a heat activated flue damper actuator employing an assembly of shape memory alloy springs with linkages to a conventionally designed contemporary flue damper . the combination of the spring material , spring configuration and dimensions , linkage / fastening scheme to the flue damper shaft and placement in the water heater &# 39 ; s heating chamber are all controlled to optimize the energy efficiency of a conventionally designed , pilot - lit or pilotless ignition , contemporary gas water heater .