X3 Immersion heaters on a single radial

[TerryE]

On 12/01/2026 at 19:12, Nickfromwales said:

 

@TerryE used solid state SSR’s to power up his heating and hot water gubbings, so the attraction is there if you want silent operation vs the clunk of a contractor.

 

I moved away from using SSRs just under 2 years ago to an ESP32 module using 24 VDC to drive contactors.  See p3 and 4 on this topic.  

 

My issue with the SSRs was that they had about a ½-1% heat loss in the SSR when on -- that's 15-30 W per relay.  This caused real overheating issues with the DIN mounted SSRs.  The contactor coil losses are a few W, so absolutely no overheating issues.  I prefer using 24 VDC for relay control as this minimised safety issues in the microcontrolled modules.  You just need to include flyback diodes to prevent the 24V relay contact arcing / wear.  You really need to add snubbers for the 240VAC switching relays for the same reason.