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Thread: Motor Control Wiring

  1. #11
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    Quote Originally Posted by kwired View Post
    What still doesn't make sense to me is regardless of what may be mis-wired, if you measured 208 volts across the coil terminals, then the coil should be drawing current unless it is open circuited, and that would pull the armature in and close the motor contacts.

    Is possible you were not measuring directly across the coil and there is an open switch somewhere between your measurement points - such as the motor overload contact.
    Yes, we’re missing some minor detail.
    Tom
    TBLO

  2. #12
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    Well, I was close but no cigar. It turned out that I was, in fact, not measuring across the coil but actually across an open contact. One side side of the contact was wired to one side of the coil (which I could not see and which would end up being phase 1 after going through the pressure and control switches). Internally the opposite side of the coil was wired to phase 2. So, when I pushed in the plunger for the contactor it locked in (through the contact), ran the motor until the tank reached its capacity and then shut down. Got on the phone with the supply house and they walked me through it. It turns out that I had to land the return wire from the pressure and control switch on the same side of the contact as the internal wire.

    I looked at the diagram 20 times and it didn't seem clear to me. This is what the controller looked like :

    http://www.eaton.com/Eaton/ProductsS...ries/index.htm

    I thought the coil was on the right side of the contactor but it was, in fact, located behind it and I was not able to see. This was the wiring diagram that came with the controller. I'm used to diagrams with more detail.


  3. #13
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    Quote Originally Posted by goldstar View Post
    Well, I was close but no cigar. It turned out that I was, in fact, not measuring across the coil but actually across an open contact. One side side of the contact was wired to one side of the coil (which I could not see and which would end up being phase 1 after going through the pressure and control switches). Internally the opposite side of the coil was wired to phase 2. So, when I pushed in the plunger for the contactor it locked in (through the contact), ran the motor until the tank reached its capacity and then shut down. Got on the phone with the supply house and they walked me through it. It turns out that I had to land the return wire from the pressure and control switch on the same side of the contact as the internal wire.

    I looked at the diagram 20 times and it didn't seem clear to me. This is what the controller looked like :

    http://www.eaton.com/Eaton/ProductsS...ries/index.htm

    I thought the coil was on the right side of the contactor but it was, in fact, located behind it and I was not able to see. This was the wiring diagram that came with the controller. I'm used to diagrams with more detail.

    That's what I was trying to convey in post #7.

    Glad you got it fixed!

  4. #14
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    Thanks. Glad I got it corrected as well. In all fairness, for those of you who are not accustomed to interpreting these wiring diagrams, would you know that you would have to run the control wiring between L1 and the # 3 terminal ? Especially when there is already a wire terminated on the # 3 terminal. Obviously if I have to wire another one of these again I'll know what to do but IMHO the drawing leaves room for improvement.

  5. #15
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    Experience is what you gained.

    Some years ago we converted a small hay mill that was built in the 50s &60s to PLC control. Their control was based on a limit(s) of varying types, being in series with the holding or seal-in contact. The Start button was parallel to them. Pressing the Start would start the motor if the overloads were not tripped. Problems with the holding contact or limits would cause the motor starter to open as as soon as the Start button was released. That was a quick method to determine where they first needed to look for problems. Divide and conquer, so to speak.
    Tom
    TBLO

  6. #16
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    Quote Originally Posted by goldstar View Post
    Well, I was close but no cigar. It turned out that I was, in fact, not measuring across the coil but actually across an open contact. One side side of the contact was wired to one side of the coil (which I could not see and which would end up being phase 1 after going through the pressure and control switches). Internally the opposite side of the coil was wired to phase 2. So, when I pushed in the plunger for the contactor it locked in (through the contact), ran the motor until the tank reached its capacity and then shut down. Got on the phone with the supply house and they walked me through it. It turns out that I had to land the return wire from the pressure and control switch on the same side of the contact as the internal wire.

    I looked at the diagram 20 times and it didn't seem clear to me. This is what the controller looked like :

    http://www.eaton.com/Eaton/ProductsS...ries/index.htm

    I thought the coil was on the right side of the contactor but it was, in fact, located behind it and I was not able to see. This was the wiring diagram that came with the controller. I'm used to diagrams with more detail.

    What other detail do you want? That diagram is a generic label from the starter manufacturer that shows how the starter was configured when it left the factory, they don't know what it will get connected to in the field, and only give you a few of the most common examples of what you may run into for basic control schemes. Anything more complex would have to be drawn by whoever put the thing together.

    NEMA starters typically do have "L2" connected to the overload then the coil if coil voltage is a line to line voltage (208,240, 480), if it is a line to neutral coil volatage (120, 277) then "wire C" isn't installed and you need to land control voltage neutral on terminal 96, which is sort of an IEC terminal identification, others are still calling the overload contact terminals X1, X2.

  7. #17
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    Quote Originally Posted by kwired View Post
    What other detail do you want? That diagram is a generic label from the starter manufacturer that shows how the starter was configured when it left the factory, they don't know what it will get connected to in the field, and only give you a few of the most common examples of what you may run into for basic control schemes. Anything more complex would have to be drawn by whoever put the thing together.

    NEMA starters typically do have "L2" connected to the overload then the coil if coil voltage is a line to line voltage (208,240, 480), if it is a line to neutral coil volatage (120, 277) then "wire C" isn't installed and you need to land control voltage neutral on terminal 96, which is sort of an IEC terminal identification, others are still calling the overload contact terminals X1, X2.
    You've obviously wired these before and it sounds like you're talking from experience. But, try looking at this from a novice's point of view. I've wired many different types of controls from fire alarm systems to motor controls for large AC units. As a general rule I would never land a wire on a terminal that already had a wire on it. In this case I had to. The symbol shown for a coil is not what I'm accustomed to seeing and that's what threw me off. Thanks for your input.

  8. #18
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    Quote Originally Posted by goldstar View Post
    You've obviously wired these before and it sounds like you're talking from experience. But, try looking at this from a novice's point of view. I've wired many different types of controls from fire alarm systems to motor controls for large AC units. As a general rule I would never land a wire on a terminal that already had a wire on it. In this case I had to. The symbol shown for a coil is not what I'm accustomed to seeing and that's what threw me off. Thanks for your input.
    All I can say is the terminals in question are ordinarily designed to land up to two conductors on them and that if you go to other brands of NEMA starters they are wired pretty much the same way and their schematic is fairly similar in that they show approximate physical locations of components as drawn. True the coil isn't using a conventional coil symbol on that one but I think they put more focus on showing where the terminals are physically located in relation to other components.

  9. #19
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    Quote Originally Posted by kwired View Post
    All I can say is the terminals in question are ordinarily designed to land up to two conductors on them and that if you go to other brands of NEMA starters they are wired pretty much the same way and their schematic is fairly similar in that they show approximate physical locations of components as drawn. True the coil isn't using a conventional coil symbol on that one but I think they put more focus on showing where the terminals are physically located in relation to other components.
    Well, like you now I can speak from experience. After taking a closer look at the drawing I can see the logic in the wiring. I still think they could have done a better job on the drawing or provide a better wiring explanation. IMHO.

  10. #20
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    Notwithstanding the exhaustive detail of the starter, I'm still waiting for an explanation on how OP could get 208 volts and not having the coil pulled in.

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