Freestanding range to cooktop + oven combo. Lots of data (kw, wiring, etc)
Long time listener, first time caller.
I am replacing an freestanding stove/oven unit with a separate cooktop and oven. I am not remodeling and this is a condo in California so running a new circuit is not preferable.
The freestanding unit is powered by a two 40 amp breakers that are connected together to if one trips, the other one trips as well.
The cable that runs from the breaker box to the freestanding unit is a 3 wire cable with a shielded ground (Black, White, Red, Green) The wire looks to be aluminum and it is very thick (much thicker than a 12 romex) but I am not sure on the exact guage yet.
The oven and cooktop are as follows:
Ikea Nutid oven: 120/240v 5.1KW 120/208V 3.8KW ( 4 or 3 wire)
Ikea Nutid cooktop: 120/240 6.7KW 120/208 5.8KW ( 3 wire)
I understand that I can power both appliances from a same branch circuit per NEC code: http://charlesrmiller.com/index.php?..._February_2009
The total KW for both appliances on a 240v circuit is: 11.8
The branch-circuit load is the maximum demand from Column C of Table 220.55 for one range. Therefore, the branch-circuit load for a circuit supplying power to one 6.7-kW cooktop and one 5.1-kW wall oven is 8 kW.
I need a circuit that is capable of handling 8kW . Converting 8kW to amps I get:
8 x 1000 = 8000 watts
8000 watts / 240 volts = 33.33 Amps
To me it looks like the current branch circuit in place is already capable of handling 40 Amps which is lower than the 33.33 amps required.
Did I miss my calculations here?
By the way, I have an electrician coming tomorrow since 240v connections confuse me but I do like to know what is going on with my house so I can be sure that the electrician is recommending the right thing.
Do you have the appliances yet?
One thing I'd be concerned with if you are planning on wiring this before the appliances arrive or till you can get a copy of the instructions, is many time the instructions spec a certain size circuit. If they do specifically spec the size circuit or wire size (sometimes they spec a wire size larger than the NEC would require) you have to go by their specs.
I looked up the oven and found it, but I couldn't find the literature on it.
Found this, not sure if its the exact same model, but its looking like you will need to run a new 240V circuit for one of the appliances.
If the cooktop is actually 120/240V like it says, then current code requires a 4-wire connection. 3-wire connections for 120/240V appliances are potentially dangerous and no longer allowed. If it is straight 240V (no neutral), then of course you only need 3 wires.
I dont have the appliances yet but I did get a hold of the manuals. Both manuals call for separate circuits. Is this a CYA recommendation from the manufacture or an actual safety issue?
Use 8 gauge copper wire.
A 4-wire or 3-wire, single phase, 240 volt, 60 Hz., AC only electrical supply is required on a separate, 40-amp circuit (30" [76.2 cm] models), fused on both sides of the line.
Use 8 gauge solid copper wire.
This oven must be connected to a grounded metal, permanent wiring system.
Models rated at 5.1 kW and below at 240 volts (3.8 kW and below at 208 volts) require a separate 30-amp circuit.
■ A circuit breaker is recommended.
■ Connect directly to the circuit breaker box or (fused disconnect) through flexible, armored or nonmetallic sheathed, copper cable (with grounding wire). See “Make Electrical Connection” section.
manufacturer specs trump the NEC
If you wire them both on the same circuit, even if you are following the NEC, and the inspector catches it, you will fail inspection.
You will also void any warranty if not to their specs.
ok. So the inspector will actually ask for the manuals.. great.
I will go find a cooktop and and oven that fit in my existing wiring since running a new cable will be a bit issue and my breaker box is full.
my second oven and cooktop choice do not required a separate circuit according to the manual . Manual is vague actually:
In this case, would the 40AMP double pole breaker and one circuit be sufficient?
Thanks for the help by the way.
You probably are not going to like this answer, but before you drop this kind of cash on these, you are going to want to make sure these can be used in the USA (I am assuming you are in the USA due to your NEC reference).
This is from the cooktop manual:
ha.. good one! they do have dealers here in the US. I will call fagor to the US manual for these appliances to see what is happening.
I thought this was going to be much easier since there is a already a freestanding unit in place. I don't understand why this requires a new circuit..
thanks for the help. Electrician will be here tomorrow to discuss but I feel like I am a lot more knowledgable about the situation right now.
To the OP: It appears you did your homework, in calculating the demand factor of the appliances, and assessing your present circuit's capacity.
I personally would not have a problem with doing the installation as you originally planned, with a single 40 or 50 Amp circuit feeding a junction box containing taps for both of the appliances.
I have seen cases where instead of a junction box, a small load center was installed and separate breakers used for each appliance. In reality such a scenario would satisfy the need for a "separate circuit" as some would advocate, but there would not be any difference in feeder capacity, making it more like an exercise in satisfying bureaucracy.
That is why the tap conductor rules of section 210.19 are present in the Code.
I agree with the above posts by KBuz My post is to help I hope clarify the possible reasoning behind the requirement.
Your free standing range is constructed and wired in such a way that it can generate up to a 40 amp load with multiple burners on and must be protected by a 40 amp ocpd.
Your new appliances combined may equal that load but individually they are not constructed to carry 40 amps thru their wiring and so if one is off and the other becomes overloaded in some fashion, the breaker might not pop before the appliance suffers a meltdown or worst case, stArts a fire.
Putting a small load center at point of use with the correct size ocpd for each appliance protects you, your appliances, AND the other residents in your building from a potential fire from an overloaded appliance on an oversized breaker.
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