The Mishmereth Hashabbath institute in Israel has published a booklet which claims that using many modern electronic devices (refrigerators, air conditioners, digital water meters) are highly problematic on Shabbat. To give some examples of issues they describe

  • refrigerators have chips that register door openings and even very small temperature changes triggered by door openings and closings
  • modern air conditioners (e.g., inverters) also continuously measure temperature to adapt the strength of the engine and opening doors/windows will trigger electric changes
  • digital water meters (replacing manual meters to save operating costs at utility companies) use electric signals to measure water used in houses

They have halachic approvals from serious rabbis (e.g., R Yosef Shalom Elyashiv, R Chaim Kanievsky, R Nissim Karelitz, R Aharon Leib Steinmann, R Shmuel Wozner) and explicitly write that one cannot rely on grama and psik reisha d’lo nichale.

The solution they propose is to disconnect all “smart features” of refrigerators and air conditioners and have them work in “fixed manual mode” on Shabbat by installing special devices. Regarding digital water meter, they recommend asking for alternatives or, if not feasible, using private water tanks.

At the same time, many observant people I know use devices normally (except for removing light bulbs). What is the halachic basis and on whose poskim do these people rely? (for instance R Moshe Feinstein or R Yisroel Belsky were known for delving deep in technological issues before ruling on new developments - I’d be interested in opinions of similar rabbanim who combined their halachic expertise with technical knowledge they acquired).

PS. I am naturally skeptical of (1) claims like these from people who offer/sell the services to fix the issue they created and (2) signatures of gedolim who might or might not have studied the issue in depth, and might rely on technical claims they do or do not understand

  • 2
    Yasher Kochacha on asking this Q and your P.S. I sense that you may have been reading or hearing about devices by tzomet institute. There's an article on their website that explains gramma and why their devices are permissible. Our shul has a "tzomet" microphone which the rav uses on Shabbat & Yom Tov. He is Orthodoz. Every other Orth. rav I've spoken to says emphatically that under no conditions could anyone ever use a mic on Shabbat, and they won't bother to read the tzomet site to at least make an educated decision on it. I hope that you get good answers on this Q.
    – DanF
    Sep 5, 2018 at 19:13
  • They might be relying on out of date rulings made about simpler devices. Chareidim aren't the only ones who noticed this problem 5tjt.com/is-your-fridge-kosher lots of modern refrigerators come with Sabbath mode for this very reason.
    – Double AA
    Sep 5, 2018 at 19:34
  • Tzomet re: modern refrigerators zomet.org.il/?CategoryID=250&ArticleID=901
    – Joel K
    Sep 5, 2018 at 19:44
  • Rav Heinemann of the Star K has a fascinating opinion about these devices (which admittedly is 'more Maikil' than most other 'mainstream' Poskim, but he is still a respected, albeit Das Yachid, Posek in his own right). It's been a while since I listened to the opinion, but if I'm not mistaken, the gist of the Heter is that most of the actions that are 'internal' and don't have any externally noticable effects are not a problem. You can hear him speak about it directly on one of the Headlines podcasts (perhaps the episode from 5/30/15, although I'm not certain). Sep 5, 2018 at 19:48
  • Are their fridges new? If not, there's that old tradition: ignorance.
    – user15253
    Sep 5, 2018 at 20:13

1 Answer 1


The disagreement with these devices(disregarding light bulbs in fridges or fans in ovens, at the moment) is whether grama or pesik reisha d'lo neicha lei are permitted on shabbat; assuming we accept the notion that using these devices on shabbat do not contain the issue of boneh, makeh b'patish, bishul, or mav'ir(see Yechave Da'at 1:32; Tzitz Eliezer 6:6; Minchat Yitzchak 3:38; Shemirat Shabbat Kehilchatah 1:28 & 29, and Minchat Shlomo 10 and p. 81).

There are poskim that forbid both grama(see Rama and Bi'ur Halacha 334:22) and pesik reisha d'lo neicha lei on shabbat(see Mishna Berura OC 321:57, Magen Avraham 314:5, Har Tzvi OC 1:151, Chelkat Ya'akov 3:179; and Minchat Yitzchak 2:16, among others) while there are poskim that permit them in certain cases(see Yabia Omer OC 1:27, and Minchat Shlomo 91:10, and the Tzomet institute among others).

Those that use the above-mentioned devices without special certification seem to be doing so by relying on the lenient sources that permit them.

It should be noted that R' Auerbach ztz"l was an expert on electricity and shabbat and was among the first to study the issues in depth.

For sources and cited sources, see links below:

https://www.zomet.org.il/?CategoryID=198&ArticleID=697 https://www.koltorah.org/halachah/opening-refrigerators-on-shabbat-by-rabbi-howard-jachter http://www.daat.ac.il/daat/english/journal/broyde_1.htm

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