wiring in a new panel - MTW wire vs THHN wire

Discussion in 'General Electronics Chat' started by dayman, Feb 3, 2016.

  1. dayman

    Thread Starter New Member

    Jul 29, 2013
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    hello

    Im wiring in a new panel and im noticing that my shop has mostly THHN wire, Im wondering if there is a preference

    im installing it to an indoor panel, operating at 120 V AC and 24 V DC
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I found THHN very stiff insulation, I either use MTW or TR64 which is small gauge and thinner insulation, where it is possible to fill a wire duct up very fast with the thicker MTW's etc.
    Many panels are wired with #14 which often is not necessary.
    Max.
     
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  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    All depends on standards that one must apply to..
    I use MTW in all my products..

    THHN is a very poor choice for control panel wiring

    MTW is a much better solution due to many reasons..

    Or course...You didn't specific any information about what a "new panel" is..
    If this is a control panel then MTW.. If a regular "breaker panel",etc.. where conduit is used then THHN may be just fine..
     
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  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    For indoor use that will NEVER see any water anywhere near the wire; either will work. If in doubt use the waterproof indoor/outdoor THHN
     
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  5. dayman

    Thread Starter New Member

    Jul 29, 2013
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    control panel for one of our automated machines,
    so then would i use THHN wire coming in from the breaker, and MTW for the rest in the control panel?
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Is it predominantly 24vdc and is there high power devices?
    What gauge are you currently using for control wiring?
    Max.
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    THHN is stiff and difficult to work with. It is very abrasive resistant and can be used around water. By using proper stress relief such as pig tail curls in the wiring and properly crimped termination sleeves for use with screw tensioned terminal blocks, THHN wire can be used inside control panels.
    If there is any oil aerosol in the air, such as a manufacturing environment, THHN is resistant to it, and it will build up over the weeks and months a machine control panel is exposed. Nothing less than perfect air tight gasket sealing will keep it out.
    Bottom line, if it is commercial or industrial in design, use the better armored THHN.
     
  8. dayman

    Thread Starter New Member

    Jul 29, 2013
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    predominantly 120 V
    18 and 14 AWG
    12 AWG for power from the breaker
     
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