Working clearance depth

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cppoly

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For depth of working space, if 277V is facing 120Vis this condition 4? or 3??

Also, for a stepdown 480/208V transformer is the front considered 480V for working clearance purposes or just the side that 480V enters?
 
Tricky question since you have over 150 volts to ground and under 150 volts to ground facing each other. Condition 3 only says live parts on both sides so I would say that it's condition 3. Arguably a transformer does not need to comply with 110.26 and could be treated as a grounded part.
 
Actually, this is not tricky at all. You need 3' of clearance in front of the 120V panel, and you need 4' of clearance in front of the 277V panel. You are not going to achieve both of those requirements without putting 4' between the panels. I agree that the transformer does not require working clearance.
 
cppoly said:
For depth of working space, if 277V is facing 120Vis this condition 4? or 3??

Also, for a stepdown 480/208V transformer is the front considered 480V for working clearance purposes or just the side that 480V enters?
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I would say that for a "common aisle" situation, the larger voltage to ground would govern.

With approval from your AHJ, one way to get around the common aisle working clearance, is to clearly label both enclosures with a warning label not to service both at the same time. This makes your situation Condition 2 for both pieces of equipment.

If one piece of equipment faces the back or the sides of another piece of other equipment (with no electrical serviceable parts), you've got condition 2 automatically. Unless you have non-metallic enclosures, in which case you have condition 1.
 
infinity said:
Tricky question since you have over 150 volts to ground and under 150 volts to ground facing each other. Condition 3 only says live parts on both sides so I would say that it's condition 3. Arguably a transformer does not need to comply with 110.26 and could be treated as a grounded part.
Click to expand...
CONCUR !:thumbsup:
 
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