Keeping Your Cool: All About Refrigerators

Few of us can remember life in the kitchen without the help of a refrigerator. Probably the most used appliance in the home, the electric refrigerator was mass produced as a home appliance in the early 1920’s. Although many improvements and modifications have taken place over the years, the basic principles employed in the home refrigerator remain the same.

How Refrigeration Works

The natural laws of physics dictate that as a liquid evaporates into a gas, it absorbs heat from the surrounding areas. In turn, these surrounding areas become cold. (If you touch the cylinder supplying gas to a barbecue grill, you will notice the cylinder getting cold and icy because the liquid in the cylinder is rapidly changing to a gas as it leaves the cylinder to provide fuel for the flame.) Although we may view our refrigerator as a machine that makes things become cold, in physical terms, the unit in reality is absorbing heat from inside the refrigerator cabinet and transferring that heat to the surroundings outside, resulting in a cold cabinet.

To accomplish this a refrigerator uses a liquid, referred to as a refrigerant, that evaporates into a gas at a very low temperature. To start the process, a thermostat in the refrigerator cabinet will sense the temperature in the cabinet to be above the desired setting. It will cause a connection to be made that starts an electric motor. This motor, known as the compressor, pumps the refrigerant gas, compressing it into sealed coils called a condenser. This puts the gas under high pressure, making it warm. In many refrigerators the condenser is the black coiled pipes behind the refrigeration unit. While going through the condenser coils, the high pressured gas is being cooled as the heat dissipates into the atmosphere, causing it to condense into a liquid. Many newer models will have the condenser under the refrigerator cabinet with a fan blowing through the coils to cool them. The liquid then passes through a narrow valve into a low pressure area. Upon entering this low pressure area, the liquid refrigerant expands and evaporates, changing back into a gas. Hence this area is called the evaporator. As stated earlier, upon evaporation the gas will absorb heat making the area cold. (In an old manual defrost refrigerator, the evaporator would be the coils in or around the freezer section.) From here the gas is pulled back to the compressor to complete the refrigeration cycle.

Frost and Frost-Free Fridges

When moisture in the air comes in contact with cold, (namely, the frozen evaporator coils) it condenses and forms frost or ice. In order to function efficiently, the freezer eventually must be turned off and the ice removed. Most new models have a frost-free design. This does not mean that there is no frost build-up. Rather the evaporator coils are located in a central location. A timer is set to turn off the compressor and turn on a heating element that is next to the frozen evaporator coils. The built-up frost then melts and flows down a pipe to a pan at the bottom of the refrigerator; from here the water evaporates into the atmosphere. Because the evaporator coils are contained in a central location, a fan is used to blow off the evaporator coils and spread the cold air through the freezer and refrigerator sections.

Shabbos and Yom Tov Concerns

Now that we have some basic knowledge of what takes place in the regular refrigeration cycle, let’s examine our refrigerator and analyze the effect the workings may have on Shabbos or Yom Tov. We know that the Torah prohibits doing an act which is classified as a melacha on Shabbos or Yom Tov. Among the prohibited acts is havarah, meaning to cause burning. Generally, the Torah prohibits actions when done with intent. When there is no intent to cause the resulting action (eino mechaven), there is no prohibition in Torah law. (However, it may be rabbinically prohibited.) This is true when the resulting action is not a definite reaction to one’s action. When the melacha comes as a direct reaction, even though it may have been unintentional, it is viewed as intentional.

Lights Out

Most refrigerators have a light that goes on when the door is opened. Turning on a light is classified as a havarah. Even though one does not intend to turn on the light when opening the door,1 this is prohibited2 since there is a direct reaction which will definitely take place. The easiest way to avoid this problem is to unscrew the lightbulb before Shabbos or Yom Tov. If one accidentally opens the refrigerator door (without unscrewing the lightbulb) and turns on the light, they may not close the door as this would be turning off the light.3

The Fan

As noted earlier, a fan circulates cold air through the refrigerator and freezers in frost free refrigerators. In some models this fan shuts off when the door is opened. Since opening and closing the door directly affects the fan function, it is prohibited on Shabbos and Yom Tov. One should check their appliance to be sure that it does not have this feature by listening to see if the fan runs with an open door. If it does not, try pressing down the door plunger (switch) and listening to see if the fan goes on. Note: Some models have two door plungers, one for the light and another for the fan motor.4

Opening the Door: Ovens vs. Fridge

As discussed earlier, the compressor motor begins the refrigeration cycle when the thermostat senses a change in cabinet temperature. When the refrigerator door opens, warm air enters the cabinet, causing the refrigeration cycle to begin earlier than it would have, had the door remained closed. There is a similar situation regarding opening an oven door. With regard to opening the oven door, the conclusion is that on Shabbos one may not open and close an oven door at random, because the cool air entering the oven chamber will cause the thermostat to have the oven burn sooner and longer to compensate for the lost heat. However we concluded that one may open the oven door one time in order to remove the food as the burning to follow is unintended, unwanted,5 and serves no purpose.6

The question is: May one open a refrigerator knowing that this will cause the compressor to work to compensate for the warm air that enters the cabinet? Over the last seventy years, many halachic authorities have addressed this question. To understand some of the reasonings involved in the different answers given, we must point out that in the case of an oven, the electricity is being used to heat the element (or in the case of a gas oven, to ignite a flame). Under those conditions, the use of electricity is considered havarah (burning of fire). The fact that the oven will burn for longer to make up for the lost heat may be categorized as mosif havarah (additional burning of fire).

In the case of a refrigerator, the electricity is not being used to burn as light or generate heat directly. The electricity is causing the compressor motor to initiate the refrigeration cycle. As it rotates, this motor may generate sparks which are not classified as havarah. Sparks are classified as nitzotzos, which are prohibited by rabbinic law as a melacha she’aina tzricha legufah.

Therefore we may note the following factors when considering the reaction a refrigerator will have toward starting the refrigeration cycle by opening the door:

  • The use of electricity is not in the Torah prohibited form of havarah.
  • In the majority of cases, the motor does not go on immediately with the opening of the door, and may not go on until a while later.
  • The reaction of the thermostat to start the compressor is a secondary reaction (which may be classified as a grama).
  • One does not intend to turn on the compressor when opening the refrigerator door (which may be classified as eino mechaven).
  • One does not want the warm air to cause the motor to go on as this is a waste of electricity and costs money (which may classify it as a psik reisha d’lo nicha lei).

Sidestepping the Issue
To avert the problem, some have placed their refrigerators on a timer so that at mealtimes the refrigerator will not be on and the door can be opened without concern for directly causing the compressor to go on. Another option is to have the refrigerator set on its highest setting but to have the refrigerator on a timer set to go on periodically. By doing so the compressor will be essentially working according to the timer.

Halachic Solutions
In view of these different criteria, rabbinic authorities have offered various opinions and suggestions, based upon their assessment of the relevance and application of these factors. Some rabbinic authorities suggest only opening the refrigerator door when the compressor motor is running. This will avert causing the compressor to go on directly as a result of your action. The additional time that it may work to make up for the incoming heat is a grama on nitzotzos eish, which is a rabbinic, not a Torah, prohibition.7 Note: To install an indicator light to be lit when then the compressor is running would be counterproductive since the continued burning of this indicator light may be prohibited as mosif havarah.

Some suggest opening the door in an unusual manner (for example using your elbow) which would not be considered m’leches machsheves. Another variation of not being categorized as m’leches machsheves is if the action typically done by one person alone is performed by two people together. Thus if two people were to pull the refrigerator door open together this would lessen the severity of the action. Combine this and the other factors listed above with the fact that opening the door itself is not a direct action to start the compressor. Therefore they conclude that one may open a refrigerator in one of the aforementioned fashions.

Other rabbinic authorities are of the opinion that in view of all the factors mentioned, one may open the refrigerator door at any time in the normal manner.8

It should also be noted that these opinions are given in reference to electric household refrigerators that function on a compressor system. Many RV refrigerators9 are gas powered. This system has its refrigerant (liquid ammonia) heated by a gas flame to begin its refrigeration cycle. Opening the door of such a refrigerator would not have the protection of the reasoned leniency used in the rulings for an electric compressor system. Consult with your rabbi before use.

Advanced Complications

Given the competitive nature of business and the constant striving to market new and improved products for sale, manufacturers try to implement new computer wizardry into their appliances. These advances may complicate the ability to use a refrigerator on Shabbos and Yom Tov.

Some of these innovations may be obvious to the purchaser as a Shabbos or Yom Tov problem. For instance, on some models, aside from the light going on or a fan going off as discussed earlier, a digital readout may be illuminated to indicate the cabinet temperature and the setting. Some models will have displays or alarms to warn that the door has been left open for too long or that the temperature rises too high. Some upper end models may have a sensor that will illuminate the refrigerator when someone comes in close proximity to it, sensing motion or even body heat. Obviously these enhancements would have to be disabled for Shabbos or Yom Tov use.

Automatic ice makers are a common attachment to new refrigerators/freezers.10 To start the cycle of production, the hanger base (located on the side of the ice maker over the ice storage bin) is in the down position. If the ice maker is empty, it sends an electronic message to a valve to open for approximately seven to ten seconds, allowing for water (which is connected to your main supply line) to enter. When a small thermostat located near the ice tray reaches a temperature of ten to fifteen degrees Fahrenheit, the harvesting of the ice begins. A small heating element warms the ice tray so that the ice will not stick and a motor will turn a sweep fork to eject the ice from the tray into the bin below. As the motor rotates the ejection fork, it raises the hanger bar. The bar is allowed to fall after the ice has been deposited into the bin, so if the bin becomes full, the bar will not come down and the ice maker will not continue production.

With regard to Shabbos and Yom Tov use, we may gather that one may not initiate the automatic ice maker mechanism to produce. In order to avert any questions, it may be preferable to lift the hanger bar to an off position before Shabbos or Yom Tov. If this is not done, one must be sure that by removing ice from the bin one is not causing the bar to move, initiating the ice making cycle.

Some newer models have an infrared sensor to measure the volume of the ice bin. If this is the case, then one should not remove ice from the bin on Shabbos or Yom Tov. (It may be possible to fool the sensor by placing a solid object in front of the sensor to make it think the bin is filled even when one has taken ice. However, this must be tested before Shabbos or Yom Tov.)

Some refrigerators offer an ice and/or cold water dispenser. The ice dispenser will initiate its action when the lever is pressed. This switches on a motor that turns an auger in the ice storage bin. The auger pushes the ice out the door into the awaiting cup. In the case of a water dispenser, the lever pressed will trigger a switch that opens an electronic valve to let water into a “water chilling chamber” located in the refrigerator. The pressure of the incoming water will push out the already chilled water in the chilling chamber. This chilled water will flow out the door to the user. In either case, one is directly switching on an electric valve or motor by pressing back the lever, an action which is prohibited on Shabbos or Yom Tov.

In an effort to conserve energy use in frost free refrigerators, some models have incorporated an adaptive defrost system. Earlier we described how a standard no frost system works. A timer will turn off the compressor and turn on a heating element next to the evaporation coils. This will melt any ice build up. It is inefficient to utilize this system on a timer that does not take into account how often the door is opened to let in fresh moist air. Therefore, some models have incorporated a computerized system that counts the number of times the door is opened and the amount of time the door is left open. Based on these variables the defrost cycle will be set into motion. In effect, one causes the heating of the defrost system to go on by opening the refrigerator door.11 Therefore, if you have such a refrigerator, this is a concern that should be addressed.

Sabbath Mode Fridge

Presently the Star-K is working with some manufacturers to incorporate modifications that will alleviate some of the Shabbos and Yom Tov concerns. Specifically: 1) to install a Sabbath mode to modify any adaptive defrost feature so that it would not react directly to opening the door or revert to a timed system when in Sabbath mode, 2) to bypass any electronic readouts, fan operation, icons or lighting that would otherwise be tied to opening the door of the refrigerator, and 3) to install a random delay feature to such Sabbath mode refrigerators to prevent the compressor from reacting directly to the opening of the refrigerator door. Rather, the temperature reading will be done at random intervals signaling the compressor into action. This would incorporate a grama with regard to the thermostat signal to start the compressor. In the meantime, we would suggest testing the refrigerator at the store before purchasing, to be sure that there are no Shabbos and Yom Tov concerns.

For information on refrigeration products under STAR-K certification, visit the STAR-K appliance page on our website.

1. Eino machaven.

2. As a psik reshah.

3. Kibuy.

4. Cold air contracts (meaning the molecules of gasses come closer together). When the door of a freezer is opened it lets in warmer air. When closed again, the air contracts as it chills. This creates a vacuum and may cause a hissing sound that can be mistaken for the sound of a motor or fan. This is a physical effect and not a concern for Shabbos or Yom Tov.

5. Eino mechaven on a psik reisha d’lo nichah lei.

6. Melacha she’aina tzricha legufah.

7. Sefer Hayovel Ezras Torah Horav Henken zt”l Minchas Yitzchok.

8. R’ S.Z.Auerbach zt”l, Yabiah Omer.

9. Refrigerators found in recreational vehicles or trailers.

10. One of the luxuries of having a freezer is the ability to manufacture ice. With respect to the general question of making ice on Shabbos and Yom Tov, we should note that some rabbinic authorities prohibit ice made on Shabbos or Yom Tov because of nolad (a new entity, i.e. ice, was created that was not there before the holiday). According to this opinion one may not use ice made on Shabbos or Yom Tov. Most rabbinic scholars are of the opinion that the prohibition of nolad does not apply in the making of ice. However there is concern for meichin. This means that one may not prepare for the following day on Shabbos or Yom Tov. Therefore one should not make ice on Shabbos or Yom Tov if the intent is not to use the ice on Shabbos or that day of Yom Tov. This means that one cannot place an ice tray in the freezer on Shabbos or Yom Tov afternoon if the ice will not be used before the day is out.

11. As noted previously, where the electricity is used to generate heat, it is considered havarah.