Shiur #03: Using a Solar Water Heater
LAWS OF SHABBAT: COOKING
03:
BISHUL
USING A SOLAR WATER HEATER
For decades, many people have used a solar water heater. Is one allowed to use this device on
Shabbat?
Solar Heaters
We will first explain how a solar heater works.
On the roof
are
collectors
-
black tubes that
absorb
the
heat of the sun, wrapped
in glass
that traps
heat. Water flows from the heater
into these tubes, and the water is heated up as it travels. After it has been heated, the water
returns to the heater, and in its place more water from the heater flows into
the tubes.
First of all, we must analyze how we relate to the water being heated up in the
tubes: is this cooking in the sun (permissible) or cooking with solar byproducts
(forbidden)?
Permissive View: Cooking in the Sun
The Tzitz Eliezer (Vol. VII, ch. 19) writes that one should be allowed to use
the water from a solar heater, since the water in it is considered to have
become hot by the agency of the sun itself.
He explains in the name of Rav Yosef Kafih that there is a difference
between hot sand (considered a solar byproduct, and therefore
rabbinically prohibited) and a solar heater. Hot sand, even if it is moved to
another place, will stay hot for some time, and therefore one might come to
mistake it for something heated by fire.
In a solar heater, on the other hand, if the tube is moved elsewhere, it
will cool immediately. Therefore,
it is clear to everyone that this tube was heated directly by the sun.
Heating by Magnifying Glass Permissible
The Tzitz Eliezer adds that if we explain that the glass helps to focus the rays
of the sun, it is considered the sun itself.
This is what he cites from the words of the Shevitat Ha-Shabbat
(Mevashel, Beer Rechovot, ch.
44), whose inclination is to allow heating by a magnifying glass that focuses
the light of the sun:
[1]
One cannot compare tubes to sand and dirt from the road
because sand and dirt
from the road have already absorbed a lot of heat from the sun, and they can now
heat and cook even in the absence of the sun: if one moves this sand to a shady
part, its heat is still sufficient to cook food.
It is only in this case that they have banned solar byproducts because of
igneous byproducts, because they are interchangeable. However, if these substances could
only make something hot while they were in the sunlight, what worry would there
be of interchanging them? We would
see that the sun is the sole actor, and without it no action can take place.
Now, in our case, should we take one of these collecting tubes to another place,
it could not heat up anything at all, and the thickness of its metal is not
sufficient to heat other substance with its own heat, and it turns out that the
water is heated directly from the sun.
In such a case, we certainly view it as being heated by the sun directly and not
by solar byproducts, and it should be permissible. Thus we should know that the glass
panels on the collector do not act at all to heat the water, and they have no
influence upon it, aside from preventing the wind and the cold air from cooling
the water that passes over the collector tubes.
This is the view of the learned.[2]
This is what is appropriate to say about this matter. I have seen something even greater
than this in the book Shevitat Ha-Shabbat; that author is inclined to say
that even when a metal vessel is heated by glass (and no flame is ignited, for
if so, it would be true fire), which focuses the energy of the sun, and through
this the food is cooked in it, this may be like the sun itself [and
permissible].
Forbidden: Cooking with Solar Byproducts
However, this is not simple.
According to the Minchat Yitzchak (Vol. IV, ch. 44),
[3]
the collectors are considered solar byproducts because they absorb solar
energy and afterwards heat the water.
On the contrary, this is actually a more sophisticated type of solar
byproducts.
Additional Problem: Ancillary Water in the Heater
There is another problem, particularly in modern solar heaters. When one opens the hot-water tap,
hot water comes out of the heater, and new cold water enters from the main. This water does not directly reach
the collectors; rather, first it goes through the central heater (see the above
diagram), and there they are heated by the water that is already in the
heater, and that water has already been heated by the collectors.[4]
The hot water in the heater certainly should be classified as a solar byproduct
(because they have been cooked by the sun), and if so, the cold water that is
heated by this heated water should be considered to be cooked by solar
byproducts. According to this,
it would be unanimously forbidden to use a solar heater on Shabbat
because the cold water is heated by the hot water.
Is a Rabbinical Pesik Reisha Permitted?
Even so, there are those who permit using a solar heater on Shabbat. Rav Ovadya Yosef (Yabbia Omer,
Vol. IV, OC, ch. 34) struggles with the issue of a pesik reisha, an
inevitable, albeit unintentional, result:
[5]
There is a question whether one is allowed to use hot water on Shabbat if it was
heated by the solar heater, because at the time that one opens the hot-water tap
in ones residence, cold water immediately comes into the heater, and this is
like cooking on Shabbat
Even
though one opening the tap has no intent to heat the cold water (which flows
immediately into the heater when the tap is opened), nevertheless, it should be
a pesik reisha, and this is like
cooking on Shabbat, because it is forbidden to cook via solar byproducts on
Shabbat
However, in our case, that one does not intend to heat and boil the water, we
have come to a dispute among the halakhic authorities about the law of
pesik reisha as it applies to
rabbinical prohibitions, whether it is permitted or not. The Terumat Ha-deshen
(ch. 64) writes that for a rabbinical prohibition, one should distinguish
between full intent and a pesik reisha
of an unintended consequence
However, the Magen Avraham (314:5) has argued strenuously and impressively,
overwhelming every occupant of the study hall with his brilliant and convincing
proofs from a number of sources that a
pesik reisha of a rabbinical prohibition is prohibited
Nevertheless, the words of our
master the Beit Yosef indicate that, halakhically, he believes that one should
different between biblical and rabbinical
pesik reisha
The determination of the law with which we began and with which we conclude is
that, by the letter of the law, one may open the tap for water that was heated
in a solar heater and use it for washing dishes, washing hands, drinking or
anything of the sort (and, similarly, it is permitted to close the tap after one
has finished using it). There is no
need to be concerned with the flow of cold water into the heater and the tubes
that come out from it where the water gets heated
[6] However, one who wishes to act
stringently and avoid using water that was heated in the solar heater because of
the concern of boiling the cold water is praiseworthy; nevertheless, those who
act leniently have upon whom to rely for practical purposes. This is how we rule, God willing,
for the tendency to permit must always be greater. May the Holy One illuminate our eyes
in His holy and pure Torah, amen.
The main reason for Rav Ovadya Yosef to permit this is the fact that the
person does not intend to heat the cold water that comes into the heater (it
has enough hot water for his needs, so he does not need to heat additional cold
water). The assumption is that the
water will indeed be heated, as a pesik
reisha; however, because this is a rabbinical ban (against solar byproducts)
we may, in his view, be lenient for a rabbinical
pesik reisha.
Magen Avraham: Rabbinical Pesik Reisha
Is Forbidden
However, there is no consensus to allow this.
The Magen Avraham (314:5) argues and forbids even rabbinical
pesik reisha (even if it is
unwanted). This is how Ashkenazim
rule, following the Remas view (314:1, Mishna Berura
ad loc. 11; Rema 340:3, Mishna Berura
ad loc. 17; et cetera). A number of Sephardic authorities
also rule this way.
Perhaps There Is No Pesik Reisha
However, many times there is no certainty that the cold water will be
heated by the hot water, since the cold water enters the solar heater from
below, and many times the water that is already there in the bottom of the
heater is cold (and that water will still need to be heated more by the
collectors, so that it may be that it is considered like the sun and not like
solar byproducts). If so, it may be
that there is no pesik reisha but
rather a doubt (or chance) of a pesik
reisha, and the Mishna Berura (316:16) permits a doubtful
pesik reisha of rabbinical
prohibition.
No Concern of Confusing with Igneous Byproducts
There are halakhic authorities who want to allow the use of a solar heater for
another reason, based on the view of the Maharshal (Responsa, ch. 61).
The Maharshal claims that the entire prohibition of cooking via solar byproducts
applies only when there is a concern of confusion or error i.e., when one may
confuse a solar byproduct with a byproduct of fire. However when it is clear to all
that the heat comes from the sun, there is no prohibition in using the
substance, even though we are talking about a solar byproduct. Based on this, the Maharshal allows
cooking food directly on a hot roof that has been heated by the sun,
because it is obviously visible that the source of the heat is the sun. Based on this allowance, there are
those who believe that it is permitted to use a solar heater, since the heating
is always being done by the sun, and the matter is similar to a hot roof,
concerning which there is no concern for error (Shemirat Shabbat Ke-hilkhata, 1st
ed., 1:29, n. 67).
Rav Auerbach: Nowadays, a Concern Exists
However, this approach is also the subject of some dispute.
First of all, the Magen Avraham (318:10)
writes that the words of the Maharshal are not conclusive; he cites Acharonim
who dispute this view and forbid to cook on a hot roof. Secondly, according to Rav S.Z.
Auerbach (Shemirat Shabbat Ke-hilkhata,
ch. 1, n. 127), even when it comes to a solar heater there is a concern for
error. Nowadays, the solar
heater generally contains a heating element (even if there is no such element,
generally the tap in ones home is also attached to a water source heated by
electricity). Thus, there is a
concern that a person may open the tap at home and think that the water is
coming from the solar heater, when the water is in fact being heated via
electricity (which has the halakhic status of fire). The concern is very significant,
since even if the boiler is currently off, if before Shabbat the water had been
heated by the electricity (and it is still hot due to this), the water remains
an igneous byproduct, and there is a concern of violating the biblical
prohibition of bishul.[7]
In Practice
Practically, it is best to avoid using a solar heater on Shabbat
because of the concern that this device has the status of a solar byproduct, as
well as the concern that one will confuse the water heated by this device with
water heated by a boiler. However,
in a time of need (e.g., for the ill or for minors), one who is lenient about
this has upon whom to rely (particularly when we are talking about a
rabbinical doubt).[8]
Translated by Rav Yoseif Bloch
[1] Furthermore,
Rav S.Z. Auerbach (Minchat Shlomo 12:2) allows one to heat using a magnifying glass.
However, the allowance is limited to one who is heating it directly by the sun.
If one uses the magnifying glass to ignite paper, then one is definitely
violating the prohibition of kindling, and then it is forbidden to cook with
such a fire.
[2] As we have said, these are the words of Rav Yosef Kafih, and this responsum is addressed to him.
[3]
This is the view of the
Shevet Ha-Levi, Vol. I, ch. 94.
[4]
We should note that there is no barrier between the cold and hot
water, because the cold water ends up on the bottom due to its weight.
[5]
This responsum is remarkably long, including the clarification
of many important laws of Shabbat, the law of
pesik reisha among them. From those familiar with Rav Yosef, I have
heard that it took him half a year to write this responsum.
[6] Nevertheless, even
according to him, it is preferable to close the pipe leading the cold water into
the heater:
However, if it is possible to close the pipe of cold water and prevent its flowing into the heater, it is proper to do this in order to avoid any question. Nevertheless, when it is impossible to do so, it is permissible to use the hot water. (If the water is very hot and one wants to open both of the faucets simultaneously, the hot and the cold, one may be lenient about this too.)
Indeed, in a practical sense, it is impossible to shut off the cold water from entering the heater, because this will also prevent the hot water from coming out, as this would create a vacuum and prevent any water from coming out.
[7] However, the Tzitz Eliezer (Vol. VIII, ch. 14) writes in a similar context
that one should not add on to the Sages decrees:
Now, I will tell him that I recently received a letter from Rav
Moshe Zvi Neria, instructor in Yeshivat Kfar Haroeh. He told me that he once had a
question about solar heaters, and he consulted the great sage and halakhic
authority, Rav Tzvi Pesach Frank.
His first thought was that it is ostensibly like that which is heated by the sun
and therefore permitted.
Furthermore, [Rav Neria] had reminded [Rav Frank] of Rashis
words, Shabbat 39a, s.v.
De-sharei: For
this is not its way of cooking, and no one would ever confuse fire with the sun,
so there is no reason to decree against the latter because of the former. This raises the possibility that, at this time, when it is
very common and this is
derekh bishul, one should include also
that which is cooked in the sun itself in the rule of the decree.
[8]We might have argued that since this is the regular way to heat
water it involves a biblical prohibition, as we suggested in the previous lesson
concerning a microwave. However,
generally the halakhic authorities have followed the path of Rav S.Z. Auerbach
(discussed in the previous lesson), which dictates that only
bishul by fire is biblically
forbidden. (See