Installing romex in EMT conduit

[Jpflex]

I think you are saying the same thing as the rest of us, just in a different way that is somewhat confusing.

The temperature ratings are _maximum limits_, not requirements. A 60C termination is limited to operating at 60C or less. A 90C wire is limited to operating at 90C or less. A 90C conductor will safely function at a 60C operating temperature because 60 is less than 90.

So if you have a 90C wire in contact with a 60C termination, you are limited to operating with a conductor current which will result in at most 60C operation at the location of the termination. The 60C termination requirement sets the maximum current you are permitted to run in the conductor, and the 90C wire is perfectly happy running at 60C. This isn't 'derating'; this is selecting the temperature limit for all components involved in the circuit at that location.

If you have 90C wire in a conduit with a 60C temperature limit, then again you are limited to the 60C ampacity because your conductor temperature must be limited by the most restrictive component in that location.

-Jon

The conductor fill and ambient temperatures are the factors altering conductor ampacity whether increasing or lowering amperes, therefore after adjustments, if the wire used does not equal to the ampacity and temp of the wire to be used For the termination specification you shouldn’t be using this wire?

 

[wwhitney]

Wayne, that is not what is confusing the OP and thanks for making it more confusing for him.

. . .

Sometimes simple to the point answers are the best.

Well, I'm all for simplification but don't want to introduce any inaccuracies while doing it.

Regardless, there are multiple respondents with different styles, and hopefully one of those styles will work for the reader.

Cheers, Wayne

 

[wwhitney]

The conductor fill and ambient temperatures are the factors altering conductor ampacity whether increasing or lowering amperes, therefore after adjustments, if the wire used does not equal to the ampacity and temp of the wire to be used For the termination specification you shouldn’t be using this wire?

Say you have an installation that uses conductors with 60C rated insulation, and it's compliant with everything in the NEC. That means that when it's operating as designed, none of the conductors should get hotter than 60C.

Now you change those conductors to have 75C rated insulation but everything else stays the same. What happens to the temperatures in the system? Absolutely nothing, they are unchanged and will stay at 60C or below.

So it's always OK to use a conductor with an insulation rating higher than required. Nothing in the NEC says otherwise.

Cheers, Wayne

 

[winnie]

The conductor fill and ambient temperatures are the factors altering conductor ampacity whether increasing or lowering amperes, therefore after adjustments, if the wire used does not equal to the ampacity and temp of the wire to be used For the termination specification you shouldn’t be using this wire?

Lets say you have a 60C termination and 90C wire. After you run all your calculations and adjustments you discover that the ampacity at the termination is 25A and your ampacity in the conduit is 15A. These two number are not equal.

But you can still use the wire, as long as the OCPD and load are 15A or less.

The point is that these values are _maximums_ for the component that cannot be exceeded, not requirements that need to be matched between the components.

60C termination touching a 90C wire? You must limit the temperature of that junction to 60C; the lower limiting value of the two components in contact.

100A ampacity wire spliced to a 40A ampacity wire? Kosher as long as the current is 40A or less.

A 90C rated wire will operate at 60C if the current is limited to the 60C value.

What is the temperature of a 90C rated wire when no current is flowing in it? Can you pick up 90C rated wire to install it without getting burned?

-Jon

 

[Jpflex]

If it's a sleeve for physical protection yes and you need 1/4 inch of it to enter the box. I only ever do it this way in basements or shops when nm was cheaper than mc by a lot.

Are you supposed to cover mk cable in attics to protect them under nec?

 

[Jpflex]

Nm cable as phone changed to mk cable

 

[letgomywago]

Are you supposed to cover mk cable in attics to protect them under nec?

I've never used that type of cable I googled it and it appears to be a custom cable you can order but that type might not be listed. NM-B doesn't need to be protected unless it is near the attic scuttle hole same goes for CAT cables although people care even less about those. If there is a permanent ladder it depends on the AHJ and running boards are the go to protection method in that instance. I feel like you've been led along with how things are done in residential have you only worked for 1 company or only done online continuing ed?

 

[rambojoe]

I feel like alot of us have been led along....
3 pages worth. You can shoot your horse and drag it to water, but why not just throw it in the truck?

 

[letgomywago]

I feel like alot of us have been led along....
3 pages worth. You can shoot your horse and drag it to water, but why not just throw it in the truck?

That's why I gave up haha but then was quoted so.

 

[roger]

I feel like alot of us have been led along....
3 pages worth. You can shoot your horse and drag it to water, but why not just throw it in the truck?

I agree and if that's not the case I don't think we can offer the OP anymore guidance.