The following is just some info about an outdoor OS installation really sees some hot conditions.
My OpenSprinkler sits in a metal box on the NW side of the house in Phoenix, AZ. It is shielded from direct sun.
I measured the temperature in the box and under the cover of OS some weeks ago when temp was in the low 100s. If I remember correctly, the temp rise under the cover was around 9 degrees F above the temp inside the box, and the inside the box was a couple degrees above ambient max.
Since the max temps were certain to be a lot higher, I removed clear plastic cover from OS. Last week, my Davis weather station recorded a max temp of 118,116, 112, 111,111,111 deg F on consecutive days, and OS seemed to survive OK. The temperature within the box was probably very close to the max temp. I checked OS this AM and noticed the preview function showed that the time was about 5 hours fast. I don’t know if there were any disruptions; we were gone the hottest days. The time error really makes no difference in my installation, and a remote reboot corrected the time. At lower temps, the clock seemed to hold reasonably well.
There are three components dissipating power in the metal enclosure at all times, a small transformer, an X-10 Appliance module, and OS. The X10 module is connected to a powerline carrier adapter which is turned off except for a couple hours in the morning when it energizes the Ethernet adapter. I never measured the steady state power dissipated in the box, but the transformer and X10 module dissipate 1 watt each plus what ever OS dissipates.
I’m going to monitor the clock every few days to see how it holds. There was never a significant error earlier at lower temperatures.