Termination limitations.

[Pinnie]

Can you cite an example of this? Square D for example lists their breakers for use with 75 degree terminations. If what you say is true, then I assume we wouldn't be able to terminate Romex to a Square D breaker since we are limited to using the 60 degree table for it. I have never seen a terminal that is rated for 60/75 degrees

Isn’t romex be rated for 90 degrees and then limited to the 60 degree ampacity?

 

[infinity]

Here's an example on a 20 amp circuit breaker.

 

[wwhitney]

I would think they would size the terminal ampacity based off the max conductor size allowed on it yeah?

The ampacity of the lug itself is hardly ever an issue, and is up to the manufacturer to deal with. The ampacity of the connection of the field installed wire to the manufacturer installed lug (or other termination provision) is what we are discussing. I'm calling that termination ampacity. And it obviously depends on the wire size used.

Why not? If you limit amperage to the 60C column of the conductor then it would be fine.

Certainly in the run of the conductor that's true. But at a termination you have both heat coming in from the rest of the wire and heat coming in from the equipment. The equipment may be designed such that the heat coming in from it will raise the terminal temperature to above 60C, even if the larger wire of the 60C column is used.

So you can use a higher temperature rated conductor but not terminal?

Again, you are conflating terminal and termination. The lug the manufacturer uses may have a 90C stamped on it; that just means it can withstand 90C. Once it's incorporated into a piece of equipment and that equipment is testing according to the listing standard, then the equipment will get a termination temperature rating of 60C, 60C/75C, 75C, or whatever.

[There's a termination rating that mean you must use 90C conductors based on their 75C ampacity; I don't know if there's a standard terminology for that. But it means that when the testing was done, the heat from the equipment causes the termination to exceed 75C, but not 90C, when the wire was sized based on the 75C column.]

Cheers, Wayne

 

[jim dungar]

There's a termination rating that mean you must use 90C conductors based on their 75C ampacity; I don't know if there's a standard terminology for that. But it means that when the testing was done, the heat from the equipment causes the termination to exceed 75C, but not 90C, when the wire was sized based on the 75C column.

This is typically the case for 100% rated equipment.

 

[Elect117]

I would also advise you try to find the UL White book AALZ section and give it a read.

This is one of those things that comes down to manufacturers, how the equipment is tested, terminations are tested, and when they put that all together, the listed rating.

Essentially, as a thought experiment, I would suggest trying to figure out how to test a terminal can handle the ampacity of 3/0 CU THWN-2 and then how a panelboard stacked full of breakers in a enclosed room with no moving or cold air, can handle the ampacity of 3/0 CU THWN-2. The manufacturer and UL will require that all of that be able to handle 200A. As a type of control to verify and list everything off of. That way when you put it on a 200A breaker, the circuit is protected. If you put it on a 300A breaker could you still say the 300A breaker protects it? What about using terminations only good for 60°C? Or what about trying to use the outside free air rating on a 75°C termination rated to hold 3/0 Cu but a breaker rated 300A. Would the terminations hold up? As you can see there are a lot of different listings and ratings that combine to make one safe circuit. So UL basically says that we are going to test this stuff to a specific rating to verify it works as intended. And those ratings are laid out in 110.14(C).

It is more of a situation where they need to be able to label the ratings to maintain the NECs safety to ensure the terminations, equipment, wire are not a point of failure. They should, when installed correctly, be able to be protected by the OCPD.

It is also why torquing has become more prevalent. You want to ensure that the wire will not escape the termination during a fault and that they are not too tight or not tight enough creating excess heat.

 

[Pinnie]

The ampacity of the lug itself is hardly ever an issue, and is up to the manufacturer to deal with.

Gotcha. I would think not. It’s their butts on the line for that issue.

The ampacity of the connection of the field installed wire to the manufacturer installed lug (or other termination provision) is what we are discussing. I'm calling that termination ampacity.

Truthfully, to be very precise it’s the temperature of the connection we care about not the ampacity. Since 110.14 cares about not exceeding temperature ratings and not necessarily ampacity. (IMO)

Certainly in the run of the conductor that's true. But at a termination you have both heat coming in from the rest of the wire and heat coming in from the equipment. The equipment may be designed such that the heat coming in from it will raise the terminal temperature to above 60C, even if the larger wire of the 60C column is used.

This is fair. Ampacity is not the only cause of heat. Does the code recognize that and require that conductors have a temperature rating equal to or greater than the terminals to which they are connected?

Again, you are conflating terminal and termination. The lug the manufacturer uses may have a 90C stamped on it; that just means it can withstand 90C. Once it's incorporated into a piece of equipment and that equipment is testing according to the listing standard, then the equipment will get a termination temperature rating of 60C, 60C/75C, 75C, or whatever.

Interesting. So they are two different ratings? (Terminal and termination)

 

[jim dungar]

Does the code recognize that and require that conductors have a temperature rating equal to or greater than the terminals to which they are connected?

Yes.
This goes back to the 60/75°C rating and the comment about needing 90°C conductors sized ar 75°C for 100% rated equipment.

 

[Pinnie]

Yes.
This goes back to the 60/75°C rating.

I am thinking the double standard comes from use caring more about our conductors? Or from the nature of equipment generating heat?

 

[jim dungar]

I am thinking the double standard comes from use caring more about our conductors? Or from the nature of equipment generating heat?

The termination has been tested by UL as protecting both the conductors and the equipment. The actual connection runs cool enough for 60°C conductors but does not overheat if the conductors are sized at 75°C.

 

[jim dungar]

Interesting. So they are two different ratings? (Terminal and termination)

Yes.
A lug (terminal) may have its own rating. Most of the common ones on the market today are rated 90°C.
A termination is everything, the lug, the component it is mounted to, and the enclosure it is in.

Many contractors have had the experience of repulling conductors because they only looked at the lug itself.

 

[tortuga]

If your lucky and get to work on older systems over 600 volts but 1000 volts and under like a 690Y/400 volt system it gets really interesting to apply the NEC.
As up until the 2017 NEC a 690 volt system fell under 110.40 where 90C terminations are standard, but now you'd be under 110.14.

 

[Pinnie]

Yes.
A lug (terminal) may have its own rating. Most of the common ones on the market today are rated 90°C.
A termination is everything, the lug, the component it is mounted to, and the enclosure it is in.

Many contractors have had the experience of repulling conductors because they only looked at the lug itself.

Is it tricky to differential the two ratings when inspecting a breaker? Is it required they are both marked?

 

[Pinnie]

If your lucky and get to work on older systems over 600 volts but 1000 volts and under like a 690Y/400 volt system it gets really interesting to apply the NEC.
As up until the 2017 NEC a 690 volt system fell under 110.40 where 90C terminations are standard, but now you'd be under 110.14.

Oh gosh my brain can’t handle that yet

 

[wwhitney]

Is it tricky to differential the two ratings when inspecting a breaker? Is it required they are both marked?

Just ignore any markings on the lug subcomponent on which you land your wires. Look only for an overall rating on the piece of equipment. For a breaker, it should be printed on the breaker case.

Cheers, Wayne

 

[Pinnie]

Just ignore any markings on the lug subcomponent on which you land your wires. Look only for an overall rating on the piece of equipment. For a breaker, it should be printed on the breaker case.

Cheers, Wayne

So they are marked in different locations based on the rating in question? Or is there a different prefix/unit before the temperature rating marking differentiating it as a terminal or termination temp rating?

 

[Pinnie]

If my questions get annoying let me know lol. I often ask too many.

 

[jim dungar]

So they are marked in different locations based on the rating in question? Or is there a different prefix/unit before the temperature rating marking differentiating it as a terminal or termination temp rating?

When you are dealing with an assembly, like a breaker, you look at the complete assembly not its individual components.

 

[Pinnie]

When you are dealing with an assembly, like a breaker, you look at the complete assembly not its individual components.

Okay dumb question time. An assembly being a prefab/assembled piece of equipment from a manufacturer?

 

[wwhitney]

So they are marked in different locations based on the rating in question? Or is there a different prefix/unit before the temperature rating marking differentiating it as a terminal or termination temp rating?

Manufacturer A makes a lump of metal that may be used by another manufacturer as a lug in an assembly. This lump of metal is incised with "90C". That is telling the other manufacturer something about the lump of metal. This information is immaterial to you; ignore it.

The other manufacturer use that lump of metal as a component in a breaker or other piece of equipment. They test the temperature rise at various places in their equipment as part of the listing standard, and come up with a termination temperature rating for the equipment as a whole. That rating will be marked on the equipment somewhere. Use that termination rating.

That termination rating will convey two pieces of information: (a) what temperature column of Table 310.16 you use (straight, no adjustment or correction) when choosing a wire size to land in the terminals of the equipment and (b) what minimum conductor insulation temperature you may use. The simplest case is where a single temperature is specified, usually 60C or 75C. In that case that temperature is both (a) and (b) above.

Cheers, Wayne

 

[Pinnie]

That termination rating will convey two pieces of information: (a) what temperature column of Table 310.16 you use (straight, no adjustment or correction) when choosing a wire size to land in the terminals of the equipment and (b) what minimum conductor insulation temperature you may use. The simplest case is where a single temperature is specified, usually 60C or 75C. In that case that temperature is both (a) and (b) above.

Why no adjustment or correction?