I put 2 new 2 ton package units on my roof 3 months ago, unfortunately they are not covered by warranty because we installed them. Both units will work for a couple weeks and then I will loose a transformer. Will blow even when the unit is not being used. It's a 240v/24v 40va transformer, I am leaning towards buying a transformer with a higher va rating since it takes so long to blow. Just fyi I am drawing only .35 amps on each leg of the 24v side of the transformer

No ac tech here, but I'd look for problem in wiring on low voltage side. Problems on high voltage side would trip breaker. Next time you have to replace get a transformer with built in breaker. That way you can reset rather than replace.