Derating question

[Ramfan4life83@gmail.com]

I could swear that I read somewhere that if the cross sectional area of a raceway is 4" or larger you do not need to derate for ampacity, but I can't find where. Can anyone help?

 

[Dennis Alwon]

Never heard of that. The pipe can be huge however the conductors will still be laying atop of each other on horizontal runs so derating must apply

 

[ggunn]

I could swear that I read somewhere that if the cross sectional area of a raceway is 4" or larger you do not need to derate for ampacity, but I can't find where. Can anyone help?

You may be thinking of gutters. They have different derating rules.

 

[infinity]

No such rule, install 4-#14 CCC's in a 4" conduit and derating still required.

 

[roger]

I could swear that I read somewhere that if the cross sectional area of a raceway is 4" or larger you do not need to derate for ampacity, but I can't find where. Can anyone help?

When you remember who told you that find them and slap em.

A heating element will heat any size oven, the larger ones just take longer.

Roger

 

[infinity]

I've always felt that this was kind of bogus, after all I can put 30-#12 CCC's in a 2X2 wireway (cross sectional area of 4" sq inches) without derating but I cannot put more than 3-12 CCC's in a 4" EMT (cross sectional area of 18.75 sq inches) without derating. :roll:

In my mind the only justification I came up with is that tubular raceways tend to be used in longer lengths than wireways but that really shouldn't matter.