What you can (or maybe lucky to get always with) and what you should do for ultimate safety, are different things. The manufacturer has a reason for the requirements. I sure as hell won't tell you to try it knowing the recommendations are different.
You can do anything you want (unless it's getting inspected), because it's your house, and very few people will care if you burn it down. What you are SUPPOSED to do, is install one 30amp breaker and one 40amp breaker. Then run two separate lines to each appliance. It's ok to use the existing wire for one of the circuits. You can probably use the same box for both wires, but every box has a maximum capacity, mostly for heat build up purposes.
Assuming you mean "Should I . . .", the answer is no, since the manufacturer recommends using separate circuits.
240V circuits don't have a neutral, and your two circuits should not share any wires.
If the box is large enough. That's entirely a box fill issue, as far as I know.
My suggestion: leave the existing 60 amp wire and box, change its breaker to 40 amps, and use it for the 40 amp load. For the other load, run a separate, new, 30 amp line with a new box.
Thanks Wayne. That's what I'm going to ask my electrician to do. I hope fishing the #10/3 thru the steel conduit with #6 wires in there won't be a problem. The good news is, the breaker box is also in the kitchen.
As far as some of the other replies go, I have no intention of going against the code, but as I said in my first post, I got conflicting answers from licensed electricians, and just wanted to clarify things.
If any licensed electrician told you anything other than using two separate circuits, stay away from him. Fishing a new wire next to an existing wire in a conduit is sometimes a pain. Depending on the size of the conduit, it might be easier (and faster) to use the existing #6 wire to pull 2 completely new sets of wire.
As long as you have a cabinet or some place to hide it. I don't think you're allowed to hide it behind the stove, and most people don't want to look at it all the time.
This is what I got from the NEC handbook 2005 (Article 220, table
220.55):
"..the branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch-circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range."
The handbook also explains (has a picture 210.21) how to pick tap conductors when installing oven and cooktop on the same circuit under
Note that the branch circuit is limited to a max of 50 Amp rating, so you would replace the 60A breaker with a 50A unit.
On a side note, if the raceway will be used as the equip ground (raceway does not contain a grounding conductor), I would verify the integrity of the raceway connections (fittings) to perform as an effective grounding means. Jim
I havn't looked at this stuff since about 1903 but my reading of the code is:
210.19A3 requires the circuit for a range to be at least the rating of the range and/or cooktop
however
422.10A allows the branch circuit for household cooking units to be sized from 220.55
220.55-table-note 4 allows combining the KVA values and treating as a single unit
220.55-table-note 1 the value that can be used for your units is 8KW +(5x5%) = 10KW = 41.7A @ 240V (this is different from the value you came up with but still a 50A circuit)
210.19A3-exception 1 allows tap conductors to your cooktop to be rated
20 amps (or larger) if the circuit they are tapped from is protected at 50 amps and tap conductors are large enough for cooktop and the tap is only as long as it needs to be (this requires you to reduce the 60A circuit to 50A as noted in Jim's post)
422.30 requires a disconnect for the units
422.31 allows a circuit breaker to be used as the disconnect but only if in sight of the appliances or if equipped with a device to lock it open (not likely in your case)
422.33A allows an accessible plug and receptacle to be used as the disconnect (that is one reason ranges are commonly connected with plugs)
422.33B allows a plug and receptacle to be used as disconnect for a range if it can be reached by removing a drawer
422.16B3 allows wall mounted ovens and cooktops to be cord and plug connected if the plug and receptacle are rated for the temperature they are exposed to
210.21 allows a receptacle to be sized acording to 220.55 (instead the unit KVA size)
(Presumably you need to figure out a disconnecting means - I don't know what is common for hardwired units. Good question for the inspector.)
You are right: 8 + ( 8 x 24%) = 9.92. (I had used 8.4kW instead of
7.2kW, but forgot to update in the post.)
in sight of the appliances These are going to be hard-wired, but the circuit breaker (panel) is also in the kitchen (right across from the oven and cooktop), so I assume I'm covered there.
I'll reduce the circuit to 50 amps. (BTW, I already have a #6 cable there.)
Bud, you are right. For 7.2kW, combined kW is 8 + 8 x 24% = 9.92. (My calculations were based on 8.4kW instead of 7.2, and I forgot to update the post.)
The circuit breaker (panel) is actually in the kitchen (just across the oven and the cooktop), so I assume I'm OK. I'm going to reduce the circuit to 50 amp (use the existing 6 gauge cable).
no, no, and subject to local code the box is probably too small. a licensed master electrician who sees the jobsite and your appliance and its manual will give you the best answer. and the electrical permit inspector will make sure he's correct. see also
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