Conduit or no?

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Old 10-05-19, 03:22 PM
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Question Conduit or no?

I will be running 10/3 cable around 30 feet to a VFD for a CNC (30 amps). I usually run regular 120 volt cables in conduit but was told by someone that you shouldn't run 10/3 (240 volt) in conduit because of temperature issues.

Is this true and is it against code, or is it OK to run the 10/3 inside some conduit?

As a side note I usually use Carlon non-metallic conduit if it makes any difference.

https://www.amazon.com/Carlon-Electr.../dp/B00FY3MUUQ
 
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Old 10-05-19, 05:14 PM
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It is not against code to sleeve NM cable in conduit as longs as some rules are followed.

The conduit must be sized large enough for the installed cables. This doesn't mean that the cable fits in the conduit. The cable cannot take up more than 40% of the conduit fill with 3 or more wires. For flat cables, the diameter is measured by the largest size. All this is to prevent heat buildup.

The conduit, if metallic, is required to be bonded to the equipment ground. In most cases this is done using metal boxes that the conduit attaches to.

Besides the items above installing cable in conduit can be difficult. The conduit needs to be fully installed before installing the wires and the outside jacket of the cable may not be removed.
 
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Old 10-05-19, 05:20 PM
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The conduit must be sized large enough for the installed cables. This doesn't mean that the cable fits in the conduit. The cable cannot take up more than 40% of the conduit fill with 3 or more wires. For flat cables, the diameter is measured by the largest size.
That would mean that 3/4" conduit would be OK to use with 10/3, correct?
 
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Old 10-05-19, 06:17 PM
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The NEC says that one wire (or cable) can use 53% of the area. So find out the diameter of your cable and do the math.
But...why do this (cable in ENT)?
 
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Old 10-06-19, 07:43 AM
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The NEC says that one wire (or cable) can use 53% of the area.
That is correct. "Cable" was added in 2014.

That would mean that 3/4" conduit would be OK to use with 10/3, correct
What is the largest dimension of your 10/3 cable?
 
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Old 10-06-19, 11:30 AM
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What is the largest dimension of your 10/3 cable?
Off hand I do not know, but I thought that wire gauge sizes were standardized so it shouldn't be too hard to find out.
 
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Old 10-06-19, 01:59 PM
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Wire, yes. Cable no. It varies between manufacturers. At one time three-wire cable was round but as of the past 5-6 years, they have gone to a flat cable.
 
 

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