Correction Factors

[Dennis Alwon]

If I install a number 8 wire with termination of 75C and the ambient temp correction factor is 1.2 then why can't I use the #8 (50 amps @75C) for 60 amps. 50 amps *1.2 = 60 amps?

 

[don_resqcapt19]

The trip point of the breaker at 10°C has probably shifted about 20 to 25%, so the 60 amp breaker will trip at 72 to 75 amps requiring a larger wire
In the corrected value is not actually in Table 310.16, and unless marked for use with ampacities in a different table, 110.14 limits you to the ampacities as found in Table 310.16.

 

[infinity]

If I install a number 8 wire with termination of 75C and the ambient temp correction factor is 1.2 then why can't I use the #8 (50 amps @75C) for 60 amps. 50 amps *1.2 = 60 amps?

Is this based on Table 310.15(B)(2)(a)? If so, where are you getting an ambient temperature below 50° F or less?

 

[Dennis Alwon]

Is this based on Table 310.15(B)(2)(a)? If so, where are you getting an ambient temperature below 50° F or less?

Alaska, IDK I just made it up--

 

[Dennis Alwon]

The trip point of the breaker at 10°C has probably shifted about 20 to 25%, so the 60 amp breaker will trip at 72 to 75 amps requiring a larger wire
In the corrected value is not actually in Table 310.16, and unless marked for use with ampacities in a different table, 110.14 limits you to the ampacities as found in Table 310.16.

I knew we were limited by 110.14 but I didn't know why a 60 wouldn't work. I figured there was some reason. I don't understand the shift you mentioned but I can see why it would not be allowed now.

 

[winnie]

I knew we were limited by 110.14 but I didn't know why a 60 wouldn't work. I figured there was some reason. I don't understand the shift you mentioned but I can see why it would not be allowed now.

Small circuit breakers have 'thermal-magnetic' trip mechanisms. These detect overcurrent by heating up. They are temperature sensitive; the colder the environment the higher the current necessary to trip them.

-Jon

 

[don_resqcapt19]

I knew we were limited by 110.14 but I didn't know why a 60 wouldn't work. I figured there was some reason. I don't understand the shift you mentioned but I can see why it would not be allowed now.

The trip curve shift to the right for lower temperatures is just something that we tend to ignore. For one brand of breaker, the manufacturer shows a 25% increase in the breaker rating where the breaker is in a 50°F ambient. That same manufacturer says there breakers are not for installation where the temperature will be below 14°F.

I attempted to place an Informational Note in 230.85 for the 2023 code in section 230.85 to call attention to this issue, but the PI was rejected in the first revision meeting. I chose 230.85, because that will is going to result in a lot of service main breakers being located outside in areas of the country that get cold and areas where outside OCDPs are not common.
Maybe Leviton will jump in on this at the comment stage as they offer hydraulic breakers that are not temperature sensitive.

 

[Dennis Alwon]

Small circuit breakers have 'thermal-magnetic' trip mechanisms. These detect overcurrent by heating up. They are temperature sensitive; the colder the environment the higher the current necessary to trip them.

-Jon

Then why do we have a correction factor that increases the ampacity. It would seem that it should have a correlation factor below 1 as temp decreases just as it increases with heat above 86 °

 

[BenRVA]

Then why do we have a correction factor that increases the ampacity. It would seem that it should have a correlation factor below 1 as temp decreases just as it increases with heat above 86 °

The correction factor is for the wire. Not the breaker. Breaker sizing has been taken into consideration elsewhere. Colder temperatures help the wire.

Most people dont realize that many breakers can sit at almost 100% load indefinitely without tripping... and manufacturers add a 25% error on top of that. So in theory a 200 amp breaker could sit at 250 amps and never trip and still be completely acceptable per the manufacturer.

As for the breakers not supposed to be installed below certain temps there are already codes about following manufacturers instructions it's just being ignored/not commonly known issue.

 

[don_resqcapt19]

....
As for the breakers not supposed to be installed below certain temps there are already codes about following manufacturers instructions it's just being ignored/not commonly known issue.

Exactly why I submitted a PI to add an Informational Note pointing out this issue.

 

[RumRunner]

Exactly why I submitted a PI to add an Informational Note pointing out this issue.

So, what happened to your submittal?

Was it also ignored as OP indicated that no one is paying attention to any proposed improvement?

If indeed they had considered the value of your proposal ...why is it being contested here?

Perhaps it will help if you post a formal letter you received (if any)-- as a response to the issue or if it was even worth a peer-review.

 

[Dennis Alwon]

So, what happened to your submittal?

He spoke of it earlier

but the PI was rejected in the first revision meeting.

 

[RumRunner]

He spoke of it earlier

When a document is SUPERSEDED, REVISED or otherwise DELETED a note is often included as addendum to the original document which is what the NEC is: a document.

Speaking about it “earlier” doesn’t mitigate the nuances that may eventually creep-in which are causing these arguments.

Whenever I make changes on a plan, schematic or simple revision of the specs, I always document them to avoid this unproductive wrangling.
It also make it authoritative rather than invite solicitations of unrequited opinions coming from both trained and untrained people on the trade.

A personnel making the request for changes could die tomorrow or quit his job. . . so, where does that take us if he only talks about it?

 

[don_resqcapt19]

....
Perhaps it will help if you post a formal letter you received (if any)-- as a response to the issue or if it was even worth a peer-review.

That is not how the NFPA revision process works. No formal notice will not be sent out. It will be published when they publish the First Revision for the 2023 code. The scheduled date for the release of the First Revision Report is 7/2/21. Right now, the rejection of my PI is not official, however they did resolve it at a Task Group Meeing with a comment that the requirements are already code as 110.3(B) requires compliance with the listing and labeling instructions for any product installed under the rules of the NEC.
My PI was just to call attention to rules that are often not followed or just plain ignored. That has been done in the form of actual code rules in the past, and I am only asking for an Informational Note, not a code rule.

Two code rules that were added to the code because electricians were not following them were termination torque rule in 110.14(D) and the rule limiting a neutral bar termination to one conductor per terminal in 408.41. Both of these were 110.3(B) instructions for decades before the rules were added to the code.

After the First Revision is published on the NFPA website, there will be a period of time where people can submit Pubic Comments, in an attempt to change the CMP's mind on the issues. I will likely submit a PC and I believe that a manufacturer of hydraulic breaker will also be submitting a supporting comment. Things often change between the First Revision and the Second Revision, and even at the annual NFPA meeting where the second revision is voted on.

 

[don_resqcapt19]

When a document is SUPERSEDED, REVISED or otherwise DELETED a note is often included as addendum to the original document which is what the NEC is: a document.
...

Again that is not how the NEC revision process works. There will be no addendum to the document. The changes will be indicated in the 2023 code by the following methods (at least those are the methods that were used for the 2020 code changes)
Shaded text = Revisions. Λ = Text deletions and figure/table revisions. • = Section deletions. N = New material.

Each PI, even those that were resolved (rejected) will have a panel statement that you can find by looking at the First Revision Report, even though the resolved PIs are a little more difficult to view. You will be able to see the proposed change, the submitter's name, who the submitter represents (if anyone), the submitter's substantiation for the change, the CMP's action on the PI and the CMP statement on why they accepted or resolved the change.
That is all on line at NFPA.org/70. For the current code you can scroll to archived revision information and see all of the submissions and panel actions that resulted in the 2020 NEC, with the exceptions of those actions that were based on motions at the NFPA annual meeting where any NFPA member can vote on the NEC changes, or actions taken after the meeting by action of the Standards Council.

 

[RumRunner]

Again that is not how the NEC revision process works. There will be no addendum to the document. The changes will be indicated in the 2023 code by the following methods (at least those are the methods that were used for the 2020 code changes)
Shaded text = Revisions. Λ = Text deletions and figure/table revisions. • = Section deletions. N = New material.

Each PI, even those that were resolved (rejected) will have a panel statement that you can find by looking at the First Revision Report, even though the resolved PIs are a little more difficult to view. You will be able to see the proposed change, the submitter's name, who the submitter represents (if anyone), the submitter's substantiation for the change, the CMP's action on the PI and the CMP statement on why they accepted or resolved the change.
That is all on line at NFPA.org/70. For the current code you can scroll to archived revision information and see all of the submissions and panel actions that resulted in the 2020 NEC, with the exceptions of those actions that were based on motions at the NFPA annual meeting where any NFPA member can vote on the NEC changes, or actions taken after the meeting by action of the Standards Council.

OK, We may have a dichotomy there.

That's not how MIL-SPECS are administered. I spent quite a bit of time working with DoD and the provisions are spelled out for designers, specs writers, compliant engineers and contractors.

Before a project is commenced during design stage, the government (DoD) put out circulars regarding changes that could affect the project.
Contractors that deal with Military Projects can request these circulars for free.
They are upgraded regularly, somewhere like monthly IIRC.

Since projects are conducted anywhere in the world. . . we are not bound to NEC.
Designers are fully versed and probably more stringent in terms of safety in undertaking big projects.

I've never heard of electricians dying or projects burning down because of laxity.

In summary, every project is tailored that is best suited for the location and other aspects like weather conditions etc.

Air quality like Saudi Arabia is salt laden for example and relay contacts turn green overnight.

Even the sand that is used as binders for concrete aggregate are shipped-in from Australia.

Crazy, considering Saudi Arabia has sand all over the place.

We used concrete for envelope to protect buried conduits and shielded cables.

 

[Dennis Alwon]

So what happens if the breaker is in a 70 degree environment and the conductor is run from the back of the panel to the outside. Would that change anything?

 

[david luchini]

Then why do we have a correction factor that increases the ampacity. It would seem that it should have a correlation factor below 1 as temp decreases just as it increases with heat above 86 °

I don't think the Code prohibits using the #8 for 60A in the ambient you have described. I think it prohibits using a termination rated for #8 and smaller conductors. The termination provisions would have to support at least a #6 conductor.