We just finished construction on our first commercial kitchen for a cupcake bakery. This is in a small space in a basement, but we wanted to be able to bake multiple pans of cupcakes, cookies, muffins, or brownies at a time. We looked into full-sized convection ovens but they were far too big for the space. We finally settled on a Unox Anna oven (electric), which we could technically fit 4 pans of cookies or 2 pans of cupcakes in. We purchased this brand new, but neither my partner or I have ever baked with convection before, so we realized it would take some getting used to.
Unfortunately, we haven't managed to get anything to bake properly yet. We tried chocolate chip cookies first, at various temperatures from 250 ranging up to 400. Each time, the top of the cookies got quite brown, but the bottom of the cookies was not brown at all and the inside was completely uncooked. Next we tried our cupcake recipe with the least moisture in the batter, and we had the same result-- except this time, the top of the cupcake collapsed into the center because it was so raw inside.
I contacted the manufacturer and they sent a tech out to check 2 things: whether the fan was shutting off (which it shouldn't), and whether the temperature was off. Neither of these things was the answer, so the manufacturer has no answers for me. They don't think the oven is faulty.
I phoned a lady in Calgary who uses the very same oven, and she has never had this problem before. She said at first when moving to convection, she had to adjust her recipes to have less liquids in them, but they were only "a little too moist", not raw on the inside. Her suggestion was that the lower element in the oven wasn't working properly... turns out there is no lower element, so that can't be the answer.
The best I can figure is that the top of the items is directly exposed to the heat in the oven and so it is baking quicker than the bottom, where the heat has to get through the pan first. But if this is the problem, I don't know what to do to fix it.