AWG 8 wire with 50amp breaker

[Lloyd]

I have AWG 8 wire running from 50amp breaker to my 14-50 plug in my garage.

Am I able to draw 40amps using my first gen mobile charger?

Your wire needs to be THW or THWN. in conduit. Romex is good only to 40 amps. This is not a safe application. Ampacity Charts

 

[DMC-Orangeville]

I'd just hire an electrician.....

 

[DMC-Orangeville]

Your wire needs to be THW or THWN. in conduit. Romex is good only to 40 amps. This is not a safe application. Ampacity Charts

Well.....wire is different in Canada.

Your reference is to US NM-B
Canadian Romex NMD and NMWU are 90C rated, but is limited to the connected equipment, which is usually 75C or 60C, so will be de-rated
THW and THWN (T90 in Canada) is not commonly used residentially. Usually RW90 (XHHW in US) or RWU will be used in conduit. More common Teck90 and AC90 - both armoured, will be run,as they do not require conduit

 

[Lloyd]

Well.....wire is different in Canada.

Your reference is to US NM-B
Canadian Romex NMD and NMWU are 90C rated, but is limited to the connected equipment, which is usually 75C or 60C, so will be de-rated
THW and THWN (T90 in Canada) is not commonly used residentially. Usually RW90 (XHHW in US) or RWU will be used in conduit. More common Teck90 and AC90 - both armoured, will be run,as they do not require conduit

Interesting. Not familiar with Canada.

 

[rdturner0]

I'd just hire an electrician.....

Or at least get one in for a consultation...

 

[jjvan]

Hence why I am here, asking for help, as table 2 of CEC says that my 8/3 90C cable has an allowed 55 ampacity.

View attachment 303181

While I understand the basic "AWG 8 -> 40AMPS, AWG6 -> 50AMPS" it clearly isn't that simple, and other factors should be considered, like the temperature rating, length, etc.

I also am not an electrician, so that's why I was hoping an electrician on here could help since I have seen similar questions answered before.

I just wanted to update this thread based on the info I found for installing a NEMA 14-50 receptacle. A 50A breaker is OK for 8/3 wire when used with NMD90 (90 degree C wire), and all the other equipment is rated for 75 degrees C conductors (see Table 2 of CEC). This is most likely the case because most newer breakers are rated for 75C. Many electricians use 40A breakers because this is what was traditionally done with the old code when breakers were rated for less than 75C.

Here is an informative thread with input from electricians:
Kitchen stove 50 A circuit: 8/3 or 6/3? - Page 3 - RedFlagDeals.com Forums

 

[amalag]

NMD90 is not part of the US electrical code, that seems to be part of Canada code. In the US they only recognize non-metallic sheathing (known as romex) as NM-B. Those assemblies are rated to 90 degrees, but the electrical code says you can only use the 60 degree ampacity rating for non-metallic sheathing. Non-metallic sheathed wires are not considered safe to operate at 75 degrees, I believe because they cannot dissipate heat. I read there are some jurisdictions which allow higher 75 degree ratings for NM-B if it is not enclosed in thermal insulation.

BTW this is all about insulators and sheathing. Romex has THHN individual wires in the sheathing which are rated to 90 degrees, so if you run THHN in a conduit or as part of an MC assembly you can use the 75 degree rating.

 

[jjvan]

NMD90 is not part of the US electrical code, that seems to be part of Canada code. In the US they only recognize non-metallic sheathing (known as romex) as NM-B. Those assemblies are rated to 90 degrees, but the electrical code says you can only use the 60 degree ampacity rating for non-metallic sheathing. Non-metallic sheathed wires are not considered safe to operate at 75 degrees, I believe because they cannot dissipate heat. I read there are some jurisdictions which allow higher 75 degree ratings for NM-B if it is not enclosed in thermal insulation.

BTW this is all about insulators and sheathing. Romex has THHN individual wires in the sheathing which are rated to 90 degrees, so if you run THHN in a conduit or as part of an MC assembly you can use the 75 degree rating.

Note that this thread is in the “Canada” category. To summarize, If the conductors and the terminations are rated for 75 degrees C or better, the Canadian Electrical Code (CEC) allows 8 gauge wire for the 50A breaker.

 

[amalag]

Note that this thread is in the “Canada” category.

Sorry about that! Sorry to intrude, I would delete my post but it doesn't let me.

I wonder if the US code will update itself in the next few years to allow NM-B at 75 degrees. I think it makes sense, I don't think the residential construction materials are that different.

 

[rhumbliner]

The regs are pretty clear on this: 40-amp ampacity. Here’s the relevant spec from SouthWire for NMB90:

https://www.mysouthwire.com/medias/...duct-specifications/h77/hfc/8854083698718.pdf

and this is the relevant paragraph:

Southwire® Romex® Brand SIMpull® NM-B (nonmetallic-sheathed) cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90°C (with ampacity limited to that for 60°C conductors) as specified in the National Electrical Code.

The table you provided clearly shows that at 60ºC your ampacity is 40 amps which means you must derate it to 32 amps.

 

[DMC-Orangeville]

The regs are pretty clear on this: 40-amp ampacity. Here’s the relevant spec from SouthWire for NMB90:

https://www.mysouthwire.com/medias/...duct-specifications/h77/hfc/8854083698718.pdf

and this is the relevant paragraph:

Southwire® Romex® Brand SIMpull® NM-B (nonmetallic-sheathed) cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90°C (with ampacity limited to that for 60°C conductors) as specified in the National Electrical Code.

The table you provided clearly shows that at 60ºC your ampacity is 40 amps which means you must derate it to 32 amps.

NM-B is a US cable. As mentioned above, a few times, IN CANADA, NMD is rated at 90 C for connected equipment with 90 C ratings. Connected equipment, if not marked is rated at 75C. The CEC is different than the NEC

 

[ZooSean]

With 8awg wire, you can pull 40amps on it, and install a 50amo breaker on the panel. I have my HWPC set to 40amps and using my previous garage to basement wire which is 8awg for my previous Nissan Leaf. I changed breaker to 50amps on the panel. I know this matches the code as we have an inspector signed of my installation as it was required to get rebate.

 

[eevee-fan]

NM-B is a US cable. As mentioned above, a few times, IN CANADA, NMD is rated at 90 C for connected equipment with 90 C ratings. Connected equipment, if not marked is rated at 75C. The CEC is different than the NEC

Curious, is the allowance higher because Canada is cooler?

 

[DeepFrz]

Curious, is the allowance higher because Canada is cooler?

Real Cool Man, Real Cool.

 

[DMC-Orangeville]

Curious, is the allowance higher because Canada is cooler?

Funny, BTW.......

Canada has developed different insulation types and standards at the same time as the USA. Some examples:
USA VS Canada
THHN PVC/Nylon single conductor - in Conduit - commonly used = T90 PVC/Nylon single conductor (same specs as THHN) - in Conduit - rarely used
XHHW XLP single conductor - in conduit - rarely used = RW90 XLP - thinner insulation 600V, RWU XLP thicker insulation - in conduit - commonly used
NM-B THHN conductors, PVC jacket - commonly used residential = NMD XLP conductors PVC jacket - commonly used residential
MC/AC90 - metal clad, Various conductors, Alum or steel armour - with or without PVC - Not common with PVC jacket - no conduit required =
Teck90/AC90 VERY common XLP conductors Alum armour. PVC jacket on Teck. No conduit required - used extensively in Resi and comm/ind
Different regions and applications may differ from the above - but it's a good generalization

Yes, there are significant differences in terms of cold temperature rating. The 90 degree rating on NMD90 has to do with the copper temperature. In the specifications, there will also be a cold temperature rating. For *most* outdoor rated cables, the rating in Canada is usually -40C, It's common in the USA to see -25C. Yes, the northern parts of Canada do see -40C, and in some cases (Like Fort McMurray AB) we would often see a -50C requirement. My part of Canada (southern Ontario) rarely sees below -25C. (lowest in the past 2 years was Friday, at -21C).

The temperature rating is the ability of the cable to safely operate at a specific conductor temperature, and the cable and connected equipment's capability to get rid of the heat.
BTW the 4 main ampacity charts of both the NEC and CEC were standardized about 6 years ago to a North American standard (Canada adopted the US charts), but the application of the different cables to the charts vary, due to the differences in cable

Disclosure: I have worked for several wire and cable manufacturers in past years.

 

[ben1628]

I have AWG 8 wire running from 50amp breaker to my 14-50 plug in my garage.

Am I able to draw 40amps using my first gen mobile charger?

I am using AWG 6 with 50 AMP Breaker to a 14-50 socket, and the wire stays cool, may get a little bit warm. I am using mobile adapter that only draws 32 AMP.

When it comes to electricity, why are you risk it??? DO it properly and have a good night sleep. Remember, it is charging overnight and you won't know there is a problem until it is too late.

Home Insurance may not cover any damages when it finds out you are not doing it properly.

Hiring a technician or getting a permit are all good, but you have to do DD yourself.