NEC 225.52(B) Exception

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erickench

erickench

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I'm looking at the 2011 NEC, haven't picked up my 2014 edition yet lol. The above exception reads:

Where the individual disconnecting means consists of fused cutouts, the simultaneous disconnection of the ungrounded supply conductors shall not be required if there is a means to disconnect the load before opening the cutouts.

What is a means that disconnect the loads before opening the cutouts? Any examples?:?
 
But isn't a circuit breaker a device that opens all the ungrounded conductors simultaneously? And what do they mean by "disconnecting the load before opening the cutouts"?
 
erickench said:
I'm looking at the 2011 NEC, haven't picked up my 2014 edition yet lol. The above exception reads:

Where the individual disconnecting means consists of fused cutouts, the simultaneous disconnection of the ungrounded supply conductors shall not be required if there is a means to disconnect the load before opening the cutouts.

What is a means that disconnect the loads before opening the cutouts? Any examples?:?
Click to expand...
This is an allowance for over 600 volt only. You could have 3 seperate fuses in this case. But note that this does not translate to under 600 volt.
 
erickench said:
But isn't a circuit breaker a device that opens all the ungrounded conductors simultaneously? And what do they mean by "disconnecting the load before opening the cutouts"?
Click to expand...
Say you have fuse cutouts as the structure disconnecting means, and it feeds only distribution switchgear with several load disconnecting means. If you open all the distribution disconnects you will have effectively removed the load.
 
erickench said:
What is a means that disconnect the loads before opening the cutouts? Any examples?:?
Click to expand...
Consider that one motivation for the rule is to avoid the likelihood of single phasing a three phase load when you manually open the cutouts one at a time.
If there are no loads connected, the primaries of the distribution transformers and any other components along the way are not going to be damaged by the temporary single phasing of the supply. But motors could get burned out.
 
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