COMMUNITY FORUM

p0ps

05:26PM | 06/02/02
Member Since: 06/01/02
9 lifetime posts
Bvelectrical
My question is this.

An existing outlet has a 10 gauge wire and 30 amp breaker on it already. I would like to put a stove in this spot now but the documentation for the stove says I should have it on a 40 amp circuit even though one of the plugs I can buy for it has 10 gauge wires in it. So, my question is do I have to re-wire the whole run for this (this will involve ripping out cabinets and drywall). Or can I get away with a 30amp breaker and 10 gauge wire for the stove?

Will the stove really need to draw over 3600watts provided by the 30 amp circuit? I can't just use the 10 gauge wire and a 40 amp breaker can I?

I've done a considerable amount of wiring before including 220v outlets. I just have never run into the situation where ripping out the 10 gauge is a nearly impossible task.

rpxlpx

06:06AM | 06/03/02
Member Since: 03/13/00
1674 lifetime posts
If your stove uses no more than 3600 watts (as you mentioned) and that's at 220/240 volts AND there's nothing else on the circuit then the 10 guage wire ought to be safe. The reason I say this is that most electric water heaters use 4500-watt/220v elements and run them on 12 guage wire (which is a size smaller).
As to the breaker size - do the math. 3600 watts divided by 220 is a little over 16 amps; divided by 240 is 15 amps.
Question: if all surface burners AND the oven were on at once, would that go over 3600 watts?

p0ps

10:45AM | 06/03/02
Member Since: 06/01/02
9 lifetime posts
Thanks for the quick response.....more clarification:

Well just to be clear. The documentation for the stove didn't say exactly how many watts it would be using. The documentation just said that you should have it on a 40 Amp circuit. And, since there is already 10 gauge wire there which is obviously capable of supporting 30amps I want to reuse what's there. I don't believe it would be safe to use a 40amp breaker with the existing wire.

I guess I'm wondering about whether or not the stove could ever consume 3600 watts. I mean is that even realistic.

What's the worst that could happen if the stove maxes out what the breaker will provide? The wiring should be rated to handle more than 30amps. The breaker should limit consumption to 30amps. Will parts of the stove just not work???

rpxlpx

05:21AM | 06/04/02
Member Since: 03/13/00
1674 lifetime posts
All parts of the stove will work properly until/unless the breaker trips.

If nobody else responds with precise numbers as to what current 10-guage wire can handle, you could stop into your local store that sells electrical wire and read the label on the 10-guage wire.
I think it'll handle a 40-amp circuit OK, but don't have the for-sure info. Assuming the 10-guage wire will safely handle the power requirement, you should be OK replacing the 30-amp breaker with a 40.

Remember, I'm assuming there's nothing else on that circuit.

[This message has been edited by rpxlpx (edited June 04, 2002).]

p0ps

06:16AM | 06/04/02
Member Since: 06/01/02
9 lifetime posts
No need to assume. There is nothing else on that circuit. It is currently a dedicated circuit with 10-3 and a 30amp breaker.


rpxlpx

08:17AM | 06/04/02
Member Since: 03/13/00
1674 lifetime posts
I just found this table on the Web.
Wire Gauge Amps
14 15
12 20
10 30
8 40
6 65
With that in mind, your stove could use up to 7200 watts without max-ing out the 10-guage wire. (30 amps X 240 volts = 7200 watts) As to why they want a 40-amp breaker, probably just for a little extra margin.

p0ps

11:07AM | 06/04/02
Member Since: 06/01/02
9 lifetime posts
I thought it worked slightly different from that.

Each hot line is still essentially only 120V. Thus when you multiply you would multiply 30 Amps X 120 volts = 3600W per line. I always thought that the applicances themselves kept the lines separate to power separate devices internally. For instance, an electric dryer would have one 120v line powering the heating element while the 2nd line would be powering the motor and the various other electronics inside.

My worry is still that the stove will use 1 120v 30Amp line to power the heating elements (which if they are all on might not be enough considering the instructions call for a 40Amp) and the other line to power the clock and other added functions the stove provides.

rpxlpx

05:43AM | 06/05/02
Member Since: 03/13/00
1674 lifetime posts
Most dryers use 120v for the motor and 240 for the heating element. Most electric stoves use 120 for the light bulb and timer and 240 for the heating elements, which are the main power users. Don't worry about the 120 in the stove. It's the 240 you should be concerned with. The 240 is obtained by using BOTH 120 lines combined.

[This message has been edited by rpxlpx (edited June 05, 2002).]

HBB

07:18AM | 08/20/02
Member Since: 08/19/02
29 lifetime posts
There's a mishmash of highly dangerous misunderstanding going on here.

NO electric range, apartment (20") or full (30") size notwithstanding, should be connected to anything less than a #8 wire. No. 10 wire is simply not heavy enough to carry the potential amperage an electric range can draw.

And a certain size breaker is not specified because it will make the range operate better; it has nothing to do with that.

Electrical conductors (wires) OPERATE a range and the breaker to which the wires are connected PROTECT the wires.

You can play with all the math you want to, but you can't escape the fact that a #10 wire is rated to carry a maximum of 30 amps and will not be protected by a breaker which won't snap until more than 40 amps hit it. A #10 wire will burn up (and burn your house down) before that 40-amp breaker even thinks about snapping.

And limiting each use to only one or two burners or just the oven will not bypass the potential for disaster. Burners burn out and when they do they can create dead shorts, causing uncontrolled amperage to run wild. When that happens, the only thing that can keep that wire from burning up inside your walls is a breaker rated at no more amperage than the maximum the wire is able to carry safely.

Apartment-size ranges require at least a #8 wire and full-size ranges require a #6 wire. You might get by with #8 and a 40-amp breaker on a full-size range, but it wouldn't be my choice.

Bite the bullet and rewire the thing for the size range you'll be connecting to.

Or forget the range and just get a hotplate for that #10 wire -- with a 30-amp breaker.

Unless, of course, you enjoy watching house fires.

EDIT: You don't necessarily have to rip out walls and cabinets. You can probably figure a route for surface-mount electrical conduit or the higher-priced Wiremold and run the new wire along baseboards, walls, etc., to a new -- and properly sized -- range outlet. And just leave the old #10 circuit for other uses.

[This message has been edited by HBB (edited August 20, 2002).]

TAM

03:32PM | 08/20/02
Member Since: 08/19/02
3 lifetime posts
Congrats, HBB. Your post says it all.

pOps, If the appliance calls for a certain min. or max. you must do it, for no other reason if you don't it will void your warranty. HBB is correct about rewiring. There may be a number of ways to do it without distroying your home. Do you have a basement? An attic? Is it on an outside wall?

rpxlpx....It would do you good to look up the word liability.

BV001360

10:41PM | 06/19/13
Why dont you just use a 30 amp breaker...

if it trips, you know not to use so many burners on high.

putting a 40 amp breaker with 30 amp wire deserves a couple dozen kicks in the groin.

-Barry Obama

BV001463

11:30PM | 07/02/13
Yes, you must run a 40 amp circuit. I run into this all the time as an electrician. People will buy a stove, dryer or other appliance only to find they do not have the circuit for it. Wire ampacity ratings, circuit design and demand factors are designed to protect you and your property. It often cost hundreds more than the appliance to run the circuit, depending on the location, building type, etc. And I would not put anything above a 20 amp circuit in wiremold, it is just too dangerous. It always amazes me how people think they can be electricians. I actually got a degree in business from a top ranked university,and was admitted to Law School, but getting my electrical licenses was much harder. I can pass all the code tests easily, but it really takes years to get practical experience. It really is easier to become a lawyer, doctor or engineer, plus you don't have to work hard. So if you think you'll just make something work electrically, its not that easy.

BV001582

10:11PM | 07/16/13
BV001463, you really think highly of your profession, don't you? Some of us are better at one thing than another. Get off your high horse and be helpful, and leave the derogatory comments out. What's the point in insulting those who are asking for advice? I'm sure there are things that you have tried, and will try, that you don't already know everything about. You learn by trying.
Back to the question at hand, the breaker should always be matched to the wire supporting the load. If the wire is 10 gauge, it should be on a 30 amp breaker. If you leave it this way, it will work. However, you WILL pop the breaker on a regular basis, you WILL void the warranty for the stove, and if you have a house fire the insurance company will probably blame it on your insufficient wiring (regardless of whether that's the cause or not) and they probably won't pay. SO, while the 30 amp circuit will work, upgrading the circuit is highly recommended.

BV001726

07:42PM | 08/01/13
What about getting a dual fuel stove? Its nice to cook with gas on the top. Then the #10 would likely work, depending on the electric oven requirements. In other words if you have to run something new, why not a gas line? Of course you would need a pro to do the gas work.

BV001738

09:37PM | 08/02/13
No. 10 AWG is rated for 40 amps. NEC states that it can only be installed on a 30 amp breaker due to derating of 60 degree wire

BV001790

04:31PM | 08/10/13
You guys are a bunch of evil experts, cut the man some slack, I say give it a whirl the way it exists with the 30 amp breaker, it'll just trip in the worst case and still protect the wire, as for the "expert" electricians on this post maybe consider the term 'safety factor' as it exsists to cover your ass when you knobs fuck something up

BV001796

10:19AM | 08/11/13
?

BV001821

04:09PM | 08/14/13
What about anyone who comes after you. If the breaker trips over and over, what do you think will be the first thing they would do? Get a larger capacity breaker of course. Ampacity ratings of wires for circuit breakers are reduced largely because a 30 AMP breaker won't trip at 31 AMPS. It could take hours of slightly over current conditions to heat up the breaker enough to trip but the wire can be cooking.

BV001844

04:36PM | 08/16/13
You gents are aware that p0ps posted that question over eleven years ago, right? His house has undoubtedly burned down long ago. It's a valuable discussion for future generations, to be sure, but addressing the OP seems futile.

(Sorry to jump in, but I've seen more than a few old threads revived in my life, but this one is downright ancient!)

BV002831

07:21PM | 12/19/13
Hey, I just read this thread because I'm in the same boat. Old stove decided to retire in the middle of making tea, and I ordered a new stovetop not really knowing much about it. So, in the end I should have done more research because I ended up with a stove asking for a 40Amp circuit but I only have a 30 amp circuit. I think what I'm going to do is what a few people suggested, just try to hook it up on the 30 amp circuit, knowing that the breaker will trip if it draws too much. Funds are kind of tight right now and since I don't believe this to be an immediate safety issue as long as i don't swap the breaker without swapping the wire I think that will be okay. That said, after the holidays I will probably have someone rerun the wire when I can afford it.

BV002904

11:17AM | 01/01/14
That's not a good choice, putting a 40A load on a 30A circuit. If you are going to be regularly taxing the capacity of the circuit you are going to be relying on the protective device over and over and over to save you. Theoretically, you should be ok but things fail. You will be putting continued heat stress on the wiring insulation, that will start to break down over time. Breakers fail or don't respond as quickly as you'd like.

NEC says that your protective devices need to match the 'weakest' part of a circuit, I don't know if it mentions about putting on a known load that exceeds the capacity of the weakest part of a circuit, irrespective of the rating of the protective device.
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