
    8

    Talking Many are not aware of this fact

    The relative humidity of the air coming out of a good A/C unit is close to 100% due to its temperature. If the fan is not run in ON the cold duct can adsorb significant moisture and grow mold on the vents.
    \
    Too high a cfm rating on the evaporator will allow the house to be cooled without extracting the humidity, giving that cave like humidity feeling. Insure that the airflow is set on the low end of the chart so that the due point can be depressed significantly. As the outlet air warms it will absorb greater amounts of humidity, drying the home. In difficult situations, system dehumidifiers may be needed. Woody

  3. #16
    Join Date
    Nov 2003
    Posts
    19
    Thanks - very much

    - tstat is TH8321.

    - There is no p-trap and manual says drain should be capped, not open on main drain, optional on secondary.


    Yes we have the cave feeling. That is perfect description. I also suspect sour smell when unit runs is due to negative pressure causing reverse stack effect. I hate to think what we are pulling in...

    Thanks very much for replies so far, all very reasonable and helpful. I will keep this thread up to date. Humidity seems headed to 60%.


    -Bob

  4. #17
    Join Date
    Nov 2003
    Posts
    19
    Update - tech advised no to p-trap, too many field problems, no way that was going to happen. Lowered speed from 450 to 400 CFM. Said to take it down in small increments and see what happens.

    Interesting that he said to set humidity between 50 to 55%. That is too high for me, I've never lived anywhere where that would be desirable with A/C. Especially when its 38% outside, but mentioned that is what he advises when people set humidity on t-stats that support humidity setting (?). Was worried that too low would cause coils to freeze.

    The adventure continues....

  5. #18
    Join Date
    Nov 2003
    Posts
    19
    Quote Originally Posted by teddy bear View Post
    Measure the supply temp/%RH on high and low speeds. Possible to catch the consdensate going to the drain for a day? Blower should be on auto.
    Using the %RH comparison from outside to inside is confusing you. Better to use the outdoor dew point compared to the inside dew point. Research the difference on the web. Outside currently 70-75^F for most of south central US. You want about 55^F dew point in side with 75^F,50%RH.
    Typically with 2-3 occupants and 100 cfm of infiltrating air, 6 lbs. per hour of moisture must be removed from the home to get to 55^F DP. 6 X 24 = 125 lbs. per day. If you are removing this much moisture per day and the home is still damp, you have excess infiltration of outside air or unusal moisture source in the home.
    Regards TB
    Thanks for reply.

    Austin dew point is about 70F (100F, 38% RH). My dew point in the house calculated using link is 62F i.e. tstat set to 78F, 58% measured RH at tstat and separate digital RH gauge.

    http://einstein.atmos.colostate.edu/.../Humidity.html

    Based on what we used to have - 78F, 45% RH (often less) - that puts the dew point in house at 55F. That is what we had for 7 years before the new unit. So I don't think we have outside air infiltration unless it was introduced somehow with new install.

    No way to catch/measure condensate without tearing apart drain. That is a good idea though!

  6. #19
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,837
    Quote Originally Posted by wraujr View Post
    Just to help the OP understand. Your video shows a duel fuel setup where the heat pump coil is on the bottom (upflow) and you can see the p-trap that was installed. The upper drain connection (that uses the tee fitting) is for condensate from the high efficiency furnace which has its own internal trap. From his description its sounds like he has an ac coil on top of furnace and that the AC coil drain uses a 'tee' fitting. Just guessing.
    I would hope the HP/AC coil is on the bottom because it's a downflow application. It is generally not considered good practice to put the coil on the bottom of an upflow furnace.

    The relative humidity of the air coming out of a good A/C unit is close to 100% due to its temperature. If the fan is not run in ON the cold duct can adsorb significant moisture and grow mold on the vents.

    I don't know where that statement originated but whoever made it has never taken a wet bulb on a supply plenum of an AC system. If the humidity was 100%, how in sam hill would the AC EVER dehumidify the house pre tell?

    bobl, 55% is the RH where mold begins to grow. You're absolutely correct to be setting is below 50%. Reducing the fan speed to 400 CFM is a step in the right direction. But if you're still not happy, don't wait to have them lower it to 350 CFM.

    Many companies do not put a P-trap on the furnace/coil combination where the coil is under positive pressure from the blower, unlike an air handler where the blower (and primary drain pan) are under negative pressure.

  7. #20
    Join Date
    Nov 2003
    Posts
    19

    visionpro 8321U

    Based on some excellent info from skippedover on the way this system works - fan runs after shutdown, I may have been confusing "low" speed with the unit turning off.

    I turned the system off at tstat and waited about 20 minutes. I then put tstat into test mode. I then selected compressor and fan turn on.

    The fan came on low speed. The outside compressor did not come on. I went out to the unit, put my ear up to the side and it was dead silent.

    I then, selected second stage. Fan speed went up and compressor came on.

    Does this seem right? Is there a way to tell if the two stages are working as designed?

  8. #21
    Join Date
    Apr 2008
    Location
    TEXAS
    Posts
    1,701
    every bit of advice you have gotten here has been very good advice. the 16i doesn't remove humidity as well as single stage systems but CAN be set up to work very well. 350 cfm and comfort R is crucial in this climate. get your guys back out asap. the drain vent can be capped with a 90 cent 3/4 pvc cap. it won't do anything to remove humidity tho. call your install company.
    "When the people find they can vote themselves money,that will herald the end of the republic" - Benjamin Franklin

    "Government is not reason, it is not eloquence, it is force;like fire, a troublesome servant and a fearful master. Never for a moment should it be left to irresponsible action"- George Washington

  9. #22
    Join Date
    Nov 2003
    Posts
    19
    Quote Originally Posted by smittyii View Post
    every bit of advice you have gotten here has been very good advice. the 16i doesn't remove humidity as well as single stage systems but CAN be set up to work very well. 350 cfm and comfort R is crucial in this climate. get your guys back out asap. the drain vent can be capped with a 90 cent 3/4 pvc cap. it won't do anything to remove humidity tho. call your install company.
    Thanks - I saw you on contractor map so I think you are S. of Austin.

    That's too bad about 16i - you are second person to mention this. Everything I could get my hands on says two stage is better at humidity control.

    Thanks for your patience - I will have to have tech back again to lower speed more because change from 450 to 400 didn't really make much improvement, if any.

    Take a look at my post above about tstat is this correct? i.e. how do I know if it is running first or second stage?

  10. #23
    Join Date
    Apr 2008
    Location
    TEXAS
    Posts
    1,701
    Quote Originally Posted by bobl View Post
    Thanks - I saw you on contractor map so I think you are S. of Austin.

    That's too bad about 16i - you are second person to mention this. Everything I could get my hands on says two stage is better at humidity control.

    Thanks for your patience - I will have to have tech back again to lower speed more because change from 450 to 400 didn't really make much improvement, if any.

    Take a look at my post above about tstat is this correct? i.e. how do I know if it is running first or second stage?
    don't stress about it too much. the 16i needs to be tweaked to work well in this climate. i have seen happy customers with 16i systems , but in almost every case it took some tweakin to get them that way. i don't have the book in front of me, but tranes tstats are geared toward certain systems (i e comfort R). the fan needs to shut off soon after system shut off and run in lower speed at start. it can be done ,just be patient.
    "When the people find they can vote themselves money,that will herald the end of the republic" - Benjamin Franklin

    "Government is not reason, it is not eloquence, it is force;like fire, a troublesome servant and a fearful master. Never for a moment should it be left to irresponsible action"- George Washington

  11. #24
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Make certain that the new duct connections to the equipment are air sealed.
    Make sure that old duct connections were not disturbed during the installation and leaking air in or out.
    Fix the drain air leak.
    Slow the fan to 350 cfm and other suggestions in post 12.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  12. #25
    Join Date
    Nov 2003
    Posts
    19
    OK - thanks. Humidity was 63% in house this morning.

    The service guy wasn't really interested in my observations - he said it is normal for high volume of air to come streaming out of drain line. No idea if this is true - it wasn't with previous unit. He also said 55% is what they recommend. I know 55% is not normal.

    If anyone else has 16i and access to drain line it would be good to know if this is normal as well as how I can tell if the unit is really working as two stage or one stage.

    This is complicated & expensive system not working well so I appreciate the help from experienced installers.

  13. #26
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,928
    Duct work may be undersized for 4 tons. Old unit may have only been 3.5 tons.
    Air handler is probably not set up right.

    Blower can be set to a slower speed. Which will improve your indoor RH.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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