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  1. #1
    Join Date
    May 2011
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    North Carolina
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    314

    Question about nviSetpoint and eff cooling setpoint



    Hope every is well!!! I have a basic question about the nviSetpoint and the effective cooling setpoint. We have a site that has the ability to set the space temp with an NRM or a network setpoint. The hi setpoint limit is 72 and the low is 68 (dead band of 4). If the user sets the network setpoint to 70 degrees the effclgsetpoint is 68 (70 - half dead band(2)) so the 68 degree value is what the VAV is controlling too? Why doesn't it control to the 70 degree setpoint? This is confusing to the end user some what and I'm having a hard time getting it explained to him in a way that he understands. All he keeps saying is, "If I set the network setpoint to 70 then that's what I want the space temp, not 68. I shouldn't have to set the setpoint to 72 to get 70 in my space!"

    Thanks again for helping the new guy out!!!

  2. #2
    Join Date
    Mar 2005
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    Pacific Time Zone
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    4,211
    What system are you dealing with?

    This a manufacturer specific issue.
    "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
    Mar 2005
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    Pacific Time Zone
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    Do you have a parameter to set the effective setpoint source?

    If so you might want to change that setting. One setting, which would be like what you are experiencing now displays the 'average/norm' setpoint (heating setpoint + cooling setpoint / 2). The other setting displays the current actual setpoint depending on what mode the unit is in, heat or cool. The problem many times with displaying the actual setpoint is when the unit switches from heat to cool. I've had numerous complaints - "Well I set it to 68 and then later in the day I see my setting changed to 72." If you're in a climate where the mode doesn't change very often then maybe this would be a more ideal setting.
    I generally use 'norm' and simply tell people it will control as needed to prevent short cycling of the heating and cooling on the people that notice. I've gotten far fewer service calls using norm than using actual setpoint.

    So if you have a 102-AX (Schneider/TAC) From http://www.tac-global.com/docnet/pdf-filer/00478381.pdf Pg. 45

    "Effective Setpoint Source (nciVAVSelctnCntl.oP.ESS)
    The Effective Setpoint Source (ESS) parameter controls the value that displays on the
    I/STAT when you select SET TEMP. A value of ACu (Actual) displays the current active
    cooling or active heating setpoint. This is the default setting. The I/STAT will display
    the setpoint that is closest to the temperature in the space. A value of nor (norm) displays
    the average of the active cooling and active heating setpoints. To select the ESS parameter,
    use the [+/-] key to toggle the selection."
    "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/


  4. #4
    Join Date
    Feb 2007
    Location
    Helena, Montana
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    2,155
    Is this a cooling only application? Does the end user understand deadband?
    Don't worry zombies are looking for brains, you're safe...

  5. #5
    Join Date
    May 2011
    Location
    North Carolina
    Posts
    314
    Hey guys! Thanks for the responses. The system is JCI. I'm not 100% sure what type of NRM's that are in the spaces. I will find out.

    crab master. Thanks for the information. I will see if I can change the settings you mentioned to help the problem.

    ControlsInMT. This VAV has 2 stages of heat in it and a fan.

    Something else. Another VAV that is the same as the one I'm asking about, with the same setup doesn't act this way. When I set the network setpoint at 70, the effective cooling is also 70. More headscratching.....

  6. #6
    Join Date
    May 2011
    Location
    North Carolina
    Posts
    314
    Oh yeah. The user doesn't want to understand dead band. He says he doesn't really care about it. He wants the space the same temp he sets the network setpoint to. He's an older set in his ways kinda guy. No reasoning or compromising for the most part. Other than that he is a great guy!!!

  7. #7
    Join Date
    Aug 2007
    Location
    Western Colorado
    Posts
    497
    It seems to me there is some problem in the EffStPt calculation. When I make a single StPt system, I ADD the Diff to the single StPt for EffClStPt and I SUBTRACT the Diff for the EffHtStPt, tell the customer the space between the two EffStPts is the
    "Zero Energy Band", (this is where he saves MONEY!). How are you ending up with an EffClStPt LOWER than StPt? What happens to the single StPt in heat mode?
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  8. #8
    Join Date
    May 2011
    Location
    North Carolina
    Posts
    314
    Quote Originally Posted by rad1 View Post
    It seems to me there is some problem in the EffStPt calculation. When I make a single StPt system, I ADD the Diff to the single StPt for EffClStPt and I SUBTRACT the Diff for the EffHtStPt, tell the customer the space between the two EffStPts is the
    "Zero Energy Band", (this is where he saves MONEY!). How are you ending up with an EffClStPt LOWER than StPt? What happens to the single StPt in heat mode?
    I'm going to have to assume (bad thing I know) that whomever did the program set it up that way. I will try to find the APD files and figure out why.

  9. #9
    Join Date
    Mar 2010
    Location
    Hot Desert SW
    Posts
    27
    Been in the same situation, and I have had people tell me to set the Occheat and OccCool setpoint the same and the EffStpt will equal nviSetpoint. I have done this but didn't feel warm and fuzzy about it. I was told there will be a "hidden" deadband of @ 1.5 deg. F, but I am not sure I believe it, although watching a controller for a bit seemed to verify the that there is a deadband built in. My solution for dealing with this situation is to explain slowly and concisely to the end user that EVERY type of thermostat has some type of deadband in it, and to explain to them that deadband is where they save $$$ as mentioned above. I also have had luck using the gas pedal / brake pedal in a car anology in reference to heating and cooling. Seems to work pretty well. Good luck

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