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  1. #27
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    Mar 2005
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    agree
    Keep it simple to keep it cool!

  2. #28
    Join Date
    Sep 2007
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    Kenilworth NJ
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    Quote Originally Posted by Spitz View Post
    .

    Sent from my SM-G960U using Tapatalk
    Handy! You got a link for that by chance?
    Hmmmm....smells like numbatwo to me.

  3. #29
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    Jul 2018
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    Wisconsin
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    ae21-1369 r4

    Search that number

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  4. #30
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    Mar 2005
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    Mountain/Pacific Time Zone Typicallly
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    Ok if this a a pet project to learn from that is one thing, but you are taking a lot of risk and there is a lot of unknowns to your system. Economizer, VAV's, area climate, etc.

    For a pet project I would add a controller to log data.
    Suction Pressure and temperature before compressor to get superheat at compressor
    High side pressure and liquid line temperature to get subcool
    If economizer mixed air temperature to verify inlet temperature isn't too low at evap.
    Supply/Discharge air temp
    Return air temp

    Logic to protect compressor (superheat calcs), ramp up/down as needed
    An EEV would be ideal, could add one with a built in controller and just pull data from that.

    It'd be a cool project, but not sure you'll save $ doing this big picture wise, very unlikely on just one unit. As you get this down and can cut install time maybe...now to add to it your not a refrigeration guy, keeping a compressor 'safe' and running long term is not a simple task on such a system.

    Also not sure what's controlling head pressure, but quick story...worked on units in which programmers were trying to save operating costs and keep head pressure as low as possible, well system wouldn't work correctly in cold weather. Head pressure ended up running so low that the minimum pressure drop across the metering device was not being maintained and therefore system wasn't operating correctly and excessive compressor replacements. Pressures setup to ensure 100 psi differential on metering device and system started working properly. Low ambient kits were not needed at this location, but something maybe you need depending on climate.
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  5. #31
    Join Date
    Mar 2005
    Posts
    1,233
    Post Likes
    Quote Originally Posted by crab master View Post
    Ok if this a a pet project to learn from that is one thing, but you are taking a lot of risk and there is a lot of unknowns to your system. Economizer, VAV's, area climate, etc.

    For a pet project I would add a controller to log data.
    Suction Pressure and temperature before compressor to get superheat at compressor
    High side pressure and liquid line temperature to get subcool
    If economizer mixed air temperature to verify inlet temperature isn't too low at evap.
    Supply/Discharge air temp
    Return air temp

    Logic to protect compressor (superheat calcs), ramp up/down as needed
    An EEV would be ideal, could add one with a built in controller and just pull data from that.

    It'd be a cool project, but not sure you'll save $ doing this big picture wise, very unlikely on just one unit. As you get this down and can cut install time maybe...now to add to it your not a refrigeration guy, keeping a compressor 'safe' and running long term is not a simple task on such a system.

    Also not sure what's controlling head pressure, but quick story...worked on units in which programmers were trying to save operating costs and keep head pressure as low as possible, well system wouldn't work correctly in cold weather. Head pressure ended up running so low that the minimum pressure drop across the metering device was not being maintained and therefore system wasn't operating correctly and excessive compressor replacements. Pressures setup to ensure 100 psi differential on metering device and system started working properly. Low ambient kits were not needed at this location, but something maybe you need depending on climate.
    in a nut shell
    Keep it simple to keep it cool!

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