90 Degree wire chart for Secondaries


When we are pulling Secondaries to switch gear, can we use the 90 Degree rating on condutors, the same way
as when we are pulling wires in emt for circuits ?
Thx Ron

charlie b

Staff member
Let's be clear here. You can use the 90C column as the starting point for derating, presuming the conductors have 90C rated insulation. If for example you plan to run more than three current-carrying conductors in the same conduit. But you cannot just take the value in the 90C column and base your installation on that value.


Staff member
Conductors from a transformer secondary to switchgear, is actually one place where you may be able to use the 90°C rating. These conductors often land on bus bar at that switchgear that does not have the 75C° limit. Same with some transformers, no 75°C limit.