How fast (or slow) will a 5 cu. ft. to 6.4 cu. ft. oven heat?

Question

I'm comparing 36" range ovens for Blue Star RNB, Electrolux, Viking, and Thermador. Their large oven capacities range from 5 cu. ft. up to 6.4 cu. ft. Does anyone know how long will it take to reach 350? I want a convection oven, but again I don't know if this affects pre-heat time. Thanks for any insight.

Answer

I can't imagine that any modern oven will take more than 10 minutes to preheat to 350. The variation will likely be a couple of minutes between models. Is this really the dealbreaker on your ultimate choice?

Answer

It really depends on the heating element more then oven volume. My large Kitchenaide reaches temperature pretty quick, especially on Convection.

Answer

It's a difficult question to answer.
You'd need to know the wattage of all heating elements that are active while it's preheating. Then you'll need to know the metal composition of the interior walls, plus either the weight of the metal, or the dimensions and thickness. Then you'll need to know the weight of all oven racks, plus *their* composition. 

Let's assume it's all stainless steel. Specific heat is about 500 joules per kilogram. A joule is one watt for one second. At 1 millimeter thickness, your oven walls would be about 1.5 square meters and contain 1500 cubic centimeters of stainless steel. A cubic centimeter of stainless steel is about 8 grams, so about 12 kilograms of stainless steel. Add in another 2 kilos of stainless for racks and such, making 14 kilos.

So, to raise the temp of all that stainless steel by one degree celsius means 14 kilos times 500 joules/kilo or about 7000 joules. You're asking about 350 degrees, which is about 175 celsius, so assuming a starting temp of 25 degrees C, means you need a 150 degree C increase. 150 degrees C times 7000 joules is a shade over a million joules. And since a joule is a watt per second, we now have a starting point to work with.

Divide a million by the number of watts your oven elements can put out, and that's how many seconds it'll take to preheat, assuming no other losses (which there are, of course).

For example, a million joules divided by 2000 watts equals 500 seconds, or between 8 and 9 minutes. Add some time because you'll have heat losses, and you're at roughly 10 minutes.

A cheaply made oven with thinner walls will preheat faster, a better made oven might preheat more slowly, an oven that preheats with top, bottom and convection elements at 4000 watts might be ready in 5 minutes.

In the US, most sheet metal thickness is specified in 'gauge'. 18 gauge is about 1 millimeter. 16 gauge is about 1.3 millimeters, so add 30% to the million joules if your oven is built with 16 gauge steel. Conversely, 20 gauge steel is about .8 mm, so reduce the million to 800,000.

Answer

So...did you get a Blue Star? Appreciate any feedback as I am looking at a Blue Star 30"

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How fast (or slow) will a 5 cu. ft. to 6.4 cu. ft. oven heat?

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