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I suspect the problem is caused by the ssr becoming too hot and its internal thermostat acting to shut off the relay. I have a query with sensata/crydom to confirm as I suspect their latest next generation* D2425 SSRs contain an electronic thermostat to protect its electronics. Certainly the D2425 specification says the maximum ambient temperature is 80C, and at this temperature and above the current it can handle must be reduced ie the device de-rated from 25A. And the reference below describes an internal thermostat within the SSR package.
* The previous SSR was an earlier generation I reckon without a thermostat. Note the original SSR was assembled in Mexico whereas the new one does not mention where it was assembled.
https://www.sensata.com/sites/defau...tection-for-solid-state-relays_whitepaper.pdf
At the moment there are two problems with the way the SSR is installed. The first is the fins are horizontal - they should be vertical to maximise cooling by convection flow of air over the heat sink. The second it appears the SSR and heatsink is within a sealed enclosure adjacent to the very hot oven chamber. The SSR even with a heatsink properly orientated will have great difficulty keeping cool enough inside this enclosure so that the internal device thermostat does not operate.
What to do?
1. Provides some sizeable vents above and below the heat sink.
2. Make sure the heat sink fins are vertical.
3. Buy a heatsink with the highest thermal conductivity - aim for 0.25C per Watt. See:
https://www.sensata.com/sites/defau...urproducts_HS-Series-Heat-Sinks_brochures.pdf
4. Incorporate a computer type cooling fan to force cooler outside air into the electrical cabinet and push out the warmer air inside the cabinet.
* The previous SSR was an earlier generation I reckon without a thermostat. Note the original SSR was assembled in Mexico whereas the new one does not mention where it was assembled.
https://www.sensata.com/sites/defau...tection-for-solid-state-relays_whitepaper.pdf
At the moment there are two problems with the way the SSR is installed. The first is the fins are horizontal - they should be vertical to maximise cooling by convection flow of air over the heat sink. The second it appears the SSR and heatsink is within a sealed enclosure adjacent to the very hot oven chamber. The SSR even with a heatsink properly orientated will have great difficulty keeping cool enough inside this enclosure so that the internal device thermostat does not operate.
What to do?
1. Provides some sizeable vents above and below the heat sink.
2. Make sure the heat sink fins are vertical.
3. Buy a heatsink with the highest thermal conductivity - aim for 0.25C per Watt. See:
https://www.sensata.com/sites/defau...urproducts_HS-Series-Heat-Sinks_brochures.pdf
4. Incorporate a computer type cooling fan to force cooler outside air into the electrical cabinet and push out the warmer air inside the cabinet.
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