NEC Class 1 Div. 2 Hazardous Location Flexible Conduit
NEC Class 1 Div. 2 Hazardous Location Flexible Conduit
(OP)
Hello,
I have several automatic shutoff valve assemblies (see example below)which have both a solenoid and a proof of closure limit switch, both of which are rated for a class 1 div 2 application. In a non hazardous environment we would typically run a short peice of liquid-tight flexible conduit from the solenoid to the switch and then bring a single cable back from the switch to my cabinet. However, in my experience this type of polymer coated conduit is not allowed for this hazardous location. Either rigid or at flexible metal conduit with an outer metal braid is required. I have not been able to find a flexible conduit which carries a class 1 div 2 rating, and I would prefer not to use rigid. Has anyone run into a similar problem or have any suggestions?
Regards
jhack

The NEC 70 section which covers this is as follows:
(B) Class I, Division 2.
(1) General. In Class I, Division 2 locations, the following wiring methods shall be permitted:
(1) All wiring methods permitted in Article 501.4(A).
(2) Threaded rigid metal conduit, threaded steel intermediate metal conduit.
(3) Enclosed gasketed busways, enclosed gasketed wireways.
(4) Type PLTC cable in accordance with the provisions of Article 725, or in cable tray systems. PLTC shall be installed in a manner to avoid tensile stress at the termination fittings.
(5) Type ITC cable in cable trays, in raceways, supported by messenger wire, afforded mechanical protection and run as open wiring, or directly buried where the cable is listed for this use.
(6) Type MI, MC, MV, or TC cable with termination fittings, or in cable tray systems and installed in a manner to avoid tensile stress at the termination fittings.
(2) Flexible Connections. Where provision must be made for limited flexibility, flexible metal fittings, flexible metal conduit with listed fittings, liquidtight flexible metal conduit with listed fittings, liquidtight flexible nonmetallic conduit with listed fittings, or flexible cord listed for extra-hard usage and provided with listed bushed fittings shall be used. An additional conductor for grounding shall be included in the flexible cord.
FPN: See 501.16(B) for grounding requirements where flexible conduit is used.
I have several automatic shutoff valve assemblies (see example below)which have both a solenoid and a proof of closure limit switch, both of which are rated for a class 1 div 2 application. In a non hazardous environment we would typically run a short peice of liquid-tight flexible conduit from the solenoid to the switch and then bring a single cable back from the switch to my cabinet. However, in my experience this type of polymer coated conduit is not allowed for this hazardous location. Either rigid or at flexible metal conduit with an outer metal braid is required. I have not been able to find a flexible conduit which carries a class 1 div 2 rating, and I would prefer not to use rigid. Has anyone run into a similar problem or have any suggestions?
Regards
jhack

The NEC 70 section which covers this is as follows:
(B) Class I, Division 2.
(1) General. In Class I, Division 2 locations, the following wiring methods shall be permitted:
(1) All wiring methods permitted in Article 501.4(A).
(2) Threaded rigid metal conduit, threaded steel intermediate metal conduit.
(3) Enclosed gasketed busways, enclosed gasketed wireways.
(4) Type PLTC cable in accordance with the provisions of Article 725, or in cable tray systems. PLTC shall be installed in a manner to avoid tensile stress at the termination fittings.
(5) Type ITC cable in cable trays, in raceways, supported by messenger wire, afforded mechanical protection and run as open wiring, or directly buried where the cable is listed for this use.
(6) Type MI, MC, MV, or TC cable with termination fittings, or in cable tray systems and installed in a manner to avoid tensile stress at the termination fittings.
(2) Flexible Connections. Where provision must be made for limited flexibility, flexible metal fittings, flexible metal conduit with listed fittings, liquidtight flexible metal conduit with listed fittings, liquidtight flexible nonmetallic conduit with listed fittings, or flexible cord listed for extra-hard usage and provided with listed bushed fittings shall be used. An additional conductor for grounding shall be included in the flexible cord.
FPN: See 501.16(B) for grounding requirements where flexible conduit is used.





RE: NEC Class 1 Div. 2 Hazardous Location Flexible Conduit
My read of those paragraphs has always been that liquidtight is OK but the fittings need to be listed.
Southwire and Thomas & Betts in the US have such listed fittings, and even print the applicability of the flex in their data sheets. Try googling the following for mroe manufacturers and sources:
liquidtight flexible nonmetallic conduit class 1 div 2
Most important, though -- ask the authority having jurisdiction how he or she interprets the code.
Good on ya,
Goober Dave
RE: NEC Class 1 Div. 2 Hazardous Location Flexible Conduit
Goober Dave's point is also well taken; all termination fittings must be listed. However, they must be listed whether in a Classified location or not. See 350.6. In a Classified location application they must also be listed for grounding/bonding.
RE: NEC Class 1 Div. 2 Hazardous Location Flexible Conduit
RE: NEC Class 1 Div. 2 Hazardous Location Flexible Conduit
The other follow up question I have is: The limit switch is rated as explosion proof. My understanding was that this would require an explosion proof fitting at any entry point. While the fittings I have found are Class 1 div. 2 rated this does not mean they are explosion proof. (ie. an explosion in the switch could propagate through the fitting and ignite the outside environment) Are you aware of any explosion-proof liquid-tite fittings? I have a call in to Thomas & Betts to see if they offer such a product.
RE: NEC Class 1 Div. 2 Hazardous Location Flexible Conduit
Actually, if the switch is in an explosionproof enclosure you will need a seal at the unit. See NEC[2002]Section 501.5(B)(1). Since it is already in an explosionproof enclosure it is likely "... required to be..."; probably per Section 501.6(B)(1)[switches in Division 2 that are required to be identified for Division 1]
Beyond the seal, "standard" Division 2 wiring methods may be used.