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  1. #1
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    The forgotten step for commercial installs....

    I have seen this overlooked for so many years I can no longer count the number of instances I have found this one issue.

    It should never be overlooked.

    It is SO quick and easy to do.

    And, you won't look like you were standing in front of a Home Depot that morning.

    Please.

    Set the right voltage.

    I know no one is mentioning it. That part is obvious. Let me explain.

    When three phase units are tested at the factory, they are using a three phase Delta supply. So, the factory is testing the unit with 240/3 volts. At one time, this was the same voltage being used in the three phase world of commercial and industrial power.

    This is no longer the case in most places.

    Today, the end use voltage is either 460/480 (and they make no distinction between those levels, as 480 is the new 460, due to rising feeder voltages) or 208/230 (or, 240).

    And that second group is the issue here.

    What used to be a Delta power setup is now more frequently a Wye setup, and as many of you know, a transformer tapped for a Wye output in this voltage range is going to have a target voltage of 208.

    Most of the time, you will have a control transformer with a 230 tap and a 208 tap. Before you leave, make sure the correct tap is selected. Easy peasy.

    Now, for you Trane guys, you have a second transformer, which is used for the hot surface ignitor and sometimes other loads. That transformer comes from the factory with the load group connected to H3, which is the 230 volt input tap. In order for the HSI and other output needs to be properly met, that primary terminal group needs to be moved over to H2. It's right in the notes on the wiring diagram.

    Once again...it's easy.

    So, in summary...

    ...make the contactors and ignitors and everything else in that unit get off to the right start, so that as the HSI ages, it can work longer, instead of being starved for source voltage, which reduces the current to the point that the HSI can no longer light the gas mixture.

    Commercial installers...stand up and do a Pro job.

    End of electrical rant for today.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

    AOP Forum Rules:







  2. Likes BBeerme, kdean1, coolairman liked this post
  3. #2
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    It's funny that you mention it because all my life I have found 208 supplied transformers wired for 240. Some of then more than 20 years old. A good long while ago I started making it the first thing I check. <g>

    It usually works when everything is now at installation - but as the equipment ages things sometimes get screwy and then - there I am. <g>.

    PHM
    -------



    Quote Originally Posted by timebuilder View Post
    I have seen this overlooked for so many years I can no longer count the number of instances I have found this one issue.

    It should never be overlooked.

    It is SO quick and easy to do.

    And, you won't look like you were standing in front of a Home Depot that morning.

    Please.

    Set the right voltage.

    I know no one is mentioning it. That part is obvious. Let me explain.

    When three phase units are tested at the factory, they are using a three phase Delta supply. So, the factory is testing the unit with 240/3 volts. At one time, this was the same voltage being used in the three phase world of commercial and industrial power.

    This is no longer the case in most places.

    Today, the end use voltage is either 460/480 (and they make no distinction between those levels, as 480 is the new 460, due to rising feeder voltages) or 208/230 (or, 240).

    And that second group is the issue here.

    What used to be a Delta power setup is now more frequently a Wye setup, and as many of you know, a transformer tapped for a Wye output in this voltage range is going to have a target voltage of 208.

    Most of the time, you will have a control transformer with a 230 tap and a 208 tap. Before you leave, make sure the correct tap is selected. Easy peasy.

    Now, for you Trane guys, you have a second transformer, which is used for the hot surface ignitor and sometimes other loads. That transformer comes from the factory with the load group connected to H3, which is the 230 volt input tap. In order for the HSI and other output needs to be properly met, that primary terminal group needs to be moved over to H2. It's right in the notes on the wiring diagram.

    Once again...it's easy.

    So, in summary...

    ...make the contactors and ignitors and everything else in that unit get off to the right start, so that as the HSI ages, it can work longer, instead of being starved for source voltage, which reduces the current to the point that the HSI can no longer light the gas mixture.

    Commercial installers...stand up and do a Pro job.

    End of electrical rant for today.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  4. #3
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    I had one of those HSI situations just last week.

    I threw the amp clamp on, and I got only 2.4 amps. Not enough to make the HSI hot enough for light off.

    My next check on this relatively new (four year old?) install was the transformers.

    Sure enough...stunods.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

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  5. Likes Ammar.almahdi, HVAC_Marc liked this post
  6. #4
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    I always check for that. But thanks for the Trane tip, I didn't know about that one.


  7. #5
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    Find that everywhere around here. Most miss the ignitor Trans. Also trane cubes. On those it's the blower. Residential unit ĺi think) used in commercial application. Comes tapped at 240 volts. Have to change to 208v at the bundle of wires in the blower compartment.

    Sent from my SM-G930V using Tapatalk

  8. #6
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    Quote Originally Posted by icy78 View Post
    Find that everywhere around here. Most miss the ignitor Trans. Also trane cubes. On those it's the blower. Residential unit ĺi think) used in commercial application. Comes tapped at 240 volts. Have to change to 208v at the bundle of wires in the blower compartment.

    Sent from my SM-G930V using Tapatalk
    Frpm the widespread nature of this issue, you would think they were all being installed by carpenters....
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  9. #7
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    Oh please. Carpenters do some pretty stunning accurate work. I think it more likely that they are being installed by the guys who flunked out of the Laborer's apprenticeship program.

    PHM
    ------------


    Quote Originally Posted by timebuilder View Post
    Frpm the widespread nature of this issue, you would think they were all being installed by carpenters....
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  10. #8
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    Carpenters do terrific work....however....how would you expect a carpenter to know how to correctly install an air conditioning unit? It's not their venue.... they would be "out of their lane," so to speak.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

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  11. #9
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    I know what you mean but a good mechanic is a good mechanic no matter what he's doing. Many skills and attitudes and Aptitudes are transferable.

    I feel like I do good refrigeration work. I'm not the best or fastest sheetrocker or tile guy - but I'll put my finished work on display. Someone who Wants to do a good job will find a way to do it.

    It's never the Situation - it's always the Man.

    PHM
    ---------



    Quote Originally Posted by timebuilder View Post
    Carpenters do terrific work....however....how would you expect a carpenter to know how to correctly install an air conditioning unit? It's not their venue.... they would be "out of their lane," so to speak.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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  13. #10
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    I have an expectation that a Pro HVAC guy will not leave a unit set up for the wrong voltage. I would not hold a master carpenter to the same standard.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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  14. #11
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    I always switch the tap. Your in there anyways wiring the controls, doing startup, checking amps etc...... how hard is it?? Not sure if its lazyness or just lack of knowledge

  15. #12
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    You're assuming that these units get a proper startup.
    Sometimes, they switch on the disconnect and walk away.


  16. #13
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    Quote Originally Posted by coolerik View Post
    I always switch the tap. Your in there anyways wiring the controls, doing startup, checking amps etc...... how hard is it?? Not sure if its lazyness or just lack of knowledge
    Considering that I see most installs being done by builders or laborers and not HVAC guys, it is lack of knowledge. That is my impression, based on how incredibly common this mistake has been.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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