9-145 Log #1138 NEC-P09 Final Action: Accept in Principle
(450.11)
________________________________________________________________
Submitter: Gaylord Poe, Inspection Bureau, Inc.
Recommendation: Revise text to read as follows:
2014 NEC Proposed - 450.11 - Marking. Each transformer shall be
provided with a nameplate giving with the following information:
1. Tthe name of the manufacturer.,
2. Rrated kilovolt-amperes.,
3. Ffrequency.,
4. Pprimary and secondary voltage.,
5. For dry type transformers, if the transformer is permitted to be connected
in either direction, it shall be marked as ?Bi-Directional?. Installation
instructions shall be provided by the manufacturer detailing how the
transformer should be connected when the primary and secondary are reversed.
6. The impedance of transformers 25kVA and larger.,
7. Rrequired clearances for transformers with ventilating openings., and
8. Tthe amount and kind of insulating liquid where used.
In addition, the nameplate of each dry-type transformer shall include the
temperature class for the insulation system.
Substantiation: Although it is common industry practice to reverse wire dry-
type transformers, the marking requirements in the current NEC do not make
the installer aware of the fact that UL 1561 does not support this practice. UL
1561 provides that the testing of these transformers includes ?...step up, step
down, and autotransformer type...? with the supply being connected to the
primary and the load being connected to the secondary, thus, making
connections in any other manner a violation of 110.3(B). Changing the marking
requirements of 450.11 will provide clarification and enhance electrical safety.
Panel Meeting Action: Accept in Principle
Revise the text to read as follows:
450.11 - Marking.
(A) General. Each transformer shall be provided with a nameplate giving the
following information:
1. The name of the manufacturer
2. Rated kilovolt-amperes
3. Frequency
4. Primary and secondary voltage
5. The impedance of transformers 25kVA and larger
6. Required clearances for transformers with ventilating openings
7. The amount and kind of insulating liquid where used
8. For dry-type transformers, the temperature class for the insulation system
(B) Source Marking. A transformer shall be permitted to be supplied at the
marked secondary voltage provided the installation is in accordance with the
manufacturers? instructions.
Panel Statement: The Panel action corrects a violation of the NEC Style
Manual relative to the formatting of lists and meets the submitter?s intent. CMP
9 concludes that a specific marking as opposed to general instructions from the
manufacturer is excessive. Submitter?s proposal was limited only to dry-type
transformers without adequate substantiation.
Number Eligible to Vote: 12
Ballot Results: Affirmative: 12