High efficiency, peak-power reducing, domestic hot water heater

Abstract

There is herein described a peak-power reducing domestic hot water heater comprising: a closed tank having a predetermined water holding capacity, a hot water outlet in a top end wall of said tank, a cold water inlet in a side wall of said tank adjacent a bottom wall thereof, three spaced apart resistive heating elements projecting substantially horizontally in said tank, each of said resistive heating elements having a temperature sensing element to enable a control of their respective activation; a bottom one of said resistive heating elements extending in said tank spaced slightly above said bottom wall and having a lowest power rating, said bottom resistive heating element being turned on when water is flowing into said cold water inlet and drawn out of said hot water outlet during a peak-power demand time period; a middle one of said resistive heating elements extending in said tank at a level which is calculated to be equal or above an average maximum daily water consumption volume drawn out during the peak power demand time periods; and a top one of said resistive heating elements extending between said middle element and said top end wall of said tank and having a highest power rating; said middle and said bottom resistive heating elements being activated simultaneously only when said top resistive heating element is inactive.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application is a Continuation-In-Part of U.S. patent application Ser. No. 11 / 556,798, entitled “High efficiency, peak-power reducing, domestic hot water heater” filed on Nov. 6, 2006.TECHNICAL FIELD[0002]The present invention relates to a high efficiency, peak-power reducing, domestic hot water heater provided with three resistive heating elements.BACKGROUND ART[0003]In U.S. Pat. No. 4,948,948, there is described a water heater with multiple heating elements having different power factors and wherein these elements are controlled by a control circuit so that the elements are switched on at different periods of a day, outside peak hours, in order to reduce the power loads on an electrical distribution network during peak electrical power demand periods.[0004]During peak hours when hot water is used, normally between 6:00 a.m. and 9:00 a.m. and 6:00 p.m. to 9:00 p.m., there is an excessive demand of power on the electrical distr...

AI Technical Summary

Benefits of technology

[0011]According to still another embodiment, there is provided a method of reducing the kilowatt demand of a domestic hot water heater during peak hour periods without reducing the amount of hot water requested by a user using a large volume of hot water between 90 to 220 liters from a hot water tank having a predetermined water holding capacity of 180 or 270 liters. The method comprises the steps of providing a hot water tank with three spaced-apart electrical resistive heating elements extending therein in a spaced-apart manner. The bottom one of the resistive heating elements has a low watt density rating in the range of from about 15 to 30 W / in2. A middle one of the resistive heating elements is positioned at a level calculated at approximately an average maximum water consumption of between about 90 to 130 liters dependent on the tank size of about 180 or 270 liters.

[0012]According to yet another embodiment, the above method further comprises operating the middle resistive heating element to maintain a water temperature at its level to approximately 140° F. to form a barrier in the hot water tank to reduce the propagation of harmful bacteria from the bottom of the tank towards a top portion of the tank where hot water is drawn.

[0014]Yet another embodiment provides a method of reducing the kilowatt demand of a domestic hot water heater during peak hour periods without reducing the amount of hot water requested by a user from a hot water tank having a predetermined water holding capacity, the method comprising the steps of: providing a hot water tank with three spaced-apart electrical resistive heating elements extending therein in a spaced-apart manner and each having a thermostat to enable a control of their respective activation; positioning a middle one of the resistive heating elements at a level exceeding an average maximum daily water consumption volume drawn during one of the peak hour periods, and activating the bottom one of the resistive heating elements when water is flowing into the cold water inlet and drawn out of the hot water outlet during the peak hour periods, and simultaneously activating the middle and the bottom one of the resistive heating elements only when the top resistive heating element is inactive.

Problems solved by technology

During peak hours when hot water is used, normally between 6:00 a.m. and 9:00 a.m. and 6:00 p.m. to 9:00 p.m., there is an excessive demand of power on the electrical distribution netwo

mers. These solutions are, however, costly to the utilities and are not popular with consu

mers. They also cause very high instantaneous demand at re-activation if too many units are turned back on at the same

eriods. These other attempts are however limited and are the cause of various other p

However, during periods of peak demand, the amount of water in the top portion of the reservoir is quickly exhausted as it has been found that many consumers will draw hot water during a single peak period of the day rather than two separate periods, which therefore requires a much larger hot water volume.

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