In my house when I switch on AC after about 15 minutes the MCB connected to a boiler switches off whereas AC keeps on running.This happens even if Boiler is switched off when AC is on. MCB connected to the boiler does not trip even if boiler is switched on for hours when AC is off. Boiler & AC are in parallel & I have single phase, 220V AC supply with frequency 50 Hz. Please suggest probable causes & remedy.