NEC Changes For #14 Ampacity

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mbrooke said:
IMO, I think you should also run 1 sample in open air, just to get an idea of where the ampacity tables stand. Do they lean toward open air or worse case?
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i have issue with such test. the table (pdf) you posted a few posts back, that says "amps at failure". basically thats a test to show how many amps can flow in open air @the specific ambient before insulation failure. i think they called it "melting". their definition of "melting" is not clearly defined.

i will run an open air test but not looking for a failure point, will simply be taking temp vs amps measurements. the UL tests wire is tested under has better defined test verbiage, meaning, the specific UL test for "pass" or "fail" has better defined limits.

if i test the wire and i see 25A @ 78C, this alone is not accurate enough to say it is safe or it is not safe. if @20A the insulation is all gooey and starting to pull away from the copper, even if temp is say 67C, that would be bad, and on flip side, if @26A i see 89C but the insulation is still perfect, this is better, but the temps may be posing the issue to its surroundings.

so just to be clear, i am only measuring temp vs amps in what NEC might consider worse case scenario for NM-B.
 
FionaZuppa said:
i have issue with such test. the table (pdf) you posted a few posts back, that says "amps at failure". basically thats a test to show how many amps can flow in open air @the specific ambient before insulation failure. i think they called it "melting". their definition of "melting" is not clearly defined.
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Granted, going by insulation failure or conductor failure is a poor idea. The links Im posting are mainly food for thought. Basically to help bild various hypothesis which will be proven or disproved based on the actual recorded temperature.



i will run an open air test but not looking for a failure point, will simply be taking temp vs amps measurements. the UL tests wire is tested under has better defined test verbiage, meaning, the specific UL test for "pass" or "fail" has better defined limits.
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Sounds good, and this is what I would do above all else.





if i test the wire and i see 25A @ 78C, this alone is not accurate enough to say it is safe or it is not safe. if @20A the insulation is all gooey and starting to pull away from the copper, even if temp is say 67C, that would be bad, and on flip side, if @26A i see 89C but the insulation is still perfect, this is better, but the temps may be posing the issue to its surroundings.
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Your thinking is on track, again, I agree.


so just to be clear, i am only measuring temp vs amps in what NEC might consider worse case scenario for NM-B.
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Ok. Id still do a 24-27 amp reading in open air to compare the two, but its ultimately the greater concern is worse case.
 
And oh, I left on thing out. Mr. Zappa, if you feel comfortable I would recommend video taping your test along with the results and eventually submitting them as part of a proposal to the NFPA. While not being a nationally recognized NRTL or testing agency (no offense), your test is still valid and can help spark interest among the CMP, or at the very least others who submit proposals. If 20 amps on #14 does indeed yield acceptable temperatures under worse case conditions, it maybe worth extending that to the NEC as the CEC has already done so.
 
mbrooke said:
What also I am wondering (and I ask anyone reading if they can help) is what drove the NEC to go from 60*C insulation to 90*C insulation in MN wire.
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Because every time a derating factor is introduced the copper cabal can hold it's 1/4ly meets in Aruba.....:)


~RJ~
 
romex jockey said:
Because every time a derating factor is introduced the copper cabal can hold it's 1/4ly meets in Aruba.....:)


~RJ~
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I am convinced our NEC is in cahoots with the copper guys. When one considers the level of heat dissipation varies dramatically based on conditions of installation not including begins to look like a poor choice.
 
ran 1st crude test of mot hack. using #2 fine strand cable, two turns around the iron, shorted the ends, went full power, it basically took my General CM660 to overload, so we have plenty of amps available to cook with. i also cooked a piece of ~18awg (in size) re-bar tie wire, about 5" long, amps jumped for a sec then settled in right around 37A while the wire sat there in red glow state.
 
FionaZuppa said:
ran 1st crude test of mot hack. using #2 fine strand cable, two turns around the iron, shorted the ends, went full power, it basically took my General CM660 to overload, so we have plenty of amps available to cook with. i also cooked a piece of ~18awg (in size) re-bar tie wire, about 5" long, amps jumped for a sec then settled in right around 37A while the wire sat there in red glow state.
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You have discovered the power of a high current source :D I make a prediction that you wont be stepping away or getting bored anytime soon :cool::cool:

(BTW, post pics) :)
 
mbrooke said:
You have discovered the power of a high current source :D I make a prediction that you wont be stepping away or getting bored anytime soon :cool::cool:

(BTW, post pics) :)
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i will indeed be using this mot hack + variac for other uses, i already have a spot weld application i can use it for, will likely build a timer (one shot) to control the primary for fine tuning welds for different weld setups, i have copper and tungsten to muck around with, etc.

pics will come.
 
FionaZuppa said:
i will indeed be using this mot hack + variac for other uses, i already have a spot weld application i can use it for, will likely build a timer (one shot) to control the primary for fine tuning welds for different weld setups, i have copper and tungsten to muck around with, etc.

pics will come.
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:D You da man :cool:
 
here's the mot, finished wrapping the secondary and welded the cap back on. the lug ends are slightly crimped and then fully soldered. some more epoxy was applied, 100% ready for use in the AM.


DSC02717.jpg
 
FionaZuppa said:
here's the mot, finished wrapping the secondary and welded the cap back on. the lug ends are slightly crimped and then fully soldered. some more epoxy was applied, 100% ready for use in the AM.


DSC02717.jpg
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And we are ready for lift off :thumbsup:

What is your open circuit voltage at 120 volts?
 
mbrooke said:
And we are ready for lift off :thumbsup:

What is your open circuit voltage at 120 volts?
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ocv 1.92vac(rms)

these mot's (which are common) give just about 1v per loop

i have to get the rigid foam and make the required channels for wire and TC's.

i will have two TC's, one touching the romex outer sheath, and one touching bare copper wire. i plan to buffer the junction points with a small piece of mica dielectric to guard against wire voltage touching the TC. you might say not needed on the sheath TC, but it will be there just in case amps causes any wire to burn through and be exposed, etc. i will use just a small bit of thermo paste on each side of the mica so we can get best heat transfer. all that said, since the whole thing is in a sandwich we should get very little heat loss (very little) at the TC junction points, so i dont see the mica being an issue for getting good temp readings, etc.

also, need to keep in mind that the TC's will be reading heat levels coming from two CCC's, so the bare copper TC temp will not be true temp of the one wire, but i dont think that matters, we want to see what the wire temp is for this scenario, etc.
 
FionaZuppa said:
also, need to keep in mind that the TC's will be reading heat levels coming from two CCC's, so the bare copper TC temp will not be true temp of the one wire, but i dont think that matters, we want to see what the wire temp is for this scenario, etc.
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i should clarify as this verbiage would be confusing if found in a lab experiment document. the temp of the bare copper (one wire) is true temp, but that temp is developed by multiple heat sources.
 
ok, getting rigid foam today. i'll be using Romex brand SIMpull 14/2 (white) wire for testing. any arguments on wire choice?
 
FionaZuppa said:
ocv 1.92vac(rms)

these mot's (which are common) give just about 1v per loop

i have to get the rigid foam and make the required channels for wire and TC's.

i will have two TC's, one touching the romex outer sheath, and one touching bare copper wire. i plan to buffer the junction points with a small piece of mica dielectric to guard against wire voltage touching the TC. you might say not needed on the sheath TC, but it will be there just in case amps causes any wire to burn through and be exposed, etc. i will use just a small bit of thermo paste on each side of the mica so we can get best heat transfer. all that said, since the whole thing is in a sandwich we should get very little heat loss (very little) at the TC junction points, so i dont see the mica being an issue for getting good temp readings, etc.

also, need to keep in mind that the TC's will be reading heat levels coming from two CCC's, so the bare copper TC temp will not be true temp of the one wire, but i dont think that matters, we want to see what the wire temp is for this scenario, etc.
Click to expand...



The OCV may be to low, but it might work out just fine. The rest sounds ok, especially the thermopaste.
 
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