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Thread: Correct circuit breaker for small single phase pump motors

  1. #11
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    For those of you wondering...

    AC-1 - This category applies to all AC loads where the power factor is more than 0.95. These are primarily non-inductive or slightly inductive loads, such as resistive loads. Breaking the arc remains easy with minimal arcing and contact wear.

    AC-3 - This category applies to squirrel cage motors with breaking during normal running of the motor.
    On closing, the contactor makes the inrush current, which is about 5 to 7 times the rated full load current of the motor.
    On opening, the contactor breaks the rated full load current of the motor.

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    You mentioned a 5Amp motor current, I am assuming that it is a 560W Single phase motor.
    Franklin Electric has a number of preset units for 370W, 560W, 750W 1.1kW, 1.5kW and 2.2kW single phase motors - and a range for 3 phase motors.
    Get hold of your local Franklin Electric Supplier, and ask for the price for a Subtronic Data 120 with a part number 830008816 which is for a 560W Single phase motor, DIN Rail mount.
    This unit is a single phase submersible motor protector, which is a plug and play.
    Supply in 2 wires, 3 wires to motor if external capacitor else 2 wires, if there is an external capacitor, then 2 wires to start capacitor, and larger motors 2 wires to the run capacitor.
    It has internal relays, so saves you the time wiring it up.
    It has over current detection, 120% of nominal, so will cover if the pump rubs, or debris gets into the pump.
    Underload protection, approximately 35% of nominal shaft power, so will cover when the pump runs dry.
    External potential free switch input with built in anti recycling.

    Maybe this is the solution you need.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Quote Originally Posted by AndyD View Post
    The thermal overloads and motor starters and even the pump control relay can all be wired for single phase or 3-phase applications. A contactor and thermal overload is the cheapest form of protection I know of unless you fit Klixon type bi-metalic....but I'd caution about their accuracy and reliability.

    One other thing I meant to caution about, when you spec your contactors or relays be sure to use their AC3 ratings, not the AC1 rating.
    However on bigger 3 phase panels ...it works out cheaper to use a manual motor starter and contactor... it saves you having to fit a circuit breaker before the contactor and overload.

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    Quote Originally Posted by Justloadit View Post
    Subtronic Data 120 with a part number 830008816 .
    Spoke to them. Cannot DIN rail mount and is really expensive if I need to buy 4 off to control each of the pumps. At R6k a shot this allows for some cheaper options. Thanks for the info as it allows for future options in designs.

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    Quote Originally Posted by ians View Post
    However on bigger 3 phase panels ...it works out cheaper to use a manual motor starter and contactor... it saves you having to fit a circuit breaker before the contactor and overload.
    And that is the crux of this exercise ... this is a single phase system for household users ...

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    Diamond Member Justloadit's Avatar
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    Quote Originally Posted by mygoggie View Post
    Spoke to them. Cannot DIN rail mount and is really expensive if I need to buy 4 off to control each of the pumps. At R6k a shot this allows for some cheaper options. Thanks for the info as it allows for future options in designs.
    They did not quote you for the DIN rail controller only, they quoted you the complete controller with IP65 enclosure caps and circuit breaker.
    The current list price is R 1,840.00 excluding VAT.

    If you don't come right, send me a private message and I will send you details of someone who will supply.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Diamond Member Justloadit's Avatar
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    The Subtronic DIN rail looks like this
    Click image for larger version. 

Name:	Subtronic.jpg 
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    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Quote Originally Posted by Justloadit View Post
    They did not quote you for the DIN rail controller only, they quoted you the complete controller with IP65 enclosure caps and circuit breaker.
    The current list price is R 1,840.00 excluding VAT.

    If you don't come right, send me a private message and I will send you details of someone who will supply.
    The lady said they cannot supply the DIN rail version ... will PM you thanks!

  9. #19
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    Quote Originally Posted by mygoggie View Post
    The lady said they cannot supply the DIN rail version ... will PM you thanks!
    BS, retro fit units are available to replace damaged units due to lightning or other failures.
    Believe me I know. I have known since 1997 when it was first known as the Blac Bocs, and have had 2 model changes since then.
    Use the part number I gave you it is a valid number.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

  10. #20
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    Quote Originally Posted by Justloadit View Post
    Use the part number I gave you it is a valid number.

    Victor, I spoke to the correct lady this time and she confirmed that the DIN rail "brain" unit is available like you said. I have asked for the design sheets for these units.

    Thanks again!

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