- Location
- Illinois
- Occupation
- retired electrician
If you have a raceway that has motor control circuit conductor and more than 3 motor circuit conductors in the raceway, are you required to derate the motor circuit conductors?
motor circuit condutor derating
- Thread starter don_resqcapt19
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TTBOMK, yes.
resistance
Senior Member
- Location
- WA
I believe I agree with Smart. Not sure if it applies, but If surface metal raceway, then see 386.22.
Since the OP mentions the more generic term raceway, that's a very good point. Also needing noted are wireway and cable tray installations having different derating requirements.
- Location
- Illinois
- Occupation
- retired electrician
I was not really thinking about raceways other than conduit.
Neither was I in my first reply
kwired
Electron manager
- Location
- NE Nebraska
I have always thought that the control conductors do not have to be counted as current carrying conductors when derating conductor ampacities. It has been a long time since I had made that conclusion and am not sure if there have been changes in code since then. What I am finding now seems to be clear that the control conductors do not need derated, but is not clear whether or not the other conductors need to include the controls when determining how many current carrying conductors are in the raceway.
I haven't looked but I think a few code cycles back some of this information was in 430 and has moved to 725, don't know if it just moved or if there were changes to the content also.
I haven't looked but I think a few code cycles back some of this information was in 430 and has moved to 725, don't know if it just moved or if there were changes to the content also.
It is still just power and lighting conductors get derated.
OP stated, "more than 3 motor circuit conductors in the raceway".
kwired
Electron manager
- Location
- NE Nebraska
Well yes you do derate the motor conductors if more than three no matter what else is in the raceway, except cold temperature in the raceway allows for uprating on top of the derating.
- Location
- Illinois
- Occupation
- retired electrician
Code section?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
the control conductors are quite likely limited energy class 1 circuits. If so, pretty much by definition they are not CCC for derating purposes IMO.
However what you asked was if you have more than 3 motor conductors. my answer would be that the control circuits are not CCC, but the motor power circuits are and thus derating applies if there are more than 3 of them.
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- Location
- Illinois
- Occupation
- retired electrician
Bob,
As I asked the previous poster, what code section requires that the motor conductors installed in a common conduit with the motor control conductors have to be derated if you have more than 3 motor circuit conductors?
As I asked the previous poster, what code section requires that the motor conductors installed in a common conduit with the motor control conductors have to be derated if you have more than 3 motor circuit conductors?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
There is a general requirement that more than three CCC in a conduit require derating. why would that not apply to motor circuit conductors? I don't recall seeing an exemption to the derating requirements for motor circuit conductors.
- Location
- Illinois
- Occupation
- retired electrician
Did you read the code section?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
what code section?
- Location
- Illinois
- Occupation
- retired electrician
The one that says you have to derate when you have more than 3 current carrying conductors in a raceway or cable.
Which code section? 310.15(B)? If so, I have read it in its entirety several times over through the years. :happyyes:
There is nothing there which excepts motor circuit conductors in conduit from ampacity adjustment.
Is there a point or purpose to this query???
Don,
I think I see what your getting at. Because the last paragraph of 310.15(B)(3)(a) does not reference Article 430, motor circuit conductors are not included. However, I think Bob is correct that there is a general rule. The last paragraph of 310.15(B)(3)(a) applies where "different systems" as provided in 300.3 are installed in a common raceway. So what are the different systems provided in 300.3? It appears to be AC, DC, or above 600 volts. Motor circuit conductors would not typically be a different system, nor would motor control circuits tapped from the motor branch circuit for that matter, and would require adjustment.
I think the intent is to differentiate control circuits from power circuits, but the method leaves a lot to be desired.
I think I see what your getting at. Because the last paragraph of 310.15(B)(3)(a) does not reference Article 430, motor circuit conductors are not included. However, I think Bob is correct that there is a general rule. The last paragraph of 310.15(B)(3)(a) applies where "different systems" as provided in 300.3 are installed in a common raceway. So what are the different systems provided in 300.3? It appears to be AC, DC, or above 600 volts. Motor circuit conductors would not typically be a different system, nor would motor control circuits tapped from the motor branch circuit for that matter, and would require adjustment.
I think the intent is to differentiate control circuits from power circuits, but the method leaves a lot to be desired.
The different systems are just that, i.e. any system powered by utility [direct], an SDS, or a DC power supply, for example.
That paragraph additionally lists Articles 210, 215, 220, and 230 regarding power and lighting conductors. What about items listed in Table 210.2 and Table 220.3?
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- Location
- Illinois
- Occupation
- retired electrician
If the article reference was not there, then I would agree that the motor circuit conductors are covered by this rule. When they added the article reference, they made is very clear that the conductors installed under the rules found in Article 430 or 440 are not required to be derated.
Maybe the rule is intentional as the motor circuit conductors are already derated to 80%.
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