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  1. #1
    Join Date
    Jul 2013
    Location
    Ontario,canada
    Posts
    56

    24 volt transformer

    why sometimes on 24 volt transformer com goes to ground and sometimes does not

  2. #2
    Join Date
    Sep 2002
    Location
    Hampton Roads, Virginia
    Posts
    1,610
    Quote Originally Posted by dav214 View Post
    why sometimes on 24 volt transformer com goes to ground and sometimes does not
    Read up about full wave and half wave rectification, that should help you understand why sometimes the transformer secondary is not grounded. Sometimes it is the installer being lazy

    Also note that if the primary voltage is above a certain voltage the National Electrical code at least in the USA requires that the secondary is grounded.

    http://www.kele.com/templates/content.aspx?id=4715

    http://www.mikeholt.com/technical.php?id=calculations/unformatted/Control&type=u&title=Control%20Circuit%20S izing%20(9-5-2K)

    Kevin

    Sent from my GT-P5113 using Tapatalk HD
    Last edited by klrogers; 07-14-2013 at 05:11 PM.
    "Profit is not the legitimate purpose of business. The legitimate purpose of business is to provide a product or service that people need and do it so well that it's profitable."

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  3. #3
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,042
    Not familiar with controls but, if the circuit uses 24V for flame rectification a reference to ground is necessary.

  4. #4
    Sometimes com is ground and other times it isn't. klrogers answered the question - answer lies on the rectification process - full-wave rectification and half-wave rectification. Rectification is done on all the appliances that converts DC-to-AC and AC-to-DC.

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