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-   -   Freestanding range to cooktop + oven combo. Lots of data (kw, wiring, etc) (http://www.diychatroom.com/f18/freestanding-range-cooktop-oven-combo-lots-data-kw-wiring-etc-139463/)

 made2last 04-06-2012 06:08 PM

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.

 k_buz 04-06-2012 06:36 PM

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.

 k_buz 04-06-2012 06:48 PM

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.

Quote:
 The oven requires its own dedicated 30 amp 240 volt circuit.
source

 mpoulton 04-06-2012 06:51 PM

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.

 made2last 04-06-2012 06:52 PM

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?

Cooktop:

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.

Oven:

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.

 k_buz 04-06-2012 06:54 PM

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.

 k_buz 04-06-2012 06:55 PM

You will also void any warranty if not to their specs.

 made2last 04-06-2012 06:55 PM

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.

 made2last 04-06-2012 07:12 PM

my second oven and cooktop choice do not required a separate circuit according to the manual . Manual is vague actually:

Cooktop
VFA70=5,9 KW
http://www.fagoramerica.com/content/...2520Manual.pdf

Oven:
3.6 KW
http://www.fagoramerica.com/content/...l%25200710.pdf

In this case, would the 40AMP double pole breaker and one circuit be sufficient?

Thanks for the help by the way.

 k_buz 04-06-2012 07:32 PM

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:

Quote:
 This device conforms to European directives 73/23/CEE and 89/336/CEE
Maybe someone else will come along to help out, but I would double and triple check.

 made2last 04-06-2012 07:38 PM

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.

 kbsparky 04-06-2012 08:47 PM

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.

 Evstarr 04-07-2012 12:19 AM

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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