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  1. #1
    Join Date
    Apr 2004
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    how do economizers work

    i come from a residential background and am now being asked to work on rooftop units, new company. any info as to how they work and troubleshooting would b great

  2. #2
    Join Date
    Nov 2010
    Location
    Missouri
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    http://www.fscc-online.com/HIW-Econo...onomizers.html

    Here is some reading material so you can grasp all that you can. I found that at google typing in economizers.

  3. #3
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    Nov 2006
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    Southeastern Pa
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    Quote Originally Posted by xpuser357 View Post
    http://www.fscc-online.com/HIW-Econo...onomizers.html

    Here is some reading material so you can grasp all that you can. I found that at google typing in economizers.
    FYI to the OP:

    The unit shown in the link is typical of the York/JCI Sunline model, usually around 5 tons of capacity.

    When you get to your first few units, write down the Honeywell number on the module that controls the economizer. We call it a "logic module."

    Take that number and look it up on the Honeywell website, and you can download docs that will explain how to test the economizers.

    The basic approach is this:

    The unit receives a call for cooling from the thermostat. The logic module compares the signal from its enthalpy sensor to the enthalpy setting on the module. If the setting dictates that the air being sensed is cool enough to provide cooling, the module will command the actuator motor to open the dampers and admit the outside air into the space for cooling. If the stat calls for second stage cooling, then the logic module will bring on the first stage circuit in a dual circuit unit to run as the second stage of cooling, augmenting the cool outside air being brought in, and cooling it further using the vapor circuit.

    If the enthalpy sensor and setting indicates that the outside air contains too much heat for cooling, then the logic module sends the Y1 call back to the control section, energizing the 1st stage compressor contactor. At that point, the economizer remains out of the picture, and a Y2 call goes right to the second stage contactor.
    [Avatar photo from a Florida training accident. Everyone walked away.]
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  4. #4
    Join Date
    Oct 2011
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    Chicagoland Area
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    Don't worry. They have all been bypassed because no one knows how they work.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  5. #5
    Join Date
    Feb 2006
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    Quote Originally Posted by 2sac View Post
    Don't worry. They have all been bypassed because no one knows how they work.
    Lol ....

    Sent from my HTC Sensation 4G using Tapatalk 2

  6. #6
    Join Date
    Jan 2010
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    Quote Originally Posted by 2sac View Post
    Don't worry. They have all been bypassed because no one knows how they work.
    Yep....Half the ones I see have never even been plugged in

  7. #7
    Join Date
    Apr 2012
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    Quote Originally Posted by kenny3412 View Post
    i come from a residential background and am now being asked to work on rooftop units, new company. any info as to how they work and troubleshooting would b great
    Depend on you where you live. Certain geographical parts of the US may require
    massive amounts of ac but because of the humidity economizers are not practical.

    Houston is a good example. Economizers everywhere but maybe used just a couple of weeks per year if that.

    They're pretty easy to trouble shoot and repair.

  8. #8
    Join Date
    May 2011
    Location
    Oklahoma
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    Quote Originally Posted by 2sac View Post
    Don't worry. They have all been bypassed because no one knows how they work.
    I've got too much to do than mess with some "logic module" when I can just bypass it and move on to the next unit. I'm an in house tech so none of this dis-service to the customer baloney, the boss is the one that showed me to plug the harness back into itself to bypass it! Too hot or cold around here for them to ever open anyway, you ought to call them "fuse test modules."

    Not to say I don't want to learn more about them, I'm just too busy to bother with that right now.

  9. #9
    Join Date
    Jan 2010
    Posts
    6,238
    [QUOTE=matt1124;13612031] Too hot or cold around here for them to ever open anyway

    Cold is when they open and save $$$$$$

  10. #10
    Join Date
    May 2011
    Location
    Oklahoma
    Posts
    362
    [QUOTE=VTP99;13612081]
    Quote Originally Posted by matt1124 View Post
    Too hot or cold around here for them to ever open anyway

    Cold is when they open and save $$$$$$
    lol either the ac is pulling down past the ambient temp OR the burners kick on for heat. This year there was only a handful of days they'd "open and save $$$$$$" and I'm sure summer to winter will be the same story

  11. #11
    Join Date
    May 2011
    Location
    Oklahoma
    Posts
    362
    I wish server rooms could have economizers, I'd keep spare boards on hand to keep those working. IT has to have their fancy Lieberts though...

  12. #12
    Join Date
    Feb 2012
    Location
    New York City
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    106
    The economizer module also handles the min OA position for ventilation needs during occupancy. If your OA and relief dampers aren't at least slightly open when your space is occupied, you likely have a code violation. Turning off minmum fresh air when occupants are around is not an acceptable strategy except say when your furnace fails completely and you need to freeze protect the building.

  13. #13
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    Nov 2006
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    Quote Originally Posted by 19characterusername View Post
    The economizer module also handles the min OA position for ventilation needs during occupancy. If your OA and relief dampers aren't at least slightly open when your space is occupied, you likely have a code violation. Turning off minmum fresh air when occupants are around is not an acceptable strategy except say when your furnace fails completely and you need to freeze protect the building.
    I don't see that aspect of the building code being addressed in the states where I work.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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