Magnetic starter rating

Old 02-02-10, 10:33 PM
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Magnetic starter rating

can someone help me with this problem?

I have a 37-A motor. I would like to know the rule of thumb in choosing the right or safe rating of the magnetic starter.

tnx in advance...

pls. reply ASAP...I will appreciate it more if you can reply thru my email...tnx again

Last edited by ibpooks; 02-03-10 at 08:28 AM. Reason: E-mail addresses are not allowed in public forums. You can subscribe to the thread to get e-mail notifications of replies.
Old 02-02-10, 10:58 PM
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Motor starters are sized according to horsepower, voltage and whether single or three phase. Once that selection has been made then the heater elements are selected according the full-load amperage of the motor. Generally the heater amperage rating is no more than ten percent greater than the full-load current but it can depend upon other specifications of the motor and the installation.

Last edited by ibpooks; 02-03-10 at 08:32 AM. Reason: Housekeeping.
Old 02-03-10, 04:59 PM
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you dont want to ballpark this, give us the exact info on the nameplate of the motor you are working down to every single detail because there is a chapter in the NEC that will allow us to do the calculations for you so reply back with that info, and someone will reply back with the exact size you need to use
Old 02-03-10, 05:32 PM
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As other mention the key issue is motor HP size and single or three phase ., and also how often the motor will kick on like every few minutes or steady run or what ?

That can affect the size of starter as well.

And there is push button in two verion and simple on / off switch as well.

Old 02-03-10, 09:08 PM
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Will you also be needing a disconnect. You can get a combination starter with fusible disconnect and save the cost and labor of installing a separate disconnect. Will you be needing pilot lights, push buttons, control power transformer, remote push buttons?

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