NMD-3 Wire

Hello, would you make a note on your inspection report if you found NMD-3 wire? If so how would you word it?



1962–1984: Grounded twin-conductor cable, NMD 3 & 6

Ground conductors were required in residential cables in 1962. NMD 3 was introduced containing a ground conductor. Homes were now wired with modern, 3-prong outlets. As with NMD1, NMD3 had an insulation temperature rating of 60°C. Later NMD6 was introduced with an increased temperature rating of 75°C.
Risk in modern homes: Many modern fixtures generate considerable heat inside the enclosure, particularly recessed lighting fixtures (pot light). A number of fires have been reported in these fixtures as a result of cables with low temperature rating. Since 1984 the electrical code requires that all ceiling fixtures be wired with a cable rated at 90°C. Cables rated at 60°C and 75°C are not suitable for modern fixtures. The house should be checked to confirm that these older cables are not used for modern lighting.


My question would be, are you sure the lighting is wired with this cable?

Is it serving a newer recessed light fixture that develops higher temperatures or serving regular octogon boxes for ceiling light fixtures?

No recessed lighting. A mix of NMD-3 and NMD-90, just wondering best way to report it.



If you didn’t observe any defects you could simply note that the older wiring is present, that it has a lower temperature rating than modern wiring so it would not be suitable for higher temperature applications like some ceiling lighting, and that similar to any older system there is the potential for future deterioration that may require repairs they should budget for.

Buying an older house is similar to buying an older used car … over time things are going to deterioate and break that will need to be fixed. Most clients can relate to that.

JMO & 2-Nickels … :wink:

Good info Robert, thanks so much.