ECN Forum Forums Code Related Discussion NEC & other Code issues Cooktop and hood fan

Can a 120V exhaust hood be hardwired to the same circuit as the electric cook top?

Please give NEC

Thank you
Edward

Unless you have a 1hp motor in that hood or supplimental O/C protection, 430.52 will do it. I suppose the manufacturer's instructions will enter into it too. 110.3(B)

I can't think of anything that would allow you to do this.

section 210-19(C) exc.1.
" Tap conductors supplying electric ranges,wall mounted ovens and counter mounted electric cooking units from a 50Ampere branch circuit shall have an ampere not less than 20 and shall be sufficient for the load to be served. The tap shall not be longer than necessary for servicing the appliance"

What is the difference (besides the obvious Exhaust hood is not a cooking unit)between a counter top cooking unit and an exhaust hood if the tap that i am using has a 20Amp capacity(12AWG)?

Edward
Thanks

It is not a "Cooking Unit" a "Range" or a "Wall mounted Oven"

Shortcircuit,
I know that and i have clearly stated my understanding that there is a differnce between a cooking unit and an exhaust fan.
My question is why a 20 Amp tap is permitted for a cooking unit with an OCPD of 40-50 Amp but you say it is not permitted for an exhaust fan.

Please explain WHY NOT? What is the reason behind it.

Edward

Edward...I'm not sure WHY NOT except that 210.19(C)prohibits it indirectly. But I will research it some more. Most of the fancy hoods that we have installed, the directions state that a seperate circuit is needed and limit the overcurrent protection to a 15 or 20 amp breaker...what type of hood fan are you installing?

Boy u were up late last nite:< )

Edward,


Because they said so!



Sorry,

I will go out on a limb here and just give a wild guess that when a cook top is designed it is done so with the knowledge that it may be tapped from a 50 amp circuit per the NEC. To that end the wiring inside the cook top is heavy enough to trip a 50 amp overcurrent protective device in the event of a short circuit or ground fault. Overload is not possible as the connected load will never increase.

I would bet that there are no conductors used in cook tops smaller than 14 AWG.

Take a look at the allowable ampacities for cords and fixture wires in 240.5(B)(1) & (2). I realize that those sections are not directly applicable but I believe they are a good indication of what size conductor the NFPA believes can safely trip a 50 amp overcurrent protective device.

Now think of the typical 120 V exhaust hood, the conductors inside are likely to be 18 AWG. Going back to 240.5(B)(1) & (2) it seems the NFPA believes 18 AWG should be on a 20 amp overcurrent protective device max.

Even though we do not think about it much, the overcurrent protection we provide is also the overcurrent protection for the utilization equipment.

IMO this is one of the reasons you can not protect a 20 amp outlet with more than a 20 amp overcurrent device or in the case of a electric water heater you can not have overcurrent in excess of 150% the nameplate current.

All of this goes hand in hand with the UL listing of the equipment.

Take all this for what it is worth, it is just my opinion.

Bob

[This message has been edited by iwire (edited 08-05-2004).]

Thank you for all your input. I am not trying to argue rather understand the reason behind it. Please allow me to explain my situation.
What homeowner had was a combo cooking,hood unit of somesort. Where the 240V provides power to all units(cooking unit and the hood) Now they have two separate unit cooktop and a hood. and all we we at that location is a 240V/40A.
I though about getting power from an near by counter receptacle but i can not because the backsplash is granit.

So what would you suggest i do?

Thank you
Edward

Edward,

That wouldn't be right either. Find an outlet on a general lighting circuit.

Bill