oven/cooktop wiring

bhoublonJanuary 5, 2011

I have a range fed by 6/2 al wire on a 50 amp breaker. I want to replace the range with a cooktop plus wall oven. They are rated at 5.8 and 7.2 kW.

If I add up and apply the demand factor I get 35amps.

Can I replace the wire with 8/3 copper and put it on a 40 amp breaker? The run is 50 feet.

Thanks

B

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brickeyee

At least part of the answer will depend on what the installation instructions for the separate pieces say.

Sharing of a larger than required branch circuit can result in wiring being to small to sustain adequate fault current to trip the protection on the circuit.

This can leave equipment wiring to act as a fuse in the circuit if a fault occurs.

.

    Bookmark   January 5, 2011 at 9:20AM
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bhoublon

The installation says 30 amp for the oven and 40 amp for the cooktop.

    Bookmark   January 5, 2011 at 9:41AM
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brickeyee

The multiple unit demand factor?

It does not apply inside a single unit.

    Bookmark   January 5, 2011 at 2:17PM
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bhoublon

It is a separate cooktop and single wall oven, installed in the same countertop space.

    Bookmark   January 5, 2011 at 3:03PM
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brickeyee

The demand factors do not apply to equipment in the same space.

    Bookmark   January 6, 2011 at 9:08AM
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bhoublon

Is that part of 220.55? I as assuming that I can handle one cooktop and up to two wall ovens on the same circuit as a range and apply the demand factor. I could not find a reference about the placement of the units.

Thanks

    Bookmark   January 6, 2011 at 9:37AM
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bhoublon

All I can find is: "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."
A range would have everything in the same space, too...

    Bookmark   January 6, 2011 at 9:52AM
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normel

I would go ahead and use 6/3 NM for the wiring. That would allow for future upgrading of the cooktop or oven. Your plan for installation is correct.

    Bookmark   January 6, 2011 at 9:54AM
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brickeyee

"...adding the nameplate rating of the individual appliances and treating this total as equivalent to one range."

That means you just add them up, no demand factor.

I would still be inclined to run separate branch circuits to avoid dealing with larger conductors.

    Bookmark   January 9, 2011 at 4:06PM
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joed

Since you plan on runnng a new cable, why not use the old cable for the oven and run a new cable for the cook top.

    Bookmark   January 10, 2011 at 8:20AM
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bhoublon

There is no space in the panel left for another 240V two-slot breaker. The current 50amp breaker has two additional 20amps on each side. I want to replace it with a normal 40amp two slot breaker, and add 2 double pole breakers in place of standard breakers to make up for the 20amp slots.
They are dishwasher and garbage disposal,so no worry of need to balance the load.
The cable is Al, I thought I would be safer with cu.

How could I connect the #6 and two #8 or one #8 and one #10 in the box and avoid a wire nut?

Thanks

    Bookmark   January 10, 2011 at 10:56AM
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brickeyee

The garbage disposal and dishwasher do not need their own 20 amp breakers.

    Bookmark   January 10, 2011 at 2:23PM
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joed

Panel is full. Add a sub panel.

    Bookmark   January 10, 2011 at 2:42PM
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