A Mode of its Own

How did Shabbos mode come to be—and what problems was it actually designed to solve? Rabbi Shmuel Katz, Rabbinic Coordinator at the cRc, joins R’ Yitzy Hisiger for a fascinating look at the history, halachic challenges, and ingenious solutions behind the Shabbos modes in today’s appliances.

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Hello everyone and welcome back to Let's Talk Kashrus, presented by the Chicago Rabbinical Council. Today I am joined by Rabbi Shmuel Katz, Rabbinic Coordinator at the Chicago Rabbinical Council. Thank you, Rabbi Katz, for joining us once again. Thank you.

The last time we met, we spoke about the concept of Shabbos mode, and you gave us a beautiful primer about the workings of Shabbos mode, halachically, practically. What I'd like to discuss with you today briefly are some of the issues that Shabbos mode came to address. I think it would be interesting to go back historically to when the original oven shailos arose. What were the issues that were discussed by the poskim, and how did Shabbos mode address those issues? So Shabbos modes were started only in the last 30 years, but the shailos have been about 100 years old.

And the shailos, the tshuvas really started with the thermostats on fridges. This was an electronic appliance, and people discovered that it had a thermostat, which meant when the temperature in the fridge gets too high, it turns the fridge back on to cool it back down. So people opened the fridge, the cold air would come in, it would make it warm and it would cause it to go on. And the poskim discussed: Can you cause the fridge to go on on Shabbos when you open the door? Can you open the door and allow it to happen? An oven's was the same thing.

It had a thermostat. You open the oven door, the cold air would go in, it would cause the temperature to drop, the fire would then go back on to do it. Ovens as well, if you open the oven door, even if the flame is on, the fire would stay on for longer because now it needs to stay on for longer, like being mosef shemen, which is a problem on Shabbos. Is that mosef shemen? And is your action of opening the oven door directly causing this? So Rabbi Shlomo Zalman has many tshuvas, and is probably the original of the heterim to open the fridge on Shabbos even when the compressor's not on.

So some solved this by just waiting for the fridge to turn on. Only when the compressor was on and it was rattling, would you open the fridge door because then you're not causing it to go on, it's already on. And the same thing with ovens, would only open the oven door when the fire was on. This is what became...

there were people who were being meikel and wouldn't worry about this shaila because of their rabbonim, and the ones who were machmir were very often just waiting for the compressor to go on or the fridge to go on. And that was the original Shabbos mode. You just spoke to your rabbi, you knew how to use it in a way that's appropriate for Shabbos. And then about 25, 30 years ago, the appliance manufacturers were tapping into this and working with, and the Star-K was a real pioneer in Shabbos modes to solve Shabbos problems.

Originally at that point, they were focused more on more new problems, not related to the old ones. So some new ovens, after 12 hours they would turn off. Who leaves their oven on twenty-four, for 12 hours? After 12 hours it would go off, and that would be a problem for Shabbos or Yom Tov for sure if you needed to keep it on. Another very practical thing, but people would like their oven to go off Friday night, set the timer so it turns off Friday night after your food's done.

So ovens come with a time-bake feature where you can set a timer, but almost all ovens they beep and they continuously beep after the timer ends, which would be very annoying on Shabbos to have the timer beeping the rest of Shabbos, and Shabbos mode would disable that. So there was a couple of those practical types of things that the Shabbos mode was solving. Then lights became common, and Shabbos mode very often were also able to solve the light. Fridges also the Shabbos mode came to solve a bunch of problems.

One of the probably biggest problems, besides for the light, those don't turn off after 12 hours like ovens do, but there's a defrost in the back of the fridge. It builds up ice, or frost-free are fridges. In the old days you had to manually defrost your fridge. Ours are frost-free, gratefully we're not dealing with the ice build-up.

But the way it does is it turns it off and it puts a heating, there's a heating element in there and it gets red hot. It actually, which we, which is esh. There's fire in there. So eventually there's a fire going to go on in the back of your fridge, a halachic fire for Shabbos purposes, that's going to melt the ice off.

So the question was what triggered that to go on and off? So in more recent models, again, recently not in the last few years but in the past decades, they've put those on, they want to do it efficiently, so they started doing it by how often the compressor runs. After a certain amount of time the compressor's running and the fridge is cooling, it assumes there's a build-up and it will go into defrost mode. Another thing they would do is count how many times you open the door, because humidity affects how much humidity's in the fridge is going to affect it, and that's going to also depend how many times you open the door and let in ambient air into the fridge. So it counts those door switches.

So eventually you'd open the door a few times, let's say it's every tenth door opening, you've that tenth one, you've opened it and it said let's turn on the defrost, and that's actually a de'oraysa shaila because it's an actual fire going on in there. So the Shabbos modes almost universally solve that by Putting it on a fixed timer. It goes on every so often automatically, unrelated to how often the compressor's running and how many times the door's been opened. It's been able to solve some of those as well.

It'll disable Shabbos modes will disable the buttons so almost all the buttons won't work on your fridges and on your oven or at least when you push them nothing will happen, nothing will be visible from it. So they've come to solve a lot of minor issues and then some practical issues and then some halachic issues as well. The Shabbos modes have become very helpful for. Got it.

Any other issues that you wanted to discuss as far as the Shabbos mode addressing? We discussed thermostats, you discussed the the defrost right. So the door switches is also something we discussed in the last episode. We discussed last time yeah. The door switch and what the door switch does.

But just to go back to the pre-Shabbos mode days of the thermostat to discuss that for a minute. Rav Shlomo Zalman was talking about in his teshuvas. He's talking about a very old thermostat that they would use then which had a capsule of gas of liquid. If it got too warm it would expand into gas and would blow up a what was called a bellows which is essentially a balloon.

And that balloon would physically push a button to contact and turn the oven on or turn the fridge on and then it would cool, it would go back into liquid, it would shrink and then the contacts would come off and that's how the compressor went off. So this was a very physical physical manual of sorts analog version of a thermostat. Thermostats have come have changed quite a bit. Our current thermostats in ovens and fridges have no moving parts.

There's just a little bit of metal in there. The computer's sending an electrical signal through what is a thermistor and it's and measures the resistance of the electric through it and that resistance changes based on temperatures. It's very minute. It changes very slightly but these are super sensitive and they can pick up the slightest changes in temperature by sending electricity through a piece of metal and seeing how it comes out the other end.

They can detect it so it's it's an entirely different thermostat than Rav Shlomo Zalman was ever talking about which does have halachic ramifications and the poskim and the certifiers of Shabbos modes work very closely with to figure out. So Rav Shlomo Zalman was was meikel in certain scenarios. There were machmirim but since then the Shabbos modes have said hey we can actually solve we might be able to solve the thermostat problem as well. So besides for making it as like an old thermostat or at least as good as the one that Shlomo Zalman was being mattir, they said we can solve it entirely and various attempts have been made at figuring out how to solve this.

Some some super creative. Some people were just putting their fridges on timers. You put your fridge on a timer it the whole fridge goes off every 15 minutes for five minutes and while it's off you quickly open it and close it and you take whatever you want out. It's not very good for the new fridges.

The new fridges have a computer in there and they have very strict cheshbonos on how they operate and when they do so it for the new fridges. Would it be good for it to be going on and off randomly? It's terrible for the fridge. The new the new fancy fridges it's completely terrible for but this is what people were doing. The old fridges could handle it because that's kind of how they were built anyways.

They were just unplugging and plugging themselves in with the bellows. But the new fridges they can't they're not built for it so you're really going to reduce the life of your fridge if you do something like that. Even taping down your door switch the whole week is bad for the fridge because they they built the fridge to be to rely on that feedback for various functions and and the experts say it'll reduce the life of your fridge if you keep it taped down the whole week. It may not even cool properly because it's it relies that when it's the door's open it will know it.

So over Shabbos it'll be okay but over to do it the whole week and just leave it like that permanently on the newer fridges they say will reduce the lifespan of your fridge. So the the ways to solve the thermostat we started with putting it on a timer some people were doing and then the agencies got involved and they were able to work with the work with them and and come up with creative solutions. So some of them have where they put it instead of constantly taking the temperature and knowing and then immediately acting upon whenever there's a change in temperature to turn the the appliance on or off it goes it's set to go on at fixed intervals. It'll take a reading right before it goes on to see if it's off a base if it's out of the window but instead of an immediate every every few minutes it'll take one it'll be set to go on and then it'll just take a baseline reading to see if it's off base and needs to skip that one.

That's how some solved it. The new Shabbos mode they do something very fascinating. They take the ambient air temperature. Instead of taking the temperature in the oven they'll take the temperature outside the oven and they'll know based on the temperature outside the oven how often the fire inside needs to go on or off.

Interesting. Another another solution some came up with was to let the oven remember from during the the fridge remember from during the week. We know that in your house this is how often the fridge the compressor needs to go on to keep your items cool because we've measured it the whole week. So it's gonna vary from house to house and appliance to appliance and use person to person depending on how you use it.

So it depends on the person, your usage of it, depends on the environment around it, depends on the ambient temperature in the room, the humidity, all things, so if you just measure that during the week you can now know pretty well how often you're gonna need to go on and you just skip the thermostat entirely and on Shabbos only use go based on a fixed time cycle that you've determined by using the week beforehand. So there've been some creative ways that the Shabbos modes have been able to solve the thermostat shaylah and make the ovens and fridges even better than they were when the tshuvos were started to be written about a hundred years ago and those tshuvos when they were struggling with the thermostat Baruch Hashem they've some of them have been able to solve it in a way that's way better than we've had in the past but again this varies from model to model, it varies from certifier to certifier and type of Shabbos mode to type of Shabbos mode it's gonna vary. So to know what you actually if you've always been machmir on the thermostat shaylah you're gonna want to know how your current one works very specifically with your specific model to make sure that it's changed enough for you to change the way what you've been doing in your house until now. Got it.

Okay, so you know the bottom line is if you have whatever appliances in your house you have to make sure that you're following the proper protocol and people who are buying appliances in addition to finding out the features, the model, the price you have to find out the halachic ramifications and components and get proper guidance so that it addresses some of the issues that you spoke about today that Shabbos mode were designed was designed to solve. Yeah. Right, and I want to add that it is very important if you have an appliance in your house to find out how it works but it's also crucial if you're going to buy an appliance understand how you want to use it and figure out if this is what you want to do with it and what the right model for you is. If you don't intend to ever kasher it for Pesach then don't worry about kashering it for Pesach when purchasing your model.

But if you do you may want to know that in advance. Here's another example on ranges. Induction burners are very popular right now. A lot of houses they're neat, they're sleek, they might even be safer because they don't get hot.

But if you have non-Jewish domestic help they're terrible because you can't turn the fire on and let them put a pot on the stove anymore as Ashkenazim because there's no fire there. So if you have non-Jewish you don't want to buy an induction burner if you have because then you have to actually put the pot on the stove for them. You can't just turn the fire on and let them go induction burner. So it's worth pre-purchase walk in don't buy the sleekest model and then afterwards call your rav and say how do I use this on Shabbos? Figure out how you want to use it and then go buy a model that fits your needs in the best halachic way possible that matches your needs as well.

Excellent. Rabbi Katz thank you this has been a tremendous lesson in the workings of our home appliances and we greatly appreciate your expertise. Thank you. Thank you.