[stix309]

With the introduction of the new Ontario code book I have noticed ampacity changes for Tables 1-4. Now NMD 90 has a 90c rating so does that now mean 8/3 NMD90 can be put on a 55amp breaker according to Table 2. There have beensome rather heated discussions amongst some of my collegues.
The standard feed to a 50amp hot tub used to be 6/3 but it now appears that 8/3 would be usable. Am i missing something or is what they are talking about correct. I still feel more comfortable with 6/3 but there is a definate cost saving using 8/3.:001_huh:

 

[Vintage Sounds]

The wire might be rated for 55A at 90 degrees but the terminations also have to be 90 degree in order to use it that way. Your breaker and the lugs in the tub are going to be 75 degree rated so you have to use the 75 degree column. Going by that though, you can still put #8 on a 50.

 

[stix309]

I assume them there is no defeatism necessary for an 8/3 cable. I'm trying to cover all bases here.

 

[stix309]

Damn auto correct. Should say no deration for 8/3 cable.

 

[Dennis Alwon]

Is Canadian code allowing NM at 75C or 60C. NEC limits nm cable to 60C--curious???

 

[Vintage Sounds]

I assume them there is no defeatism necessary for an 8/3 cable. I'm trying to cover all bases here.

Well if you have to derate, that has to do with the conditions where the wire is installed i.e. ambient temperature or number of conductors in a raceway etc but I'm guessing you're talking about a normal situation going from a panel across a basement ceiling and out to a disconnect, in which case, no I don't think so.

Is Canadian code allowing NM at 75C or 60C. NEC limits nm cable to 60C--curious???

We can use 75C ampacities unless one of the links in the chain, either termination point or wire, is only rated for 60. One example is NMWU, our version of UF. It's only good for 60 so if you transition to another wiring method down the line you still have to treat everything as 60 rated.

Our regular old NMD90 is like the name says, rated for 90. Not a lot of situations where it would get used that way though. Too bad you guys have to stick to 60.

 

[Dennis Alwon]

Our regular old NMD90 is like the name says, rated for 90. Not a lot of situations where it would get used that way though. Too bad you guys have to stick to 60.

Our NM has 90C wire inside but because it runs thru insulation etc they have decided that it can only be used at 60C. We can however derate at the 90C rating. The final amp just cannot exceed the 60C rating

 

[stix309]

So are panels and breakers rated at 75C or 60C for termination here in Ontario. What is the final answer. 50 amp or 40 amp for an 8/3 romex.

 

[Vintage Sounds]

So are panels and breakers rated at 75C or 60C for termination here in Ontario. What is the final answer. 50 amp or 40 amp for an 8/3 romex.

50. Take a look at the breaker to know the termination temperature rating, it will say 75. It's not about the province, it's the manufacturer.

 

[stix309]

Ok the breaker I have here says both 60C and 75C on it. Because the wire has a 90C rating I would assume I can use the 75C rating from the table.

 

[Dennis Alwon]

Ok the breaker I have here says both 60C and 75C on it. Because the wire has a 90C rating I would assume I can use the 75C rating from the table.

As a rule all of today's breakers and terminations are rated 75C

 

[Shockdoc]

Canada- For the electrician
USA- for the manufacturer.

 

[mertabird]

In our NEC code book, art 110.14(c)(1)(a) It says that terminations for circuits rated 100 amperes or less, or marked for 14 AWG through 1 AWG conductors shall be used with conductors rated 60 c or conductors with higher ratings provided the 60 c ampacity of the conductor be used... unless the equipement is listed and marked otherwise. So better double check those listings, before you throw 50A on a number 8, right?

 

[Vintage Sounds]

In our NEC code book, art 110.14(c)(1)(a) It says that terminations for circuits rated 100 amperes or less, or marked for 14 AWG through 1 AWG conductors shall be used with conductors rated 60 c or conductors with higher ratings provided the 60 c ampacity of the conductor be used... unless the equipement is listed and marked otherwise. So better double check those listings, before you throw 50A on a number 8, right?

Nope, this is Canada and we have the opposite rule. We would not default to 60C under normal circumstances unless the wire or termination point was rated only for 60. Unless using NMWU it's rare that a residential electrician would ever need to use the 60 column, and the OP is talking about a residential situation.

4-006 Temperature limitations (see Appendix B)
(1) Where equipment is marked with a maximum conductor termination temperature, the maximum
allowable ampacity of the conductor shall be based on the corresponding temperature column from
Table 1, 2, 3, or 4.
(2) Where equipment is not marked with a maximum conductor termination temperature, 90 °C shall be used
by default.

 

[Dennis Alwon]

In our NEC code book, art 110.14(c)(1)(a) It says that terminations for circuits rated 100 amperes or less, or marked for 14 AWG through 1 AWG conductors shall be used with conductors rated 60 c or conductors with higher ratings provided the 60 c ampacity of the conductor be used... unless the equipement is listed and marked otherwise. So better double check those listings, before you throw 50A on a number 8, right?

That only applies if you don't know the temp rating of the lugs etc.

 

[123]

CEC rule 4-006 (2)
Where equipment is not marked with maximum conductor termination temperature, 90 degrees C shall be used by default.

 

[Laroc3]

CEC rule 4-006 (2) Where equipment is not marked with maximum conductor termination temperature, 90 degrees C shall be used by default.

Usually all equipment is marked, unless it's a meter socket or a splitter.

 

[eddy current]

Our NM has 90C wire inside but because it runs thru insulation etc they have decided that it can only be used at 60C. We can however derate at the 90C rating. The final amp just cannot exceed the 60C rating

Our code CEC is almost the same. We can derate using the rated temp of the wire as long as the final amp doesn't exceed the 75 degree rating

 

[BlackHowling]

Our code CEC is almost the same. We can derate using the rated temp of the wire as long as the final amp doesn't exceed the 75 degree rating

Do you have the rule number for that? Doing sweating in class and this hasn't come up

 

[mertabird]

Ok, wow. I did not know there was such a difference between our allowable ampacities and yours. So tell me, how many amps can you guys put on a #12 wire?