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Placing food on top of an oven which will be turned on later: [Although we rule like the stringent opinion regarding placing food directly on a heater, that it is forbidden to be done unless the Chazara restriction are fulfilled,] nevertheless prior to the Tanur being turned on the custom is to be lenient to [allow] to place [fully cooked] food [which if contains liquid is also still warm] on top of [the solid covering] without placing an [additional] separation. [Now], even though the oven will later be heated when it turns on, in which case there will then be a suspicion that one may come to stoke the coals, nevertheless one need not protest against those which do this being that they have upon whom to rely on. [See Q&A]
Placing cold liquid food by an oven on Shabbos: However by cold food [which contains liquid], even before the oven has been lit, it is forbidden to even place the food next to the oven.
Placing liquidly food near a heater which will eventually be lit: To place food near a heater which is not swept or covered, even if it has fire in it, is permitted in all cases, as is our custom as explained above, as long as the food is [still] a little hot if it contains liquid, if it is Yad Soledes by the area that is next to the heater. However, if it is not Yad Soledes there next to the heater then even if the food [which contains liquid] is completely cold, it is permitted to place it there in all cases, as explain above [in Halacha 21].
However, if one knows that the gentile will [eventually come to ] stoke the heater later on in order to heat up the house, which is permitted on Shabbos as will be explained in chapter 276, then if the heater will be heated up so much to the point that it will also heat up the food that was placed next to it to the point that that food will become Yad Soledes, it is forbidden to place the food there [if it is a liquid which has fully cooled down]. Rather one must remove it from near the heater before the gentile stokes it.
The reason for this prohibitions is because: this is like one who places a pot [over a stove] and someone else comes and lights it up under it, in which case although the former person [which placed down the pot] is not liable [to bring a sin offering, or get the death penalty] nevertheless it is Rabbinically prohibited to do so.
B. Telling a gentile to place food by a heater which will only turn on at a later time:
It is permitted to tell a gentile to place [even uncooked] food by the heater, [even though that] eventually he will turn on the heater in order to heat up the house and this will cause the food to consequently also heat up [past Yad Soledes].
The reason for this is: because the main intention of the gentile when he turns on the heater is not [to heat up] the food, but to heat up the house, which is permitted for him to [be told] to do, and the food then consequently also heats up. Now even though [the heating of the food] is an inevitable occurrence [when the heater is turned on] [nevertheless] there is no prohibition in telling the gentile [to do so] for the same reason as explained above [in Halacha 10].
Other Opinions: However, there is an opinion which forbids [one to tell the gentile] do this, since the gentile also intends to stoke the heater for the benefit of the food, being that it was placed on top of the heater, or next to it [in a way that is obvious to the gentile that the Jew wants it heated up]. Now, even though the gentile’s main intention is to heat the house, this does not help at all [to permit the gentile to be told to do so].
The Final Ruling: The custom is like the first opinion. Nevertheless, every man who is meticulous should be stringent upon himself in a circumstance that he does not need so much [to heat up the food].
C. Telling a gentile to place water in the heater:
However [despite the stringent opinion mentioned in the previous Halacha] if the gentile placed water into the pot that was fixed into the oven to prevent this pot from shattering when the oven is turned on, and then afterwards the gentile heated up the oven and the water boiled, [nevertheless] the Jew is permitted to benefit from this water on Shabbos. Furthermore, it is even initially permitted according to all opinions to tell the gentile to place water into the [fixed] pot before he lights the heater.
The reason for this is: because [the Jew] does not have in mind at all to heat up the water but rather to heat up the house, as one is only placing water into the fixed pot so the pot does not break.
If the Jew desires the water to be heated: (Nevertheless if the Jew desires that the water be heated so he can use it to wash vessels, then it is forbidden to tell a gentile to place water into the fixed pot.
The reason for this is: because the Jew himself is prohibited from placing the water there from even close to Shabbos, if he desires it in order to clean vessels) due to a decree that maybe he will come to stoke the coals after the oven is heated up, [therefore] it is [likewise] forbidden to tell a gentile to place it there, as everything explained in this section which is forbidden to be done because of the decree that one may come to stoke the coals, or because it appears like one is initially cooking [the food on Shabbos], then it is forbidden to tell a gentile to do.
May the Jew place the water inside the fixed vessel? Even if one does not desire at all that the water be heated, [nevertheless] it is forbidden to place the water there himself even before the oven has been stoked.
If the gentile intends to heat up the water: According to the custom that we are accustomed to follow the first opinion mentioned in the previous Halacha, it is permitted [to ask the gentile to place water in the fixed pot] even if the gentile’s intention in placing the water is in order to heat it up, since his main intention in heating up the oven is for the need of the house.
If the gentile places the water in the pot after he already began heating the oven: [However] if he put the water in the pot after he had already stoked the oven, then even if the pot was still cold when he placed the water in it, [nevertheless] if one knows for certain that the gentile placed it there in order to heat up the water, then it is forbidden according to all opinions until enough time has passed after Shabbos for one to have been able to heat up the water, just as is the law when a gentile does a complete prohibited action on behalf of a Jew. However [if one does not know for certain that the gentile placed it there to heat up the water then] we assume that it was placed there in order to prevent the pot from shattering.
Summary: May one place food on an oven which will eventually turn on?
· For a Jew to put it:
Has all the restrictions of Chazara, unless there is a solid sheet of metal or earthenware sitting over the fire, and one wishes to place the food on that sheet, in which case some are accustomed to allow to place the food directly on that sheet [without another intervening material]. However there may not be any cooking prohibitions involved, thus the food must be fully cooked, and if the food contains liquid, it may not be cold. One may place food that does not have a cooking prohibition near an oven which will eventually turn on.
· To ask a gentile to put it:
Near or on top of a heater: If a heater will be turned on in order to heat up the house then the custom is to allow to have a gentile place a food near the heater or on the heater, even if the food is not cooked, although every meticulous person should be stringent [by foods which have a cooking prohibition]. However if the oven will be turned on for purposes of cooking then it is forbidden according to all to ask a gentile to do so.
Inside a heater; on a Kirah; Near a Tanur: Furthermore, even when the gentile intends to heat the house, it is forbidden according to all to ask a gentile to place [any food] in an area of the oven where it would be forbidden for a Jew to do so due to the suspicion that he may come to stoke the coals or due to that it appears like cooking. Thus the gentile may not place it inside the heater [or on top of a Kirah oven, or even near a Tanur oven].
May one on Erev Shabbos place food on his electric plate which is not yet on but will later turn on with the timer?
If the food contains a cooking prohibition: If the food is not cooked or not fully cooked or it contains liquid that has fully cooled down, it is forbidden to set up a Shabbos clock to turn on the electric plate on Shabbos.
If the food is fully cooked but the electric plate is not covered: Then if the electric plate has more than one heat setting and is not covered, it is forbidden to place food there before Shabbos if the food is cold. However if the food is still hot, there is a dispute amongst the Poskim and it is proper to be stringent.
Food is fully cooked and electric plate is covered: If the electric plate is covered, or has only one setting it is allowed to place on it before Shabbos fully cooked food [which will still be warm by the time the clock turns on if the food contains liquid].
Water urn: Practically, due to the above one may not leave a boiler attached to the Shabbos clock being that by the time the clock turns back on, the water has completely cooled off and will become re-cooked on Shabbos.
Radiators: The custom is to allow to set up a radiator from before Shabbos to turn on through a Shabbos clock on Shabbos, even if the radiator contains liquids inside its coils that will be heated as a result.
May one on Shabbos itself initially place food on his electric plate which is not yet on but will eventually turn on with a timer?
No. This applies even if the food is fully cooked and is a solid, and even if it was originally on the electric plate when Shabbos began and was then removed [without fulfilling the conditions of Chazara].
May one place food into an oven which will eventually turn on?
No, as in addition to the problem explained in the previous answer [in footnote there], here it would furthermore forbidden being that the fire is not covered and there is thus suspicion that one may come to higher the flame.
May one before Yom Tov set up his electric plate on a timer for it to turn on during Yom Tov to have food placed on it?
Yes. However, when doing so for Shabbos, such as when Yom Tov falls on Erev Shabbos, one must place the food on the electric plate with enough time for it to heat up before the entrance of Shabbos.
 Admur 253:26
 Back in the day due to the cold climate it was allowed to have a gentile stoke up the heaters on Shabbos. Thus here it is discussing a case that the heater was not yet lit, but will be lit latter on.
 Kitzur Dineiy Shehiyah and Hatmanah 259
 Admur 253:27
 Meaning in all cases of whether or not one has intention etc. etc, however regarding the type of oven, it is explained in Halacha 253:20 that by a Tanur oven of back then it is always prohibited to place food even near the oven.
 Admur 253:28
 So is evident from the previous Halacha that Admur states one may always place food that has liquid which is still warm near an oven which is already on, however not liquid which will become cold by the time it turns on. He then continues to say in the next Halacha that “However to ask a gentile..”. This clearly implies that one may ask a gentile to place even foods that have a cooking prohibition near the oven.
 Admur ibid; M”A 253:41; See Tehiula Ledavid 336:4 that learns from here that it is permitted to aska gentile to perform an action of Pesik Resihei even if it is Nicha Lei.
 Lit. “Cut off its head and it will not die?”
 In the Kitzur Dineiy Shehiyah and Hatmanah Admur summarizes this law as follows: “However by cold food [which contains liquid], even before the oven has been lit, it is forbidden to even place the food next to the oven, with exception to if this is done through a gentile before the oven is lit, in which case it is permitted [to place the food] even on top [of the oven]. However once the oven has been lit, then it is forbidden to even place the food there through a gentile, unless it is being done for a sick person, or a child which does not have anything else to eat.”
 Admur 253:29
 Admur 253:26
 Admur 253: 27
 Meaning it contains no liquid, or does contain liquid but will still be warm by the time the fire turns on.
 Admur 253:28
 Admur 253:27 discusses placing the food near the heater
 Admur 253:28 discusses in the second opinion placing the food on the heater. This does not contain a stoking suspicion being that the case is discussing a heater which according to some opinions [mentioned in 253:26-Halacha 4 above] does not have a suspicion of stoking its coals.
 However, regarding foods which have no cooking prohibition and simply did not fulfill the Chazara restrictions, even a Jew himself may place it near the heater [253:27], and according to some even on the heater even when on and certainly when not yet on. [253:26] Hence, certainly a gentile may place it there when not yet on.
 Admur 253:29
 Even if fully cooked and dry.
 Shabbos Kehalacha Vol. 1 pages 244-247; See SSH”K 1:26
This question is dealt with extensively by many different Poskim of the previous and current generation. Some, including the Munkatcher permit it entirely. Others, including the Minchas Yitzchak and Sheivet Haleivi rule that [Lechatchilah] this is completely forbidden, for the reason that it appears like belittling of Shabbos. Others, including the Chazon Ish, Igros Moshe, and Rav Shlomo Zalman Aurbach rule that if the food is fully cooked and the flame is covered, it is allowed. The ruling here is based on this latter opinion.
 Igros Moshe 4:60
The reason: This is forbidden due to Zilzula Deshabbosa, belittling of Shabbos, as it appears one is doing a Melacha on Shabbos. It is not similar to placing a non-fully cooked food on a hot electric plate from before Shabbos. [ibid]
 Shabbos Kehalacha p.247; Oatzros Shabbos in Piskeiy Teshuvos 2:59; See Igros Moshe ibid from which it is understood that certainly one is allowed to do so, just like one is allowed to ste uop the lights to the Shabbos clock.
The reason: The entire reason to forbid using a Shabbos clock on Shabbos to cook with is because of Zelusa Deshabbasa. The Igros Moshe ibid however explains that by those matters that some Poskim allow to be done through a gentile then certainly it may be done through a Shabbos clock, and there is no belittling of Shabbos applicable. Hence certainly here regarding a radiator of which the Sages permitted even asking a gentile to turn it on [being that the cold can lead to illness as explained in 266:15 and 253:28] it is permitted to set it up with a Shabbos clock. [Shabbos Kehalacha ibid] This is in addition to the fact that the water of the radiator has already been precooked and it is disputed as to whether we apply the prohibition of cooking towards it [see 318:9], and hence there is more room to be lenient.
 Shabbos Kehalacha Vol. 1 page 247
 The reason for this ruling, despite the fact that in Halacha 26 Admur brings that there are those which are accustomed to be lenient in this and one is not to protest, is because a) Nevertheless Admur agrees that one is to not do so initially as is evident from the terminology of simply not to protest and b) Back then it was indefinite whether the gentile will in truth turn the heater on while today with electricity the electric plate will definitely turn back on. [See Shabbos Kehalacha ibid]
 Rav Asher Lemel Kohen
 As cooking is allowed on Yom Tov and thus there is no real belittlement of Shabbos involved.
 As is always the law regarding setting up one’s food before Shabbos.