Extending a Shabbat Clock

Bsd Shalom Can i add more time in a shabbat clock ,so that the air conditioning system will not stop working, during Shabbat?

Shalom!

Thank you for your question.

Touching timers is a very sensitive issue in Halacha as there a number concerns.

For example, one must be very careful not to cause anything to go on or off when adjusting a timer. This can easily occur due to a misjudgment when playing with the “teeth” of the timer and it could also happen if one accidentally moves the dial while adjusting the teeth. There is also a concern that adjusting a timer is a violation of “makeh b’patish” as one creates new circumstances when adjusting a timer. Finally, the timer, including the teeth, are deemed to be muktza by many authorities.

As for a matter of practice, many authorities rule strictly based on some or all of the considerations above and forbid any adjustment of a timer on Shabbat.

It is the view of our rabbi, Rav Amram Fried, that it is permitted to have a non-Jew adjust the teeth of a timer when needed. However, it must be clear, that when adjusting a timer it is only permitted to adjust it to maintain the current status. In other words, if the appliance is currently off, one may adjust the teeth that it remains off and not go on when originally intended. So too, if it is currently on, one can adjust the teeth so that the appliance remains on and does not turn off when originally intended. It should only be done if there is an urgent need.