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  1. #1

    Humidity Control Problem with Honeywell VisionPRO IAQ

    Bald Loonie or other Honeywell and Trane Gurus,

    From Austin, Texas....just had a 3-ton Trane XL15i AC, XV80 indoor system, and a HW VP IAQ thermostat installed....based in large part on the knowledge gleaned from this forum.

    Two interrelated problems still at this point, described below. I suspect the stat may not have been properly installed but don't know for sure.

    Problem 1: I set the thermostat at a 45% humidity level. But the system only comes on when the temp goes above the setting (usually at 77 or 78). The humidity reading on the thermostat varies from 48-50%, which is not bad but it is not the level desired and not what the stat is set for. My understanding was the the system would operate until the desired humidity level was reached and would go as much as 3 degrees below stat setting, but that is not happening.

    Problem 2: My understanding was the thermostat would/could control the variable fan speed of the XV80 to dehumidify. But that doesn't appear to be happening either. When the fan comes on, it always goes through the SAME 3-step ramp up and 2-step ramp down process (low-medium-high-medium-off). I expected that if humidity were still high after temp level is reached, the stat would just trigger a low or medium fan speed till the humidity setting is reached. The only way a 45% humidity level can be reached is if I set the temp at 74-75, but is too cold for us and less efficient.

    Is this the way the VisionPro IAQ (with the XV80) is supposed to work or there likely a wiring or setup problem between stat and the XV80? Any tips,tricks, or questions I could share with the installer, who I hope to get back here tomorrow?

    Seems like any ol thermostat could do what the IAQ is currently doing.

    Thanks, Masterofnone

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,295
    Not totally sure on the overcool feature as I have mine turned down but the humidity may have to be lots more than a few points above setpoint for the overcool to happen. Seems to me that's the way it works.

    Also dehumidify on demand has to be specifically wired in & turned on with the IAQ and the furnace board to do anything. If the installers didn't bother to do that, you don't have it.

    My last furnace was an XV80, when I added the IAQ to it, I shut off the slow ramp, Comfort R and let the DOD control things. House was more comfortable and more even with the blower coming up to 100% right away. The ramp up is fine if you don't have the DOD capability but I wouldn't use both. Could be lots of times you don't need humidity control yet the ramp up is costing you capacity anyway.

  3. #3
    Bald Loonie, I doubt if my installers were as knowledgeable as you. It sounds like the XV80 and stat have the functionality available; it just hasn't been set up or wired the way it needs to be. Any recommendation on where I could specifically direct them, to some manual or to a HW rep, to set the system up the way you describe, which would seem to be more comfortable and efficient. Thanks

  4. #4
    Join Date
    Mar 2010
    Location
    Downriver, Michigan
    Posts
    14
    Parameter number 379 should be set to 1 for "dehumidify with air conditioning"
    Option 1 uses dehum terminal as a normally closed relay to wire to a low-speed fan terminal.

    D

    Check here: http://customer.honeywell.com/techli...69-1815EFS.pdf

  5. #5
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,085
    interestingly enough, how many of you have actually listened to a blower drop during a call for dehumidification?

    I have. I thought I wired it wrong, because I didn't hear the difference. It's because noise wise, there is no difference.
    10% drop in blower speed is only 120cfm on a 3 ton. Thats out of 1200 cfm. It's not a difference noticable to the ear.

    Before calling a tech out, heres something for you:

    In the honeywell installation guide for the IAQ, it shows the user how to enter into test mode. It also shows you how to test dehumidification mode. If the AC comes on, then dehumification works.

    As far as checking to see if the blower is being slowed......take a picture of your IAQ module at the furnace with the IAQ door off. I can make a good estimate based on it.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  6. #6
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    992

    I would

    call the installing co. and explain this to them. You might have to talk to the service manager. Hopefully either he or one of their more experienced techs will check it out for you. Things are changing so fast in the HVAC world it's sometimes hard to keep up with all the technology.

  7. #7
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
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    5,085
    Quote Originally Posted by StahlMaster View Post
    Parameter number 379 should be set to 1 for "dehumidify with air conditioning"
    Option 1 uses dehum terminal as a normally closed relay to wire to a low-speed fan terminal.

    D

    Check here: http://customer.honeywell.com/techli...69-1815EFS.pdf
    not exactly.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  8. #8
    Join Date
    Mar 2010
    Location
    Downriver, Michigan
    Posts
    14
    Quote Originally Posted by hvacvegas View Post
    not exactly.
    Then there must be an error in the installation manual as I've quoted from page 16 of the VisionPro IAQ Total Home Comfort System Installer Set-up menu Table #3 ISU Parameter Number 379 "Dehumidification Control"

    D

  9. #9
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,085
    Quote Originally Posted by StahlMaster View Post
    Then there must be an error in the installation manual as I've quoted from page 16 of the VisionPro IAQ Total Home Comfort System Installer Set-up menu Table #3 ISU Parameter Number 379 "Dehumidification Control"

    D
    Whats a low-speed fan terminal?
    High voltage, low voltage?

    Some would consider a low-speed fan terminal to below a low speed tap on a PSC blower. Which is not what this is used for.

    Which is why I said: "Not exactly", instead of "your wrong".
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  10. #10
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,713
    there should be a 20% reduction in air flow when the unit is in dehumidify they probably did not do any thing with the bk or wire the thermostat correctly

  11. #11
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    Quote Originally Posted by hvacvegas View Post
    interestingly enough, how many of you have actually listened to a blower drop during a call for dehumidification?

    I have. I thought I wired it wrong, because I didn't hear the difference. It's because noise wise, there is no difference.
    10% drop in blower speed is only 120cfm on a 3 ton. Thats out of 1200 cfm. It's not a difference noticable to the ear.

    Before calling a tech out, heres something for you:

    In the honeywell installation guide for the IAQ, it shows the user how to enter into test mode. It also shows you how to test dehumidification mode. If the AC comes on, then dehumification works.

    As far as checking to see if the blower is being slowed......take a picture of your IAQ module at the furnace with the IAQ door off. I can make a good estimate based on it.

    Noise depends a lot of # & size of registers and duct sizing. My home for example is marginal on the duct size, so I can hear even a 100 CFM change. When it goes from low speed to med-hi, it's a huge difference esepcially on my upstairs system.


    There is one problem with overcooling to dehumidify. While you ar eincreasing run time, as you lower the temperature, with the same dewpoint the RH will increase. If hte system isn;t rpoperly sized, you'll find that unless it's near design termpature, you'll more often than not find yourself "overcooled" most fo the time.

    You can however, then readjust the setpoint in your program accordingly to compensate for this.


    Keep in mind that achieving a 45% RH in many homes in most climates is not realistic. Either the unit to too big, or the home is too leaky to achieve that level... especially with higher effeciency equipment with their large coil surfance areas.

  12. #12
    Join Date
    Aug 2011
    Location
    Northwest Indiana
    Posts
    40
    For things to ask the installing company to check - the EIM will have to be wired to the DH (or equivalent) terminal on the furnace in order to control fan speed on an call for Dehumid. That will involve jumping R over, etc. as shown here:http://franklinheatandair.com/pdfeqm...ell/hwiaq2.pdf
    I'll stop there for fear of giving too much DIY info. If configured correctly (both wiring and stat config) the indoor unit should be able to run at the low fan speed for the purpose of dehumidification up to 3 degrees below cooling setpoint. If the installer doesn't have the proper install manuals (they should!) I'll save you the trouble finding that as well - http://www.ntsupply.com/files/produc...AQTECHDATA.pdf

    Best of luck - sounds like you have a great system, now just need to get it "under control" the way you want it to be.

  13. #13
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,357
    Quote Originally Posted by motoguy128 View Post

    Keep in mind that achieving a 45% RH in many homes in most climates is not realistic. Either the unit to too big, or the home is too leaky to achieve that level... especially with higher effeciency equipment with their large coil surfance areas.
    Untrue. I do it every day in summer with single stage cooling. Lately indoor humidity levels have been in the low 40% range.

    I also live in what's known as a "mixed-humid" climate. It's been very dry this year, which may partly explain my performance, but we had rain Saturday, higher humidity yesterday, and I still stayed in the low forties, no sweat (literally!). In fact I even turned the ceiling fan off at one point in the afternoon and raised the stat one degree.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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