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Choosing the right VFD protection

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    #16
    Originally posted by Jraef View Post
    If the drive says that you need Class J fuses per their UL listing and does not say you can use circuit breakers as an alternate, using the CB alone means you are not using it in the manner intended by the manufacturer and therefore violating the NEC.

    Looked at the other way, the only way you can use a CB alone is if the drive mfr specifically states that this is an approved option. Some drive mfrs do, some do not. Almost any drive will pass the UL SCCR listing requirements when protected by current limiting fuses, but not all designs will pass with CBs alone, and some mfrs are unwilling to do the expensive destructive testing only to find out they will not pass. So they “bury the lead” in their installation/technical documents by simply stating that fuses work. As a general rule, if a mfr has gone to the risk and extreme expense of getting their drive UL listed behind CBs alone, they make that very clear because it gives them an advantage in the market over those that do not.

    If you don’t feel this is stated clearly enough for you in the Siemens instruction manual, you should ask them for a specific response in writing to clear it up.
    Got it,
    Thanks

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