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ctraut 11-12-2006 12:01 PM

Is existing microwave and oven wiring safe?
I am presently remodeling my kitchen. The existing microwave and oven are wired as follows:

A #6 wire 240 volt circuit protected by a 50 amp fuse runs to a metal junction box in the cabinet. The oven is wired directly to the the 240 circuit. Also wired in this junction box is a #12 wire connected to one of the hot conductors and going to a 20 amp receptacle for the microwave. Is this a safe wiring practice? I would prefer to not have to run a new 120 volt dedicated circuit for the microwave as it would be alot of work and be expensive. If the existing wiring is not safe, is there another way of wiring the microwave and oven off of the same circuit without having to pull a new circuit? Any help or suggestions would be greatly apppreciated.

Electrical Requirements for the new microwave:
120 volt, 60 Hz, 15 amp circuit and draws 1.8 kilowatts.

POWER / RATINGS for the new oven:
Amp Rating at 208V 20
Amp Rating at 240V 20
Bake Wattage 2700
Broiler Wattage 3600
Convection Wattage 2500
KW Rating at 208V 3.0
KW Rating at 240V 4.0


Square Eye 11-12-2006 06:11 PM

You need a separate 20 amp circuit.

The #12 wire could get extrememly hot before the 50 amp breaker would blow... house-fire hot..

You'll be far better off with a new circuit.
Welcome to the forum,

petey_racer 11-12-2006 06:12 PM

The way it is now is absolutely not safe.
This oven does not have a very large draw. I would assume somewhere along the line a larger oven was replaced by this smaller one.

The only ways this can work is if you:
a) run a new circuit to the micro
b) are able to use the existing line as a sub-feed to supply a small sub panel. From this panel you can install a 2-pole 20 for the oven and a single pole 20 for the micro.

Two key factors must be met:
1) You have an accessible place to put the panel that meets clearances.
2) The existing cable is a 3-wire plus ground cable.

Provide some more info about these two issues.
What is written on the cable.

ctraut 11-12-2006 06:33 PM

Petey Racer and Square Eye,

Thanks for your help. I thought that was probably the case. The supply wire is a 4 wire (2 hots,1 neutral and 1 ground). I considered the possibility of putting in a small subpanel (30 amp 2 pole circuit breaker for the oven and 20 amp circuit breaker for the microwave). Is it legal by code to place a subpanel in an easily accessible kitchen cabinet? The cabinet is 36" w x 36" tall. Based on the wattage it would appear that a 20 amp 2 pole breaker would work for the oven. Is 30 amp too large?

Thanks again for your help.

petey_racer 11-12-2006 09:27 PM

You cannot have the panel in the cabinet. The clearance must be 30" wide and 36" deep, 6'6" high.

ctraut 11-14-2006 08:45 AM

Thanks to everyone for the help. I have decided to pull a new home run for the microwave.

I have a similar problem at the kitchen island which has a cooktop. Again I have a #6 romex 4 wire feed protected by a 50 amp circuit breaker coming up through the slab. Originally this supplied the power for both the cooktop and an exhaust fan. I plan to install a new cooktop and telescopic downdraft fan and then by code I need 2 new receptacles. I am planning to sawcut from a perimeter kichen wall and feed the exhaust fan and 2 receptacles off of one of the kitchen circuits (a 20 amp circuit for the dishwasher).

Power requiements for new appliances:

POWER / RATINGS for Cooktop
Amp Rating at 208V 30
Amp Rating at 240V 40
KW Rating at 208V 5.6
KW Rating at 240V 7.4

POWER / RATINGS for Ehaust Fan
Amp Rating at 120V 4.0

POWER / RATINGS for Dishwasher
Calrod Heater Watts 875
Volts/Hertz/Amps 120V ; 60 Hz ; 9.1 A

Is this a good way to supply the power for these appliances or is there a better way? Also, if I sawcut the slab what depth of concrete coverage do I need over the conduit. I'm planning to use 1/2" liquid tight flexible nonmetallic conduit type LFNC-B. Will this work?

Thanks again for the help.


Square Eye 11-15-2006 11:53 AM

If I were you, at the island, I would mount a flush mount circuit breaker protected disconnect on one of the least noticeable places you can find. Make sure it doesn't interfere with the movement of the drawers, mount it so it's accessible from outside the cabinets and flush with the surface. It needs to have a cover over the breakers, but a waterproof enclosure is not necessary. Run your #6 to the disconnect, into 20 amp breakers, and run #12 to the receptacles.

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