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#45606 - 12/03/04 10:51 AM adapting 240v to 120v  
rmiell  Offline
Joined: Nov 2000
Posts: 242
La Junta, Co. USA
Here is a question I received on another board. Any thoughts?

Question -
I am in the process of remodeling my kitchen. I have purchased a separate single built in Oven and a separate built in microwave oven to be installed directly above the oven. These two new separate units are replacing a single combination oven / microwave. The issue is the old unit was simply hard wired to a 220 / 240 connection, there was only one connection to power both units. My new oven requires the 220 / 240 but the microwave is simply corded for 110/120. My question is this can I tap off of the 220/240 and create a 110 / 120 outlet for the microwave and still hardwire the oven to the same 220 / 240 line. While I believe the simple answer to this is yes will it be to code (I am in California) and do I have ample circuit protection on the microwave as it will be on the 220 / 240 circuit which I believe is a 50A? My alternative is to tap into an existing wall outlet which is possible but more work. Which is the best solution?
Answer -
Hi Tom.

You cannot tap onto the 50amp circuit for a 120v outlet. I would also suggest that you do not tap into an existing circuit for the microwave, but get a new dedicated circuit pulled in for it. The microwave is a large load, so a seperate 20amp, 120volt circuit should be used for it.

Hope this helps.

Rick Miell

follow-up question

Rick - thanks for the answer, the interesting thing here is that I received a different answer from another qualified source. Can you explain the specific on why I should not tap off from the 240?

In addition to the standard 120 outlet nearby which all agreed is not a good source as the micro will like trip the breaker I have a Fridge outlet which I think is at least 20A maybe 30A. Could I tap into that to get the microwave outlet (it is being used by the Fridge) as a options to pulling a new dedicated line.


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#45607 - 12/03/04 11:13 AM Re: adapting 240v to 120v  
jdadamo  Offline
Joined: Nov 2004
Posts: 37
Calgary, AB, Canada
They could put a 50A sub and then run 40A to the stove and 20A to the microwave... right?

Are US stoves 40A yet or are they still 50A?

Diversity of loads should allow this, eh?

#45608 - 12/03/04 05:39 PM Re: adapting 240v to 120v  
Electricmanscott  Offline
Joined: Jan 2002
Posts: 1,457
Holden, MA USA
Sounds like this person has no business doing this work.

#45609 - 12/03/04 06:24 PM Re: adapting 240v to 120v  
Steve Miller  Offline
Joined: Aug 2001
Posts: 325
Loudoun Cty, VA
Ref tapping the 240: 1) where are you getting the neutral? Was it a 4 wire? Using the third wire on a 3 wire range circuit for the neutral is a no no. 2) The 120 outlet is rated for 20amp max. If you tap the 240 that's 40 or 50. jd has the right solution (sub panel and 2 circuits) and that assumes you have 4 wires (or 3 insulated and a metal pipe).

[This message has been edited by Steve Miller (edited 12-03-2004).]

#45610 - 12/03/04 06:39 PM Re: adapting 240v to 120v  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,211
SI,New Zealand
This doesn't sound too cool.
I'd personally go along with Rick and recommend the new dedicated circuit from the panel. [Linked Image]

Let's face it, these days if you're not young, you're old - Red Green grin

#45611 - 12/03/04 06:51 PM Re: adapting 240v to 120v  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Steve I agree we can not tap the range outlet for a 20 amp outlet

I do want to comment on this.

Using the third wire on a 3 wire range circuit for the neutral is a no no.

The wire you are talking about is a neutral it is not a grounding conductor, the stove or dryer uses this conductor to run the 120 volt loads, motors, lamps etc.

The code did permit the neutral to be used as EGC, it did not allow the EGC to be used as a neutral.


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