Any electricians/electrically inclined here?

[djberta]

Joe The 40amp on the #8 circuit to your garage lends me to believe it maybe a 60 degree circuit. If it is a 75 degree then you should be ok to go to 50amp. But with your numbers above this may not stop the tripping it just will make it less likely. As your putting a lot of amps down the line for the welder. I would say you should be okay going to a larger breaker but I think you may have a bigger problem with capacity on the circuit. As other have stated contact your local inspection authority and see what they will allow. Most inspection groups will talk to you and give you a better idea of what is good for your situation. I do not think you will be running in to any weird local rules but one never knows. As others have alluded to compliance limits your liability for insurance.

 

[mickeyf]

The inspector also griped about me pulling 6Ga wire instead of 8Ga - but the wire was legal, and he couldn't bounce me for it.

I have never had an inspector gripe when I did more than the code required - heavier gauge, higher temp rating, etc. Told me I could have saved some money, and how, but complained? Nope!

 

[TorontoBuilder]

I have a question about upgrading the breaker running to my garage from the current 40a to a 50a. I believe the wiring is all good to do so according to CEC but would like better verification.

It's a detached laned home garage. 100a main panel in basement, 8/3nmd90 ~30ft inside home. 8awg rw90 x3 in ~45ft conduit underground to garage. 8/3nmd90 inside garage ~20ft.

I believe 6/3 used to be what would be accepted until ~2012? And now 8/3 is acceptable because it is good for 50a @75c however reading the internet it's a 50/50 yes/no and although I did download a copy of the CEC it's so large and I have no idea which table to look at.

Home is in Cochrane, Alberta if it differs from province to province. Here's a photo for detached wiring for Airdrie which is about all I could find but makes me believe 50a is acceptable with the nmd90/rw90 combo

You may.

IF it is to serve OTHER THAN a continuous load. So not for an EV, but yes for a welder.

Why?

CEC Table 2: Ampacities of Insulated Copper Conductors

This table applies to up to three insulated copper conductors inside a raceway or cable. For #8 AWG copper,

The key amp ratings are:

60°C Column: 40 A
75°C Column: 50 A (the rating applicable with 75°C terminals)
90°C Column: 55 A

Your wire rating must be derated down to match the rating of the typical 100 amp residential electrical panel terminals... That's 75°C.

See temperature rule limit link if you want the detailed explanation.

The #8 AWG row in the 75°C column establishes an allowable amperage of 50 Amps. Since both the wire and the modern breaker align at the 75°C rating, #8 copper wire is fully approved for a 50A breaker by code

This woman explains a few examples if anyone wants to know more.

 

[BaitMaster]

1) the RW90 is good for installation in underground conduit. Underground conduit is considered a Cat 1 wet location. Table 19 shows RW 90 is good for installations in wet locations, whereas NMD90 or T90 would NOT be good.

2) As long as BOTH ENDS of the #8 cable have a known Termination Temperature Rating of at least 75 deg you are good to put the 50 A breaker in. Rule 4-006 2) a states that if the termination temperature is unknown for circuits under 100a or designed for conductors smaller than #1, a termination temperature of 60 deg must be assumed if no markings are present. If both have 75 deg you can use the 75 deg column on table 2, which is 50a. If one or both ends are unknown termination temperature rating you have to use 60 deg column, which is 40a.

Hope that helps.

 

[TorontoBuilder]

1) the RW90 is good for installation in underground conduit. Underground conduit is considered a Cat 1 wet location. Table 19 shows RW 90 is good for installations in wet locations, whereas NMD90 or T90 would NOT be good.

2) As long as BOTH ENDS of the #8 cable have a known Termination Temperature Rating of at least 75 deg you are good to put the 50 A breaker in. Rule 4-006 2) a states that if the termination temperature is unknown for circuits under 100a or designed for conductors smaller than #1, a termination temperature of 60 deg must be assumed if no markings are present. If both have 75 deg you can use the 75 deg column on table 2, which is 50a. If one or both ends are unknown termination temperature rating you have to use 60 deg column, which is 40a.

Hope that helps.

Yep, where connector ratings are unknown 60°C must be assumed.

However, as baitmaster also clarified, if you know both ends are rated "60/75°C" or "75°C then the higher apmerage in permissible.

Rule 4-006 (1) explicitly states "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...

Practically all modern residential breakers and panels manufactured over the last few decades, brands like Schneider/Square D, Siemens, and Eaton are explicitly stamped by the manufacturer with "60/75°C" or "75°C Only" right on the side or face of the breaker.

It's such an easy check... or in this case an easy breaker swap at both ends.

 

[Jswain]

50a breaker on both ends has been installed and working great for quite sometime. I also do not have the precision Tig 225 anymore so I could likely put it back down to the 40a breaker that was originally installed.

I will check if I can determine the 60/75c next time I am home

 

[TorontoBuilder]

50a breaker on both ends has been installed and working great for quite sometime. I also do not have the precision Tig 225 anymore so I could likely put it back down to the 40a breaker that was originally installed.

I will check if I can determine the 60/75c next time I am home

IF it is already in place you may as well leave it. It's code compliant and paid for.