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Thread: Low Voltage Transformer Wiring-Michigan

  1. #1
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    Low Voltage Transformer Wiring-Michigan

    Hello,

    I am being told by an inspector if a low voltage lighting fixture in a store has a Class 2 transformer it must be hardwired.

    Also that It must be placed in a metal enclosure, which I do not see in UL-962 & UL-65.

    Typically we don't hardwire the LED lights and the transformer and we never use a metal enclosure for the transformers. We use UL-Listed Transformer without a metal enclosure which comes with a plug that directly plugs into the wall.

    Could it be because this specific transformer is located in a metal enclosure and the plug is hardwired inside the metal enclosure?

    Inspector is suggesting to remove the plug and attach a metal conduit which must be hardwired by an electrician at the store. I am trying to understand that why does a low voltage transformer require a metal enclosure and why is a metal conduit required for the cord plugging into the low voltage transformer. I understand if it was a quadbox or a jbox or a combination of the two but it is just a class 2 transformer rated less than 100W..

    I tried to look up the code for Michigan to see if it any different but I am can't find any related information..

    Can you some one please advise?

  2. #2
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    See 411.4(A) and (B)

    About the transformer.

  3. #3
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    A little more about the location of this transformer and receptacle. Anything above a ceiling? Does either the power cord or the LV wiring have to go through a hole in the wall or ceiling?

    -Hal

  4. #4
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    Quote Originally Posted by iwire View Post
    See 411.4(A) and (B)

    About the transformer.

    Thank you for the guidance.

    As per 411.A the secondary end of an isolated transformer shouldn't be grounded, which is fine because we never ground the secondary (DC) side of the wiring

    411.B requires an isolation transformer for low voltage lightings an automated transformer is not acceptable as primary and secondary are not isolated.


    Here is my understanding of the isolated and non-isolated transformer. An Isolated transformer has a Line and Neutral on the primary side. When a 3 prong plug is attached to an isolated transformer the ground wire of that plug needs to be grounded to metal. Hence, the adapter must be placed in a metal enclosure so that ground wire from the plug can be attached to the metal.

    A non-isolated transformer is all one assembly. A 3 prong plug from the receptacle directly plugs into the adapter which is already grounded therefore the adapter does not need to be placed in metal enclosure and hence no additional grounding is required.

    Typically we never use the isolated transformers for our lightings which is why were never asked to "hardwire" the primary side of the transformers by any inspector. In this specific project the vendor who wired the fixture for us used a non-isolated transformer and I am suspecting that that is the reason why we are asked to hardwire the plug coming out of the low voltage transformer...

  5. #5
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    Quote Originally Posted by hbiss View Post
    A little more about the location of this transformer and receptacle. Anything above a ceiling? Does either the power cord or the LV wiring have to go through a hole in the wall or ceiling?

    -Hal
    We have a store fixture which is placed directly against the wall. The transformer is located at the top of the fixture inside an enclosure and only the transformer cables coming out of the fixture and plug into the receptacles. None of this is visible from the outside.

    None of the receptacles and transformers are located above the ceiling. Power cord doesn't travel through the wall but it plugs into the wall. Low voltage lightings are only wired within the fixture for the lightings therefore they never go through the wall or the ceiling.

  6. #6
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    Quote Originally Posted by Sarray View Post
    Thank you for the guidance.

    As per 411.A the secondary end of an isolated transformer shouldn't be grounded, which is fine because we never ground the secondary (DC) side of the wiring

    411.B requires an isolation transformer for low voltage lightings an automated transformer is not acceptable as primary and secondary are not isolated...
    Don't know where you got that from.

    411.4 Specific Location Requirements
    (A) Walls, Floors, and Ceilings. Conductors concealed or
    extended through a wall, floor, or ceiling shall be in accordance
    with (1) or (2):
    (1) Installed using any of the wiring methods specified in
    Chapter 3
    (2) Installed using wiring supplied by a listed Class 2 power
    source and installed in accordance with 725.130

    (B) Pools, Spas, Fountains, and Similar Locations.
    Lighting systems shall be installed not less than 3 m (10 ft)
    horizontally from the nearest edge of the water, unless permitted
    by Article 680.

    Quote Originally Posted by surray
    We have a store fixture which is placed directly against the wall. The transformer is located at the top of the fixture inside an enclosure and only the transformer cables coming out of the fixture and plug into the receptacles. None of this is visible from the outside.

    None of the receptacles and transformers are located above the ceiling. Power cord doesn't travel through the wall but it plugs into the wall. Low voltage lightings are only wired within the fixture for the lightings therefore they never go through the wall or the ceiling.
    This is what I thought, it's a store fixture that is plug and cord connected. NEC is not applicable so I have no idea why the inspector is even involved. Maybe Canada is different?

    -Hal

  7. #7
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    Quote Originally Posted by hbiss View Post


    This is what I thought, it's a store fixture that is plug and cord connected. NEC is not applicable so I have no idea why the inspector is even involved. Maybe Canada is different?

    -Hal
    OP specified Michigan. If he is having problems with an inspector making up code, he can call the state.

    Contact the Electrical Division:
    Phone: 517-241-9320
    Fax: 517-373-8547
    E-Mail: bccelec@michigan.gov

    The Electrical Division is responsible for the administration and enforcement of the Michigan Electrical Code and the electrical provisions of the Michigan Residential Code by conducting inspections of electrical wiring and installations. The division also follows up on violations of the Michigan Electrical Code and assures proper electrical permits have been issued.
    Cheers and Stay Safe,

    Marky the Sparky

  8. #8
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    Quote Originally Posted by hbiss View Post
    Don't know where you got that from.

    411.4 Specific Location Requirements
    (A) Walls, Floors, and Ceilings. Conductors concealed or
    extended through a wall, floor, or ceiling shall be in accordance
    with (1) or (2):
    (1) Installed using any of the wiring methods specified in
    Chapter 3
    (2) Installed using wiring supplied by a listed Class 2 power
    source and installed in accordance with 725.130

    (B) Pools, Spas, Fountains, and Similar Locations.
    Lighting systems shall be installed not less than 3 m (10 ft)
    horizontally from the nearest edge of the water, unless permitted
    by Article 680.



    This is what I thought, it's a store fixture that is plug and cord connected. NEC is not applicable so I have no idea why the inspector is even involved. Maybe Canada is different?

    -Hal
    It was a US Store inspector in Michigan who flagged the fixture

    Store Inspector flagged the fixture and said that the Cable carying Line voltage to the adapter MUST be hardwired, which has never been a concern in the past.
    Typically what we have done in the past is use the a low voltage lighting set up where we don't have to worry about any grounding or metal enclosures. Plug from the wall directly goes into the Adapter, out of the Adapter we have connections straight to the low voltage lightings.

    In this specific case our vendor who built the units used the non-isolated low voltage transformers....These transformers are hardwired within a metal enclosure. Line Neutral from the Plug wired to Line and Neutral of the adapter and the Ground from the plug is connected to a grounding bolt attached to a metal enclosure. I am assuming due to this set up we are being asked to hardwire the AC side of the adapter?

    Instead of retrofitting and hardwiring every single fixture, can simply use isolated transformers so there is no hardwiring and grounding the AC side is involved?

  9. #9
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    Quote Originally Posted by Sarray View Post
    It was a US Store inspector in Michigan who flagged the fixture

    Store Inspector flagged the fixture and said that the Cable carying Line voltage to the adapter MUST be hardwired, which has never been a concern in the past.
    Typically what we have done in the past is use the a low voltage lighting set up where we don't have to worry about any grounding or metal enclosures. Plug from the wall directly goes into the Adapter, out of the Adapter we have connections straight to the low voltage lightings.

    In this specific case our vendor who built the units used the non-isolated low voltage transformers....These transformers are hardwired within a metal enclosure. Line Neutral from the Plug wired to Line and Neutral of the adapter and the Ground from the plug is connected to a grounding bolt attached to a metal enclosure. I am assuming due to this set up we are being asked to hardwire the AC side of the adapter?

    Instead of retrofitting and hardwiring every single fixture, can simply use isolated transformers so there is no hardwiring and grounding the AC side is involved?
    Cold be the OP is dealing with an inspector that does NOT work as an inspector under Michigan's AHJ. It sounds like the inspector works for the store and is enforcing company policy, not the Michigan codes or the NEC. As such, we have no idea what the company inspector will allow. I think we are dealing with more of a contract/legal issue if the store is making requirements above the codes. It's entirely possible any advice given here, based on the NEC, may also get shot down by the company inspector.
    Cheers and Stay Safe,

    Marky the Sparky

  10. #10
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    Quote Originally Posted by K8MHZ View Post
    Cold be the OP is dealing with an inspector that does NOT work as an inspector under Michigan's AHJ. It sounds like the inspector works for the store and is enforcing company policy, not the Michigan codes or the NEC. As such, we have no idea what the company inspector will allow. I think we are dealing with more of a contract/legal issue if the store is making requirements above the codes. It's entirely possible any advice given here, based on the NEC, may also get shot down by the company inspector.

    Thank you for your input. It might be the case that the inspector is requesting something not related to any code

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