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#53623 - 06/30/05 03:52 PM raceway fill
drgnz23 Offline

Registered: 02/17/02
Posts: 56
Loc: los angeles
I having a discussion with one of the older guys about conductors in a 1/2 conduit. I look it up in the code book but its kind of confusing. For example (SIMPLE) 1/2 emt only 9 thhn wires .Is one of those a ground?

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#53624 - 06/30/05 03:55 PM Re: raceway fill
resqcapt19 Offline

Registered: 11/10/00
Posts: 2209
Loc: IL
The wire fill is a physical count of the wires in the raceway. What function the wires serve does not enter into this.

#53625 - 07/01/05 08:12 AM Re: raceway fill
Radar Offline

Registered: 04/30/04
Posts: 349
Loc: Los Angeles, CA
This information is based on Table 1 in Chapter 9 of the NEC, which specifies maximum raceway fill:

53% max for a single conductor in the raceway (i.e. - grounding conductor)
31% max for two conductors
40% for 3 or more conductors

The unused volume of air space within the raceway is needed for cooling of the conductors which tend to warm up due to conductor heating caused by current flow thru the circuit conductors. Overstuffing a raceway, aside from making for a difficult pull, would contribute to conductor overheating by reducing the cooling medium.

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