Navigating Kitchen Appliance Technology

Rabbi Eli Gersten

Technology has both simplified and complicated our lives. The use of refrigerators on Shabbat and the limited use of ovens on yom tov have long been sanctioned by many rabbinic authorities. As technology advances, kitchen appliances have become more and more complex, sometimes presenting special challenges for Shabbat observers.

Concepts to Consider

Havara  Kindling
On Shabbat it is forbidden to kindle or increase a fire or a glowing element. On yom tov it is permitted to increase a fire or glowing element, but one is not permitted to kindle a new fire.

Kibui  Extinguishing
On Shabbat or yom tov it is forbidden to extinguish or decrease a fire or shut off a glowing element. On yom tov one may decrease a fire for the sake of cooking.

Gerama  Indirect Causation
Prohibited activities, when done indirectly, can be a mitigating factor and under certain circumstance may be permitted (i.e., one may enter one’s home on Shabbat even though opening the door will let in cold air that will activate the thermostat, thus turning on the heater).

It is generally accepted that one may not turn on, off or adjust electric appliances on Shabbat. On yom tov one may increase or decrease an electrical flow for the sake of cooking.

Computer Chips
Computer chips are widely used behind the scenes in today’s appliances to perform functions. Actions that will be detected by computer sensors that will not result in any forbidden act are permitted. To directly program a computer device may entail the violation of muktze.


If you are in the market to purchase new kitchen appliances, a fuller awareness and understanding of some of the technologies that may be present in newer devices will help you make more educated decisions. If you already own some of these devices, we hope the following will help unravel the complexities of their permissible use on Shabbat or yom tov.

With today’s available technologies, appliances have a lot more going on behind the scenes, and only an expert can really understand the ins and outs of these appliances and gadgets. Recently, the OU sat down with two such experts, father and son Messrs. Meir and Tzvi Herman (both of whom service major appliances in the tristate area), to help us understand and keep abreast of the latest developments and how they pertain to kashrut and kashering. The following are based on the positions of the OU’s poskim.

Today’s Ovens

Today’s ovens are made to be more energy efficient. One of the methods for conserving energy is that newer ovens’ programming does not allow the burners to turn on when the door is open. In addition, burners will turn off completely if the door is left open for an extended period of time. The exact duration will differ from one model to the next (test your oven to see how long it takes for the burners to turn off when the oven door is opened, i.e. 60, 90 seconds). Some ovens turn off after as little as two seconds. Please note that it may be difficult to determine when electric oven elements are on or off. These functions are not disabled even if the oven has a functioning “Sabbath mode.” What this means for Shabbat and yom tov is that the oven door may not be opened when the fire is off, since opening the door in effect turns off the oven, and closing the door in effect turns the oven back on. However, when the fire is on, one may open the door, provided that they remove the food quickly before the fire shuts off.

Stovetops and Temperature Adjustments

The knobs on the newer electric stovetops are connected to a computer. Adjusting a knob on yom tov does not only allow more electricity to flow (like in the older style rheostat knobs), but also reprograms the computer to increase the temperature — so this is not permitted.

Induction stovetops may not be used on yom tov at all. Heat is created when the pot is placed on the stove, which is not permitted on yom tov.

Refrigerators and New Technology

Lights, bells and whistles Today’s refrigerators can have all types of electronic readouts that illuminate when the door is opened. Those with a “Shabbos mode” will disable the readouts, but the functions will continue as normal.

Refrigerators feature either mechanical or magnetic switches. Mechanical switches can be taped up before Shabbat. Placing magnets in specific locations can deactivate some magnetic switches; magnets designated for the outside of the refrigerator are preferable, as they can be attached on Shabbat (if one forgot to do so before) prior to opening the door.

Electronic dampers, newer refrigerators make use of motorized dampers (air valves) to control the flow of cold air from the freezer into the refrigerator. If the refrigerator door is opened and warm air is allowed in, the damper will open wider to allow more cold air to flow.

Defrost heaters, probably the most sensitive issue regarding refrigerator use on Shabbat and yom tov is the defrost heater, which is found in every frost-free refrigerator. The defrost heater is a glowing filament, which is halachically considered a fire, that melts the ice that accumulates on the cooling coils. Obviously, one is not permitted to ignite this heater on Shabbat or yom tov, yet opening the door of the refrigerator can indirectly affect when the heater turns on, and in some cases might even be the direct cause.

Refrigerators utilize various defrost detection methods and understanding them is the best way to avoid potential issues associated with defrost heaters:

Cumulative Run-timers, this simplest method relies on timers that turn on the defrost heater after the compressor has been on for a set amount of time. For example, the heater will turn on after eight hours of compressor runtime. Opening the refrigerator will cause the motor to run longer and thus cause the heater to turn on sooner. However, there is reason to consider this a gerama (or less), since the timer is moving on its own.

Adaptive Defrost Control with this type of system, a computer monitors all usage of the refrigerator and adjusts the frequency and duration of the defrost cycle accordingly. Opening the refrigerator at any point will cause the motor to run longer and thus cause the heater to turn on sooner.

Refrigerators and Door Opening

Some refrigerators have counting devices in the doors. It notes how many times the door is opened and determines how often the defrost turns on. Deactivating the switch may mitigate the halachic concerns, but can result in damage to the refrigerator if left inactive for a three-day yom tov period. Ice can quickly build up and the refrigerator will “think” that it was not being used.

Freezer Frost Sensor

The newest technology relies on sensors to detect ice buildup and then turns on the defrost heater to melt the ice. Opening the fridge or freezer does not directly trigger the sensor, but it allows in moist air. When the door is closed and the moist air condenses and freezes on the coils, it causes ice buildup.

Variations in Compressor Speed

Some newer technology refrigerators use linear compressors, which run continually. Changes in temperature cannot turn off the compressor, but it can cause variations in the operating speed. Even the slightest change in temperature will cause a change in the speed of the compressor; simply opening the door for one second will cause the compressor to pump faster.

Water/Ice Dispensers

One may not use water spouts or ice dispensers on Shabbat and yom tov. Even a water spout that appears to be a simple mechanical spout is often hooked up to electrically operated pumps and valves.

Ice Makers

Traditional ice makers that generate ice and fill a bucket work automatically and only shut off once the bucket is filled. If one empties the bucket prior to Shabbat or yom tov, and one is certain that it has not filled to capacity on the day, one may take ice from the bucket on Shabbat and yom tov.

One can avoid all of the above-mentioned issues by purchasing one of the OU certified refrigerators manufactured by GE in conjunction with Zman Technologies (see for a complete list). These specially designed fridges are preprogrammed with a thirty-year calendar that will automatically take over all the functions of the fridge every erev Shabbos and erev Yomtov into a specially enhanced Shabbos Mode that negates all the concerns mentioned above. The refrigerator door may be opened at any time, without any concern of activating the compressors, the defrosters, or any other electronic features.


Although dishwashers cannot be operated on Shabbat and yom tov, they are frequently used to store dirty dishes to get them out of the way. Many of the newer models have light-up displays that illuminate when the door is opened. Those who use dishwashers for storage on Shabbat and yom tov should avoid these models when purchasing a new appliance.

Vent Hoods

Newer vent hoods will turn on automatically if heat builds up under the hood. One should be careful when cooking on yom tov to either work with a flame farthest from the hood, or minimize temperatures or smoke that would cause the vent to turn on.

Questions about specific appliances or about certifying a product, can be directed to Rabbi Tzvi Ortner, Director of Halacha and Technology.  212-613-8265


Rabbi Eli Gersten
Rabbi Eli Gersten serves as OU rabbinic coordinator and recorder of OU policy.

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