Conductor ampacity

Jpflex

Jpflex

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Electrician commercial and residential
After reviwing the nec 110.14(C)(1) it is apparent that a lot of electricians have been determing wiring ampacity wrong and or posting incorrely here in mike holts forum.

For example, I recall one post here on Mike Holts forum of an electrician trying to justify assigning a higher ampacity to a wire based on NEC table 310.17.

Although he would appear correcect in doing this for the free air conductor wiring method he claimed to have, it would be incorrect according to the opening wording of NEC code 110.14 (C) (1) which states:

"Unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on TABLE 310.16"

on this particular post everybody agreed that he could use this wire and terminate on equipment with the higher rated wire ampacity for conductors in free air


So what would be the purpose of having multiply wire ampacity tables? I believe they would only be useful to start at higher ampacities to be adjusted or corrected lower and used within the ampacity for temperature limits of table 310.16?
 
Jpflex said:
After reviwing the nec 110.14(C)(1) it is apparent that a lot of electricians have been determing wiring ampacity wrong and or posting incorrely here in mike holts forum.
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310.16 and 310.17 are for two entirely different applications. Post some links to these threads so we can read along.
 
infinity said:
310.16 and 310.17 are for two entirely different applications. Post some links to these threads so we can read along.
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The post was way back when i was an industrial electrician at a mine and is impracticle to find.

Table 310.16 is for wires with not more than 3 conductors in a conduit, etc, while table 310.17 is for conductors with better cooling properties in free air wiring method.

However, from the wording in 310.14 C1, you cannot just simply assign a higher ampacity to a wire just because it is in free air unless the part being terminated is listed and marked for this.

The NEC book says terminated wires in equipment must be based on table 310.16
 
Jpflex said:
After reviwing the nec 110.14(C)(1) it is apparent that a lot of electricians have been determing wiring ampacity wrong and or posting incorrely here in mike holts forum.

For example, I recall one post here on Mike Holts forum of an electrician trying to justify assigning a higher ampacity to a wire based on NEC table 310.17.

Although he would appear correcect in doing this for the free air conductor wiring method he claimed to have, it would be incorrect according to the opening wording of NEC code 110.14 (C) (1) which states:

"Unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on TABLE 310.16"

on this particular post everybody agreed that he could use this wire and terminate on equipment with the higher rated wire ampacity for conductors in free air


So what would be the purpose of having multiply wire ampacity tables? I believe they would only be useful to start at higher ampacities to be adjusted or corrected lower and used within the ampacity for temperature limits of table 310.16?
Click to expand...

110.14(c) is used to determine your conductors temperature rating applicable to your installation when using 310.16 to determine the ampacity of your conductors based on the wiring method chosen


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O and then thete is 310.14 which contradicts this by allowing all tables.

Since wires are iften terminating on equipment rhis makes this a huge mess of confusion
 
Jpflex said:
O and then thete is 310.14 which contradicts this by allowing all tables.

Since wires are iften terminating on equipment rhis makes this a huge mess of confusion
Click to expand...

When under 100 amps if the application is not subject to the restrictions of 240.4(d)(1-8) , wiring methods not restricted to 60 c ampacities, can size our conductors temps of the equipment permitted by 110.14(c)(1)(a)(3) , when using 310.16


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Jaybone812 said:
110.14(c) is used to determine your conductors temperature rating applicable to your installation when using 310.16 to determine the ampacity of your conductors based on the wiring method chosen


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Click to expand...
Nec says the conductor ampacity to be terminated must be based on tabble 110.14 C 1

However a wire by itself without termination appears to have an ampacity equal to any table from 310.16, 310.17 etc etc but when do you often have a wire that is not terminated to use these other tables?
 
What is throwing this off is that 310.14 C 1 is not saying other tables other than 310.16 may be used in determining cinduvtor ampacity per terminating temperature at a specific ampere rating

If i were to assume that nec is not excluding other tables to be used to do this rhen there woud be no provlem
 
It
Jaybone812 said:
When under 100 amps if the application is not subject to the restrictions of 240.4(d)(1-8) , wiring methods not restricted to 60 c ampacities, can size our conductors temps of the equipment permitted by 110.14(c)(1)(a)(3) , when using 310.16


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Click to expand...
Look at NECs example it is saying what ive said at the beginning, table 310.16 must be used and the other tables only for adjustment ir correction
infinity said:
There is no 310.14(C)(1) in the 2017, 2020 or 2023 NEC.
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My bad i meant to type 110.14 C 1. According to nec this seems to be the case
 

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Jaybone812 said:
110.14(c) is used to determine your conductors temperature rating applicable to your installation when using 310.16 to determine the ampacity of your conductors based on the wiring method chosen


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Yes but my point is that you cannot use the ampacities of most other tables besides 310.16 unless you start with the higher ampacities from other tables but after ampacity correction and adjustment you end up with the conductor ampacity values on table 310.16
 
Jpflex said:
It

Look at NECs example it is saying what ive said at the beginning, table 310.16 must be used and the other tables only for adjustment ir correction

My bad i meant to type 110.14 C 1. According to nec this seems to be the case
Click to expand...
Ok your point . 310.16 must be used is a broad statement. . Other factors apply to which temp rating in 310.16 applies to the ampacity of your conductors .certain applications permit the use of a higher conductor ampacity based on the equipment and terminal temperature rating . And uou need to know these things to apply thr correct value for your branch circuit conductor ampacity
 
Jpflex said:
Yes but my point is that you cannot use the ampacities of most other tables besides 310.16 unless you start with the higher ampacities from other tables but after ampacity correction and adjustment you end up with the conductor ampacity values on table 310.16
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What are you even talking about , 310.16 is the only table in the nec we use for the ampacity of our branch circuit conductors . The other tables are used for to find the demand factor that applies when ampacity correction is required. Everything comes down to the ampacity values listed in table 310.16 based on temp rating of the conductors
 
Yes, this issue almost got cablebus, Article 370 removed from the code. The ampacity if the conductors in cablebus is based on Table 310.17, but there are few places where you can actually terminate conductors at those ampacities.

In the field this is often ignored unless the conductors are directly terminated on a breaker. In many cases the conductors of the cablebus are terminated on the transformer secondary bushings, and on the line side bus bar of multi-section switchgear. In those cases, I have seen the restriction to use the 310.16 ampacities ignored.
 
don_resqcapt19 said:
Yes, this issue almost got cablebus, Article 370 removed from the code. The ampacity if the conductors in cablebus is based on Table 310.17, but there are few places where you can actually terminate conductors at those ampacities.

In the field this is often ignored unless the conductors are directly terminated on a breaker. In many cases the conductors of the cablebus are terminated on the transformer secondary bushings, and on the line side bus bar of multi-section switchgear. In those cases, I have seen the restriction to use the 310.16 ampacities ignored.
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Exactly , and branch circuit conductor ampacity comes down to the values listed in 310.16 after applying all the required adjustment factors and required temp rating
. guys don’t understand that circuits less than 100 amps are not always restricted to 60 c ampacity unless the wiring method is restricted 60 c ampacities . For instance specific conductor applications part of 240.4(g) can size their branch circuit conductors to both the terminal temp rating and temp of the equipment in accordance with 110.14(c)(1)(a)(3)


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Jpflex said:
What is throwing this off is that 310.14 C 1 is not saying other tables other than 310.16 may be used in determining cinduvtor ampacity per terminating temperature at a specific ampere rating

If i were to assume that nec is not excluding other tables to be used to do this rhen there woud be no provlem
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That’s because 310.14c(1) doesn’t exist in the any recent edition of the nec and also because 310.16 is the only table the nec allows us to use for the ampacity of our branch circuit conductors after all required adjustment factors are applied
 
I don't see much difference from the manner we treat the 90° column in 310.16. 310.17 is simply addresses another location where the conductors ampacity is effected by the environment. The final allowable ampacity is effected by various factors such as ambient and termination limitations.
 
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