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  1. #1

    wiring stand alone CO2 into economizer

    I am relatively new to the field and i had a question that will come probably realatively easy to you guys. i have installed the CO2 already in the space and the wire is at the economizer module area. the economizer is a Honeywell W7212 and the CO is a a Honeywell C7232a. Its pretty self explanatory where its getting the 24volts, but the question is there is 4 wires left over. analog output common,analog output signal,relay output normally open and finally relay output common. Thank you for any help offered in advance.

  2. #2
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    928
    http://customer.honeywell.com/techli...0s/63-8594.pdf

    Starting PDF page 127 or actual document page number 121.

  3. #3
    you need to know what signal your controller or actuator takes the co2 sensor usually will have your 24v to power it then puts out a 2 to 10 vdc signal out usually to a specified terminal or actuator to open osa dampers.

  4. #4
    Join Date
    Mar 2012
    Location
    Balto Md
    Posts
    2
    The 2 to 10 volts or 4 to 20 mili amp unit selectable, signials to EMS energy management
    which trends the levels. The relay output dry contact controls fan and damper output.
    the 24 volt hot wire usually operates device and connects to dry contacts for fan and damper operation. Be carefull when connecting two seperate power sources it must be correct. I have seen factory and engineering drawings incorrect in this area

  5. #5
    Join Date
    Feb 2012
    Location
    New York City
    Posts
    106
    Just a heads up, the way DCV works is on space CO2 below max setpoint it allows you to modulate the OSA damper closed to save energy from the minimum position (which might correspond to 20% OA for example), rather than modulating it open toward the 100%/economizer position to aggressively maintain that setpoint. A lot of people get this wrong including controls PMs I've dealt with at JCI.

  6. #6
    Join Date
    Feb 2012
    Location
    Upstate SC
    Posts
    84
    Quote Originally Posted by 19characterusername View Post
    Just a heads up, the way DCV works is on space CO2 below max setpoint it allows you to modulate the OSA damper closed to save energy from the minimum position (which might correspond to 20% OA for example), rather than modulating it open toward the 100%/economizer position to aggressively maintain that setpoint. A lot of people get this wrong including controls PMs I've dealt with at JCI.
    I am glad you brought that point up. I did an install several years ago and thought it to be a good idea. Large space lightly occupied most of the time with high occupancy for short durations. Why do 6 air changes an hour based on max occupancy?

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