Bosch single oven with delayed timing

[Myfuchia]

Last week I had the above fitted and I find when the oven had the delayed timer set a fan inside the oven starts. I've contacted Bosch and they say this is ok. My electrician phone them and spoke to the technical dept who say its new legislation to protect the food in the oven before it starts cooking. I disagree as its using power for no reason. Has anyone else found this problem

[Myfuchia]

I can't find any legislation on ovens except for the rating model etc. I've never known a fan running at the setting point. I think this oven has to go back