Summer 2024
As electricity began to be used as an energy source in the late 1800s and early 1900s, poskim considered how to view electricity from a halachic perspective. The posek hador, Rav Chaim Ozer Grodzinski zt”l, ruled that electric incandescent lighting is considered fire and, to reinforce this psak, he himself would recite Borei Meorei Haesh on an unfrosted incandescent light bulb. While this psak rapidly gained universal acceptance,[1] it only covered incandescent light bulbs, which are very similar to fire in that they generate both light and heat. What about the many other applications of electric power which do not share these characteristics?
Electricity and Halacha
There are two basic approaches to this issue. The Chazon Ish writes that activating any electric device is boneh (building), since the completion of a circuit involves attaching two parts and bringing the electrical device “to life.”[2]
Other poskim, especially Rav Shlomo Zalman Auerbach zt”l, argue that there is no melacha d’Oraysa inherent in turning an electrical device on and off;[3] rather, we look at the result to determine if a melacha d’Oraysa occurred. For example, grinding food on Shabbos is the melacha of tochein. Turning on a food processor is not, unless there is food inside it. If the processor is already on, adding food to it is tochein – the chopping of the food determines the melacha, not the action of the electricity. Similarly, turning on an electric fan is not a melacha d’Oraysa, since there is no melacha involved in spinning fan blades or moving air.
Looking in the Fridge
With this principle in mind, Rav Shlomo Zalman analyzed the operation of a refrigerator. Refrigerators create a cold environment not by adding cold to the cabinet but by removing the heat from inside it.
The refrigerator cabinet (see Fig. 1) contains an evaporator, which is a low-pressure tube.
A liquid refrigerant enters that tube through the expansion valve and quickly evaporates in the low-pressure environment, absorbing the heat around it. The warm gas then exits the cabinet and is re-pressurized by the compressor and fed into a condenser – a higher-pressure tube outside the refrigerator – where it cools back down and condenses into a liquid before being fed once more into the evaporator.
Rav Shlomo Zalman pointed out that none of these activities (condensing, expanding, moving air and refrigerant) constitute a melacha d’Oraysa.
A second point of his analysis was that the effects of opening the door on the temperature control system of a refrigerator are generally neither immediate nor direct. Any effect is therefore a grama. This creates a situation of gram melacha d’rabanan which, he writes, is permitted lechatchila.[4] Thus, according to Rav Shlomo Zalman, refrigerators may be opened on Shabbos as they are during the week.[5] Although there are other opinions, the accepted minhagin America has been to follow this psak.[6]
Addressing New Technologies
As technology advances, new questions have arisen as to whether the above discussion still applies or if the advanced technology renders the psak obsolete.
► Thermostats – In the 1960s, the refrigerators Rav Shlomo Zalman wrote about had a mercury ampule inside the thermostat that would open and close the circuit which controlled the cooling system. In 2024, that technology is obsolete and illegal. Instead refrigerators use liquid-vapor switches,[7] bimetallic strips,[8] or solid-state “digital” thermistors.[9] Does his logic still apply to these systems? Is it still a gram d’rabanan?
Liquid vapor and bimetallic strips are essentially similar to the thermostats discussed by Rav Shlomo Zalman, in that they physically control the switch as they react to the changing temperature, and any effect will remain a grama.[10]
► Computer Tracking – Solid state thermostats, on the other hand, take continuous readings of the temperature and use a microprocessor to compare that reading to the set temperature, then control the cooling system based on that reading. Similarly, many refrigerators track the number of door openings and adjust the defrost cycles accordingly. Is this a problem on Shabbos?
Some are concerned that the fact that the computer tracks this information may violate the prohibition of koseiv (writing). As established above, however, electrical activity (which is how computers transmit and store information) in and of itself does not constitute a melacha. Since there is no visible display of that stored information, and koseiv by definition requires a visible result, there is no halachic issue with the computer tracking data on Shabbos.
If, however, the temperature in a refrigerator or oven were to be displayed, that would be a concern of koseiv, and indeed, all displays and icons that respond to appliance usage are deactivated in STAR-K Sabbath Mode.
►Fans and Dampers – Another aspect of modern refrigeration technology is the use of fans and dampers to control the temperature in the various compartments of refrigerator/freezers. These are controlled by electric motors, which are in turn controlled by the unit’s computer. Every time the door is opened, the temperature rises, potentially activating these devices. Is this an issue on Shabbos?
Again, to answer this question we must look beyond the fact that there is electricity involved and analyze the activity being done to see if it is a melacha. Fans and dampers serve to control airflow, which is no more a melacha d’Oraysa than opening a window to cool off a room. Therefore, as discussed above, as long as they do not activate as an immediate result of opening the door, it is, at worst, a grama of a d’rabanan, and permitted on Shabbos. STAR-K Sabbath Mode specifications require a delay before any response to door activity, to ensure that it always remains a grama.
►Door Alarms – To ensure food safety, most manufacturers include door open alarms, which cause the refrigerator to beep, or even flash its lights, if the doors are left open or the temperature rises. Turning off an alarm or light is indeed forbidden on Shabbos, and one would be required to leave their refrigerator open for the rest of Shabbos. To avoid this problem, STAR-K Sabbath Mode either disables the alarms entirely, or requires that they turn off after sounding to allow the user to close the door.
►Motorized Door Assist – To allow for a clean, modern look, some high-end refrigerators are designed to be mounted flush with the cabinetry, with no handles. Instead, they open with a motorized door assist, which is activated by a touch sensor. In STAR-K Sabbath mode, the sensor and the motor are disabled so that the door can be opened manually.
►Smart Refrigerators – Smart refrigerators have a host of capabilities, using advanced touchscreen controls and phone apps to change settings, alert about door openings or alarms, send live videos of the inside of the refrigerator, or even create customized shopping lists. Displaying any of this information on a fridge or phone screen is koseiv (writing) m’drabanan, and strictly forbidden on Shabbos. STAR-K Sabbath Mode disables all reactive displays and cameras in the refrigerator, ensures that the phone apps are not alerted.[11] STAR-K also requires that all certified appliances be usable without a smartphone.
►Active Defrost Systems – The most serious concern in modern refrigerators is active defrost systems. Frost-free refrigerators use a heated electric coil to defrost the evaporator coils. To conserve energy, this heating element is only activated after a certain number of door openings or compressor activation time. Since the insides of these coils glow red, this is a serious concern of the melacha d’Oraysa of maavir (creating a fire). STAR-K Sabbath Mode puts the defrost heating element on a clock-based timer, so as not to be affected in any way by the door openings.
New Sabbath Mode
As mentioned above, Rav Shlomo Zalman allows the compressor to be activated by a thermostat on Shabbos. To cater to the needs of users who would like to avoid affecting their appliance in any way, STAR-K certifies certain models as “New Sabbath Mode.” Ovens and refrigerators with this designation do not use thermostatic controls at all, relying instead on preprogrammed on/off cycles to control the unit’s temperature.
[1] Achiezer 3:60. See also Beis Yitzchak YD II:23 who rules that lehadlik ner shel Shabbos may also be said on incandescent light bulbs. These rulings do not apply to fluorescent and LED bulbs.
[2] O.C. 50:9, see Minchas Shlomo 1:11.
[3] Minchas Shlomo 1:9-11. There may be a rabbinic prohibition of molid (creating) in activating certain electric circuits.
[4] Rav Shlomo Zalman writes that this logic would permit an unwanted melacha d’Oraysa as well, since every psik reisha dlo nicha lei is only forbidden d’rabanan. This is why Rav Moshe Heinemann shlit”a rules that an oven may be opened only once on Shabbos, even if the oven is in Sabbath Mode: when the oven door is opened, the temperature inside drops rapidly, which causes the thermostat to light the flame. If you remove all the food, the subsequent activation of the flame is undesirable, as you have no use for the fire in an empty oven. If you leave the food inside, it is obviously beneficial to have the flame since it serves to keep the food warm.
[5] Provided, of course, that the lights are deactivated.
[6] See Sefer Shmiras Shabbos K’hilchasa (3rd ed., 10:12-14), who writes that one who wishes to avoid any questions should set his refrigerator on a timer and only open it when the device is off. Rav Heinemann points out that this does not actually avoid all questions: since opening the refrigerator will raise its temperature, this can cause the thermostat to activate the cooling cycle sooner once the timer turns the fridge back on. Granted, this, too, is only a grama, but we would still need the psak of Rav Shlomo Zalman.
[7] Essentially, a bulb filled with a fluid that expands and contracts as the temperature changes. As the temperature changes, the fluid expands or contracts, the pressure of which closes and opens the electrical switch that starts the cooling system.
[8] Bimetallic thermostats use a strip composed of two metals that expand and contract at different rates. One metal is very sensitive to temperature changes, and the other is not. Changes in temperature cause the strip to warp towards or away from the switch controlling the cooling system, closing and opening the circuit.
[9] Thermistors (a portmanteau of thermal and resistor) are semiconductors that becomes more or less electrically conductive/resistant as the temperature changes, which allow for continuous, precise readings.
[10] The only difference is whether it is the mercury in the ampule or the strip which completes the circuit.
[11] In practice, most manufacturers disable the communication between the refrigerator and the app entirely. Ironically, this means that you can enter Sabbath Mode through the app – but not exit it!
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