Hooking up a new double oven today at one of our sales guys house, the exsisting wiring was #10, the new oven is a 9kw, manufacture calls for 40 amp ocp. With this being a 37.5 amp load, a 40 amp breaker and circuit will not meet NEC minimum breaker size. Do I violate the NEC with a 40 amp breaker? or do I violate the manufactures instructions with a 50 amp breaker?
My take on this (just trying to work it out - not saying this is correct...)
Based on 2008 NEC:
Appliances:
422.10(A) "...Branch circuits and branch-circuit conductors for household ranges and cooking appliances shall be permitted to be in accordance with Table 220.55 and shall be sized in accordance with 210.19(A)(3)."
Table 220.55, Column C for 1 appliance (I'm assuming, since you have 1 nameplate and your are under 12KW), permits the branch circuit to be sized for a maximum 8KW demand.
This equals 33.3A at 240V, so your branch-circuit is rated at 33.3A. The conductor size is based on this, and the OCP is based on the conductor size.
8AWG and 40A seems appropriate.
Sound good?
kent