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Electrical Wiring

4 wire oven, 3 wire circuit

17 years ago

I hate to rehash this, but I'm a little confused by previous threads on the topic.

This is the situation:

I have a 240v oven in my kitchen that was probably installed in the 80's. It is a 4 wire oven, and it is connected to a 3 wire 240v circuit, where the bare copper and the white from the oven are connected to the white wire fron the wall.

I have a new 4 wire oven that I want to install in the same spot.

Looking through Gardenweb, it seems like it might be against code to wire the new 4 wire oven into the 3 wire outlet, even though it's already done that way.

This only needs to last 6-9 months, since we are tearing out the kitchen, and we just happened to get this new oven early in the process.

Also, assuming it is ok to wire it this way, the wire looks thinner than the wires that go to the electric cooktop (difference circuit). How can I tell what the gauge of the wire is? It's a double ckt breaker in the electrical panel, but I didn't check the amperage of the breaker.

If I need to get a new wire run, any thoughts on how much an electrician might charge for this? We have a crawlspace, it's maybe 25' from the electrical panel, and we don't care if the electrician drills through the floor of the bottom cabinet.

Thanks for any help, sorry to rehash!

--Carey

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Comments (4)

petey_racer
17 years ago
An existing ungrounded "3-wire" feed can be used for a new 4-wire appliance. You just cannot run a new ungrounded 3-wire feed any more by code.

The code is not retroactive so that you have to rip this circuit out right now. Wait until you remodel.
ckk1
Original Author
17 years ago
Thanks for the quick reply!

Any idea how to tell if the wire gauge is good enough? I assume if it's a 20 amp breaker, then the wiring is probably up to handling the new 20 amp oven (I worry that the current draw of a new modern convection oven will be higher than a 20 year old oven, but it might actually be less given modern materials...)
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How to wire 240v 4 wire appliance to 3 wire in wall?
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"The manual did stated that 110V or 240V was acceptable." I highly doubt this. I bet it was more like 120/240v, which is what a 240v 4-wire circuit is. The 120v receptacle on a 30A breaker is also a nice big code violation. You first need to confirm the requirements of the range. More than likely if it is a free standing electric range a 40A circuit is sufficient. If the old wire IS in fact #8 then you do have what you need to make it work. You can use an old 3-wire non-grounded 120/240v circuit if it is existing. This is one of the rare cases this is allowed. Confirm the wire size and get back to use. PLEASE don't just hook this thing up to #10 wire because it is there. You want to keep your family safe, and not trip breakers every time you cook.
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Ignoring the ground wires(since you know where they go) I can't be any clearer than this. You have two terminals(the part where you push the wire in next to the screw terminal is the same terminal, maybe that is your sticking point?) on the old switch. Let's call them line and load. The line terminal is the one with the 'mystery' wire. The load terminal is the other one. Take All the wires on the load side, marrette them to the load Side wire on your new device. Take the wire from the other terminal, marrette it to the other wire on the new device. Ta-da!
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thyron
17 years ago
if your existing circuit is 20 amps it is 12 guage wire. typically an electric range will require a 40 amp circuit which needs 8 guage wire. if its a gas range then a 20 amp circuit should be plenty.
ckk1
Original Author
17 years ago
Thanks!

--Carey

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