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  1. #1
    Join Date
    Jul 2004
    Location
    London, ON
    Posts
    497
    Looking for a simple way to set up a lockout/reset on a standalone 20T Carlyle compressor to avoid short cycling on safety controls. Can figure it out myself, but don't need to reinvent the wheel...........Thx

  2. #2
    If noone posts one soon I'll dig up a Trane schematic and cut it out of that, what voltages are you working with ?

  3. #3
    Join Date
    Jul 2004
    Location
    London, ON
    Posts
    497
    575V 3PH Compressor
    Using 24 volts for controls/contactor/overloads/safeties
    120V for crankcase heater only

  4. #4
    Join Date
    Mar 2005
    Location
    Virginia
    Posts
    1,144
    Not fully understanding what you want. Do you want it to lock-out on any safty until someone manual hits a reset button? Or do you want it to reset automatically after a determined amount of time?

  5. #5
    Join Date
    Jan 2005
    Location
    steeler nation
    Posts
    2,083
    grainger sells all kinds of nifty timers.

  6. #6

  7. #7
    The lochout circuit stats at 1TB3-5

    Ignore lines, 1TB3-4 and -6

    Just caught the different voltages, I'll adjust it.

    No adjustment necessary if you are using 24 volts contactor,

    [Edited by TitleLess on 02-05-2006 at 11:53 AM]

  8. #8
    Join Date
    Jul 2004
    Location
    London, ON
    Posts
    497
    Thank you TitleLess. My memory has been jogged. Been awhile since I had to set one of these up from scratch. My company is in a small city, so I can't afford to specialize--i.e. I wind up wearing a lot of hats--a little refrig, some control work, some heating, some hydronics, some air conditioning, etc.etc.--then when you own the business you are also the boss, employer, occasional bookkeeper, occasional salesman, etc.--the head gets stretched a bit & it is easy to forget a few things........

  9. #9
    No problem hope it helps,

    If you use this on 24 volts, try to use a pilot duty relay,,,

  10. #10
    Join Date
    Apr 2004
    Location
    Michigan
    Posts
    295
    Thought it might be worth mentioning that you need to use a relay designed for a lockout circuit, with a high impedance coil.
    If you use just any standard relay, it might not work right. Like this one:
    http://www.white-rodgers.com/pdfs/04...Cat_pg_123.pdf

  11. #11
    Originally posted by lenb
    Thought it might be worth mentioning that you need to use a relay designed for a lockout circuit, with a high impedance coil.
    If you use just any standard relay, it might not work right. Like this one:
    http://www.white-rodgers.com/pdfs/04...Cat_pg_123.pdf
    This is true,

    although I have never had a problem , as long as I made sure the relay coil was tighter than the contactor coil,,but Len is right here, there is a chance that it will not work with normal relays and contactors,

  12. #12
    Join Date
    Feb 2006
    Location
    SouthEastern Virginia
    Posts
    1,075
    definitely right about the high impedance relay.

  13. #13
    Join Date
    Oct 2003
    Location
    Minnesota
    Posts
    1,380
    Originally posted by duke of earl
    definitely right about the high impedance relay.
    Has to be, actually.

    Sometimes folks don't realize that in this usage (things wired as in the schematic in prior post) a high impedance coil relay is needed, since they just use matching replacement from manufacturer, or one bought using same part number and supply house provided proper replacement.

    But it's simple Ohm's law stuff.

    Let assume high impedence lockout relay with 230 ohm coil. And compressor relay with normal coil, with a resistance of 10 ohm. (numbers are imaginary, just being used for example purpose) Control circuit is 24VAC.

    In series, that's 240 ohms. 24VAC supply. Amps would equal 0.1. Thus, 23 volts would be dropped across lockout relay coil, and only one volt across compressor relay coil. Lockout will have plenty juice to pull in and stay in, compressor relay isn't even gonna chatter much less pull in.

    That's if any of the safeties are tripped.

    If they aren't, electrons like path of least resistance. Taking normal control path, with only compressor relay coil in the path (10 ohms), is a lot easier than taking the combined 240 ohms path.

    BTW, high impedance relays are also often used in ground fault protection circuits.


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