Wire insulation temperature VS. Termination temperature (Again)

[Sparky2791]

Greetings!
I Have a project where we designed the replacement of all existing panels installed in a middle school (circa 1965). Scope of work is to disconnect and remove existing panel & panel feeder, retain existing panel feeder raceway for installation of a new panel feeder. Install new panel in existing location, install new feeder in existing conduit (conduit size was confirmed acceptable for new feeder) and reconnect all existing branch circuits to new circuit breakers.
Drawings were reviewed and approved by a third party reviewing agent for permits. Now local inspector is indicating that the since the existing wiring in the building only used 60-degree insulation he wants every existing circuit from termination @ panel to nearest junction point or device to be replaced with wiring with 90-degree insulation. Not the entire circuit, just the portion of the circuit which terminates on the new panel.
I started investigating this so I thought I would put it out the on the forum to get some other opinions. I thought terminating wiring with 60-degree insulation on lugs rated for 75-degree wire is acceptable. Keep in mind all circuits are rated 100A and under (majority are 20A circuits)

Article 110.14 (C)
The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor or device.

This inspector seems to think the temperature rating of the conductor’s insulation must meet or exceed the temperature rating of the termination.

Am I missing something here? I did not receive shop drawings from the contractor but assume the lugs on the new panels are rated for 75-degree wire as most are only rated for this.

Thank you in advance for your response.

 

[Carultch]

Greetings!
I Have a project where we designed the replacement of all existing panels installed in a middle school (circa 1965). Scope of work is to disconnect and remove existing panel & panel feeder, retain existing panel feeder raceway for installation of a new panel feeder. Install new panel in existing location, install new feeder in existing conduit (conduit size was confirmed acceptable for new feeder) and reconnect all existing branch circuits to new circuit breakers.
Drawings were reviewed and approved by a third party reviewing agent for permits. Now local inspector is indicating that the since the existing wiring in the building only used 60-degree insulation he wants every existing circuit from termination @ panel to nearest junction point or device to be replaced with wiring with 90-degree insulation. Not the entire circuit, just the portion of the circuit which terminates on the new panel.
I started investigating this so I thought I would put it out the on the forum to get some other opinions. I thought terminating wiring with 60-degree insulation on lugs rated for 75-degree wire is acceptable. Keep in mind all circuits are rated 100A and under (majority are 20A circuits)

Article 110.14 (C)
The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor or device.

This inspector seems to think the temperature rating of the conductor’s insulation must meet or exceed the temperature rating of the termination.

Am I missing something here? I did not receive shop drawings from the contractor but assume the lugs on the new panels are rated for 75-degree wire as most are only rated for this.

Thank you in advance for your response.

Some devices are dual rated 60C / 75C, in which case it allows you to use 60C insulation on the wires with 60C sizing, and also allows 75C+ insulation with 75C sizing. Other devices are straight rated 75C, in which case you have to use 75C+ rated wire, and cannot use 60C wire even with 60C sizing.
http://www2.schneider-electric.com/...7/en_US/Wire Terminations 0110DB9901R2-02.pdf

 

[charlie b]

Other devices are straight rated 75C, in which case you have to use 75C+ rated wire, and cannot use 60C wire even with 60C sizing.

I disagree with this, with the local inspector, and with statements on your 15 year old PDF. A #12 wire with 60C insulation has an ampacity of 20 amps. You can protect it with a 20 amp breaker. The current flowing through the 75C terminations on the breaker will not cause overheating. Current that will not overheat a wire that is only rated for 60C is not going to overheat a termination that has an even higher temperature rating.

 

[Sparky2791]

I disagree with this, with the local inspector, and with statements on your 15 year old PDF. A #12 wire with 60C insulation has an ampacity of 20 amps. You can protect it with a 20 amp breaker. The current flowing through the 75C terminations on the breaker will not cause overheating. Current that will not overheat a wire that is only rated for 60C is not going to overheat a termination that has an even higher temperature rating.

I agree with Charlie b and that is exactly the way I was looking at it. Kind of like, just because the main lug only panel is rated for 1000A does not mean you must feed it with 1000A. Just because the lugs are rated for 75-degrees does not mean the wire feeding it must be rated for 75-degrees. Lets see if there are other opinions on this topic
Anyone Else???? Also - Please reference code articles to clarify as we will need to respond to this inspector and it is good to have the backing of the code articles. Always seems to put things to bed.

Thanks again folks!

 

[MasterTheNEC]

I agree wholeheartedly with Charle b on this one. Also if it was our wire then I would put that in written form for you....but chances are it's not...

 

[publicgood]

Suggestion: If you have a specific question of use, it would be easier to discuss this subject if we were given types such as THHN rather than ##-degree rated wire.

Article 110.14 (C)
The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor or device.

This inspector seems to think the temperature rating of the conductor’s insulation must meet or exceed the temperature rating of the termination.

Your 110.14(C) reference is correct. It is fine to use 60C conductors for less than 100A, with 75C terminations, as per 110.14(C)(1). For over 100A, you inspector would be correct - 75C conductors. Read 110.14(C) for specific allowances such as using 75C conductors for less than 100A motor branch circuit B, C or D motors.

Now local inspector is indicating that the since the existing wiring in the building only used 60-degree insulation he wants every existing circuit from termination @ panel to nearest junction point or device to be replaced with wiring with 90-degree insulation. Not the entire circuit, just the portion of the circuit which terminates on the new panel.

I am confused by your description. Does this mean the old conductors are TW and the inspector wants the new wire to be THHN? Or does this mean the inspector wants you to use the 90C column for ampacity? If it is the latter, the allowable ampacity is larger at 90C then it is for 60C...this would be much more relaxed then the NEC allows.

Am I missing something here? I did not receive shop drawings from the contractor but assume the lugs on the new panels are rated for 75-degree wire as most are only rated for this.

Even if your breaker lugs are 75C, one cannot guarantee all devices on the receiving end of branch circuits are rated for 75C; thus, the requirements from 110.14(C) apply.

Note, unless your local jurisdiction does not allow (I've seen this), with some restrictions...the larger 90C may be used for derating say homeruns even if the are connecting to 75C terminations.

 

[Carultch]

I disagree with this, with the local inspector, and with statements on your 15 year old PDF. A #12 wire with 60C insulation has an ampacity of 20 amps. You can protect it with a 20 amp breaker. The current flowing through the 75C terminations on the breaker will not cause overheating. Current that will not overheat a wire that is only rated for 60C is not going to overheat a termination that has an even higher temperature rating.

Did that Schneider Electric white paper at one point apply? What would be the reason for rating a breaker's terminals for 60C/75C, if the rating of 75C is backwards compatible by default?

 

[infinity]

Did that Schneider Electric white paper at one point apply? What would be the reason for rating a breaker's terminals for 60C/75C, if the rating of 75C is backwards compatible by default?

I was thinking the same thing. Why is the 60 degree C rating even on the breaker?

 

[JFletcher]

If anything, I'm surprised he doesnt want the other end (from light to 1st jbox) replaced as lights now require 90*C insulation.

I agree with others in that 60*C wire can be used at regular ampacities ala NM.

 

[Smart $]

I was thinking the same thing. Why is the 60 degree C rating even on the breaker?

To permit the use of 60°C-rated wire.

This is not a matter of physics. It's all about the terminal's listing. Where a terminal is rated 75°C, as part of its listing it is only tested at 75°C. If a terminal is not rated 60°C, you cannot use 60°C-rated conductors.

 

[Carultch]

To permit the use of 60°C-rated wire.

This is not a matter of physics. It's all about the terminal's listing. Where a terminal is rated 75°C, as part of its listing it is only tested at 75°C. If a terminal is not rated 60°C, you cannot use 60°C-rated conductors.

That's what I originally stated. That a 75C equipment terminal rating is not backwards-compatible by default with 60C wire, unless dual rated 60C/75C.

 

[infinity]

To permit the use of 60°C-rated wire.

This is not a matter of physics. It's all about the terminal's listing. Where a terminal is rated 75°C, as part of its listing it is only tested at 75°C. If a terminal is not rated 60°C, you cannot use 60°C-rated conductors.

That was always my understanding but is the minority opinion in this thread.

 

[rbalex]

Did that Schneider Electric white paper at one point apply? What would be the reason for rating a breaker's terminals for 60C/75C, if the rating of 75C is backwards compatible by default?

The Schneider white paper was never correct. The author was also the "proposer" for what became the current Section 110.14(C). He is a brilliant man but misunderstood the 'thermodynamics' of the contents of UL Category Code AALZ that the Proposal was based on. (He is also the current NFPA President). He and I have "discussed" thermodynamics in a few other issues. He has always graciously come back and ultimately agreed with me.

Get a copy of the UL "Whitebook" and read the AALZ Sections on "Appliance and Utilization Equipment Terminations" and "Distribution and Control Equipment Terminations".

Charlie b is absolutely correct and any combination of temperature ratings may be used together as long as no single component's temperature rating is exceeded in its "condition of use". See the definition of ampacity in Article 100. I will note a termination's "condition of use" is determined by the conductor size NOT the conductor's insulation rating.

 

[david luchini]

Charlie b is absolutely correct and any combination of temperature ratings may be used together as long as no single component's temperature rating is exceeded in its "condition of use". See the definition of ampacity in Article 100. I will note a termination's "condition of use" is determined by the conductor size NOT the conductor's insulation rating.

:thumbsup:

 

[Smart $]

The Schneider white paper was never correct. The author was also the "proposer" for what became the current Section 110.14(C). He is a brilliant man but misunderstood the 'thermodynamics' of the contents of UL Category Code AALZ that the Proposal was based on. (He is also the current NFPA President). He and I have "discussed" thermodynamics in a few other issues. He has always graciously come back and ultimately agreed with me.

Get a copy of the UL "Whitebook" and read the AALZ Sections on "Appliance and Utilization Equipment Terminations" and "Distribution and Control Equipment Terminations".

Charlie b is absolutely correct and any combination of temperature ratings may be used together as long as no single component's temperature rating is exceeded in its "condition of use". See the definition of ampacity in Article 100. I will note a termination's "condition of use" is determined by the conductor size NOT the conductor's insulation rating.

I do not agree.

My understanding is that it is not only a matter of the wire not exceeding the 60°C temperature based on the current it will handle, but that the equipment is rated 75°C and permitted to reach that temperature under normal operation. When it does, the insulation temperature of the wire will have been exceeded. There is no accepted method to "derate" 75°C-rated equipment for use with 60°C-rated conductors.

 

[rbalex]

I do not agree.

My understanding is that it is not only a matter of the wire not exceeding the 60°C temperature based on the current it will handle, but that the equipment is rated 75°C and permitted to reach that temperature under normal operation. When it does, the insulation temperature of the wire will have been exceeded. There is no accepted method to "derate" 75°C-rated equipment for use with 60°C-rated conductors.

Did you read the Whitebook?

 

[wwhitney]

Did you read the Whitebook?

Is this the paragraph of interest?

Except as noted in the general Guide Information for some product categories, the termination provisions are based on the use of 60°C insulated conductors in circuits rated 100 A or less, and the use of 75°C insulated conductors in higher rated circuits as specified in Table 310.15(B)(16) of the NEC. If the termination provisions on equipment are based on the use of other conductors, the equipment is either marked with both the size and temperature rating of the conductors to be used or with only the temperature rating of the conductors to be used. If the equipment is only marked for use with conductors having a higher (75 or 90°C) temperature rating (wire size not specified), the 60°C ampacities (for circuits rated 100 A or less) and 75°C ampacities (for circuits rated over 100 A) should be used to determine wire size. Conductors having a temperature rating higher than specified may be used, though not required, if the size of the conductors is determined on the basis of the 60°C ampacity (circuits rated 100 A or less) or 75°C ampacity (circuits rated over 100 A).

Cheers, Wayne

 

[rbalex]

Did you read the Whitebook?

It's readily available.

 

[Smart $]

Did that Schneider Electric white paper at one point apply? What would be the reason for rating a breaker's terminals for 60C/75C, if the rating of 75C is backwards compatible by default?

The Schneider white paper was never correct. ...

A Cooper Bussman publication agrees with the Schneider paper...

http://www.cooperindustries.com/con...ary/BUS_Ele_Tech_Lib_Conductor_Ampacities.pdf
(see last section)


UL Category Code AALZ states the following:

Some distribution and control equipment is marked to indicate the required temperature rating of each field-installed conductor. If the equipment, normally intended for connection by wire sizes within the range 14-1 AWG, is marked "75C" or "60/75C," it is intended that 75°C insulated wire may be used at full 75°C ampacity. Where the connection is made to a circuit breaker or switch within the equipment, such a circuit breaker or switch must also be marked for the temperature rating of the conductor.

http://productspec.ul.com/document.php?id=AALZ.GuideInfo

 

[Smart $]

Did you read the Whitebook?

See my last reply.