# Expobar G10 Overheating taking out the PRV



## Coffeeafix (Jun 16, 2015)

Hi I have been working on the Expobar G10, it is taking out the prv by overheating, As these are electronically controlled, Any idea of the likely cause? Solid state relay or temp sensor, although this does read okay in the display

Electrically it all tests okay

Cheers


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## espressotechno (Apr 11, 2011)

Solid state relays tend to fail "off".

The electronic temp. sensor is probably faulty. Replacement is fairly cheap & easy to fit.


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## DavecUK (Aug 6, 2013)

espressotechno said:


> Solid state relays tend to fail "off".
> 
> The electronic temp. sensor is probably faulty. Replacement is fairly cheap & easy to fit.


SSRs actually tend to fail shorted and mechanical relays tend to fail off. It's not to say that these failure modes cannot be reversed. it's why SSR circuite ideally should cater for a failure mode with an electromechanical relay to break the circuit in the case of an SSR "short" failure condition.

If the sensor is indeed showing the correct temperatures and over temperatures, then it could be possible the SSR has failed "shorted", which should be easy for them to test.

http://www.allaboutcircuits.com/textbook/digital/chpt-5/solid-state-relays/

https://www.omron.com/ecb/products/pdf/precautions_ssr.pdf


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