Gauge Tables

[tyler.martin]

Once upon a time when I was loading in a show somewhere in the US. I saw a sheet with some tables on it that had the max allowable Amperage per AWG size. It also had the de-rating factor when running multiple conductors in parallel, ie. Socapex.

Does anyone have such a table/list/guide?

 

[STEVETERRY]

View attachment Table_400.5(A)(1).pdfView attachment Table_400.5(A)(3).pdfView attachment Table_520.44.pdf


First, please go buy a copy of the NEC.

Since I know you will do that, I am going to help with the tables:

Use 400.5(A)(1) for normal 60 degree C cables.
Use 400.5(A)(3) for ampacity adjustment for more than 3 current carrying conductors.
Use 520.44 for 75 and 90 degree multicables where diversity is 50% minimum.

For explanation of diversity, see my article in the CB Wiki under Diversity, Electrical.

Cheers

ST

 

[tyler.martin]

View attachment 9386View attachment 9387View attachment 9388


First, please go buy a copy of the NEC.

Since I know you will do that, I am going to help with the tables:

Use 400.5(A)(1) for normal 60 degree C cables.
Use 400.5(A)(3) for ampacity adjustment for more than 3 current carrying conductors.
Use 520.44 for 75 and 90 degree multicables where diversity is 50% minimum.

For explanation of diversity, see my article in the CB Wiki under Diversity, Electrical.

Cheers

ST

Thanks Steve,

I found a 1998 copy of the CEC buried in our shelves of manuals, and i noticed some differences between NEC and CEC... Ive attached the CEC copy. View attachment CEC_Tables.pdf

 

[Chris15]

It could be related to the fact that down here we have a common set of wiring rules with New Zealand but different current carrying capacity tables because the ambient temperature is warmer here than there.

Likewise, Canada is probably cooler and so can eek a bit more capacity out of the cable safely

 

[STEVETERRY]

Thanks Steve,

I found a 1998 copy of the CEC buried in our shelves of manuals, and i noticed some differences between NEC and CEC... Ive attached the CEC copy. View attachment 9390

Did that table come from the CEC or is it someone's "interpretation"?

While the notes reference "not more than 3 conductors in cables", the table lists 4/0 copper at 235 amps--which would be wrong for a single conductor 90 degree 4/0 feeder. That cable is rated 405 amps in the NEC. Also, the correct code term would be "3 current-carrying conductors".

I would be very suspect of this table--it looks like someone has mixed in portable cables and wire in conduit. Also the wording of note 5 is especially "un-code-like".

This is another reason to have the code document itself in front of you--then there is no question of the wording.

Finally a 1998 CEC is old!


ST

 

[tyler.martin]

Did that table come from the CEC or is it someone's "interpretation"?

While the notes reference "not more than 3 conductors in cables", the table lists 4/0 copper at 235 amps--which would be wrong for a single conductor 90 degree 4/0 feeder. That cable is rated 405 amps in the NEC. Also, the correct code term would be "3 current-carrying conductors".

I would be very suspect of this table--it looks like someone has mixed in portable cables and wire in conduit. Also the wording of note 5 is especially "un-code-like".

This is another reason to have the code document itself in front of you--then there is no question of the wording.

Finally a 1998 CEC is old!


ST

That was from the organization that manages entertainment safety(Not a government organization) in my province.

I found the 2012 Code Amendment PDF, and it has a ratings table in it as well. It seems that they are mixed in. Ive attached the page in question.

The BC Safety Authority is the trades AHJ in BC. View attachment BCSA Cable Ratings.pdf

 

[STEVETERRY]

That was from the organization that manages entertainment safety(Not a government organization) in my province.

I found the 2012 Code Amendment PDF, and it has a ratings table in it as well. It seems that they are mixed in. Ive attached the page in question.

The BC Safety Authority is the trades AHJ in BC. View attachment 9399

But that table does not cover ampacities of portable cords and cables. It's just for not more than three current-carrying conductors in a pipe or wireway.

ST

 

[derekleffew]

But that table does not cover ampacities of portable cords and cables. It's just for not more than three current-carrying conductors in a pipe or wireway.

ST

Is there a difference? Do the electrons care whether they're in a portable cable or in wire in a conduit?

/rhetorical
.

 

[sk8rsdad]

Is there a difference? Do the electrons care whether they're in a portable cable or in wire in a conduit?
.

It's all about the heat. Cable in conduit is sized to manage heat buildup from multiple conductors in an enclosed space. It's also why the maximum number of conductors in a conduit is less than than will fit. Portable cable has a few other considerations around the insulator and durability but that is beside the point.

 

[gafftaper]

Is there a difference? Do the electrons care whether they're in a portable cable or in wire in a conduit?
.

Oh I've wondered this too. Other than the durability, flexibility, resistance to oil etc... on the exterior of the cable, is there an internal difference between portable cable and permanent installation cable?

 

[FMEng]

Oh I've wondered this too. Other than the durability, flexibility, resistance to oil etc... on the exterior of the cable, is there an internal difference between portable cable and permanent installation cable?

The conductors are the same. The difference is how efficiently the heat from the conductor is transferred to the environment around it. The amount and type of insulation affects it, as well as whether it is in conduit or free air. If conductors get severly hot, the resistance increases which then increases the amount of heat produced, a viscious circle.

A wise electrician taught me to never pile or bunch portable cable that is handling significant current. It needs air around it to avoid head build up. This is especially true when excess cable is rolled up.

 

[BillConnerFASTC]

And a major factor if using cable reels. Experience taught me that.

 

[mstaylor]

I saw a company bring their feeder trunk in, it was soaked from a festival. They choose to leave the100 ft 4/0 in the trunk and use it as a short jumper. It became so hot it started steaming the case. We had to pull it out and cool it before bringing it back up.

Sent from my C771 using Tapatalk 2

 

[church]

It could be related to the fact that down here we have a common set of wiring rules with New Zealand but different current carrying capacity tables because the ambient temperature is warmer here than there.

Likewise, Canada is probably cooler and so can eek a bit more capacity out of the cable safely

The temperature ranges in Canada are extreme, in South West Ontario we can see -20 centigrade in the winter to + 35 centigrade in the summer, these are outdoor temperatures of course, indoors we heat and cool our buildings.

Please note that the Provincial Electrical Codes are the governing documents, they basically follow the Canadian Electrical Code but each province has the authority to adopt codes and standards they wish. the same approach applies to building, fire and gas codes etc. It is best practice to use the applicable provincial code for where you are working.

The adoption of the Canadian codes into the provincial codes normally allows for equipment to be used in all provinces - but it is not foolproof. Where I work we continue to have to modify mchine tools that meet the Canadian requirements but do not meet Ontario requirements before they can be used.

 

[STEVETERRY]

Is there a difference? Do the electrons care whether they're in a portable cable or in wire in a conduit?

/rhetorical
.

Yes. They.Do.

Totally different thermal environments, totally different ampacities.

ST

 

[STEVETERRY]

The temperature ranges in Canada are extreme, in South West Ontario we can see -20 centigrade in the winter to + 35 centigrade in the summer, these are outdoor temperatures of course, indoors we heat and cool our buildings.

Please note that the Provincial Electrical Codes are the governing documents, they basically follow the Canadian Electrical Code but each province has the authority to adopt codes and standards they wish. the same approach applies to building, fire and gas codes etc. It is best practice to use the applicable provincial code for where you are working.

The adoption of the Canadian codes into the provincial codes normally allows for equipment to be used in all provinces - but it is not foolproof. Where I work we continue to have to modify mchine tools that meet the Canadian requirements but do not meet Ontario requirements before they can be used.

So, let me get this straight. The entertainment articles of the CEC are a total shambles due to many decades of inattention by CSA and the Canadian entertainment industry, but everything is OK because the provincial rules take up the slack? I am sorry to say this, but our colleagues in Canada need to get their Code act together!

For those not familiar with the depth of the problem and for a backwards trip though time, please take a look at Section 44 of the CEC.

We did it in the US in 1980, you guys can do it too!


ST

 

[JChenault]

The conductors are the same. The difference is how efficiently the heat from the conductor is transferred to the environment around it. The amount and type of insulation affects it, as well as whether it is in conduit or free air. If conductors get severly hot, the resistance increases which then increases the amount of heat produced, a viscious circle.

A wise electrician taught me to never pile or bunch portable cable that is handling significant current. It needs air around it to avoid head build up. This is especially true when excess cable is rolled up.

Huh
I thought that most if not all permanent cable was solid core while portable cable uses stranded wire. Is this not so, or did I misinterpret the question?

 

[STEVETERRY]

Huh
I thought that most if not all permanent cable was solid core while portable cable uses stranded wire. Is this not so, or did I misinterpret the question?

Portable cables are stranded. The number of strands is defined by the "class" of stranding. See Class K Stranding in the CB wiki for some examples.

Permanent conductors are available solid or stranded in the smaller gauges, stranded only in the larger gauges.

ST

 

[JD]

I do not recall ever seeing this written about, but there is one factor on finer stranded conductors that must have a detrimental effect on it's rating. We make the assumption that all strands are in conduction, but anybody that has put a connector on rubber insulated cable has run across the oxidization of strands. I can't help but believe that even with a good crimp, all strands are not brought into conduction. I don't know whether the problem has got to do with the manufacturing process, or oxygen permeation of the rubber itself, but it cannot benefit conduction. Even new stock may appear this way, although I have seen some that incorporates a thin plastic wrap between the insulation and the conductor that appears to fair much better. Compare this to THHN, where the copper is almost always shiny and clean.

I have to wonder if any studies have been done on this. In fact, I have to think that there must have been studies and I just never happened on one.

</somewhat_of_a_tangent>

 

[gafftapegreenia]

I do not recall ever seeing this written about, but there is one factor on finer stranded conductors that must have a detrimental effect on it's rating. We make the assumption that all strands are in conduction, but anybody that has put a connector on rubber insulated cable has run across the oxidization of strands. I can't help but believe that even with a good crimp, all strands are not brought into conduction. I don't know whether the problem has got to do with the manufacturing process, or oxygen permeation of the rubber itself, but it cannot benefit conduction. Even new stock may appear this way, although I have seen some that incorporates a thin plastic wrap between the insulation and the conductor that appears to fair much better. Compare this to THHN, where the copper is almost always shiny and clean.

I have to wonder if any studies have been done on this. In fact, I have to think that there must have been studies and I just never happened on one.

</somewhat_of_a_tangent>

I swear I've heard something about how the older a cable gets the more those find strands end up broken, thus reducing the actual load capacity of the cable.