boiler vs central heating

boiler

noun
  • An apparatus for heating circulating water or other heat transferring liquid. 

  • An old woman. 

  • A device consisting of a heat source and a tank for storing hot water, typically for space heating, domestic hot water etc., disregarding the source of heat. 

  • A sunken reef, especially a coral reef, on which the sea breaks heavily. 

  • A person who boils something. 

  • A steam boiler. 

  • Boilerplate. 

  • A tough old chicken only suitable for cooking by boiling. 

  • A kitchen vessel for steaming, boiling or heating food. 

central heating

noun
  • Any of various heating systems in which a central source of heat is used to distribute heat (and sometimes hot water) throughout a building in a controlled manner. 

How often have the words boiler and central heating occurred in a corpus of books? (source: Google Ngram Viewer )