SSR MELT DOWN...please help

[erinh]

Oh man with 7 days untill Christmas I am screwed. After successfully putting my controller together, my SSR melted down on the first project. I had a kiln project running for about 5 hours until the heat was too much for the relay. The kiln is 20 amp and the SSR was 40 amp. What should I do? Would a fan keep the relay safe? Should I use a higher amperage SSR? My whole Christmas is counting on this. Please help me...

[richiem]

I just joined today and have just seen your post. Sorry I couldn't help in time.

1) use at least a 60A SSR.
2) use a heatsink on it -- they are available, and often come with the SSR. Use thermal grease between the SSR and heatsink.
3) if needed, fan-cool the heatsink.

SSRs only carry their full rated current when heat sunk and at a specified base-plate temperature. There should have been some literature with the SSR showing its derating curve for various ambient temps and currents. A look at that will answer many questions. I'm controlling 12 amps of load with a 60A SSR on a hot tub with no problems, but be aware that as an electronic device, SSRs can randomly fail and that operating conditions can really speed that failure up.