240.21(F) covers both motor feeder [430.28] and branch [430.53] circuits... which seem to put us back to 430.53(D) for a single motor... and thus the reason for 240.4(E)(6). Keep in mind a motor branch circuit can supply more than one motor.
Tap terminating on a listed combination starter
- Thread starter corvalan
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- Engineer
I don't see it. As you say, 240.21(F) covers both motor feeder and branch circuits. 240.4(E)(6) covers a specific motor branch circuit that is already covered by 240.21(F).
Or in other words, 430.53(D) is a part of 430.53 which is referenced in 240.21(F). 240.4(E)(6) is redundant.
I agree with you on that part. On the other hand I see 240.4(E)(6) as a direct entry compared to the beat-around-the-bush entry of (E)(3).
CobyRupert
Member
- Location
- NY
What if transformer secondary tap to instantaneous breaker set at "1"
What if transformer secondary tap to instantaneous breaker set at "1"
I too have a similar situation (but different!). Should I post this as a new thread?
In my situation I have a 500 kVA, 480V transformer, less than 10' feet away and supplying a 600 amp (frame) instantaneous only (electronic!) breaker that is (let's assume) part of a listed combination controller. (Actually its a VFD). The transformer has NO secondary protection.
What I think is interesting (significant) is that the (electronic!) instantaneous breaker of the starter has an adjustment setting of "1" (i.e. a vertical line at 600amps on the current-time curve). My understanding is that being electronic it's not relying on magnetic forces of an "instantaneous" current.
Can I use this setting of "1" (600amps) to protect my 620amps worth of transformer secondary tap conductors? If set to "1", doesn't this provide the same protection as a electronic breaker with long time, short time, inverse time capabilities (i.e a breaker analogous to a thermal-magnetic breaker)? Is 240.21.(C)(2) fulfilled?
What if transformer secondary tap to instantaneous breaker set at "1"
I too have a similar situation (but different!). Should I post this as a new thread?
In my situation I have a 500 kVA, 480V transformer, less than 10' feet away and supplying a 600 amp (frame) instantaneous only (electronic!) breaker that is (let's assume) part of a listed combination controller. (Actually its a VFD). The transformer has NO secondary protection.
What I think is interesting (significant) is that the (electronic!) instantaneous breaker of the starter has an adjustment setting of "1" (i.e. a vertical line at 600amps on the current-time curve). My understanding is that being electronic it's not relying on magnetic forces of an "instantaneous" current.
Can I use this setting of "1" (600amps) to protect my 620amps worth of transformer secondary tap conductors? If set to "1", doesn't this provide the same protection as a electronic breaker with long time, short time, inverse time capabilities (i.e a breaker analogous to a thermal-magnetic breaker)? Is 240.21.(C)(2) fulfilled?
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