iwire said:the nec allows a 40 amp breaker to carry 37 amps for up to 3 hours at a time. There is no way that unit will ever draw 37 amps for more than 3 hours continuously
40A @ 80% = 32A
I dunno, I'm with pfalcon on this one. The NEC has to address such a grand range of issues that it's requirements and recommendations can't help but contain inaccuracies. The mfg. requirement may look lower numerically, but they may provide the more stringent protection.
Are you new to this biz? :grin:
This is so not true based on some of the stuff I've installed through the years.
Just didn't want to give a newbie the impression they could put a continuous load of 37A on a 40A breaker... that's all.Yes, thanks for pointing out what I already knew. :grin:
You already managed to answer for me ...Can you now tell me why your pointing it out?
Hillbilly's load was actually 37.5 but I was simply pointing out the 40 amp breaker could carry 40 amps (exceeding his 37.5 amp load) for 3 hours or less.
As a side note, the manufacture did not print the 40 amp as being the "Max size brkr", so #6 and a 50 amp would be legal.
...manufacture calls for 40 amp ocp...
... or do I violate the manufactures instructions with a 50 amp breaker?
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:
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.