Operating a clothes dryer on Friday that will continue to work on Shabbat
Question
Oftentimes, I have wet laundry on Friday and I want to operate the dryer so that it will continue to work on Shabbat. If I do not operate the machine, I fear that the laundry will be ruined and become moldy. This has happened in the past and the clothes are very dear to me and they’re delicate. Is this permissible?
Answer
Principally, this is forbidden. However, in a case of significant loss, one may rely on those who permit it. The reason for this is that if you have a device that you are not allowed to operate on Shabbos, it is forbidden for it to work on Shabbos if it makes noise (even if you turned it on before Shabbos), as this is disrespectful of the Shabbos and appears as if it was operated on Shabbos itself. This includes both the case where the device was operated on Friday and did not finish its operation, and when it is operated on Shabbos by a Shabbos timer.
Source
Remo (Orach Chayim, Chapter 252, §5; Mishnah Berurah, ibid.)