617.
The efficiency of a modern boiler using coal and heat recovery equipment is about-
ব্যাখ্যা: Modern boilers are more efficient than older boilers for several resons , but their main homage is that are condensing. A condensing boiler recovers more heat from the exhaust flue gas and uses it to heat the central heating water, making a more efficient that old boilers. It’s near about 85 to 90%