Junction Box Requirements for Foundation Fieldbus

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.

The box construction shall meet the following requirements:

1. Type 304 or 316 stainless steel body, door and hardware.
2. Continuously welded seams, finished smooth.
3. Stainless steel hinge with removable pin.
4. Stainless steel captive clamps.
5. Data/Print pocket on inside of door.
6. External mounting brackets.
7. Collar studs for mounting inside panel.
8. Ground stud for terminating A/C safety ground wire.
9. Painted steel panel (back-pan); in ‘severe corrosive environments’ a stainless-steel panel shall be used.
10. All field junction boxes shall be mounted vertically, i.e., the door shall open from left-to-right or from right-to-left.
11. Junction boxes having an internal volume exceeding 2,000 cm³ shall be provided with Type 304 or 316 stainless steel breather and drain fittings, or a combination breather and drain fitting.