Patent ID: 6971585

Claim:
A back-up heating system for a building having a first, enclosed compartment containing tooling for semiconductor fabrication, and a second, enclosed compartment containing electrically powered air handling equipment for constant exhaust of air from and intake of air into said first compartment, and a first, hot water heat exchanger having a first flow path, through which water heated by a boiler remote from said building is circulated, and a second flow path, through which building level heating water is circulated to absorb heat from said boiler-heated water prior to transfer, through at least one hot water radiation heater, of some of said heat to the air in said building, said back-up heating system comprising: a) a liquid cooled, internal combustion engine and generator for generating electricity during periods of primary power outage to operate said air handling equipment; b) a heat rejecting radiator for selective connection to receive liquid coolant from said engine, reject heat from said coolant and return said coolant to said engine when outside temperature is above said predetermined value; c) a second heat exchanger positioned within said building and having a third flow path, for selective connection, alternatively to said radiator, for circulation of liquid coolant from said engine, and a fourth flow path, for selective connection to receive said heating water from said heater prior to circulation of said heating water through said second flow path; d) first means selectively operable to control flow of said coolant between said radiator and said third flow path; and e) second means selectively operable to control flow of said heating water between a direct connection from said heater to said second flow path and connection to said fourth flow path and thence to said second flow path.