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  1. #1
    Join Date
    Jan 2001
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    7,520

    Humidification/Dehumidification

    I am installing a Neptronic SK 300 Humidifier in a printing room at a plant.

    It is the bacnet model and uses a HRO 20 Humidistat/Wall controller.

    I am having to do both humidification and dehumidification for the room and have no experience in setting up control strategies for either.

    Our plan is to let the HRO 20 do the control and just monitor the room for the graphics etc using the bacnet.

    Its a honeywell system...jace.....and Im using a spyder to control the air handler and condensing units.

    Im fine with letting the humidifier control the humidity. This is a plant, the air handler is always on and the humidifier has safeties to prevent it from running with no airflow and there is also a high humidity safety in the supply duct.

    Right now Ive got some logic in the spyder to control dehumidification using a wall mounted zio with space temp and a humidity sensor. Im letting a pid control the cooling based on humidity and a heat pid working off the space temp to maintain the space temp.

    What Im wondering is if I can use the Neptronic SRO 20 humidistat to control dehumidification also.

    The HRO 20 instructions show a dehumidification analog output and a dehumidification binary output.

    The instructions give no clue how to set up and use these two outputs but Im thinking I can use the SRO dehumidification output to solely control my condensers..... there will be no cooling pid whatsoever and the only heating/cooling logic in my spyder will be a heat pid to maintain space temp.

    Does this sound reasonable ???

    Ive also considered using the SRO to control dehumidification but also putting in my own cooling pid in the spyder and using the SRO 20 dehumidify BO to enable and disable the cooling pid....... this way...in times when they might need cooling but not dehumidification.....the cooling can work.

    I dont see the above scenario occuring.....but the logic would be there just in case.

    Any helpfull feedback would be appreciated.

  2. #2
    Join Date
    Mar 2005
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    Pacific Time Zone
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    Quote Originally Posted by corny View Post
    Right now Ive got some logic in the spyder to control dehumidification using a wall mounted zio with space temp and a humidity sensor. Im letting a pid control the cooling based on humidity and a heat pid working off the space temp to maintain the space temp.

    What Im wondering is if I can use the Neptronic SRO 20 humidistat to control dehumidification also.
    Sounds like you might have things potentially fighting/short cycling doing this. I'd pick one as the main control and then use the other as a 'backup' or use both but make both call for dehumidify, not one or the other.

    Quote Originally Posted by corny View Post
    The HRO 20 instructions show a dehumidification analog output and a dehumidification binary output.

    The instructions give no clue how to set up and use these two outputs but Im thinking I can use the SRO dehumidification output to solely control my condensers..... there will be no cooling pid whatsoever and the only heating/cooling logic in my spyder will be a heat pid to maintain space temp.

    Does this sound reasonable ???
    No, not completely - what about the fan and fan proof, also what about a low room temp/low supply temp limit?

    Quote Originally Posted by corny View Post
    Ive also considered using the SRO to control dehumidification but also putting in my own cooling pid in the spyder and using the SRO 20 dehumidify BO to enable and disable the cooling pid....... this way...in times when they might need cooling but not dehumidification.....the cooling can work.

    I dont see the above scenario occuring.....but the logic would be there just in case.
    This makes more sense as you can still use the controller logic for other built in safeties. Since you mentioned condensers I assume more on off control so it'll be tougher to keep your cooling coil just above dewpoint when you don't want to dehumidify, but another thought for you. Ideally you only let you cooling coil get below dewpoint when you need dehumidificaton.
    "How it can be considered "Open" is beyond me. Calling it "voyeur-ed" would be more accurate." pka LeroyMac, SkyIsBlue, fka Freddy-B, Mongo, IndyBlue
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  3. #3
    Join Date
    Aug 2011
    Location
    Florida
    Posts
    5
    In dehumidification at over 50% (adj stpt) I would discharge 55 deg F at the cooling coil and use the heating coil to modulate the discharge air temperature to maintain the room temperature setpoint. When dehumidification is complete at say below 40% I would release the heating and cooling to maintain room setpoint. I would bring on the humidification system when the humidity falls below 20% and turn it off when it increases to over 30%. You can adjust those numbers and see if that helps.

  4. #4
    Join Date
    Jan 2001
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    7,520
    Thank you for the replies.

    I also hope its obvious that I am totally clueless on dehumidification and dehumidification strategies.

    The folks want that room to be 70 degrees at 50 percent humidity... within reason... The old setup maintained space temp plus or minus 5 degrees and humidity plus or minus 10. They want that tightened up a bit.

    Ive just got a couple of pids in it now with the dehumidification setpoint running the ac and the heating pid maintaining spacetemp.

    Crude..I guess...but its working.

    Am I wrong in my thinking that I should be controlling the ac with dehumidification setpoint and the heat with roomtemp ???

    I also have a fresh air intake but left it closed for now as I wasnt sure how to bring it into play..... After reading some I now know that its going to be best to use fresh air both to help with dehumidification and also to keep the room pressurized...

    Anyhow.. for now it seems to be under control....but I would like to do this thing right...got a couple of weeks...I hope.... before I go back and have to get everything operational.

    In the end Im going to want the humidifier controller to control space humidity in both humidify and dehumidify modes and let the space temp sensor just worry about outside air and maintain room setpoint.

    Im fine with building the logic to do this....just need a proper strategy.

    Any help, suggestions or criticisms are welcome.

  5. #5
    Join Date
    Mar 2005
    Location
    Pacific Time Zone
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    What is your location? Say for example Florida vs Arizona? It'll make a difference especially now you mention outside air control.

  6. #6
    Join Date
    Jan 2001
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    Location is Tennessee.

    Some of the equipment in the room has exhaust fans and Im going to have to replace that air. Im planning on having a minimum position on the outside air dampers and limiting their operation on humidity and temperature of the outside air.

    There are safeties in the system also, freeze stat, high humidity limit in the duct, fan proving switch,

    Going to be there next week so I will have an opportunity to get my final logic installed and monitor the system for a few days while working the bugs out.

  7. #7
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    Quote Originally Posted by corny View Post
    I also have a fresh air intake but left it closed for now as I wasnt sure how to bring it into play..... After reading some I now know that its going to be best to use fresh air both to help with dehumidification and also to keep the room pressurized...
    Quote Originally Posted by corny View Post
    Location is Tennessee.
    I am not saying I know your climate, but I would think you're more humid. You better check your psychometric chart on your various outside air conditions. I would bet you would be needing to dehumidify that outside air quite often.

    This is where a energy recovery equipment would be highly effective. Wheels/coils transferring the energy from the exhaust air to the outside air and possibly dehumidifying the outside air before it comes in.
    "How it can be considered "Open" is beyond me. Calling it "voyeur-ed" would be more accurate." pka LeroyMac, SkyIsBlue, fka Freddy-B, Mongo, IndyBlue
    BIG Government = More Dependents
    "Any 'standard' would be great if it didn't get bastardised by corporate self interest." MatrixTransform
    http://threedevilskennel.com/ - not my website.
    Versatile Hunting Dog Federation - www.vhdf.org/


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