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  1. #1
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    Grounding 24 volt transformer

    Hey guys
    I’ve got a 120volts to 24volts transformer ..I need to ground the secondary 24 volts side, but there’s no indication on the transformer or from the manufacturer on which one of the two wires coming out of the secondary side of the 24 volts to ground ..which one of the two wires do i ground on the 24 volt side of the transformer..?

    Thanks

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    Take your pick. The 24V side is the opposite of the common side.

    There have been some posts here about phase(?) on the transformer and relationship to neutral on the line voltage side but I have not encountered a situation that required switching them. Perhaps someone will comment who has experienced it.
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    There = not here. Their = possessive pronoun. They're = they are
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    Thread Starter
    What do you mean by take your pick...any of the two wires coming of the the secondary side i could ground?

    Thanks

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    yes. Whichever you pick to ground, the other side will be 24V. The 24V side is the one that gets switched, common should be uninterrupted.
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    Thread Starter
    Thanks ..

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    You're welcome. I hope it solves the issue for you.
    AOP Rules: Rules For Equipment Owners.

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    There = not here. Their = possessive pronoun. They're = they are
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    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
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    Quote Originally Posted by kdean1 View Post
    Take your pick. The 24V side is the opposite of the common side.

    There have been some posts here about phase(?) on the transformer and relationship to neutral on the line voltage side but I have not encountered a situation that required switching them. Perhaps someone will comment who has experienced it.
    Thats a possibility with systems where there are two transformers wired in parallel. Two 24v xfmrs with the secondaries wired in parallel will give 24 volts at the secondary. If they are wired out of phase, the secondary voltages will sum to 48 volts. Similar to measuring from hot to neutral at the panel vs hot to hot.


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    polarity= L1 to ground, 120V. neutral to ground, 0 volts
    ground/bonding= ground (EGC) to chassis, 0 volts
    phasing a transformer= L1 to R, 96 volts. Out of phase= L1 to R= 144 volts.
    correct phase= primary voltage minus secondary voltage, out of phase, voltages add together.

    for what is worth.......
    my boss thinks its possible to repeal the laws of physics

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    Quote Originally Posted by Cisco007 View Post
    Hey guys
    I’ve got a 120volts to 24volts transformer ..I need to ground the secondary 24 volts side, but there’s no indication on the transformer or from the manufacturer on which one of the two wires coming out of the secondary side of the 24 volts to ground ..which one of the two wires do i ground on the 24 volt side of the transformer..?

    Thanks
    The only transformers that were grounded on the secondary side I had to replace because some electrician thought everything needs to be grounded! Don't ground low voltage secondaries! Why would you want to ground L1 or L2?? You do not ground live wires. if the secondary goes to ground it is screwed down to grounded metal. You are confused about the American 120 VAC system that uses a neutral instead of just using 240 VAC system like Europe. We use 120 VAC because A. Edison was in a war with Tesla about electrical distribution. Edison lost because he was completely wrong and wanted to use DC. We run 765,000 VAC in transmission lines to lower amperage and wire size then just drop VAC as necessary thru transformers. Most people die of electrocution from a 120 VAC circuit that has lost a path to ground (neutral).
    " The more I learn the more I realize how much I don't know"

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    Quote Originally Posted by stumpdigger View Post
    The only transformers that were grounded on the secondary side I had to replace because some electrician thought everything needs to be grounded! Don't ground low voltage secondaries! Why would you want to ground L1 or L2?? You do not ground live wires. if the secondary goes to ground it is screwed down to grounded metal. You are confused about the American 120 VAC system that uses a neutral instead of just using 240 VAC system like Europe. We use 120 VAC because A. Edison was in a war with Tesla about electrical distribution. Edison lost because he was completely wrong and wanted to use DC. We run 765,000 VAC in transmission lines to lower amperage and wire size then just drop VAC as necessary thru transformers. Most people die of electrocution from a 120 VAC circuit that has lost a path to ground (neutral).
    ???????????
    Wire per the vendor diagrams. I have had gas valve open with no safeties because of loose or disconnected 24vt grounds, solid state controls intermittently not function and other fail because of inadequate grounding.

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    Quote Originally Posted by ehsx View Post
    ???????????
    Wire per the vendor diagrams. I have had gas valve open with no safeties because of loose or disconnected 24vt grounds, solid state controls intermittently not function and other fail because of inadequate grounding.
    Wondering if I understand. Are you saying a poor chassis ground on a 24 VAC causes your circuits not to funtion properly? Are you sending current through the chassis? Never saw that, circuit boards always worked just fine for me.
    " The more I learn the more I realize how much I don't know"

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    If this transformer is going on a unit that has heating with flame rectification to sense the flame, polarity of the transformer and which side gets grounded is critical.

    So you always fire off the heating to be sure you don't/won't have a call when it gets cold.
    I do a triple evac with nitro to remove non condensables.

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    Quote Originally Posted by stumpdigger View Post
    Wondering if I understand. Are you saying a poor chassis ground on a 24 VAC causes your circuits not to funtion properly? Are you sending current through the chassis? Never saw that, circuit boards always worked just fine for me.
    In the United States, for example:

    ◆The National Electrical Code® requires (section 250.20) grounding transformers for AC systems of less than 50 volts if the primary voltage exceeds 150 volts to ground or if the main transformer supplying power to the building is ungrounded.

    ◆Some municipal electrical codes more restrictive than the NEC may require that the secondaries of all transformers that supply 24 VAC be grounded

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