If one has only one oven, is it permissible to use that oven for merely warming food of either meat or dairy or parve and not have to kasher the oven if the oven is only used for warming (meaing a lower temperature) and not for actual cooking (which would necessitate a higher temperature)?
Please send sources.
Thank you.
Answer:
In general, once the temperature reaches the level of ‘yad soledes bo’ (43C or 110F) it no longer makes a difference if the purpose is for heating or for warming.
However, there might be some difference with regard to ovens, because at a lower temperature the food will not be giving off steam.
In principle is it permitted to use the same oven for meaty and dairy foods, provided the foods are dry.
The problem of using a meaty over for dairy foods is generally limited to foods that are moist, and therefore give off steam: If both meaty and dairy steam are absorbed by the walls of the oven, the oven becomes treif.
Even for dry foods, as an additional precaution some prefer that different racks be used for meat and dairy, or that the rack be covered with new aluminum foil before the dairy dish is placed in the oven.
Because is it hard to determine which food is “dry,” and because any time we discern steam rising from the dish it is considered “moist,” it is generally preferable to have two ovens, one for meaty and one for dairy.
If the same oven is used for meaty and (moist) milky foods, the foods should covered up well, and a better option is to actually perform a basic kashering procedure (cleaning and turning on at high temp.) between use for dairy and meaty dishes — though some rule that this procedure should not be used on a regular basis (Chelkas Yaakov 2:136).
Concerning covered foods, see Shulchan Aruch, YD 108:1; Ksav Sofer 54; Igros Moshe YD 3:10; concerning dry foods, see Igros Moshe YD 1:40 (and 1:59, concerning baking a challah) based on Pischei Teshuvah 92:6.
