US 11,703,254 B2
Electronic control system for electric water heater
Raheel A. Chaudhry, Montgomery, AL (US); Stephen M. Maciulewicz, Wetumpka, AL (US); and Jozef Boros, Montgomery, AL (US)
Assigned to Rheem Manufacturing Company, Atlanta, GA (US)
Filed by Rheem Manufacturing Company, Atlanta, GA (US)
Filed on Apr. 29, 2019, as Appl. No. 16/397,779.
Application 16/397,779 is a division of application No. 14/080,422, filed on Nov. 14, 2013, granted, now 10,274,226.
Claims priority of provisional application 61/770,381, filed on Feb. 28, 2013.
Prior Publication US 2019/0249903 A1, Aug. 15, 2019
Int. Cl. F24H 9/20 (2022.01); F24H 1/20 (2022.01); G05D 23/19 (2006.01); H05B 1/02 (2006.01); H05B 3/42 (2006.01)
CPC F24H 9/2021 (2013.01) [F24H 1/202 (2013.01); G05D 23/1934 (2013.01); H05B 1/0283 (2013.01); H05B 3/42 (2013.01)] 20 Claims
OG exemplary drawing
 
1. An electric liquid heating apparatus comprising:
a tank for storing liquid to be heated;
an electric heating element extending into an interior of said tank;
a temperature sensor operative to sense a temperature representative of a temperature of the liquid in said tank; and
an electronic control system operative to control said electric heating element and prevent dry firing thereof, said electronic control system functioning, upon startup of said electric liquid heating apparatus, to sequentially:
(1) sample a first temperature detected by said temperature sensor,
(2) wait for a predetermined first time period,
(3) sample a second temperature detected by said temperature sensor,
(4) turn on said electric heating element,
(5) determine a difference between said second and first temperatures,
(6) set a dry fire offset, for use in dry fire detection, based on the difference between said second and first temperatures, sampled prior to turning on said electric heating element, multiplied by two, wherein the dry fire offset is set to one when the product of two multiplied by the difference is greater than one,
(7) set a dry fire threshold, for use in the dry fire detection, based on a sum of a third temperature and the dry fire offset,
(8) wait for a predetermined second time period,
(9) turn off said electric heating element, and then
(10)(a) shut down said electric heating element if a fourth temperature detected by said temperature sensor is greater than the dry fire threshold, or
(10)(b) permit normal operation of said electric liquid heating apparatus if, after an expiration of a predetermined third time period, said temperature sensor does not detect a temperature greater than said dry fire threshold.