STORAGE-TYPE WATER HEATER AND CONTROL THEREOF BASED ON WATER DEMAND

摘要

A storage-type water heater with a controller. The controller controls anupperheating element such that an upper zone water temperature is maintainedproximate atemperature setpoint. The controller calculates a temperature differentialbased on adifference between an upper zone water temperature and a lower zone watertemperature.The controller controls a lower heating element such that the temperaturedifferential doesnot exceed a first limit during periods of low predicted water demand and suchthat thetemperature differential does not exceed a second limit during periods of highpredicted waterdemand. Periodically, the controller switches from the first limit to thesecond limit duringperiods of low predicted water demand.