I have a customer that recently installed several high end ovens in their stores. They teach cooking and the store managers are complaining that the oven isn't holding the temp. They also say the oven takes too long to pre-heat. The service going to the appliance is correct. After speaking to the manufacturer their telling me the oven needs a constant 234Vac or more to heat properly.

How do I size the buck/boost properly for a 240Vac 60amp single phase appliance?