NEC 110.26 (A) Interpretation

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DataCenterGuy

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Designing location for a large UPS (250 kVA) Nominal 208 V service meeting Condition 2 (grounded cabinets behind live parts access). Since Voltage Phase to Ground is only 120 V, does this require 36-inch or 42-inch clearance? (Sorry if this is an old question. New to Forum and haven't learned yet how to search 1,000 pages.)
 
For that voltage 36" is all that required for any of the three conditions.

Welcome to the forum.:)
 
DataCenterGuy said:
Designing location for a large UPS (250 kVA) Nominal 208 V service meeting Condition 2 (grounded cabinets behind live parts access). Since Voltage Phase to Ground is only 120 V, does this require 36-inch or 42-inch clearance? (Sorry if this is an old question. New to Forum and haven't learned yet how to search 1,000 pages.)

You may need to look at the DC bus voltage and consider that voltage to be the 'yardstick' -so to speak- if it is higher than the I/O voltage when considering working space.
 
Good point. I like lots of clearance and am usually doing 480 or 600 volt service to begin with, but this time have an architect pushing me for space, and had to actually think about it. I should have thought about the DC bus as well. Thanks.
 
For service access, yes. But there's the usual "Compliant with Codes" statement, which is dependent on installation conditions, not on actual service need. I've also seen stuff that calls for 42" as a "CYA", but when you ask them, they tell you 36" is fine if it meets Code.
 
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