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Thread: Motor Starters

  1. #1

    Motor Starters

    How do you know when you need a motor starter and when you don't? For example, I am working with (2) 480V/3p/1.5hp belt drive fans. I believe the fans come with thermal overload protection so I was planning on putting them both on the same circuit with a 15A breaker?? How do I know when and what kind of motor starter to use?

  2. #2
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    Re: Motor Starters

    The equipment manufacturer should have the information you need.

    How are you going to start and stop these motors?

    Rarely are 1.5HP motors supplied with integral protection, so I would plan on providing my own. If they all run at the same time I would use a single magnetic contactor (for on-off) feeding individual "manual motor controllers" (i.e. Square D type GV). If they run individually then use motor starters.

    see 430.53(C)and 430.109(6)
    Just because you can, doesn't mean you should.

  3. #3
    Join Date
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    Re: Motor Starters

    All motor's need a starter, may just be a switch on the wall, that can be called a starter (or controller), It's just a manual starter. All depends on what you want to do with them. They all also need a disconnecting means, can just be a cord and plug. What you need to figure out is size of starter from what you show you could use a size 0, I personally prefer to not go below a size 1. Then you need to size your overloads and that depends of FLA 430.110. You have to decide if you want both fans on same disconnect 430.112. NEMA starter size for HP ratings is not in the NEC I don't think. Somebody on here will definitely correct me if I'm wrong. But there is a chart available usually in the catalog you order from.

  4. #4

    Re: Motor Starters

    ok, i called out a disconnect mounted on the fan itself. how do you know when it needs a true nema starter or just a switch as a starter? these are just exhaust fans so an off and on would be sufficient. thanks for the help so far!

  5. #5
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    Re: Motor Starters

    why would it need a nema starter in the first place? a $20 iec starter will work fine.
    Bob

  6. #6
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    Re: Motor Starters

    Just up to you to decide. Cost's any type of control's, automatic starts, just somebody going to turn it on or off. Sometimes you just need to make a decision. Once you decide there is all the guidance on how to connect it up and size the equipment. I personally have not problem if it were just fans that will probably run almost all the time anyway, put them on a manual starter and be done. Do you want to worry about energy concerns though if it's running and nobody there and they forgot to turn it off? You just have to figure out what you want to do.

    By the way, they also make just a straight switch that can start a 3 phase 480 volt motor and you can put overloads in it. Personally I don't like those, would prefer the small push button manual starter.

    [ May 12, 2005, 05:37 PM: Message edited by: 69boss302 ]

  7. #7
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    Re: Motor Starters

    It is strictly the designer's choice.

    A starter is simply a combination of a motor controller (430 part VII) and an overload protective device (430 part III). The motor controller can be magnetic (allows remote or automatic control) or manual. The overload device can be properly sized fuses but more typically is a dedicated overload relay.

    Personally, I am not a believer in always blindly sizing motor starters as being a minimum of a NEMA Size 1. In this case the motor has an NEC FLC of 3A and a Size 1 starter is rated for 27A, talk about overkill.
    Just because you can, doesn't mean you should.

  8. #8
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    Re: Motor Starters

    petersonra; there are some "people" I will use that term, perhaps more polite and the moderators won't blank out my post. That are staunchly against IEC. I would believe if you chose magnetic starter in this case IEC would be perfect.

    Also sorry Jim, that is still a thing that some "people" used to force on the electricians in the steel industry. Just the same as "No conduit smaller than 3/4" or no wire smaller that #12 anywhere aloud in the plant. Money flows freely for some I suppose.

    Edit: should read these things over before I post them.

    [ May 12, 2005, 05:55 PM: Message edited by: 69boss302 ]

  9. #9
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    Re: Motor Starters

    Actually, there are many valid reasons for minimum sizes of products especially for continuous process industries. The ability to quickley change out any starter (or wire) without having to worry about physical sizes is not always a trivial matter when down time is measured in $000s/minute. My point is that there should be a reason.
    Just because you can, doesn't mean you should.

  10. #10
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    Re: Motor Starters

    There are good reasons to use #12 a s a minimum wire size too. It's far less likely to be damaged in pulling.
    Bob

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