NMD90 or NMWU Wire For AC or Heat Pump?

harry muscle · 2025-09-28T13:43:17-0400

My existing AC installation uses 12 gauge NMD90 wire and is run a few feet outside in liquid tight conduit. My contractor will be replacing the cable with 10 gauge wire for my heat pump install. He normally would also run NMD90 and likewise run it a few feet in liquid tight conduit to get to the disconnect box. In Canada NMD90 is rated for dry and damp locations but depending on who you ask to interpret the CEC, liquid tight conduit outdoors can still be considered a wet location, meaning it would require NMWU wire.

Is it pretty common to just use NMD90 wire for AC or heat pump installs? Or should I definitely ask him to use NMWU wire?

Thanks,
Harry

TechmanTery · 2025-09-28T15:12:43-0400

I am pretty sure that 'romex' is not allowed inside of a conduit due to the conduit holding in the heat produced within the romex which overheats the romex and the wire insulation.

pecmsg · 2025-09-28T15:53:34-0400

You question everything this contractor does

NMD90 or NMWU Wire For AC or Heat Pump?

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