Does anyone have the specs for the stock shelly thresholds, or a ‘best practice’ I should try out?
Right now it’s low 60F outside, and my shelly’s are around 100-110F while on (say a 50F delta). It often gets over 100F here, so I expect those shelly’s to hit like 150F in the heat of summer. I’m running esphome, so gone are the original protections. My plan is to use the temperature to shut off the relay(s) when they get too hot, then allow normal operation after they cool back down. I also plan to provide similar overload protection based on wattage feedback as well. 180F?
FWIW, I researched some thermal limits. We have the typical FR4 pcb with a Tg ~ 170C, and an esp8266 with a max operating temperature of 125C (likely other IC’s onboard will have similar 125C or higher ratings). Not having the layout of the PCB, I don’t know how well the thermistor temp correlates to esp temps. I would imagine the esp will be slightly warmer that it’s surroundings, and given the very compact nature of Shelly circuits, the PCB temp will be very close to ‘ambient’ inside the case. So, my thoughts are to keep the thermistor below 90% of esp max temp… which would be <=113C (or 235F).
After having my shelly 2.5 with one of it’s relays on overnight, I saw a max delta of about 60F. With heating of the exterior wall during summer I expect ambient inside the electrical box to peak around 130F… so about 190F at the PCB if one relay is on. This is well within my proposed safety limit of 235F. So I that’s what I’ll use for now.
I bumped because I’m still curious what others think about this subject. I’ve copied thermistor code for esphome. So I am certain I’m not the only one making use of this for actual safety, but there’s precious little info on what max temperature ppl are using. Surely, folks are doing more than looking at a graph of shelly temps… what cutoff limits is everyone else using?
There’s quite a bit of discussion about Shelly’s warm/hot to the touch on their Facebook group. Just join the group and search for “warm”.
I’ve attached a few screen grabs I did for Shelly 2.5. Mine sit at about 60DegC (140F) with no load. Wow. And when running two 8W LED downlights it rises to 75C (167F). I’m nervous about this being inside my wall!! Seems the thermal cutout is 90 deg C. Screen Shot 2020-02-23 at 6.47.04 am|542x500
Thank you for posting your research. Interesting. I have a 1 outside controlling some strip lighting in a weatherproof enclosure but I expect summer temps of 45C (115F) so I have been contemplating switching it to a 1PM for overheat protection but it should be okay going off your research.
