Originally Posted By: bbadger
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First, Thanks Roy C I had never even imagined that this would be used in a residence.
I am used to calling this product "MI" which for the users of the NEC means Mineral-Insulated, Metal-Sheathed Cable.
"Type MI mineral-insulated, metal-sheathed cable consists of one or more solid copper conductors insulated with highly compressed magnesium oxide and enclosed in a continuous copper or alloy steel (e.g., stainless steel) sheath with or without a nonmetallic jacket. It is manufactured in size 16 AWG to 500 kcmil single conductor; 16 AWG to 4 AWG, two and three conductor; 16 AWG to 6 AWG, four conductor; and 16 AWG to 10 AWG, seven conductor. The cable is rated 600 volts."
The MI that was run to the meter base that Roy showed us was multi conductor.
The MI in my pictures above and below is single conductor MI.
As this is single conductor MI you can see it is groups of four, Phase A, Phase B, Phase C and Neutral. The copper outer sheath serves as the grounding conductor.
These pictures where taken in a hospital, but we install MI in many building types. It is used to distribute emergency power from generators to the panels.
The reason it is used is it can survive running right through a fire for up to two hours.
It is a major pain to work with, its is heavy and stiff.
You would be very "unhappy" if you saw this stuff running through the ceiling and decided to tap into it for a new water feed.
Electrical Construction & Maintenance
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