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Thread: Electrical curiosities, take 2

  1. #1
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    Electrical curiosities, take 2

    In this episode of “Is that how it’s supposed to be”

    On today’s service call I saw the common side of a low voltage coil hooked up to the ground…

    last time I made an assumption about how I think it should be.. I was wrong.. so I won’t make any assumptions and will just wait for the yays or nays


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  2. #2
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    I have seen the common side of the ac contactor hooked to the lineset and it worked too .

    Sent from the Okie state usin Tapatalk

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    It works like that but should be run back to the common of the transformer. At that point it can go to ground.

    The chassis of the unit is not designed to be a current carrying device. Also, if the transformer does not make a good connection to the chassis of the unit then your voltage to the contractor can get inconsistent and poor results will happen. You don’t want to be the guy who causes the customers inconvenience or be the cause of that bill.
    Quickly, I must hurry, for there go my people and I am their leader!

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  6. #4
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    Quote Originally Posted by R600a View Post
    I have seen the common side of the ac contactor hooked to the lineset and it worked too .

    Sent from the Okie state usin Tapatalk
    I’ve seen electrical arc blast it’s way through a copper pipe before. I hope they used some quality electrical tape to secure that connection.
    Quickly, I must hurry, for there go my people and I am their leader!

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  8. #5
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    Quote Originally Posted by thatguy View Post
    I’ve seen electrical arc blast it’s way through a copper pipe before. I hope they used some quality electrical tape to secure that connection.
    That aught to be fun with flammable refrigerants.

    Sent from the Okie state usin Tapatalk

  9. #6
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    Did you look at the common side of the transformer? It was likely connected to the ground as well.

    Is what you saw Right? No; of course not.

    Is it legal? No; of course not.

    Will it work? Almost certainly.

    Did the common wire have continuity end-to-end?

    How difficult would it be to run a new wire from this coil you saw and the transformer location? <g>

    BTW: What did the wiring diagram show?

    PHM
    -------


    Quote Originally Posted by Sabr7 View Post
    In this episode of “Is that how it’s supposed to be”

    On today’s service call I saw the common side of a low voltage coil hooked up to the ground…

    last time I made an assumption about how I think it should be.. I was wrong.. so I won’t make any assumptions and will just wait for the yays or nays


    Sent from my iPhone using Tapatalk
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

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  11. #7
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    As PHM asked, what does the wiring diagram show for the factory xformer set up?

  12. #8
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    Electrical curiosities, take 2

    (Logged in as wrong user)

  13. #9
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    Quote Originally Posted by Shakur View Post
    Wiring diagram? No such luxuries at this run down spot. Hard enough getting the model and serial


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    Internet?

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    Quote Originally Posted by pecmsg View Post
    Internet?
    Yeah what the heck , had problems logging in to the server


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    Quote Originally Posted by Poodle Head Mikey View Post
    Did you look at the common side of the transformer? It was likely connected to the ground as well.

    Is what you saw Right? No; of course not.

    Is it legal? No; of course not.

    Will it work? Almost certainly.

    Did the common wire have continuity end-to-end?

    How difficult would it be to run a new wire from this coil you saw and the transformer location? <g>

    BTW: What did the wiring diagram show?

    PHM
    -------
    Okay, logged in now..
    As I was saying, no wiring diagram


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by Sabr7 View Post
    Okay, logged in now..
    As I was saying, no wiring diagram


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    Sometimes the Common is broken on safety devices.

    There should always be a common wire going back to the transformer, there is may be grounded!

  17. #13
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    The rest of the questions are important too. <g>

    PHM
    --------


    Quote Originally Posted by Sabr7 View Post
    Okay, logged in now..
    As I was saying, no wiring diagram


    Sent from my iPhone using Tapatalk
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  18. #14
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    Quote Originally Posted by Poodle Head Mikey View Post
    Did you look at the common side of the transformer? It was likely connected to the ground as well.

    Is what you saw Right? No; of course not.

    Is it legal? No; of course not.

    Will it work? Almost certainly.

    Did the common wire have continuity end-to-end?

    How difficult would it be to run a new wire from this coil you saw and the transformer location? <g>

    BTW: What did the wiring diagram show?

    PHM
    -------
    End to end continuity - yes
    Difficulty running new wire - not hard at all
    Will be out returning with a mechanic (I’m an apprentice) and I’ll see what he does


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  19. #15
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    Lennox has been grounding the common since probably the mid 70's

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  21. #16
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    Quote Originally Posted by theoldscroll View Post
    Lennox has been grounding the common since probably the mid 70's
    I was grounded commonly for not doing my homework most of my childhood.

    Sent from the Okie state usin Tapatalk

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    Quote Originally Posted by R600a View Post
    I was grounded commonly for not doing my homework most of my childhood.

    Sent from the Okie state usin Tapatalk
    I chose to take detention over homework, took up less of my time.

    I've grounded common in a pinch, like having a shorted thermostat wire but not enough any spare wires. 24VAC common is almost always earth grounded anyway, so in my opinion it doesn't really matter.
    Everything I’m going to say today are my conclusions and my opinions, my opinions are based on my education, my training, my experience. Different people have different experiences, so they have different opinions and I make no claim that my opinion has its origin in the mind greatness. - Paul Harrell

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  24. #18
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    One exception I know of to chassis carrying "current" is return path for the flame sensor.

    Quote Originally Posted by thatguy View Post
    It works like that but should be run back to the common of the transformer. At that point it can go to ground.

    The chassis of the unit is not designed to be a current carrying device. Also, if the transformer does not make a good connection to the chassis of the unit then your voltage to the contractor can get inconsistent and poor results will happen. You don’t want to be the guy who causes the customers inconvenience or be the cause of that bill.
    “A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.”
    ― Robert A. Heinlein

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  26. #19
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    The common side is almost always bonded to ground, the ones that aren't you'll read 12v to ground on both sides of the secondary, you will still have 24v total and it will work. I don't know how all manufactures do it but but some have a jumper straight from the common side of the transformer.

    I was skeptical the first time someone told me that too but you can check for yourself. Take a transformer on a bench(i think a lot of the transformers themselves bond to their mount in the unit) and measure secondary to 120v ground, you'll get 12v each, then take one side of the secondary and bond it to said ground, you'll get 24v to ground on the other side. Neutral in 120v is similar it is a current carrying conductor but it only reads 0v to ground because its bonded to ground.

  27. #20
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    Im thinking I see grounded transformers in Commercial units more often than Resi

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