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Thread: Interlocking as to not overload a 75kva

  1. #21
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    Quote Originally Posted by iwire View Post
    Does unlikely have a diffrent meaning than cannot?

    If so it should not mater who you talk to.
    Should not, could not, would not doesn't matter....


    ... unlikely means the likelihood of occurence is nil or next to it.



    People by their very nature may assign a different likelihood to the same scenario...


    ...and who are you to say they are wrong.




    I'll never get there. No matter where I go, I'm always here.

  2. #22
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    I think this will work:
    Timeclock1 pulls numerous NO poles closed when time. Closed contacts = lights on
    TC1 also pulls numerous NC poles open disabling load 2.
    TC2 can only allow current flow when 1 is not energizing contactor coils of load 1.
    Timeclocks are in parallel and there is no way for both loads to be on at the same time

  3. #23
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    Quote Originally Posted by justin13me View Post
    I think this will work:
    Timeclock1 pulls numerous NO poles closed when time. Closed contacts = lights on
    TC1 also pulls numerous NC poles open disabling load 2.
    TC2 can only allow current flow when 1 is not energizing contactor coils of load 1.
    Timeclocks are in parallel and there is no way for both loads to be on at the same time
    Sorry, please edit to:

    I think this will work:
    Timeclock1 pulls numerous NO poles closed when time. Closed contacts = lights on
    TC1 also pulls a NC pole (from TC2) on an auxiliary relay, open disabling load 2.
    TC2 can only allow current flow when 1 is not energizing contactor coils of load 1.
    TC2 when time (NC aux) pulls in numerous NO contacts to turn on load 2.

  4. #24
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    Quote Originally Posted by justin13me View Post
    Sorry, please edit to:

    I think this will work:
    Timeclock1 pulls numerous NO poles closed when time. Closed contacts = lights on
    TC1 also pulls a NC pole (from TC2) on an auxiliary relay, open disabling load 2.
    TC2 can only allow current flow when 1 is not energizing contactor coils of load 1.
    TC2 when time (NC aux) pulls in numerous NO contacts to turn on load 2.
    Ladder diagram?
    Tom
    TBLO

  5. #25
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    Quote Originally Posted by JFletcher View Post
    Yes. Unlikely = not probable to happen. Cannot = not possible to happen.

    ofc that is assuming failsafe engineering and proper use of the terms in the first place.

    It is unlikely that my home will burn down today due to the failure of a FPE breaker.

    It would be impossible for my home to burn down due to electrical failure if I did not have an electrical service. I realize there are some incredibly far-fetched scenarios where this may happen, but for all intents and purposes it is so far beyond the realm of possibility as to be 0.

    eta: interlocks are not intrinsically failsafe. I dealt with interlocked equipment for many years, and while they worked, you were not allowed to turn off a breaker to say the ash screw to the bin (last eqpt in the long chain of eqpt than must run) and use its interlock to shut off the bucket elevator; if you were working on the bucket elevator, its breaker must be secured.

    would a lead/lag system work for the OP?

    Again while I am talking code you are talking personal likes and dislikes. That is fine but the bottom line is the NEC uses the term 'unlikely' so physical interlocks not required.

  6. #26
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    Quote Originally Posted by Smart $ View Post
    Should not, could not, would not doesn't matter....


    ... unlikely means the likelihood of occurence is nil or next to it.



    People by their very nature may assign a different likelihood to the same scenario...


    ...and who are you to say they are wrong.




    I am saying it is wrong to look at 220.60 and state that section requires physical or electrcal interlocking.

    Who am I to say so? A reader of the English language.

  7. #27
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    Quote Originally Posted by iwire View Post
    Again while I am talking code you are talking personal likes and dislikes. That is fine but the bottom line is the NEC uses the term 'unlikely' so physical interlocks not required.
    Quote Originally Posted by iwire View Post
    I am saying it is wrong to look at 220.60 and state that section requires physical or electrcal interlocking.

    Who am I to say so? A reader of the English language.
    Nothing wrong with your interpretation.
    But it amounts to nothing more than a personal opinion.

    I'm not saying interlocking is required. Others may and do. They are not wrong either. A human mistake or programming error may make loads coincidental by accident. How does that weigh into 'unlikely'? Users choice IMO.
    I'll never get there. No matter where I go, I'm always here.

  8. #28
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    Quote Originally Posted by Smart $ View Post
    Nothing wrong with your interpretation.
    But it amounts to nothing more than a personal opinion.

    I'm not saying interlocking is required. Others may and do. They are not wrong either. A human mistake or programming error may make loads coincidental by accident. How does that weigh into 'unlikely'? Users choice IMO.
    I am sticking with 'they' are wrong using the NEC as justification, the words in the NEC do not support it.



    We will remain in disagreement on this one.

  9. #29
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    220.60 Noncoincident Loads. Where it is unlikely that two or more noncoincident loads will be in use simulta-neously, it shall be permissible to use only the largest load(s) that will be used at one time for calculating the total load of a feeder or service.





  10. #30
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    Line/ ladder (?) Diagram above.. I'm not too good with making drawings but I like to work it out this way to make sure things'll work out on site.
    The 4 timeclocks control 2 rooms. Only 1 (same) room can be on at a time. Being inductive loads, one room turns on half, 10 minutes before the other half. When that happens it's not possible for the other room to be on, thanks to the auxiliary relays.
    Hours later the first half turns off, then 10 minutes later the second half of the room (turns off). Then after about ten minutes, half the second room turns on then the other half another ten minutes later.
    If for whatever reason the first room was to turn on; the second would turn off automatically (overide). The second room however can not overide the first but the interlocking /physically not possible part is still achieved.

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