Code for temperature of wire?

[Kaizen]

In preparation for doing my garage subpanel I realized I really needed to clean up the house wiring so I don’t have any issues with inspection. In the process I ran across a situation and not sure if it’s an issue.
I have a few holes drilled in floor joists and each hole has several Rome’s wires going through each. The joists in question have radiant heat running through them for the floor above the water is about 120 degrees and the bay is insulated. Would this cause an issue with wire temp or is there any code that refers to this? Would this temp in addition to normal wire temp cause an issue? I can’t insulate the whole loop and not cover the wires.


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[Lelandwelds]

Electrical specs are written for 104°C temperature rise or something. Your attic must be an alternate doorway to the Hades Multiverse.

 

[crazyjim30]

So, NM-B (Romex) is temperature rated. It breaks down into several different classes, the lowest of which is 60° C (147° F). Tbh, sizing for the proper amperage is more important than the temperature rating. 14 Gauge wire for 15 amp circuits and 12 for 20 amp ones. YMMV. Just in case I'm wrong, ask a licensed electrician.

If you're really uncomfortable with your level of understanding, before you run any wire, find a school that offers a NEC (National Electrical Code) class and take it.

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[rburke65]

I’m sure you are not the first to have this situation. I wo7ldnt loose any sleep over this. As always.....just my opinion.

 

[Lelandwelds]

find a school that offers a NEC (National Electrical Code) class and take it.

That's not a class. It is a religion! Cult. Calling. Protectionist trade organisation. Euro soccer hooligans.

And, an old ladies quilting circle.

 

[ard]

That's not a class. It is a religion! Cult. Calling. Protectionist trade organisation. Euro soccer hooligans.

And, an old ladies quilting circle.

Word.

 

[Muzzy]

I'm having a hard time visualizing this. Could you please post a picture?

 

[Kaizen]

Thanks for the input. I do not have any doubts in my ability to install to code. My question was more about if the wire heat rating would be an issue for an inspector in this situation IF all of my circuits are well below the total amperage for that size wire. Seeing that the lowest temp is above 140 as noted above I don’t think this will be an issue as the highest it should get is about 120. Here is a pic to demonstrate what I’m talking about.

I removed this insulation but it has an r13 batt sealing it normally



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[ard]

What is that purple wire/hose?

If the max possible temp is 140 (not 'what it usually is') then I think 310.16 applies. You cannot use 60C conductors. For 75C conductors you derate to 0.58, for 90C conductors derate to 0.71.

To cut down on the back and forth, what is the temp rating on the wires you are currently using? 60? 75? 90?

Also, what are the sizes? All #12? Other stuff?


I believe #12 is good for 25A (although it cannot be used on more than a 20A circuit). So if you had a #12 @60C, and needed to derate at 0.58, then 25x0.58=14.5A. You would need to use a 15A breaker to limit that.

I think.

Answer the questions above and I am sure others will chime in...

 

[Kaizen]

What is that purple wire/hose?

If the max possible temp is 140 (not 'what it usually is') then I think 310.16 applies. You cannot use 60C conductors. For 75C conductors you derate to 0.58, for 90C conductors derate to 0.71.

To cut down on the back and forth, what is the temp rating on the wires you are currently using? 60? 75? 90?

Also, what are the sizes? All #12? Other stuff?


I believe #12 is good for 25A (although it cannot be used on more than a 20A circuit). So if you had a #12 @60C, and needed to derate at 0.58, then 25x0.58=14.5A. You would need to use a 15A breaker to limit that.

I think.

Answer the questions above and I am sure others will chime in...

The white wire and the new ones I am installing are 190 degree f rated. The purple looking tube is radiant underfloor heat....the cause of my concern/question. The space when insulated is max 120 degrees. All of it is either 20 amp on 12ga or 15amp on 14ga. Appreciate your time


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[ard]

All the wood floor radiant stuff Ive seen has the tubing attached to the underside, sometimes with AL plates to spread heat.....

Edit- wonder if radiant barrier film, paper or bubble up against the hose will make that more efficient, projecting more heat up into the floor??

Take a quick look at page 2: http://www.cooperindustries.com/con...r_Derating_Ambient_Temperature_Correction.pdf

From your posts, sounds like you have:

existing wires, 12Ga, 20A, unknown temp rating
existing wires, 14Ga, 15A, unknown temp rating
new wires, 12 or 14?, and "190F rated"

Correct??

Most wire ive seen is rated in C, and converting 190 to C I get 87.7C. Maybe double check? 90C is 194F, so if you do have 194 then you use that 90C column

In terms of 'what temp will the code 'say' that space really is', there is no way to say what eactly an inspector will decide. Is he OK with your statement "i measurewd it a few nghts and it never went over 120" or will he say "We use the the maximum possible temp on the thermostat, or what the manufacturer says it might generate". Dunno

120 vs 140 F

If you look at the table on page two, this chart is where the ambient 'interacts' with the temp ratings.....with your new wires, I assume they are 90C rated, at 120F you derate to 82% (or 0.82)

This means a #12 which can handle 25A is derated- 25x0.82=20.5A. Still fine for a 20A circuit.

But if you are held to 140F, derating is 0,71, so 25x0,71= 17.75. I **think** you can use 'the next stard size fuse' and still use a 20.

Doing the math on 14G wire, 20x.71=14.2, 15A breaker 20x.82=16.4, still limited to 15A on #14 wire (ie the derating has no impact)

If you can get the temp ratings or other details off the wires already installed, you will need them.

 

[Kaizen]

All the wood floor radiant stuff Ive seen has the tubing attached to the underside, sometimes with AL plates to spread heat.....

Edit- wonder if radiant barrier film, paper or bubble up against the hose will make that more efficient, projecting more heat up into the floor??

Take a quick look at page 2: http://www.cooperindustries.com/con...r_Derating_Ambient_Temperature_Correction.pdf

From your posts, sounds like you have:

existing wires, 12Ga, 20A, unknown temp rating
existing wires, 14Ga, 15A, unknown temp rating
new wires, 12 or 14?, and "190F rated"

Correct??

Most wire ive seen is rated in C, and converting 190 to C I get 87.7C. Maybe double check? 90C is 194F, so if you do have 194 then you use that 90C column

In terms of 'what temp will the code 'say' that space really is', there is no way to say what eactly an inspector will decide. Is he OK with your statement "i measurewd it a few nghts and it never went over 120" or will he say "We use the the maximum possible temp on the thermostat, or what the manufacturer says it might generate". Dunno

120 vs 140 F

If you look at the table on page two, this chart is where the ambient 'interacts' with the temp ratings.....with your new wires, I assume they are 90C rated, at 120F you derate to 82% (or 0.82)

This means a #12 which can handle 25A is derated- 25x0.82=20.5A. Still fine for a 20A circuit.

But if you are held to 140F, derating is 0,71, so 25x0,71= 17.75. I **think** you can use 'the next stard size fuse' and still use a 20.

Doing the math on 14G wire, 20x.71=14.2, 15A breaker 20x.82=16.4, still limited to 15A on #14 wire (ie the derating has no impact)

If you can get the temp ratings or other details off the wires already installed, you will need them.

Thanks ard. Looks like I’m ok with those numbers. I will verify the code on the old wires.
The tube for heat is attached to the floor with aluminum plates just out of site. It has to come down at the end to go through the hole in the floor joist. Thanks again


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