Derating question

Status
Not open for further replies.

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
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

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
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.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
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

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
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.
 
Status
Not open for further replies.
Top