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  1. #1

    A Couple of Questions About Humidity Control

    My new system:
    Condenser: Carrier 24ACB736A003 (two stage)
    Coil: Carrier CSPHP4212ATA
    Furnace: Carrier 58PHA090-16 Furnace (ECM motor)
    Media Filter: Honeywell F100
    Thermostat: Honeywell VisionPro 8000 with Humidity Sensing

    I live in southeast Texas. I went for this system thinking that the enhanced de-humidification of a two-speed system would be worth it. It appears to be a very popular system in my area. I had two MAJOR Carrier dealers quote me the same system, and they both referred to it as their standard "gold" system, for what thats worth. I've only owned the system for two weeks now and I'm already having remorse.
    I'm presently running the thermostat in "permanent hold" mode until we decide on how we'd like to program.

    My first issue: the condenser unit never seems to go into low speed mode - its either on or off. For example, Temp setting: 75F, Humidity setting: 50%. When the thermostat reads actual temperature of 75F, if the humidity is still high, say 54%, the blower goes into low speed mode and the condenser shuts off. What combination of settings can I try to verify that the low-speed stage on the condenser unit is/is not working?

    My second issue: in low-humidity conditions (yes! it happens here, albeit rarely), the system wants to increase humidity. For example, Temp setting: 75F, Humidity setting: 50%. When the thermostat reads actual temperature of 75F, if the humidity is lower than the humidity set point, say 43%, the blower goes into low speed mode and the condenser shuts off. After a few minutes the system is putting out tepid air, and will continue to do so until the room temperature rises above set point. I would really rather the system completely simply shut off instead of trying to raise the humidity. Is that even possible with my equipment?

    Maybe its just the wrong thermostat for my preferences? Any help or advice would be welcome!!

    Thanks-

    Rick

  2. #2
    Join Date
    Jan 2004
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    Lancaster PA
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    Sounds like thermostat is set up wrong. And possibly the system is wired wrong.
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  3. #3
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    The Infinity controller may be a better choice. Carrier expert will soon follow.

    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"

  4. #4
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
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    Quote Originally Posted by teddy bear View Post
    The Infinity controller may be a better choice. Carrier expert will soon follow.

    Regards TB
    Can't be used with the 58PHA furnace (Performance series), unfortunately. This furnace doesn't have a variable speed blower, which is preferable with 2-stage condensers, but it has 5 pre-programmed speeds. The installer chooses one of these speeds for high-stage cooling, and low-stage cooling operates with the constant fan airflow.

    OP: By your description, it sounds like the fan is constantly running whether there is a call for cool or not. This will tend to raise the indoor humidity, but the thermostat is not "trying" to raise the humidity. The 8000 doesn't work this way. Is the thermostat fan setting auto? Also, with the 8000 thermostat, it is normal for the condenser to shut off even if the humidity setpoint isn't completely met (e.g., 54% instead of 50%). Your installer can adjust the overcooling range (1-3 deg) for better humidity control.
    Last edited by RyanHughes; 10-29-2012 at 10:22 PM.

  5. #5
    Join Date
    Jul 2008
    Location
    Rochester NY
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    Quote Originally Posted by RyanHughes View Post
    Can't be used with the 58PHA furnace (Performance series), unfortunately. This furnace doesn't have a variable speed blower, which is preferable with 2-stage condensers, but it has 5 pre-programmed speeds. The installer chooses one of these speeds for high-stage cooling, and low-stage cooling operates with the constant fan airflow.
    Too bad, Infinity with 2 stage CU is so nice. Funny how big the incremental cost looks at decision time and how small it looks with hindsight and regret.

    Sounds like they told him it had an ecm...
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  6. #6
    Join Date
    May 2007
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    DC Metro Area (MD)
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    Quote Originally Posted by tedkidd View Post
    Sounds like they told him it had an ecm...
    They probably did, and it does. But as you know, not all ECM motors are variable speed, which is a point of confusion for some people. The 58PHA has a fixed-speed ECM motor with 5 speed taps. It will work with a 2-stage outdoor unit. Blower speeds need to be set properly for the CU size

    I agree with you on the Infinity upgrade. The Infinity really does a good job handling humidity when matched with the Infinity furnace and Infinity-compatible outdoor unit. For a bit more money upfront it sure is a nice upgrade over the "standard" 2-stage system.

  7. #7
    Not constantly on but pretty near. The fan is set to "Auto". As I mentioned above I'm running in "Permanent Hold" system mode until we decide on programming. I just can't wrap my head around the fact that if the measured temperature is the same as set temperature and the measured humidity is less than the set humidity by more than about 2% then the fan comes on in low mode with the condenser unit off. My installer told me that this is normal so as to increase humidity. I would much rather the system simply shut off completely. Overcooling is presently set to 3 degrees but I'm thinking with experimenting with that as well as it appears to be a simple thermostat setting change. Thank-you Ryan for trying to help!

  8. #8
    Join Date
    Jul 2008
    Location
    Rochester NY
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    You get how your humidifier works? Water flows across a screen as air flows through it, evaporating water into the air delivered to your house.

    Humidity is "latent" heat. Comfort is a function of latent (relative humidity) and sensible (temperature) heat.

    So imagine things reversed. Imagine the system shut off when target humidity was achieved irrespective of temperature. That would not make you happy.


    If you don't like that it runs because your humidity target is not met, turn your humidity target down. But remember it's not the equipment fault when your lips chap and sinuses bleed.

    How leaky is your house? If you tighten the house you'll lose less of both types of heat to outdoors.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  9. #9
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Quote Originally Posted by rbdavis2 View Post
    Not constantly on but pretty near. The fan is set to "Auto". As I mentioned above I'm running in "Permanent Hold" system mode until we decide on programming. I just can't wrap my head around the fact that if the measured temperature is the same as set temperature and the measured humidity is less than the set humidity by more than about 2% then the fan comes on in low mode with the condenser unit off. My installer told me that this is normal so as to increase humidity. I would much rather the system simply shut off completely. Overcooling is presently set to 3 degrees but I'm thinking with experimenting with that as well as it appears to be a simple thermostat setting change. Thank-you Ryan for trying to help!
    The 8000 does not communicate anything with regards to humidity to the furnace. The dehumidification control is internal to the 8000 thermostat, and it won't run the fan to increase humidity. It will overcool (run the compressor) up to 3 degrees below setpoint to dehumidify. It does not control humidification. So, if your fan is running when set to Auto and there is no active call for cooling, then something may not be set up correctly within the furnace.

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