Junction Box Requirements for Foundation Fieldbus
- Two (2) dedicated connections for the fieldbus homerun/trunk cable.
- Trunk connections shall be non-sparking (no arcing) i.e., Ex nA.
- Integral short circuit protector for spur connections, maximum current to spur shall be no more than 60 mA.
- Spur connections shall be rated nonincendive (energy limited), i.e., Ex nL and shall have ‘live disconnect’ capability (including junction boxes).
- Pluggable (removable) ‘trunk’ and ‘spur’ connectors with retaining screws.
- LED indicator for each spur connection indicating when a spur is shorted and is in overcurrent mode.
- LED to indicate when bus power is available.
- Segment wiring block shall be CENELEC (ATEX) Ex nA[L]; Class 1, Zone 2, Gas Group IIC.
- Wire capacity: 12-24 AWG.
- Temperature range -45 to 70 deg C.
- DIN rail mounting.
- Available in four (4) spur and eight (8) spur configuration.
- A warning label must be prominently affixed on the junction box door (inside) stating the following: (red lettering with white background) “WARNING: Explosion Hazard – Do not connect or disconnect the ‘trunk connections’ on the wiring-block unless power has been switched off or the area is known to be non-hazardous.”
- An information label must be prominently affixed on the junction box door (inside) stating the following: (black lettering with white background) “The spur connections may be connected or disconnected while the circuit is live, i.e., you may connect or disconnect the spur on the wiring-block or at the device without sniffing the area for combustible gasses.”
- The wiring-blocks shall be mounted vertically in the field junction box.
- The DIN rail(s) in the junction box shall be designed with enough spare length to allow the future addition of one 8-spur or larger wiring-block.
- Junction Boxes shall contain only FF signal wiring.
- The junction box shall be a single door IP65 box.