several Gedolim both in the North America and Israel have forbidden the use of "Sabbath-mode" ovens on Yom Tov*.See the details at Wolf, including the Kol Koreh that the Rabbonim signed explaining why; R' Heinemann's original teshuva that allowed them is here. I'm more curious to see how it plays out from a practical point of view: Assuming R' Heinemann stands by his psak, will we see people stick with it? Or will the majority of the people pick the more machmir point of view simply to be "safe". Of course, it's not a great example, what with this being an easily verifiable set of facts, unless the question is whether that is actually chillul Shabbos, but it's still interesting.
* Note -- by not allowing, what is not allowed is to change the temperature. You can still use the oven as a regular oven on Yom Tov according to the above rabbanim.
UPDATE: (hat tip: Princess D'Tiara)
June 5, 2008So now the question is only what the community will do. Interesting.
Regarding Star-K certified Sabbath Mode ovens:
Rav Heinemann, shlita, stands by his Psak that it is permissible to raise and lower temperatures on YomTov on ovens equipped with that particular Sabbath Mode feature.
Please see Star-K website: http://www.star-k.org/cons-appl.htm, or call our office for details about your particular model. Star-K will, in the next few days, post an audio presentation from Rav Heinemann explaining his views.
For those who wish to refrain from placing their ovens in Sabbath Mode and still use their oven on YomTov, please be aware of the possible serious "Michshol" on many models. Opening the oven door will immediately shut off the heating elements, an act clearly forbidden on YomTov. Thus, even if you don't raise or lower the temperature, it is still important to keep the oven in Sabbath Mode.