Greetings...I am installing warming drawer and convection microwave into an island cabinet in my kitchen. Although not zero clearance, the clearance is less than idea. I was planning to install a ultra quiet cabinet fan in the cabinet with some strategically placed ventilation holes. Here is my problem. Neither appliance itself will require additional venitilation, but both on at the same time might. I thought I could buy a relay that would switch on the fan when both appliances are being used? Can someone direct me to what I would need to buy? Each of the appliances will be on their own 15amp circuit.

thanks!!