Ques. Every electrical appliance gets overheated in the house. Recently in one of the flats the ac got burned. Can there be an electrical problem in the house. If so what can be the solution . Does this affect electricity bill. The apartments are 30 years old .
There can be two reasons for electrical appliance over heating.
If the appliance over heats when connected on a particular switch board: the connections on the switch board are loose because loose connection generate a high wattage leading to appliance over heating
If the overheating is encountered all over the house then the Neutral wire should be earthed properly.
Neutral to Earth Voltage difference should be zero.
This does not affect your electricity bill, The only thing that affects electricity bill is it's usage.