According to NFPA 70 Clause 392.9, the following definition can be read ;
- 392.9 Clause (B) Multiconductor Control and/or Signal Calbes only- a ladder or ventilated trough cable tray ----> cable fill rate of such tray is defined as less than 50%
- 392.9 Clause (D) Solid bottom cable tray- Multiconductor control and/or Signal cables only ---> cable fill rate of such tray is defined as less than 40%
In my thinking, solid bottom type ( such as instrument Duct ) is capable of having a little higher fill rate than ladder tray case which have 'rungs' with another occupancy inside ladder tray.
Could anyone please let me know why a ladder type tray fill rate is higher than solid bottom case ?
Thanks a lot in advance.
- 392.9 Clause (B) Multiconductor Control and/or Signal Calbes only- a ladder or ventilated trough cable tray ----> cable fill rate of such tray is defined as less than 50%
- 392.9 Clause (D) Solid bottom cable tray- Multiconductor control and/or Signal cables only ---> cable fill rate of such tray is defined as less than 40%
In my thinking, solid bottom type ( such as instrument Duct ) is capable of having a little higher fill rate than ladder tray case which have 'rungs' with another occupancy inside ladder tray.
Could anyone please let me know why a ladder type tray fill rate is higher than solid bottom case ?
Thanks a lot in advance.