Type SIS wiring where is it used? 2

[bdn2004]

There is a specification on our project that calls for SIS wiring for all internal cabinets control wiring. The PTB are interpretting this as meaning any wiring that comes into the cabinet - which would include a lot of field wiring. We think that is a mistake.

Has anyone ever seen this specified for wiring outside of a control cabinet, MCC, switchgear etc.? Is there any drawbacks to using this kind of wire? Like is it made for pulling without damage? the heat ratings, can it be used in wet locations, etc? I'm looking for some reasons why we insist we are correct and they are misinterpreting this requirement.

 

[dpc]

I think that is a misinterpretation of the intent of the specifications. To be used outside of a panel, it would have to have a UL listing matching the intended use. SIS wire can be purchased with an XHHW rating. I've never seen anything except single conductor SIS wire. Not sure if multi-conductor would even be available.

 

[xnuke]

Per the 2014 NEC Table 31O.104(A) Conductor Applications and Insulations Rated 600 Volts, SIS is for use in switchboard and switchgear wiring only. It is not listed as suitable for building wiring per 310.10.

xnuke
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[dpc]

But it can have multiple ratings.

 

[111R]

Is SIS actually an acronym for anything? I always wondered where that name came from.

 

[jraef]

Stranded Insulated Switchboard wire.

The issue is that for switchboards and the like, the insulation is more resistant to high temperature and less likely to deteriorate over time than PVC insulation, what is found in common building wire like THHN (Thermoset High Heat Nylon jacketed) or MTW (Machine Tool Wire). The insulation on SIS is not an extruded "thermoset PVC jacket, but rather a heat-shrunk (thermoformed) tube of cross-linked polyethylene (XLP) into which the conductor is inserted and then the tube is heater to shrink to it. That's why it is usually also marked as XHHW (XLP High Heat Water resistant) for use as a building wire as well. They are not always exactly the same though. The difference is a Vertical Flame Test. XHHW wire, as a "Building Wire" must have it, SIS does not need to, but in reality most wire mfrs do not bother to make both versions so they just dual mark the wire.

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