Thanks everyone, good stuff.

Mikel81; You make a very good point about losing two racks with one failure. Hadn't considered that. Which begs the question, is channel failure a common occurance? If one had to ship out a unit for repairs, what is the least expensive t-stat you could get away with to power a rack/incubator temporarily. Can you run a rack on a Hydrofarm while unit is being repaired. Might want to keep a back up on hand.