The relays have worked well. Solid state would certainly be less noisy; there is a pretty much constant clacking of one contactor or another. I will research SSRs. We tried some a couple or years ago, but had issues with them overheating and went back to the original contactors that came in the power packs. The equipment we are using was actually used in industrial heat treating using similar heating elements and is rather robust. It's just implementing new controls to make it do exactly what we want that is tricky (for me anyway). We have another division that is using flexible ceramic heaters at 80v/45Amps and they are talking about switching us over to those, which will almost certainly happen as soon as I get the bugs worked out of this system, lol. Those units use the exact same contactors.