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  1. #1
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    Grounding existing 2 wire no ground

    On a replacement install of an AH. the chassis is connected to the fault circuit conductor via metallic conduit. To appease the inspector we run a wire from AH chassis to a copper water pipe with the existing ground still attached. I see a problem with this, anyone else. What is code related to the subject?

  2. #2
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    That is not a code requirement.

    The metallic conduit is an accepted ground fault path with the proper bushings and locknuts.

    No wires need to be run to any pipes to ground the air handler cabinet.

    If the inspector believes this is required, ask which code section specifies the use of such a conductor.
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  3. #3
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    Thanks timebuilder

  4. #4
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    Quote Originally Posted by Core_d View Post
    Thanks timebuilder
    Many inspectors are doing that job because they like the feeling of authority, so you have to choose carefully how you challenge what they say.

    "Oh, that's interesting. Can you show me where that is a code requirement?"
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  5. #5
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    Just to be clear...

    What we are actually talking about is called "bonding."

    That part starts with 250.90 (General) and 250.104 gives the requirements for bonding piping systems and structural steel.

    Note that these bonds to piping are not coincidental to a piece of equipment; they are simply required, and are usually made somewhere near the service panel.

    250.104 B explains that gas piping ("other metal piping") is also to be bonded.

    If you run conduit to an air handler (or other utilization equipment) and you use the proper bushings and locknuts where required, the metal raceway IS an approved "low impedance ground fault current path" that connects the normally non-current carrying parts of the air handler and connects them to ground via the grounding bar in the service panelboard cabinet, and through the main bonding jumper and the grounding electrode conductor, to the grounding electrode, the last element in that chain of connections, and the one that is actually in contact with the earth in some approved manner, such as rebar encased in concrete, etc.

    So, this chain of bond connections does indeed lead to "ground."
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  6. #6
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    One more thing.

    250.118 gives you a handy list of things that can make up the low impedance ground fault current path.

    The first item is conductors (wires).

    Items 2, 3, and 4 are:

    Rigid metal conduit
    Intermediate metal conduit
    Electrical metallic tubing

    ...to make it easy
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    2 Tim 3:16-17

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  7. #7
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    Thanks again, I do not think this was done on behalf of one certain inspector, this is our lead installers standard practice when the ground wire is not run directly to the unit. I did point out that the unit was infact on the fault circuit already. I have no intention on changing his habits if no harm is done with this practice. My line of thought was this could be a code violation in and of itself. I have also been told by atleast 2 instructors that 2wire with a ground is now required. So im glad you have cleared this up for me.

  8. #8
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    With the conduits I described and correctly installed, you DO have two wires with a ground.
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    2 Tim 3:16-17

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  9. #9
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    Quote Originally Posted by Core_d View Post
    On a replacement install of an AH. the chassis is connected to the fault circuit conductor via metallic conduit. To appease the inspector we run a wire from AH chassis to a copper water pipe with the existing ground still attached. I see a problem with this, anyone else. What is code related to the subject?

    Just for the record....

    Describe for me the "conduit" you saw. A pic would be great...
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    2 Tim 3:16-17

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  10. #10
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    On furnaces with flame rectifiers its imperative to have a proper ground to the furnace. I've had some that work fine for years with 2 wire and no ground then all of a sudden it starts locking out until a ground is run to the furnace. That's probably why the lead tech has made a habit of it.

  11. #11
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    Quote Originally Posted by timebuilder View Post
    Just for the record....

    Describe for me the "conduit" you saw. A pic would be great...
    This is not the unit but same type of flexable metalic conduit ImageUploadedByTapatalk 21371328924.010817.jpg

  12. #12
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    Quote Originally Posted by jtrammel View Post
    On furnaces with flame rectifiers its imperative to have a proper ground to the furnace. I've had some that work fine for years with 2 wire and no ground then all of a sudden it starts locking out until a ground is run to the furnace. That's probably why the lead tech has made a habit of it.
    Thank you for the reply. That is a thread with in its self. I dont think that is the case here but ill be sure to keep you up dated if thats the case.

  13. #13
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    Quote Originally Posted by Core_d View Post
    This is not the unit but same type of flexable metalic conduit ImageUploadedByTapatalk 21371328924.010817.jpg

    Only certain types of that kind of cable are eligible for use as a grounding conductor.

    Generally, what is shown in that pic is not suitable.

    Glad I asked.
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