mbrooke
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What rules apply to de-rating of control and signal wiring? How do I determine what CCC is used?
De-rating control and signal wire
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mbrooke
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Thanks, checking that out
Also, are signal wires limited to LV or do they include 120 volts?
jumper
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Thanks, checking that out
Also, are signal wires limited to LV or do they include 120 volts?
Are you referring to a Class 1 circuit?
mbrooke
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I guess I have to ask, how are class, 1, 2 and 3 classified from on another?
jumper
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Honestly I get a headache trying to sort it out.
They are all covered in 725.
Chapter 9 Tables 11A and 11B deal with the difference between Class 2 and 3.
I get cross eyed looking at.
As far as what $Smart said, here are two links that may elaborate a little. They mention when Class 1 is a CCC or not.
http://ecmweb.com/code-basics/classifying-and-using-class-1-2-and-3-circuits
http://forums.mikeholt.com/showthread.php?t=67679
mbrooke
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Ok, class one is 30 volts and under limited to 1,000 va.
If you wanted to go 120V AC, you'd have to go Class 3, Not Inherently Limited Power Source(Overcurrent Protection Required), Over 100 and through 150. See Chapter 9 Table 11(A).
mbrooke
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Do you know the rule number?
My thinking was this (correct me if its wrong)
Assume worse case 1.5-2 amps per conductor and use the 90*C column 310.15 B (16) with de-rating from 310.15 (B) (3) (a). Would this in theory be permitted? Conductor type is THHN/THWN-2.
If you look at Table 11(A) you'll see you're limited to a 1A ocpd. Any power level greater than that is considered power and lighting.
As to the scenario you mentioned, derating would be required... but exactly what do you want to know is permitted? Put 'em all on 2A fuses and you can stuff a conduit... :happyyes:
mbrooke
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The typical 120 volt motor control circuit is a class 1 circuit. Only class 1 power limited circuits are required to be 30 volts or less.
Darn... I keep forgetting about (B).
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That is probably the most common Class 1 circuit, by far.
mbrooke
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Wait Im confused now. (Not your fault, this is just a tough subject to understand on my part) :dunce:
What is the difference between class 1 , 2 and 3? :blink:
With all three, it is basically the classification of the power source and its power limitations... and permitted wiring methods follow...
...but with Class 1 non-power limited of 725.41(B), the circuit power source and overcurrent protection requirements are very similar to normal 600V power and lighting circuits... but these circuits can only be used for remote-control and signaling purposes.
mbrooke
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Got it.
BTW, an engine start circuit for a back up gen would fall under what category?
Yeah... I know... but for some reason my brain just treats the wiring like a normal P&L circuit because the CCC count has seldom been an issue in my experience. Not saying it's never an issue... just saying I've not run into it personally.That is probably the most common Class 1 circuit, by far.
One of the three... :slaphead:
Now how am I supposed to say which of the three without the pertinent details. :angel:
mbrooke
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Oh, but what would make either or fit a certain category?
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