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