Thermocouples in Class 1 Div II Equipment

[fifty60]

to clarify, when I say TC cable I mean thermocouple wire, not "tray cable" wire. Would I be correct to apply 501.15(E)(3) to this type of cable and not peel the thermocouple jacket back to the boundary of the enclosure? The thermocouples I have are ring type, probe type, and stranded end type. The non metallic outer jacket covers the entire run except the tip that is in the hazardous area.

Can someone recommend a type of thermocouple (or RTD) that I can use that will definitely have the appropriate sheath/jacket

 

[fifty60]

If I considered the T/C to be wire instead of a cable, would that change my approach to this problem? If I bring the T/C's in through conduit and use a sealed fitting do I then have to have cable seals inside of the Hazardous area?

 

[Smart $]

From the UL White Book

POWER AND CONTROL TRAYCABLE (QPOR)
...
Regarding cable seals outlined in Article 501 of the NEC, Type TC cable has a sheath which is considered to be gas/vapor tight but the cable has not been investigated for transmission of gases or vapors through its core.

This is the last sentence under "PRODUCT MARKINGS". Several other cable types have similar statements.

While I believe fifty60's clarification moots your comment, I wanted to point out that he would then likely have a "installed outside a raceway or cable tray system" violation under 336.12(2) inside the hazardous location boundary [... if this is even under the NEC]

 

[fifty60]

I can make the argument that the ring or probe thermocouples meet 501.15(E)(3). The stranded thermocouple that attatches directly to the sheath heaters might not. It is possible that I can strip the jacket back on the stranded t/c and seal it at the entry point of the enclosure. If I strip the jacket back to the boundary, would silicone applied around the jacketless t/c wire suffice as a seal?

 

[Smart $]

...

Can someone recommend a type of thermocouple (or RTD) that I can use that will definitely have the appropriate sheath/jacket

See if you can find any mineral-insulated metal sheathed T/C's or RTD's that serve your purpose...

 

[rbalex]

See if you can find any mineral-insulated metal sheathed T/C's or RTD's that serve your purpose...

That would work - so would Types ITC, TC and PLTC.

From the UL Wire and Cable Marking and Application Guide
(A White Book Appendix):

Cable Marking and Application Guide
6. WIRE AND CABLE MARKING

(59) The overall jacket on Types ITC, TC and PLTC is a ?gas/vapor tight continuous sheath? as
discussed in Sections 501.15(D) and 501.15(E) of the NEC?.

So would corrugated Type MC.
EDIT ADD: Virtually any T/C cable will be ITC or PLTC - or it won't be listed.

 

[Smart $]

...so would Types ITC, TC and PLTC.

From the UL Wire and Cable Marking and Application Guide
(A White Book Appendix):

So would corrugated Type MC.
EDIT ADD: Virtually any T/C cable will be ITC or PLTC - or it won't be listed.

Yes, but fifty60 has not established whether or not the process will cause a pressure in excess of 1500 pascals [approx. 6"H₂O, 0.2PSI... differential, I assume]. Just the fact there is heating involved could cause such a pressure differential.

 

[rbalex]

Yes, but fifty60 has not established whether or not the process will cause a pressure in excess of 1500 pascals [approx. 6"H₂O, 0.2PSI... differential, I assume]. Just the fact there is heating involved could cause such a pressure differential.

Yes, so he has to seal the ends of the cable - which he keeps suggesting he plans to do.

 

[Smart $]

Yes, so he has to seal the ends of the cable - which he keeps suggesting he plans to do.

I didn't really get that from his posts (and not going to re-read them all)... only that he didn't want to strip the jacket to seal somewhere along the length. Desire to not do one thing is not confirmation that one will do something else...

 

[fifty60]

Does sealing the thermocouple necessarily entail stripping the jacket back all the way to the boundary? C1D1 states this, but C1D2 does not spell this out? What kind of sealing compounds are there? Can I leave the T/C intact inside the HA and then strip the insulation back at the boundary and use a sealed fitting at the boundary?

 

[Smart $]

Does sealing the thermocouple necessarily entail stripping the jacket back all the way to the boundary? C1D1 states this, but C1D2 does not spell this out? What kind of sealing compounds are there? Can I leave the T/C intact inside the HA and then strip the insulation back at the boundary and use a sealed fitting at the boundary?

Considering your current design, seal at the termination enclosure. Read second sentence of 501.15(E)(1). Note a listed fitting is required. Not certain what is available for your application...

 

[fifty60]

Still confused on where I need to seal. What does the "termination enclosure" mean? I really do not want to strip the jacket back and risk nicking the t/c wire. Would I seal at the entry point around the cable and not strip the jacket back?

 

[Smart $]

Still confused on where I need to seal. What does the "termination enclosure" mean? I really do not want to strip the jacket back and risk nicking the t/c wire. Would I seal at the entry point around the cable and not strip the jacket back?

Control cabinet.

The individual conductors must be exposed then sealed in the cable seal fitting.

 

[fifty60]

How can a cable have a "gastight/vaportight continuous sheath capable of transmitting gases or vapors through the cable core." ? If the sheath is gastight/vaportight that would imply no gas or vapors entering? Would this be describing the T/C wire with the exposed tips?

 

[GoldDigger]

It describes an insulation covering which would allow gas to pass from one stripped or separated end to another inside the covering.
Much more likely to happen with stranded wire or multiconductor cable than with insulation on solid wire.

Tapatalk!

 

[fifty60]

would Fluorinated ethylene propylene meet this description? I also have a metallic Fluoropolymer insulation available.

 

[Smart $]

Transmission is via the cable core... meaning through gaps or transmitting materials within the sheath. Sealing can technically be at either end. If the cable core has a gas/vaportight seal at the T/C end, it does not need to be sealed at the control end.

 

[fifty60]

I have an intrinsically safe RH transmitter/sensor. The transmitter will be installed in the unclassified location and the RH sensor will be installed in the Class I Div II location. It would not make sense to have to peel back the jacket on the sensor cable would it? I would most certainly void any warranty and intrinsically safe rating of the RH sensor/transmitter. Would only sealing around the sensor cable be advisable here?

 

[Smart $]

I have an intrinsically safe RH transmitter/sensor. The transmitter will be installed in the unclassified location and the RH sensor will be installed in the Class I Div II location. It would not make sense to have to peel back the jacket on the sensor cable would it? I would most certainly void any warranty and intrinsically safe rating of the RH sensor/transmitter. Would only sealing around the sensor cable be advisable here?

How do you plan to terminate if you do not remove any jacket???

Cable as a whole is usually sealed at penetration. Assuming the cable is capable of gas transmission, prevention is done by sealing at conductor exposure for termination, either end, and does not have to be any particular distance from the penetration. In my experience, at the terminal enclosure using a connector seal. While other methods are likely permitted and available, I am not aware of any. I only did H.L. work on occasion through my career and far from being an expert on the matter.