Cable tray vertical heights order (MV/LV)

[mendizi]

Is there any code rule that prohibits that a cable tray holding medium voltage cables be installed below (less height) than a cable tray for low voltage cables? Thanks in advance for your help.

 

[iceworm]

None I know of.

I've seen installations that have three trays:

MV (13.8kv)
LV (480V)
Instrument
​

Although they usually are stacked in descending order I've never heard of a code rule.

the worm

 

[mendizi]

Thanks iceworm. A colleague tell me about IEEE standards 422 and 525 for Generation Facilities and Substations respectively, where it is explicit that stacked cable trays should be arranged by descending voltagelevels, with the higher voltage at the top, but apart from that standards any mandatory rule seems nonexistent.