contactor diagram

Discussion in 'The Projects Forum' started by eric_s88, May 5, 2014.

  1. eric_s88

    Thread Starter Member

    Apr 20, 2011
    157
    1
    Hi everyone!
    I want to use a contactor to on/off a pump. in this case I have a daily timer which has a 16A relay in the output.. so anybody knows the diagram circuit ??

    thank you

    Eric :)
     
    Last edited: May 6, 2014
  2. BillB3857

    Senior Member

    Feb 28, 2009
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    Single phase or 3 phase? Input voltage for timer? How much current does motor draw? Coil voltage on contactor?
     
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  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Here's a few combinations!
    Max.
     
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  4. eric_s88

    Thread Starter Member

    Apr 20, 2011
    157
    1
    single phase ! 220V for timer , I dont know about motor current draw and coil voltage :(
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    16amp for the timer contact is ample for picking up a contactor, if you do not have it now, you have to decide what coil voltage and AC or DC.
    Then as previously mentioned, you need to select the contactor for current or HP rating.
    If you obtain a 3ph version that will cover for both 1ph and 3ph.
    Also do you need a manual override or stop?
    All things to consider.
    Max.
     
    Last edited: May 5, 2014
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  6. BillB3857

    Senior Member

    Feb 28, 2009
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    If the motor is single phase and low enough current, do you really need a contactror?
     
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  7. #12

    Expert

    Nov 30, 2010
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    As a crude estimate, 16 amps of 220V will easily run 2 or 3 horsepower worth of pump. What BillB said, You might not need a contactor.

    something like this?
     
    Last edited: May 6, 2014
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  8. eric_s88

    Thread Starter Member

    Apr 20, 2011
    157
    1
    thank you all.. I think the pump has a 1HP motor. and as #12 said, a 16A timer would run this motor easily. but what about start of the motor ?? I think it would draw much more of current at the startup.. would't it ??
     
  9. #12

    Expert

    Nov 30, 2010
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    Yeahbut...contacts are rated for start surges.
    If that was not true, I'd need an 80 amp contactor for my 2 HP air conditioner.
     
  10. eric_s88

    Thread Starter Member

    Apr 20, 2011
    157
    1
    thats a good news. thank you Mr #12 ;-)
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Timer and relay contacts are rated by AC resistive, inductive and DC load.
    So the 16a most likely is the AC resistive load.
    If the timer is an expensive unit, you might consider using an intermediate device to carry the current to avoid failure of the more expensive unit.
    Max.
     
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  12. eric_s88

    Thread Starter Member

    Apr 20, 2011
    157
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    thank you... :) if the timer relay contacts are able to carry the surge current of motor start, thats affortable to use the timer... I think, right ?
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That's the chance you take.
    As I said, it depends on the value of the timing device and/or if you want to take the gamble. ;)
    Max.
     
  14. eric_s88

    Thread Starter Member

    Apr 20, 2011
    157
    1
    I've found out sth not good! in the timer datasheet I read that the 16A output current could be used for resistive loads. and only 3A for incudtive loads.. so I have to use contactor for driving a 1HP motor.. and I think.. I'm right friends ?
     
  15. #12

    Expert

    Nov 30, 2010
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    Couldn't hurt, and cheaper to fix when it wears out.
    Does this look familiar?
     
    Last edited: May 11, 2014
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