Sounds like you need to buy different hotplates.
I had repeated issues with one brand, Thermo Cimarec hotpplates. They never turned themselves on; they would suddenly go to maximum temperature without any adjustment.. I was told that the rheostat was failing.
I switched back to Corning hotplates and haven’t had this problem since. I run many unmonitored, overnight experiments and have many years. The only issue I’ve had with Corning hotplates is nonuniform temperature across the surface, however, I had that issue with Cimarec and would assume that it occurs in all hotplates.
Considering the history I would think contacting the manufacture, if that has not been done, to alert them of the problem and to suggest a recall. I am not sure if this appliance falls under the purview of the CPSC but letting that agency know of the potential hazard it may want to get involved.
In the past year, we have had a series of issues with "runaway" hot plates. In the first instance, a hot plate in the off position began heating in an unoccupied laboratory resulting in a hood fire. Since then we've observed another hot plate that was heating while in the off position as well as a hot plate that heated uncontrollably while on a low setting. The hot plates that were in use were all relatively new and issues look to be caused by failed circuit boards.
I presented some of the lessons that we learned from these events at the recent ACS National Meeting and was surprised with how many researchers stopped by my poster to indicate that they have observed the same issues. Descriptions of some of these events and additional details can be found at the following links:
We're advising our folks to keep hotplates unplugged when not in use and use stirring-only hotplates where possible. In addition, some groups are considering getting rid of their existing hotplates and buying new models, but I fear that these may have the same potential issues. The possibility of installing an on/off switch on the cord has also been discussed, and while this will prevent hot plates from heating while in the off position, it might not help the issue of hot plates running away (uncontrolled) when the hot plate is intentionally turned on.
I'd like to poll the group- has anyone else had similar issues, and more importantly.... what kind of solutions have you identified?
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