NEC vs MEC (Massachusetts), for Ampacity Adjustment factors (derates)

[Carultch]

I have a design in Massachusetts, which is taking credit for the Massachusetts-specific values that override Table 310.15(B)(3)(A).
http://www.mass.gov/eopss/docs/dfs/osfm/cmr/527cmr12-00.pdf

NEC values are more conservative than Massachusetts values. For 43 and above wires, Massachusetts allows 50% derates, while the NEC requires 35% derates.

Does this table apply to all circumstances where numerous conductors are in the same raceway, in Massachusetts? Both continuous and non-continuous loads, regardless if the circuit operation is simultaneous or diverse?

Is there a reason why Massachusetts allows this, but the rest of the nation does not?

The reason I ask is I have a design reviewer thinking that the NEC should override the MEC. But if that is the case, it wouldn't make sense that the MEC would even have this table in it, unless it were more strict.

 

[iwire]

I have a design in Massachusetts, which is taking credit for the Massachusetts-specific values that override Table 310.15(B)(3)(A).
http://www.mass.gov/eopss/docs/dfs/osfm/cmr/527cmr12-00.pdf

NEC values are more conservative than Massachusetts values. For 43 and above wires, Massachusetts allows 50% derates, while the NEC requires 35% derates.

Does this table apply to all circumstances where numerous conductors are in the same raceway, in Massachusetts? Both continuous and non-continuous loads, regardless if the circuit operation is simultaneous or diverse?

Is there a reason why Massachusetts allows this, but the rest of the nation does not?

The reason I ask is I have a design reviewer thinking that the NEC should override the MEC. But if that is the case, it wouldn't make sense that the MEC would even have this table in it, unless it were more strict.

As far as I know it applies to all circumstances in MA.

As far as why, MA is using the same table the NEC used to use. When the NEC changed to the more conservative table MA decided to stick with the old table.

You can still find the table in the NEC in the rear.

 

[don_resqcapt19]

Table B310.15(B)(2)(11) (Annex B) and the MA table are based on the conductors having "load diversity". The reason this table was removed form the code itself and placed in the Annex was because no one could agree on what the term "load diversity" meant.