A Question about Electrical Breakers and Amps

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So, after the microwave fire that my son created I think we're just going to replace the microwave and stove built ins and upgrade. We're looking at putting in a double oven in its place and going with a new coutertop microwave.

The oven that we are eyeing up has electrical specs of 30.8 amp draw at 240v and 26.9 amps at 208v and recomends a 40 amp breaker. The outlet that it would be using and corresponding breaker is 30 amps and wired with 10 ga wire. Talked with an electrician and he said that 10 ga wire would not support a 40 amp breaker, and since the basement is finished running new wires across the house is not a practial option.

What would be the likelyhood of the 30 amp breaker being a problem? We really would only be using both oven at the same time a couple of times per year for family get togethers. I'm not too concerned with overheating the wires as the 30 amp breaker would probably trip well before the wires would cause any problem.

Anyone have a similar setup that can share their experiences? Thanks.
 
I wouldn't do it. It would be against the electrical code and if there was ever a fire or other problem in the house and the inspector saw it, you would be up the creek. While it *may* never be an issue, it's just not worth the risk.
 
Originally Posted By: threeputtpar
I'm not too concerned with overheating the wires as the 30 amp breaker would probably trip well before the wires would cause any problem.


You should be.

Regardless, if you install it AGAINST manufacturer recommendations (the 40 amp circuit) then you are not complying with Code (read as if there was a fire your insurance could be voided). Unless you have a 3 phase residential service - unlikely, you'll have a 240 volt service - hence the 30.8 amp draw. That's why it is sized for a 40 amp breaker.

It may not be "practical" but it is certainly doable for any competent electrician to upgrade your circuit OR find some appliances that will work with your existing.
 
Are you planning on installing the breaker?

The electrician would be a moron and should get his license yanked knowing you are going to overload the circuit and still install it. My electrician won't even tap any existing circuit unless he installed it himself and knows the entire route of wires etc.

Pick an oven with less load requirements or have it correctly installed.
 
Many breakers are continuous use rated for only 80% of their interrupting capacity.

Even a 100% rated breaker will likely experience frequent nuisance trips under these circumstances. This is a bad idea. Either bite the bullet and rewire, or continue to use separate appliances on separate circuits.
 
I believe your double oven should get #8-4 wire with the 40amp breaker. I'm with AandPDan that if you can't rewire, buy another oven.
 
How hard would it be to find the same oven derated a bit? IE same controls etc but with a smaller element and the all-important spec plate to go with it?

Like off by one model # digit at sold at Best Buy, Walmart, etc.
 
Thanks fells, all very good points and that is why I'm doing all the research before buying it. We're just at the beginning of the hunt and this model that we're looking at matched the fridge and dishwasher we purchased two years ago. Ideally, we'd like all the appliances to match, but they don't at this point so it's not a hard requirement.

Can anyone comment on the spec listed at 208v? I've never seen that and don't know why they list it. I thought that a 2 pole breaker is always 240v. Would this oven run at 240v or 208v?

Edit: This is the specific oven that we are looking at.

http://www.frigidaire.com/Kitchen-Appliances/Wall-Ovens/Double/FGET3065PF/

Edit 2: Looking at some of the Professional serirs ovens, one of them actually specs out at 41.5 amps at 240v and only recommends a 40 amp breaker. How can that be?
 
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Originally Posted By: threeputtpar
Can anyone comment on the spec listed at 208v? I've never seen that and don't know why they list it. I thought that a 2 pole breaker is always 204v. Would this oven run at 204v or 208v?

Two pole breakers are 240V, not 204. 208V is for three phase service. You won't find three phase service in any residential building, except large apartment buildings. You most likely have single phase service, which is only 120/240V.
 
Oops, clerical error on 204v. I corrected my original post to say 240v.

Thank you for the explanation of the 208v listing, I didn't know that about 3-phase. And Happy Birthday!
 
http://en.wikipedia.org/wiki/Three-phase

Three phase power:
its often used in commercial and industrial equipment.. hardly ever in residential.

Example the 15hp electric motor on a cardboard baler.

or a Wire EDM Machine(with separate transformer)

usually 400+ volts
 
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Sometimes you find 208v single phase on farms and in spots down South (?). Being a resistive load, the less volts you stuff through, the less amps it takes-- though it'll warm up slower.
 
Originally Posted By: eljefino
Sometimes you find 208v single phase on farms and in spots down South (?). Being a resistive load, the less volts you stuff through, the less amps it takes-- though it'll warm up slower.


Can you explain why it would use less amps at a lower voltage?

I understand why it would use less Watts.
 
Originally Posted By: eljefino
Sometimes you find 208v single phase on farms and in spots down South (?). Being a resistive load, the less volts you stuff through, the less amps it takes-- though it'll warm up slower.

For a given wattage, the less volts you have, the MORE amps it will use. Power (watts) = Volts * current (amps). So for example 1000 watts at 240V = 4.17 Amps. 1000W at 208V = 4.8 amps.
 
That is true, but since these are simple resistive loads, they will simply draw less current with less voltage, thus less work (output) and the current derating on 208v. if this were another type of (non-resistive) load that required a certain amount of work output, then yes it would draw more amps with lower voltage to equal the same work.
 
Back to my question I added with an edit. Fridigaire has one oven rated at 41.7 amps at 240v and says the minimum breaker size is 40 amps. Wouldn't that cause the same problem that I'm facing now with the oven rated at 30.8 amps running on my current 30 amp breaker?

Did they just put the recommendation of 40 amp breakers in all of their models just as a CYA move?
 
Whether you interpret it as a "recommendation" doesn't matter. What does you in with the other appliance is this:

"Minimum Circuit Required (Amps): 40A"

You must comply with the manufacturers requirements for installation.

How much does your electrician want to install a new 40a circuit?
 
I would not go less that what is required. Maybe settle on a single oven. This is not a case of a motor with a starting load then a lower run time draw. A normal oven heating element is either on or off. When its on it draws a certain current. Times two for top and bottom oven.
 
Originally Posted By: AandPDan
Whether you interpret it as a "recommendation" doesn't matter. What does you in with the other appliance is this:

"Minimum Circuit Required (Amps): 40A"

You must comply with the manufacturers requirements for installation.

How much does your electrician want to install a new 40a circuit?


Yes, I called technical support to get more info that what their website provides and they reitterated the 40A requirement. They couldn't explain why one model still has that requirement but actually can draw more than 40A.

And yes, the warranty would be voided as long as only 30A service was installed, even if that did not cause the problem.

My father is the electrician and is still in Florida, so running #8 wire and upgrading to 40A isn't practical at this point. Also, I wouldn't want to be ripping out drywall to run this all the way across the house if not necessary.
 
You might call another electrician. 8 gauge isn't the easiest thing to work with but I've seen some very good and creative wire pullers who installed it in places where others wouldn't even try.
 
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