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gleblanc

Insulation types

6 posts in this topic

I've seen dozens of threads on wire color codes and labeling, but I haven't seen any on insulation types. Do you folks use MTW, THHN, or something else for wiring your panels?

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I personally prefer MTW when it comes to connecting to terminal strips, but for field wiring we typically use THHN (its cheaper????).

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I'd have to say 90+% of what we run for single strand wire is THHN/THHW dual rated.

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THHN/THHW and MTW Edited by robh

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I might be the oddball but depends on application. For panel wiring, it's THHN except where temperature is a concern in which case some variation on TFE such as "alarm wire" is about the only safe way to go for "moderate" temperatures where the upper limit of THHN (140 F) is less than that of some instruments that can push up to 180 F. For field wiring, THHN is strictly for conduit. Otherwise, TC-EL allows you to go just about anywhere and cable trays are less expensive than conduit. TC-EL is both armored and has an outer jacket. In the mine, we use TC-EL for some applications even without the tray though it's a Code violation it holds up better than the correct alternative for portable apps which would be SEOOW. For medium voltage in the mine, we go for SHD-GC. Otherwise for pole mounted stuff there's either good old ACSR or if corrosion is an issue, concentric neutral cable. For simple "low voltage" power wiring where TC-EL is a bit on the small side, there is a three or four conductor individual cables wound around a messenger wire that goes by different names but has THHN-like ratings and tends to be very inexpensive due to the fact that it matches well with light industrial/housing wiring specs if you need pole mounted wiring but don't need the capacity and don't want the height problems of ACSR.

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Hi Majority wire we use for control and I/O is MTW 90Deg C. and we don't go below 18AWG, same for power we also use MTW and we don't go below 14AWG for 220V and above. For power feed to distribution block we use SRML or Radix wire which is rated above 150 Deg. C. MTW wire is easier to work with, we also use other wires but it really depends what environment panel is going to and what NEMA rating enclusure it's in. Singnal wire is usualy one of the belden multiconductor with shield like Belden 8760.

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