Issue:
Clarification of National Electrical Code section NEC 450-21(b)
Clarification of National Electrical Code section NEC 450-21(b)
Product Line:
LV Transformers
LV Transformers
Environment:
Applies to Ventilated and Non-Ventilated SquareD/Schneider Electric Transformers with a Class 220 insulation system
Applies to Ventilated and Non-Ventilated SquareD/Schneider Electric Transformers with a Class 220 insulation system
Cause:
Code Section NEC450-21(b) may call for clarification in some installation situations
Code Section NEC450-21(b) may call for clarification in some installation situations
Resolution:
This is not a concern to SquareD/Schneider Electric low voltage dry type transformers with enclosures as we comply with 1999 NEC 450-21(b) Exception No. 2, which states ``Transformers with Class 155 or higher insulation systems and completely enclosed except for ventilating openings.``SquareD/Scheider Electric Ventilated and Non Ventilated low voltage dry type Transformers utilize a Class 220 insulation system, which is higher than a Class 155.
The previous versions of code section 450-21(b) used to reference 80?C rise as the differentiation point. The intent for that was to require units with Class 150 insulation to be in the fire-rated room, and one aspect of a Class 150 insulation system transformer is a standard 80?C rise. This created unnecessary cost for those using a Watchdog 80C rise transformer which utilizes a Class 220 insulation system. The change in the code was done to clarify the intent of this section.
Released for: Schneider Electric USA
