allowable ampacities of insulated conductors

[liquidtite]

is the 90* column for table 310.16 for d- rateing.? and do you use the 60* column for thhn or the 75* chart.or does it matter at what temp you will be apllying the insulation under

 

[97catintenn]

It depends on the terminals, which most of the time will be the 75* column even though thhn is rated for 90*. Only use 90* if all the terminals are stated to be rated at that temp, otherwise, they won't hold up to the heat.

 

[augie47]

For most all applications, the 90? rating is only useful for derating as you sumised.
Take a look at 110.14 which limits your ampacity to the rating of the equipment at terminations, mist commonly the 75? rating.
There is some equipment rated for 90? but it is not common.

 

[ceb58]

is the 90* column for table 310.16 for d- rateing.? and do you use the 60* column for thhn or the 75* chart.or does it matter at what temp you will be apllying the insulation under

For the most part the 90 deg. is for derating unless you run into special equipment with 90 deg. terminals. The 60 deg. is used for UF and under the 08 code SE and SER cable. Under the 11 code SE and SER can go back to the 75 deg. if not in insulation. For the most part the rating will come from the 75 deg.

 

[liquidtite]

so will it tell you on the nameplate rateing what degree it shall be terminated at .allong with ocps

 

[ceb58]

so will it tell you on the nameplate rateing what degree it shall be terminated at .allong with ocps

Depends on the equipment. The breaker will tell you what temp. rating it is. Most A/C units will have on the name plate min. circuit ampacity and max. fuse or breaker.

 

[infinity]

is the 90* column for table 310.16 for d- rateing.? and do you use the 60* column for thhn or the 75* chart.or does it matter at what temp you will be apllying the insulation under

For derating start with the insulation type and it's intended location. For example, THHN/THWN is a 90? C conductor when used in dry locations but only a 75? C conductor when used in wet locations.

 

[Pierre C Belarge]

The temperature rating is not limited to the conductor insulation, and equipment. It is dependent on all portions of the circuit and components of the circuit.
1. the enclosure rating
2. conductor insulation rating
3. Overcurrent rating
4. equipment rating
5. and any other component in the system
*Take a look at the temperature rating of PVC.

There may be portions of the circuit rated at 90degree C, but the weak link is what the circuit will be rated at. I am positive that all enclosures are rated at 75degree C. Most if not all circuit breakers are rated at 75degree C. And as has been mentioned, the last sentence of 110.14 is where we will find the temperature rating of the conductor insulation for final ampacity application is 75Degree C.

 

[Smart $]

The temperature rating is not limited to the conductor insulation, and equipment. It is dependent on all portions of the circuit and components of the circuit.
1. the enclosure rating
2. conductor insulation rating
3. Overcurrent rating
4. equipment rating
5. and any other component in the system
*Take a look at the temperature rating of PVC.

There may be portions of the circuit rated at 90degree C, but the weak link is what the circuit will be rated at. I am positive that all enclosures are rated at 75degree C. Most if not all circuit breakers are rated at 75degree C. And as has been mentioned, the last sentence of 110.14 is where we will find the temperature rating of the conductor insulation for final ampacity application is 75Degree C.

Nothing wrong with yours and others statements, for the most part.

However, we must keep in mind that we are making generalizations. Yours is regarding circuit rating... but the topic of discussion is the allowble ampacities of insulated conductors. It is possible that there can be portions of a circuit to which the full conductor insulation rating can be applied.

Additionally, I do not agree that all enclosures are rated at 75?C. I believe, for example, a "bare", uninstalled steel enclosure has no temperature rating at all, as far as this topic is concerned. It only becomes rated when devices and equipment are "enclosed". As such, an "enclosure" may be rated higher [or lower] than 75?C.

A common example is the splice-terminal junction box which is made up of all 90?C or higher rated equipment and wiring.

 

[liquidtite]

The temperature rating is not limited to the conductor insulation, and equipment. It is dependent on all portions of the circuit and components of the circuit.
1. the enclosure rating
2. conductor insulation rating
3. Overcurrent rating
4. equipment rating
5. and any other component in the system
*Take a look at the temperature rating of PVC.

There may be portions of the circuit rated at 90degree C, but the weak link is what the circuit will be rated at. I am positive that all enclosures are rated at 75degree C. Most if not all circuit breakers are rated at 75degree C. And as has been mentioned, the last sentence of 110.14 is where we will find the temperature rating of the conductor insulation for final ampacity application is 75Degree C.

how could their be so many factors involving allowable ampacities of insulated conductors? how do u put all those factors into it and come up with a final ampacity for that insulation

 

[augie47]

how could their be so many factors involving allowable ampacities of insulated conductors? how do u put all those factors into it and come up with a final ampacity for that insulation

Just one of many reasons, electrical work should be performed by a professional and not a hobbyist.

 

[liquidtite]

r u saying im a hobbyist

 

[augie47]

r u saying im a hobbyist

no, but Pierre's post is illustrative of the knowledge needed to be a real professional in this trade. Your profile indicates you are an apprentice so it's doubtful you have reached that point. Your participation in the Forum indicates that you have the desire to do so.

 

[liquidtite]

:happyno: im trying to learn as much as i can and appreciate your guys time

 

[liquidtite]

so how do you come up with a final degree to take the insulation at the termination degree is in the 75coloum but the type of insulation si in the 60*

 

[infinity]

so how do you come up with a final degree to take the insulation at the termination degree is in the 75coloum but the type of insulation si in the 60*

You would use the lowest temperature of all of the factors. Say you had a 75? C terminal but the conductor was only rated for 60? C, NM cable for example, then you would use the 60? C ampacity.

 

[Smart $]

so how do you come up with a final degree to take the insulation at the termination degree is in the 75coloum but the type of insulation si in the 60*

What 110.14(C) does is establish the minimum size conductor that can be used to make the termination, regardless of the conductor's [insulation] temperature rating. It even applies to bare conductors that have no insulation temperature rating. Other sizing (ampacity) requirements can increase the minimum size conductor, but they cannot decrease the minimum size as determined under 110.14(C).