Well I got one set closer today to my eBrewery, as I purchased two DC triggered 45amp SSRs. They are mande by Opto 22 and I got two for $20 shipped so I couldn't pass up the deal. I realize that a 4500watt element only needs 21A, but that would give me room to grow, possibly 20+ gallon system in the future running two elements per relay.
Relay Product Page
My concern is the heat sink used, as they are rated for 45amp, does that mean if only using 50% of it's rating 21amp, would I not need as large of a heat sink? Also would it be possible to mount both relays on the same heat sink if it was large enough?