I know a question about warming drawers was already asked, but I have a different question. I have learnt that with almost all warming drawers, when they are opened, cool air goes in and the drawer will then need to bring the temp back up to the set temperature. Wouldn’t it then be a problem to open a warming drawer on shabbos?
The Poskim dealt with a similar question regarding a refrigerator on Shabbat. There are Poskim who allow to open the fridge only when the motor is running and therefore by opening the fridge and increasing the temperature it will not cause the motor to start. There are however other Poskim who allow to open the door at all times for a short period of time, whereby the fridge would not be warmed up that much that it would cause the motor to start. It seems that these two views would apply in the case of the warming drawer. Where according to the more lenient opinions if you open the drawer only for a small amount of time, it will be permitted. Rabbi Baruch Kitay