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Is the Plus 2PM run as hot as a 2.5 ?


jeremypsl

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Hello,

i tried to control a 2 speed house ventilation with a Shelly 2.5 but it was placed under the roof and on a sunny day it’s pretty hot in there and the 2.5 reached 85 degres celcius. I replaced it with 2 1PM, much colder. 
i was wondering if the Plus 2PM run cold like a 1PM or pretty hot ?

thanks. 
 

edit : oups wrong device, can you move my post to the Plus 2PM section please ?

Edited by jeremypsl
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  • jeremypsl changed the title to Is the Plus 2PM run as hot as a 2.5 ?
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Heat buildup in a „PM“ Shelly is caused by (a) a steady heat source (CPU, other ICs, power supply dissipation) and (b) a variable heat source (the thermal dissipation in the shunt). This heat is radiated in a certain volume, which is rather equal between various Shelly types, cause the volume of the shell is nearly equal.

Comparing Shelly 2.5 with plus 2PM, we recognise identical shunts (4mΩ) in both types. Thus, the variable heat sources (factor b above) are the same and are depending from the switched power of the appliance only. Otherwise, heat source (a) shall be slightly larger with a Shelly plus 2PM, cause the more powerful CPU (ESP32) will consume more power than the slower ESP8266 in the 2.5 device. Hence, a Shelly plus 2PM should get more temperature than a Shelly 2.5, seen from a theoretical perspective.

Comparing the heat dissipation of ONE Shelly 2.5 with the dissipation of TWO Shelly 1PM is misleading, cause we find the double volume and a smaller shunt (1mΩ in the 2 1PM) with a single volume and higher shunt resistance (in the Shelly 2.5).

 

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IMHO, Generation 1 Shellies like the Shelly 2.5 don’t shut down caused by overheating. With Generation 2 devices, a separate temperature sensor was applied near be the relay(s) to realise a thermal shutdown. Moreover, a further reason for the incomparability of both series.

Edited by thgoebel
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At least for the Gen1 devices, the reported temperature is the CPU Core temp, not the device's temperature "to the touch".
It's not uncommon for a CPU core to reach temps of 70-80℃, just have a look at a computer's CPU core temp under heavy load and then look at the cooling fins and fans that are installed to keep it from overheating.

That being said, The Shelly Knowledge Base does list an operating range of "-20 °C to 40 °C / -5 °F to 105 °F" ambient temperature.
So if you often/easily have temperatures near 40℃ under your roof, it's best to look for a different mounting location and/or to provide plenty of airflow to move the heat generated by the Shelly itself away.

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