300V. verses 600V.

[Rocketman2k3]

Why does the Canadian Electric Code require a min. of 300 volt (NM-D) and the National Electric code in the United States require a min. of 600 volts(NM-B)?

[bigrockk]

Hello
In general terms, most places that NMD-90 can be used; the voltage to ground cannot exceed 150V,most commonly it is 120 volts to ground and does not exceed 240 volts between conductors. Which obviously makes the 300-volt insulation quite adequate.
I cannot comment on the NEC, as I am not familiar with it.

[ctomat]

Does the new code state that you have to run a ground wire in EMT conduit or is the conduit sufficient ground?

[neil seidner]

More specifically,

"12-502 Nonmetallic sheathed cable shall not be used where the voltage exceeds 300V between any conductors.

12-504 Non metallic sheathed shall be permitted in or on buildings of combustible construction..."

Rocketman: Do you know the exact wording of the N.E.C. requirement?

[frenchelectrican]

ok for usa NEC requriement it do have some limitation of useage but the list is very long. but i will cut to chase short as possible 120/240 and 120/208 volts is very common voltage for using the romax wires but some area can use 277/480 volts ( this is more common in office and other area but resticted useage) but i will concat my freind he will give me the nec codes numbers to post it here. but which way you want it?? genral useage or what ??? and i can understand that your nm wire say "NM-D" is about the same as NM-B with 90 C conducters if i am correct here.


merci, marc

[neil seidner]

Thanks Marc. The non-metallic cable we use in Canada is described as loomex and has the designation NMD-90 (non-metallic-dry-90C). It is equivalent to romex or NMB, I believe the 300V vs 600V is the only major difference (also I do not know what the "B" stands for). The voltages I work on the most are 120/208V and 600/347V. In Canada I don't think you would find a 277/480V system in a wood frame building (I believe high-rise office buildings and unusual equipment are the only application here). I am interested in what the N.E.C articles say.