"Bob Giel" > wrote in message
nk.net...
> How much can an oven's temperature vary and still give good results?
>
> If set at 350 degrees F., what is the most it should go above or below the
> set temperature?
> Is there actually a standard or "generally accepted range"?
> Is the acceptable range a percentage of the target temperature (e.g. up or
> down 5%) or is it an absolute (e.g. up or down 10 degrees F maximum?)
>
> My oven is way out of whack, can vary as much as 150 degrees too low and
> 39
> degrees
> too high when set at 250 deg F (yep, down to 100 and up to 289!) and +/-
> 70
> degrees when set at 350.
> Obviously this is crazy and totally unacceptable, but I need to know what
> is
> acceptable for good
> reliable baking. The repair people are worthless in this regard, and I'm
> sick and
> tired of throwing out food, as one time it burns, the next it is raw, and
> sometimes it comes out with an additional hour of oven time!
>
> I've searched the internet for weeks and found NOTHING even remotely like
> an
> industry
> standard, nor can I find a "rule of thumb" standard in any baking/cooking
> site, so far.
> I posted this message to rec.food.baking and they told me about
> this group (much more likely to know).
> Please help!
>
> TIA
> Bob in Los Angeles

Not really an answer, but..........
From Cook's Illustrated (part of article):

Conversations with David Anderson, senior product manager at Whirlpool,
revealed that the average oven designed for home use does not simply heat up
to the temperature set on the dial and then stay there. Anderson noted that
an oven's heating elements are either on at full power or off-with no middle
ground. To maintain the desired temperature, the heating elements cycle
within a manufacturer-determined tolerance, heating up and cooling down to
temperatures just above and below the desired temperature. The precise
temperature tolerances and timing of the cycles vary from manufacturer to
manufacturer. For instance, Anderson said that Whirlpool uses one-minute
intervals, so the elements will be on for one minute, then off for the next,
then on again, and so forth as necessary. This cycling process is regulated
by an internal temperature sensor located in the oven cavity.

We wanted to put this information to the test, so we hooked up our ChartScan
Temperature Data Recorder to an electric oven in the test kitchen and
programmed it to record the temperature once every 10 seconds for 1½ hours.
We placed 15 temperature sensors, called thermocouples, at different
locations up and down and side to side in the oven cavity and set the dial
to 350 degrees. At the dead-center location in the oven, we found the
temperature cycled within a range of roughly 25 degrees, from a low of about
335 degrees to a high of about 361 degrees. We analyzed a gas oven in the
same manner and found the temperature spread to be somewhat narrower,
between 343 and 359 degrees.

A careful look at the numbers generated by our ChartScan tests also
confirmed the common assertion that the heat within an oven cavity is not
consistent; that, in effect, there are hot and cold spots. Though we might
have suspected otherwise, we found that the bottom of our electric test oven
tended to run hotter than the top, usually by between 5 and 15 degrees. We
also found that the rear of our oven ran hotter than the front by roughly 5
to 10 degrees. There was also a stunning difference from right to left in
our oven, with the right side sometimes running up to 50 degrees hotter than
the left!

The uneven heat is the reason why many cookbook authors suggest rotating
pans in the oven when you bake. We ran a simple test of baking sugar cookies
to confirm this advice. Sure enough, the cookies were browned a little less
evenly from one side of the pan to the other when we failed to turn the
cookie sheet partway through the baking time.

Curious as to whether there was any truth to the common kitchen wisdom that
electric ovens heat more evenly than gas ovens, we repeated the ChartScan
tests on a gas range in the test kitchen. The temperatures recorded in our
tests bore out some validity in this axiom. For instance, the temperature
differential between the bottom and top of the cavity was closer to 50
degrees, where it had been just 5 to 15 degrees in the electric oven.