I have 2 Taco zone valves powered by 1 24-vac transformer rated at 40 va. Transformers keep failing. I'm thinking that there might be some kind of wiring problem that I can't identify, or that sometimes the zone valves are all on at once and use more than the rated 40 va. I am considering a Honeywell AT72D transformer. It has something they call "override protection". Does any body know exactly what override protection is? If it is something that protects the transformer from damage when more that 40 va is being used, than I think it may solve my problem.