Chapter 23
Housekeeping and Use of Domestic Facilities on Shabbath and Yom Tov.
CENTRAL HEATING
22.a. Subject to the very important limitations set out in ef Chapter 13, paragraph 25, a timer which was set before Shabbath to turn the central heating on or off at a predetermined hour may be adjusted on Shabbath
1) to turn it on or off at a later time, but
2) not to turn it on or off at an earlier time.
22.b. Subject to those same limitations, a timer may be adjusted on Yom Tov
1) to turn the heating on or off at a later time, or
2) to turn it on earlier, but
3) not to turn it off earlier.
23.a. Where a Jew has turned on the central-heating system of an apartment building, even in deliberate violation of the Shabbath, one need not leave the building or turn off (See paragraph 19 above.) the radiators to avoid benefiting from the transgression, but
23.b. it is certainly forbidden to come nearer to the radiators or lean against them in order to warm oneself.
23.c. If at all practicable, one should bring polite but firm persuasion to bear, in an attempt to have a timer installed so that the heating can be operated automatically in the future.
23.d. See Chapter 30, paragraph 53 regarding buildings in which the central-heating system is operated by a non-Jew.
