The Dometic fridge/freezer "bleeps" when the door is left ajar. But, it also bleeps when the voltage supplied drops too low. Does anyone know how low the voltage has to be for this to happen? The reason I'm asking is that I'm complaining to EDF that the voltage supplied is not always 220 volts (or there abouts) and just need to quote an approximate figure. Everything else works as normal and it's not like it all the time