[michaelburt]

I have a 12/3 Alcatel F NMD90 cable in my wall which connects a 240V plugin to a 20A 2-pole breaker. My question is this:

The Canadian Electrical Code (2012) says that for 90 degree cable insulation, a 12 guage 3 conductor cable is good up to 30 amps.

When you look up manufacturer specs for a 12/3 NMD90 cable they say its good up to 20A. I find this strange, considering the Canadian Electrical Code says its good up to 30A.

I have a 6000W generator I want to connect to the 240V plug mentioned above. I'm going to upgrade the breaker from 20A to 30A. Can I keep the 12/3 NMD90 cable for the 30A breaker? Or do I need to upgrade to 10 guage?

Thanks,
Mike

 

[Black Dog]

I have a 12/3 Alcatel F NMD90 cable in my wall which connects a 240V plugin to a 20A 2-pole breaker. My question is this:

The Canadian Electrical Code (2012) says that for 90 degree cable insulation, a 12 guage 3 conductor cable is good up to 30 amps.

When you look up manufacturer specs for a 12/3 NMD90 cable they say its good up to 20A. I find this strange, considering the Canadian Electrical Code says its good up to 30A.

I have a 6000W generator I want to connect to the 240V plug mentioned above. I'm going to upgrade the breaker from 20A to 30A. Can I keep the 12/3 NMD90 cable for the 30A breaker? Or do I need to upgrade to 10 guage?

Thanks,
Mike

What will be the full load current on the cable?

 

[michaelburt]

Worst case scenario FLA of 20-25A. The starting current would be much higher but I assume the generator is designed to handle that? (not sure). This is for running and oil furnace an a pump for a well. Obviously if I can I'll run lights and some other things in the house.

EDIT: You can find this info on CSA 22.1 on page 303, Table 2

 

[Dennis Alwon]

Mike at 90C #12 is 30 amps but the terminations are not rated 90C so you cannot use that column except for de-rating. If the CEC is the same as the NEC then NM cable is only rated 60C and it cannot be on a 30 amp breaker except in a few instances

 

[crookcirca80]

12 gauge copper is rated for 30 amps, but you cannot fuse it any higher than 20 amps, as per rule 14-104(2). I believe the code was changed to accomodate de-rating more reasonably than code editions prior to this one.

 

[michaelburt]

Thanks all...

I guess I don't really understand the derating concept yet.

In other words, I need a bigger cable? 10 guage?

BTW the generator is fused at 30A.

 

[crookcirca80]

Thanks all...

I guess I don't really understand the derating concept yet.

In other words, I need a bigger cable? 10 guage?

Actually I believe you need 8 gauge on a 40 amp breaker.

6000W/240V = 25 amps.

Maximum load on a 30 amp plug is 24 amps.

 

[michaelburt]

Thanks again. I was just hoping to not have to pull wires lol but safety first!!

 

[99cents]

Motors are in Section 28.

 

[crookcirca80]

Are you planning on feeding your panel through that plug?

 

[michaelburt]

Yeah, I have an interlock that works with the main breaker and the top right hand corner 2 pole breaker. It ensures that only one of the two can be on at once. The idea is to feed the panel through the top right hand corner 2 pole breaker with a generator in an emergency situation

 

[crookcirca80]

Does the interlock disconnect the neutral?

 

[michaelburt]

Nope it does not, but the neutral-ground bond is separated at the generator. The company who makes the generator sent out a bulletin on how to do it. When it's done correctly, the only ground-neutral bond should be at the panel when the generator is feeding the circuit.

 

[michaelburt]

By the way I haven't done any of this yet, but ive bought the generator and this is my plan.

Also, oddly enough, they suggest removing the neutral from the bonding at the generator and leaving the ground connected. Does this sound
Right?

 

[crookcirca80]

Ah ok great, glad to hear that. Some people over look whether or not the neutral-ground bond exists at the generator.

 

[crookcirca80]

Well I think it sounds right, but a better idea would be calling the ESA inspector who will be approving the permit you have pulled for this. He will give the right answer.

 

[michaelburt]

Update... Had a closer look at the generator schematic. Turns out the two 120V lines are on 25A breakers on the generator. Interestingly enough this is in the "gray" zone which the code doesn't specify. Obviously to be on the safe side I'm going with the 10 guage wire when I can...

But in an emergency situation I'd use the existing 12 guage in the wall and here's my logic:

The 12 guage cable which connects my generator to my panel (with 90C insulation) is rated to 30A and the upstream generator breakers will turn off at 25A. I can't see a scenario where the line gets too hot. Downstream from that is a 20A 2-pole breaker in my panel (that's what's currently there). So I know I'm good from that end too.

I live in a place where outages are all too frequent and its very cold in the winter. So hopefully I will have this set up properly before the winter!! With the proper set up I'd have a 30A 2-pole breaker in the panel with 10 guage cable running to my generator.

Also...not sure if I mentioned this but my setup also uses a sliding lock which prevents my main breaker and my breaker on my panel for my generator from being on at the same time.

Sent from my Nexus 5 using Tapatalk

 

[crookcirca80]

Update... Had a closer look at the generator schematic. Turns out the two 120V lines are on 25A breakers on the generator. Interestingly enough this is in the "gray" zone which the code doesn't specify. Obviously to be on the safe side I'm going with the 10 guage wire when I can...

But in an emergency situation I'd use the existing 12 guage in the wall and here's my logic:

The 12 guage cable which connects my generator to my panel (with 90C insulation) is rated to 30A and the upstream generator breakers will turn off at 25A. I can't see a scenario where the line gets too hot. Downstream from that is a 20A 2-pole breaker in my panel (that's what's currently there). So I know I'm good from that end too.

I live in a place where outages are all too frequent and its very cold in the winter. So hopefully I will have this set up properly before the winter!! With the proper set up I'd have a 30A 2-pole breaker in the panel with 10 guage cable running to my generator.

Also...not sure if I mentioned this but my setup also uses a sliding lock which prevents my main breaker and my breaker on my panel for my generator from being on at the same time.

Sent from my Nexus 5 using Tapatalk

Do not do this. I already pointed out that fusing 12 gauge wire at anything above 20 amps is against code. There is no "grey area" here, it is simply wrong.

If the generator is fused at 30 amps, EVERYTHING must be rated for 30 amps, cord ends, disconnects, etc. As I have stated twice before, I'll say it again, while the code says 12 gauge wire is rated for 30 amps, this is strictly for de-rating purposes inside of a conduit, and the 12 gauge wire cannot be protected above 20 amps. Period.

Unless anyone can provide other codes that prove me wrong, and I'd be open to seeing them, you cannot proceed as you just wrote. It is against code. Also, get a permit and get it inspected, I'm getting the impression you are not planning on doing that.

 

[AllWIRES]

Update... Had a closer look at the generator schematic. Turns out the two 120V lines are on 25A breakers on the generator. Interestingly enough this is in the "gray" zone which the code doesn't specify. Obviously to be on the safe side I'm going with the 10 guage wire when I can... But in an emergency situation I'd use the existing 12 guage in the wall and here's my logic: The 12 guage cable which connects my generator to my panel (with 90C insulation) is rated to 30A and the upstream generator breakers will turn off at 25A. I can't see a scenario where the line gets too hot. Downstream from that is a 20A 2-pole breaker in my panel (that's what's currently there). So I know I'm good from that end too. I live in a place where outages are all too frequent and its very cold in the winter. So hopefully I will have this set up properly before the winter!! With the proper set up I'd have a 30A 2-pole breaker in the panel with 10 guage cable running to my generator. Also...not sure if I mentioned this but my setup also uses a sliding lock which prevents my main breaker and my breaker on my panel for my generator from being on at the same time. Sent from my Nexus 5 using Tapatalk

I've seen #12 and #10 burn up under the code specified overload protection, usually at the connection point. There's no gray area here. Maybe the gray color of ashes.

 

[BlackHowling]

Do not do this. I already pointed out that fusing 12 gauge wire at anything above 20 amps is against code. There is no "grey area" here, it is simply wrong. If the generator is fused at 30 amps, EVERYTHING must be rated for 30 amps, cord ends, disconnects, etc. As I have stated twice before, I'll say it again, while the code says 12 gauge wire is rated for 30 amps, this is strictly for de-rating purposes inside of a conduit, and the 12 gauge wire cannot be protected above 20 amps. Period. Unless anyone can provide other codes that prove me wrong, and I'd be open to seeing them, you cannot proceed as you just wrote. It is against code. Also, get a permit and get it inspected, I'm getting the impression you are not planning on doing that.

(c) as provided for by other Rules of this Code.
Except as provided for by Subrule (1)(c), the rating of overcurrent protection shall not exceed
(a) 15 A for No. 14 AWG copper conductors;
(b) 20 A for No. 12 AWG copper conductors;
(c) 30 A for No. 10 AWG copper conductors; and
(d) 15 A for No. 12 AWG aluminum conductors.


You can use higher OCPD when sizing for motors/heating/transformer and other equipment with rules that supersede 14-104