Multiconductor Instrumentation cables in C1D1 areas

[paulyang]

Can someone confirm that multiconductor instrumentation cables (ex. Thermocouple, coax, analog, low voltage 0-10Vdc/4-20mA) can be routed through a sealed conduit in a Class 1 Div 1 area?? Granted the cable ends will also be sealed within the C1D1 area to minimize vapors travelling into the cable core. Is this an approved wiring method in a C1D1 area??

Do the multiconductor cables have to be armored??

I have an Insturmentation Junction box with thermocouple jacks, coaxial jacks, and ms connector jacks inside a C1D1 area, and I am trying to find the best wiring method of getting the cables from the C1D1 area to a C1D2 area.

Any insight would be greatly appreciated.

 

[petersonra]

501.10 Wiring Methods. Wiring methods shall comply
with 501.10(A) or 501.10(B).
(A) Class I, Division 1.
(1) General. In Class I, Division 1 locations, the wiring
methods in (a) through (d) shall be permitted.
(a) Threaded rigid metal conduit or threaded steel intermediate
metal conduit.

As a practical matter, you are pretty much limited to rigid or IMC for this kind of application.

The code does not really care much what kind of conductors are inside the raceway.

 

[kameele]

Armored may end up being a little easier to use. if you use conduit, you don't have to separate the individual conductors at the seal (each cable is considered as an individual conductor), but you do have to seal each cable end in the box. (501.15 (D) (2) ) If you use armored cable (MC-HL), that sealing is furnished as part of the connector.

And you won't need a boundary seal. depending on the size of the conduit, you may need a seal at the box and then a boundary seal.

BTW--is this an Xproof box? And are the jacks inside or outside the box? Not sure about Div 1 rated plugs for all those apps.

 

[petersonra]

Armored may end up being a little easier to use. if you use conduit, you don't have to separate the individual conductors at the seal (each cable is considered as an individual conductor), but you do have to seal each cable end in the box. (501.15 (D) (2) ) If you use armored cable (MC-HL), that sealing is furnished as part of the connector.

And you won't need a boundary seal. depending on the size of the conduit, you may need a seal at the box and then a boundary seal.

BTW--is this an Xproof box? And are the jacks inside or outside the box? Not sure about Div 1 rated plugs for all those apps.

Can you even get MC-HL cable with coax and T/C wire in it?

 

[rbalex]

Can you even get MC-HL cable with coax and T/C wire in it?

T/C is definitely available although is is more likely to be marked ITC-HL.
Coax availability is limited in MC-HL, but if coax is an absolute necessity, a judiciously selected single-conductor MI construction may suffice; the primary dependence will be the overall length of the circuit in the Division 1 location and the overall effect of the mineral insulation on the electrical capacitance of the circuit. The latter is usually negligible, but it may take some ?tweaking? at the receiver end. I've only done this once, so I can't make a general statement.

 

[IamJonscranium]

On a pump station where we have cables in a C1D1 area to a control panel, we run a GUB, then a seal. This way you can replace a TC or whatever your instrument/equipment is without destroying and redoing the seal.

Explosion proof or intrinsically safe?


Edit: Our pump stations use multi-conductor cables for the pumps. Power and temp/leak detection.

 

[petersonra]

T/C is definitely available although is is more likely to be marked ITC-HL.
Coax availability is limited in MC-HL, but if coax is an absolute necessity, a judiciously selected single-conductor MI construction may suffice; the primary dependence will be the overall length of the circuit in the Division 1 location and the overall effect of the mineral insulation on the electrical capacitance of the circuit. The latter is usually negligible, but it may take some ?tweaking? at the receiver end. I've only done this once, so I can't make a general statement.

T/C = thermocouple.

 

[rbalex]

T/C = thermocouple.

Yes, I was aware of that. Instrument Tray Cable (ITC), is also available both with thermocouple conductors and a continuous corrugated metallic sheath. Shielded pairs/triads are also permitted. See Section 727.6. There's a pretty general set of acceptable constructions. I haven't seen it in coax, but I suspect it would be if there were a great enough market.

 

[kameele]

I was going to say that Okonite makes it in their CLX series, but when I went to the catalog, they have only T/C, and it's just Div 2. (no -HL designation) Ooops

I do remember using an armored coax for an A-B netowrk a long time ago, but I can't remember where I got it. i'm betting that it was also only Div 2.

 

[dtappen]

Can someone confirm that multiconductor instrumentation cables (ex. Thermocouple, coax, analog, low voltage 0-10Vdc/4-20mA) can be routed through a sealed conduit in a Class 1 Div 1 area?? Granted the cable ends will also be sealed within the C1D1 area to minimize vapors travelling into the cable core. Is this an approved wiring method in a C1D1 area??

The EXCEPTION in NEC Articl 501.5(D)(2) states that multiconductor twisted pair cables shall be permitted to be treated as a SINGLE CONDUCTOR by sealing the cable in the conduit 18" from the enclosure and the able end within the enclosure by an approved means.

Does this mean that the OUTER JACKET of the multiconductor cable does NOT need to be removed? What is an APPROVED sealing method for the end of the cable?