Changes to 620.51 from 2005 to 2008

[mr_rhino]

Greetings-

Didn't see anything related in the forum (or external links) regarding this change.

Does anyone have any visibility as to why 620.51(C)(1) has been changed for 2008 to require that a non-fused (as opposed to fused) disconnect be used when the controller is located in the elevator hoistway?

This now reads significantly different (in terms of layout/implementation) than the same code from 2005.

Thanks,
Jeff

 

[mr_rhino]

Specifics of situation

Specifics of situation

Main (fused) disconnect is mounted to elevator control panel outside of hoistway.
Fuse in this primary disconnect is sized to protect the wiring that feeds the combined load of the elevator control panel (~2KVA continuous) and a variable-frequency motor drive (<40KVA non-continuous).

A second (fused) disconnect (wired in series with the output from the primary disconnect), is located adjacent to the motor drive, both located within the elevator hoistway. The fuses (Class-J Very High Speed) in this secondary disconnect are sized only to protect the semiconductors within the motor drive that is less than 6 feet away. (Unfortunately the motor drive has no fuses, but has been CSA-certified for use with these Class-J fuses). Standard practice to replace these Class-J fuses in the secondary disconnect would require that the Main (primary) disconnect be opened first. Nevertheless, warning labels could be affixed to this secondary disconnect indicating that the feed into this disconnect could potentially be live (as with virtually any fused disconnect).

In light of how [2008] 620.51(C)(1) reads, does anyone see any reason why the secondary disconnect cannot have these Class-J fuses installed?

Thanks,
Jeff