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Thread: Define Twinning

  1. #14
    Join Date
    Apr 2002
    Location
    waco,tx
    Posts
    85
    Originally posted by mayguy
    Wouldn't it be cheaper to just just an air handler in rather the furnace that will not be used for heating???

    I'd think that's a waste??
    one of the main criteria of twinning is that you use identical units...identical airflow etc..

    not really a waste if you think about the when/if one of the operational furnaces needs a heat exchanger, inducer motor, gas valve etc
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  2. #15
    Join Date
    Mar 2004
    Location
    New England
    Posts
    224
    Inventive idea for a job.I have done serveral twins over the years and I am interested how you set up the controls.Normaly the boards communicate by running feed to each board thus the fan speed is the same for the mode the system is in.Can you run the jumper to more than two boards?Also did you add hi temp limits on the blowers?
    An apprentice is half a journeyman ,two apprentices is a call back.

  3. #16
    Join Date
    Apr 2001
    Location
    Camel City, NC
    Posts
    6,232
    Looks good. Try and get pic of old equip. next time. Makes the new stuff look even better.
    Be safe not fast. body parts don't grow back

  4. #17
    Join Date
    Nov 2005
    Location
    Chattanooga, TN
    Posts
    13

    Bypassing Air

    Question: Can I assume there is staged capacity control for heating and cooling? If so, what would be the sequence of operation ...say 50 capacity ...assuming some fans on and some
    fans off...would this let supply air into and back flow through the "turned off" furnances. Assuming they are connected to the same connected supply ductwork? Does this allow the "turned off" fan motors to free wheel when not in operation?

    [Edited by mss control on 12-20-2005 at 02:14 PM]

  5. #18
    Join Date
    Apr 2002
    Location
    waco,tx
    Posts
    85

    Re: Bypassing Air


    all fans run simultaneously in heating and cooling. furnaces have belt drive, single speed fan motors. each triplet of furnaces have a master and 2 slaves...

    system sequence of operation in heating mode is:

    2 master furnaces against back wall start then all 6 fans start.....
    2nd stage heat is 2 furnaces in foreground gas valves, inducer etc..

    system sequence of operation in cooling mode is:

    all 6 blowers fire off simultaneously.

    stage 1 - both 20 ton condensers (with electric unloaders) start unloaded with 4 solenoid valves energized.

    stage 2 - remaining 2 solenoid valves energize and load remaining cylinder(s)



    [Edited by chriskmb5150 on 12-20-2005 at 09:14 PM]
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  6. #19
    Join Date
    Apr 2002
    Location
    waco,tx
    Posts
    85
    Originally posted by onesidedcoin
    Inventive idea for a job.I have done serveral twins over the years and I am interested how you set up the controls.Normaly the boards communicate by running feed to each board thus the fan speed is the same for the mode the system is in.Can you run the jumper to more than two boards?Also did you add hi temp limits on the blowers?
    the stat has its own transformer that controls the units thru relays mounted in the box on the back wall.
    master furnaces are controlled in parallel off of said relays.

    all furnaces have high temp limits on the blowers wired in series to heating control relay coil and freeze stats on all coils wired in series to cooling control relay coil.

    if you have autocad email me at: ductmaster2112@yahoo.com for details if you like.
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  7. #20
    Join Date
    Jul 2001
    Posts
    3,112
    Get a qualified person in there to replace that illeagle gas line installation.

  8. #21
    Join Date
    Apr 2002
    Location
    waco,tx
    Posts
    85
    Originally posted by troyorr
    Get a qualified person in there to replace that illeagle gas line installation.

    get a qualified person to post for you that can spell illegal



    gas lines were subbed out to plumbing co. and yes there were legal when this job was done (3 years ago). the only code requirement that Has changed is that you have to run hard line from the gas valve to a minimum of 2" out of the cabinet then you can run flex.

    i dont know where youre from but around here (central TX) they're all done this way.
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  9. #22
    Join Date
    Jul 2001
    Posts
    3,112
    Bite me. Running flexible lines that penetrate the cabinet is wrong. So you subbed the work out and the sub did it wrong. You are responsible.

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