Adding 240v Range to Sub Panel

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Old 02-20-16, 08:41 PM
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Red face Adding 240v Range to Sub Panel

I've added basic outlets through existing and new lines before and have a fairly basic DIY-level understanding. However as this job is a bit more involved with a 240v/40amp appliance and a subpanel, I thought I'd ask for some advice first (if any of you are so kind to help).

My wife just bought us new appliances for the kitchen. Our existing GE range is gas (it has a 120v plug). The new range is a Samsung "dual fuel" oven, which has a gas connection for the cooktop and two electric ovens below it. According to the manual it requires a 240v/40amp power supply to run the ovens.

In the basement I have a 100amp (I believe) subpanel. I say "I believe" because the breaker for the subpanel in the main panel has no amp info on it. There is Romex 6/3 NM-B w/g 600v cable running to it. The subpanel box labeling says 100amp max on it, but there are currently 115amp in breakers installed (1 120v/15amp, 5 120v/20amp, 1 240v/20amp, 1 open). The 240v line goes to a single outlet which I have no use for, and 3 of the 4 120v/20amp lines each go to single outlets that I don't use (the previous owner, whose son was a builder and built the house for him, had a lot of power equipment in the basement so he had his son install dedicated lines).

So... I am thinking I can simply:
a. Pull out 2 of the 120v/20amp breakers/lines (disabling those outlets); and
b. Pull out the 240v/20amp breaker/line (disabling that outlet); and
c. Replace that 240v/20amp breaker with a 240v/40amp breaker; and
d. Run 8 guage wire from it up to the range

Am I missing anything? Did I do that all correctly? Or is there a better way to achieve this anybody would recommend?

Also... any recommendations for 3-wire vs 4-wire? The range install manual has directions for both, so not sure which is ideal.
 
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Old 02-20-16, 09:32 PM
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4-wire is required by current code. You will need 8-3 NM-b. Does the manual recommend a cord?
100amp max on it, but there are currently 115amp in breakers installed
100 amp refers to actual load not the total for the breakers. You do not determine loads by adding breaker amps. There is no need to pull any breakers unless you don't have room for a 240 volt breaker.
 

Last edited by ray2047; 02-20-16 at 11:04 PM.
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Old 02-20-16, 10:52 PM
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Thanks Ray. Makes sense. I don't know why I had it in my head that the breakers couldn't exceed... I guess it's unlikely you'll ever be running all at 100%.

Thanks again!
 
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Old 02-20-16, 11:05 PM
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I guess it's unlikely you'll ever be running all at 100%.
That is correct and there is the breaker supplying the subpanel to protect it.
 
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Old 02-20-16, 11:10 PM
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Thanks Ray! Appreciate the help... this doesn't sound nearly as hard or complex as I was making it out to be.
 
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Old 02-21-16, 06:21 AM
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You should do a load analysis before installing the range. The results may or may not require that you upgrade your service wiring and main panel.

Even if you don't need to upgrade the service, you should also do a "mini load analysis" for the basement. The subpanel fed by 6 gauge wire can handle 60 amps. The range takes 2/3 of that capacity. The calculated load imposed by the other circuits and receptacles would have to fit in the remaining 1/3 (about 20 amps at 240 volts) capacity.

(The number and ratings of breakers in the panel do not figure into the load analysis calculation.)

How easily could up upgrade the #6 feed to the subpanel with #4 or even #2?

Decommissioning the tool 240 volt receptacle could make a load analysis pass when it might otherwise fail.
 
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Old 02-21-16, 12:00 PM
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If the sub-panel is fed with 6/3 Romex then the unmarked feeding breaker in the main panel should be no larger than 60 amps. You are pushing it by adding a 40A circuit on top of what you have.
 
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Old 02-21-16, 01:43 PM
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the sub-panel is fed with 6/3 Romex then the unmarked feeding breaker in the main panel should be no larger than 60 amps.
Welcome to the forums. Good catch. I missed considering that that in my replies.

The question is what is the actual amperage of the ovens. How often will both ovens be used?

A good thing to do next is turn on all the existing loads to the subpanel that are likely to be in use at the same time and take a reading with a clamp on amp meter.
 
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Old 02-21-16, 08:01 PM
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So... finally was able to identify the breaker on the main panel as a Challenger C230... 30amps. Seems like a strange choice to have a sub-panel via 6/3 with only a 30amp breaker, no?

So, given that there is 6/3 being used, can I just swap out that Challenger 30amp breaker with a 60amp version?
 
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Old 02-21-16, 09:00 PM
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can I just swap out that Challenger 30amp breaker with a 60amp version
But it leaves the question of if the subpanel will support everything. Based on
1 120v/15amp, 5 120v/20amp, 1 240v/20amp, 1 open). The 240v line goes to a single outlet which I have no use for, and 3 of the 4 120v/20amp lines each go to single outlets that I don't use (the previous owner, whose son was a builder and built the house for him, had a lot of power equipment in the basement so he had his son install dedicated lines
I think you should be okay. I might connect all the receptacles to a single breaker partly to limit all receptacle load to 20 amps* and replace the 240 breaker with a 40 amp breaker for the stove. That should give you plenty of capacity for the oven. (The 15 amp I'm guessing is lights and probably an actual load of less than 15 amp.)

*If you want to connect all the receptacles together to keep things neat in the panel I'd mount a 4x4 box next to the panel and do the connections there. If you remove the four unneeded 20 breakers you will need fillers for the panel cover openings.
 
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Old 02-22-16, 07:05 AM
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Thanks again Ray. Besides there existing 240v breaker, there are 4 20amp and 1 15amp breakers. 3 of the 20amp breakers aren't being used (I have a mitre saw hooked to one which I maybe use 2 minutes a month). The other 20amp breaker runs the lights and an outlet I use to power my computer and some monitors. The 15amp line is a UF and powers my outside back-of-house sockets. The only thing I use them for is my low-watt outdoor lighting and an electric smoker... but it's highly doubtful I'd be running the electric smoker and both ovens simultaneously except maybe on Thanksgiving.

Your idea of using a clamp to read the load is a good one and I'll do that next.

Thanks again... very helpful!
 
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Old 02-22-16, 07:36 AM
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If you have a Challenger panel/breakers you should check on replacing the panel because they have been known to start fires because of the bus overheating and or breaker failure.
 
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Old 03-03-16, 07:36 PM
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So thanks again for all the great info. I have received the range and re-examined my current setup, and as a result the situation has changed a bit.

My main panel has a 30-amp breaker for the sub-panel. The cable from the main panel is 8/3 for the first approx. 27', then there's a jbox, and finally 6/3 for the approx. 33' remaining to the sub-panel.

While the install guide says to put it on a 40 amp breaker, the range itself says "Max Electric Load: 26.5 A" (see label image below).

So... given that it's unlikely I'll be running this thing at max load very often (it's a double oven) and given that there's not a whole lot otherwise on that sub-panel (a few lights and a single outlet I have my laptop/monitor hooked to)... can I just run a new 240v outlet with an 8/3 line the 10' from the range to my sub-panel and call it a day?

Again, many thanks to any who offer feedback.

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Old 03-03-16, 07:39 PM
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It would be be better to keep the larger loads in the main panel.
 
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Old 03-03-16, 08:34 PM
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To be NEC compliant the range needs to be on a 40A circuit.
 
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Old 03-03-16, 08:36 PM
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To be NEC compliant the range needs to be on a 40A circuit.
It isn't really an electric range. This is a dual fuel stove. Only the oven is electric.
 
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Old 03-03-16, 09:34 PM
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As I said, the range/stove/oven/whatever you want to call it needs to be on a 40A circuit.
 
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Old 03-03-16, 10:25 PM
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As I said, the range/stove/oven/whatever you want to call it needs to be on a 40A circuit.
Yes, because it draws ~30 amps. My statement was I'm not sure it qualifies as an electric range because only the oven is electric.
 
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Old 03-03-16, 11:39 PM
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As I said, the range/stove/oven/whatever you want to call it needs to be on a 40A circuit
I'm curious as to why this is, I know I'm going to run into this situation.
If a 30amp circuit can feed this, why use 40?
If you had a under the counter wall oven with a gas cook top above, many of the ovens are only 20 amps (double pole) and that's all you would need to run, not 40 amps and the install would pass any inspection.

Are you saying this is considered an "Electric Range", even though it's technically not?
 
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Old 03-04-16, 07:23 AM
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If a 30amp circuit can feed this, why use 40?
1 - The manufacturer says to use 40A circuit.
2 - 26.5A exceeds 80% load on a 30A circuit.
 
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Old 03-04-16, 07:33 AM
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Are you saying this is considered an "Electric Range", even though it's technically not?
Calling it a Range is just semantics. It's a househole cooking appliance. I believe the demand on the circuit can be no more than 80%.
 
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Old 03-04-16, 04:16 PM
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I don't believe it's semantics. There are household cooking appliances, such as ovens and cook tops that only require 30amps, some as low as 20amps. (None are free standing electric ranges which I agree require 40amps).

So let's say the dual fuel range only requires 30 amps (and be below the 80%), I would say the 40 is not required.

So my question is does the fact that a cooking appliance is "free standing" make it a range regardless of the configuration? I would think not and the install at 30amps would pass inspection.
 
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Old 03-04-16, 04:45 PM
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So my question is does the fact that a cooking appliance is "free standing" make it a range regardless of the configuration? I would think not and the install at 30amps would pass inspection.
I'm not following the reasoning of your question as to freestanding vs. built-in as to how it pertains to the required circuit size. The OP stated the manufacturer manual stated 40A circuit and the data plate shows 26.5 max amps. That information dictates that the supply circuit needs to be 40A, not 30A. I'm sorry that I'm not following how other cooking appliances may require 20A or 30A pertains to the OP's cooking appliance. I just used the term "range" because that's what the OP called it. The fact of being built-in or freestanding (range) has no bearing in the amp size of the required circuit. The wiring methods are different, but that's it.
 
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Old 03-04-16, 05:31 PM
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As I said, the range/stove/oven/whatever you want to call it needs to be on a 40A circuit
Bear with me, I think I see the problem. In the quote you said "the" range, meaning the OP's and not "any" range. I took it to mean any electric range.

So would you agree that IF you were installing a dual fuel range that only requires 30amps, and you have that cable already in the area, use it.
 
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Old 03-04-16, 05:34 PM
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The OP stated the manufacturer manual stated 40A circuit and the data plate shows 26.5 max amps. That information dictates that the supply circuit needs to be 40A, not 30A. I'm sorry that I'm not following how other cooking appliances may require 20A or 30A pertains to the OP's cooking appliance.
No one is disagreeing with your statement as applies to this cooking appliance. I think what we misunderstood was your statement in post #15
To be NEC compliant the range needs to be on a 40A circuit.
We read that as the NEC saying all cooking appliances that use electric for ovens and/or burners need to be on a 40 amp circuit. Probably just a misunderstanding of what you meant.
 
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Old 03-04-16, 06:42 PM
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We're on the same page now. Yes, I was referring to the OP's range/stove only, not all ranges/stoves in general. Phew...the written word can be misleading if not written in a precise manner. Plus typing and voice entry on a not so smart phone can be challenging.
 
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Old 03-04-16, 07:11 PM
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Good deal. This could save people a lot of work in situations where there are both gas and electric available, but the electric is suspect.
 
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Old 03-20-16, 10:04 AM
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Thanks again for everybody that assisted me with advice on this.

At the end of the day I decided this job was beyond my depth and hired an electrician to come in and do it. They put a new 40amp breaker in the main panel and ran #8 all the way to the range, or oven, or whatever it is you guys all agreed to call it

Even though I decided against doing this job myself, I appreciate all the insight that arrived me at that decision.
 
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Old 03-20-16, 11:06 AM
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Thanks for the followup. Enjoy the new range.
 
 

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