A ledger in the Townesend family archive contains a reference to a Robert Johnson being paid for six days work ‘laying sume stepts & hang the Boiler in the Kicthing’ at Christ Church.

MS. Don. c. 210, fol. 92 – The installation of a boiler in the kitchens at Christ Church, Oxford, February 1718
The Oxford English Dictionary defines a boiler as ‘a vessel in which water or any liquid is boiled’ and cites Daniel Defoe’s 1725 publication A New voyage round the world, by a course never sailed before as the first use of the word. The reference in the Townesend archive dates from February 1718 [new style]. Could this be the earliest reference to a boiler?