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Thread: L1 and L2!!

  1. #1
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    L1 and L2!!

    Until recently I was led to believe that in refrigerator circuits both legs of AC power were feeding into the circuit...but, I read that one leg, typically labeled as L1 will feed power into the circuit for mainly the switch sides of the circuit, and L2 (neutral) carries the current back out of the circuit or away from the component (motor, switch, etc.) Can someone please confirm which is true?

    The reason this confuses me is in this schematic.

    http://imageshack.us/photo/my-images...ngbq0.jpg/sr=1

    which side of power is neutral and which one is hot?

    also, i need a better understanding of how capacitors work. the common terminal is for power in, but in what specifications would a jumper be used to go back out of the common terminal?
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    Last edited by eye in the sky; 11-28-2011 at 12:08 AM.

  2. #2
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    Your common on the compressor is going to be your line voltage. The capacitor causes voltage to lead the current, throwing the voltage and current out of phase. This phase shift is what allows the motor to start turning. I don't understand what your asking about a jumper on the common. You don't want to add any jumpers to this circuit.

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    The word "circuit" is derived from the Latin, meaning "circle." L1 or L2, "hot" or "neutral" are merely words.

    Your typical outlet uses BOTH main connections, the slots, to power a device. The same current is moving through BOTH wires. On a 208 - 230 volt circuit used to power a condensing unit, same thing applies.

    A capacitor is placed in series with a motor start winding to create a change in the phase relationship between voltage and current. This provides an advantage of torque to start the motor rotating. If the cap is not removed from the circuit after the motor starts, we call it a run cap. If it gets removed, its a start cap. The caps themselves are designed slightly differently, but their job is the same.

    Does that help?
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    thanks for the replies

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    Quote Originally Posted by Tiger93rsl View Post
    Your common on the compressor is going to be your line voltage. The capacitor causes voltage to lead the current, throwing the voltage and current out of phase. This phase shift is what allows the motor to start turning. I don't understand what your asking about a jumper on the common. You don't want to add any jumpers to this circuit.
    So what is the function of the run winding? Is it used to lead out voltage, as I've been told, or lead voltage in for the motor?

    I suppose I'm wondering about capacitor design. For instance, in a run capacitor there is power going into common, then a jumper coming out of common (and a jumper from 'fan') for the fan motor. So in other words, the common terminal can be used for power in or out, right?

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    Quote Originally Posted by timebuilder View Post
    The word "circuit" is derived from the Latin, meaning "circle." L1 or L2, "hot" or "neutral" are merely words.

    Your typical outlet uses BOTH main connections, the slots, to power a device. The same current is moving through BOTH wires. On a 208 - 230 volt circuit used to power a condensing unit, same thing applies.

    A capacitor is placed in series with a motor start winding to create a change in the phase relationship between voltage and current. This provides an advantage of torque to start the motor rotating. If the cap is not removed from the circuit after the motor starts, we call it a run cap. If it gets removed, its a start cap. The caps themselves are designed slightly differently, but their job is the same.

    Does that help?
    The start capacitor is wired through the common of the run capacitor, then feeds to the relay, then the start winding and relay are connected through the hermetic terminal of the run capacitor? Then counter EMF backfeeds to open 'normally-closed' to throw out the start capacitor. In this cirumstance, however, isn't voltage still going into the start winding?

    Could you please explain 'phase'.

    I really appreciate y'alls help!

  7. #7
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    Quote Originally Posted by eye in the sky View Post
    So what is the function of the run winding? Is it used to lead out voltage, as I've been told, or lead voltage in for the motor?

    I suppose I'm wondering about capacitor design. For instance, in a run capacitor there is power going into common, then a jumper coming out of common (and a jumper from 'fan') for the fan motor. So in other words, the common terminal can be used for power in or out, right?

    I'm not sure what you have been told, but throw away any ideas about one side of a circuit having one function or another, versus the other side off the circuit.

    The ENTIRE circuit has current movement when energized, and the ENTIRE circuit loses current movement when de-energized.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  8. #8
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    Quote Originally Posted by eye in the sky View Post
    The start capacitor is wired through the common of the run capacitor, then feeds to the relay, then the start winding and relay are connected through the hermetic terminal of the run capacitor? Then counter EMF backfeeds to open 'normally-closed' to throw out the start capacitor. In this cirumstance, however, isn't voltage still going into the start winding?

    Could you please explain 'phase'.

    I really appreciate y'alls help!
    If you want help with a particular circuit, then post a copy in the post where you are asking the question.

    You seem to be focused on connections, and not the concepts. When you understand the concept of what a circuit is supposed to do, then the method of circuit design will begin to make more sense.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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  9. #9
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    [QUOTE=timebuilder;11819692]I'm not sure what you have been told, but throw away any ideas about one side of a circuit having one function or another, versus the other side off the circuit.

    The ENTIRE circuit has current movement when energized, and the ENTIRE circuit loses current movement when de-energized.[/QUOTE

    I'm not sure either why circuit voltage was described in the way I mentioned, but in this video this dude specifically clarifies the wrong thing...thank you for clearing it up.

    http://www.youtube.com/watch?v=4vPYHW26RlQ

  10. #10
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    Quote Originally Posted by timebuilder View Post
    If you want help with a particular circuit, then post a copy in the post where you are asking the question.

    You seem to be focused on connections, and not the concepts. When you understand the concept of what a circuit is supposed to do, then the method of circuit design will begin to make more sense.
    In reality, I understand the function of the circuits and a capacitors purpose, but needed reassurance on my understanding of how the components were wired together.

  11. #11
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    I can't watch youtube on my "dumb phone" because youtube is coded using Flash, but I will check it when I get home tonight. I have to wire a store today for EMS control.

    That said, I would caution all new techs about what they find on the net as being reliable information. You guys (or gals) should be getting Pro membership status as soon as you can, so you can 1) gain access to the educational forums and 2) ask technical questions in the Pro Residential or Commercial forums.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  12. #12
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    Quote Originally Posted by timebuilder View Post
    I can't watch youtube on my "dumb phone" because youtube is coded using Flash, but I will check it when I get home tonight. I have to wire a store today for EMS control.

    That said, I would caution all new techs about what they find on the net as being reliable information. You guys (or gals) should be getting Pro membership status as soon as you can, so you can 1) gain access to the educational forums and 2) ask technical questions in the Pro Residential or Commercial forums.
    thanks for the info. and i will do that. from your pro. opinion, does what i said in post 6 sound accurate?

  13. #13
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    I'll have to check it tonight.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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