Cathodic corrosion and dry fire protection apparatus and methods for electric water heaters

Patent metadata

Field	Value
Publication number	US-11698209-B2
Application number	US-202016950423-A
Country	US
Kind code	B2
Filing date	Nov 17, 2020
Priority date	Jun 24, 2013
Publication date	Jul 11, 2023
Grant date	Jul 11, 2023

Abstract

The metal tank portion of an electric water heater is protected against corrosion utilizing a corrosion protection system that detects a voltage potential between the sheath portion of a tank water-immersed electric heating element and the tank. In one embodiment of the corrosion protection system the sensed sheath/tank potential is utilized to enable a user of the water heater to accurately gauge the necessity of replacing a sacrificial anode extending into the tank. In another corrosion protection system, the sensed sheath/tank potential is utilized to provide impressed current cathodic protection of the tank and also to prevent dry firing of the electric water heater.

First claim

What is claimed is:

1. An electric heating element for insertion into a liquid storage vessel of a liquid heating apparatus through a mounting opening in a wall portion of the liquid storage vessel, the electric heating element comprising:
a mounting portion connectable in the mounting opening to the liquid storage vessel;
an electrically conductive hollow sheath structure comprising an outer end secured to the mounting portion, and an inner end spaced apart from the outer end and being insertable through the mounting opening into the interior of the liquid storage vessel;
an electric heating filament extending through the interior of the electrically conductive hollow sheath structure and being electrically isolated therefrom;
an insulating structure associated with the outer end of the electrically conductive hollow sheath structure and operative to electrically isolate the outer end of the electrically conductive hollow sheath structure from the liquid storage vessel when the electrically conductive hollow sheath structure is installed in the liquid storage vessel;
a first connection structure, coupled to the electric heating filament, through which electrical heating current can flow to the electric heating filament;
a second connection structure, electrically isolated from the first connection structure, through which an electrical voltage may be impressed on the electrically conductive hollow sheath structure; and
a control portion configured to sequentially (1) measure a voltage between the liquid storage vessel and the electrically conductive hollow sheath structure, (2) record a magnitude of the voltage measured if the voltage measured is above a predetermined value, (3) apply the electrical voltage that may be impressed to the electrically conductive hollow sheath structure equal in magnitude to the magnitude of the voltage recorded plus a predetermined additional impressed voltage, and (4) terminate the electrical voltage that is applied to the electrically conductive hollow sheath structure, and restart the sequence.

2. The electric heating element of claim 1 wherein:
the electrically conductive hollow sheath structure comprises an elongated, generally U-shaped configuration.

3. The electric heating element of claim 1 wherein:
the second connection structure includes an annular, electrically conductive connection member in electrically conductive communication with the outer end of the electrically conductive hollow sheath structure, and a connection screw threaded into the annular, electrically conductive connection member.

4. The electric heating element of claim 1 wherein:
the insulating structure extends through the mounting portion.

5. The electric heating element of claim 1 wherein the electric heating element is configured to be coupled to a protection apparatus.

6. The electric heating element of claim 5 , wherein the protection apparatus comprises:
a sensing portion configured to measure a voltage between the liquid storage vessel and the electrically conductive hollow sheath structure when the electric heating element is operating and installed in the liquid storage vessel, wherein the control portion is further configured to determine whether a sacrificial anode installed within the liquid storage vessel is depleted.

7. The electric heating element of claim 5 , wherein the protection apparatus comprises:
a sensing portion configured to sense a voltage potential between the liquid storage vessel and the electrically conductive hollow sheath structure when the electric heating element is operating and installed in the liquid storage vessel, wherein the control portion is coupled to the sensing portion of the protection apparatus and is operative to:
(1) if the voltage potential measured is greater than a first predetermined magnitude, provide an indication that a sacrificial anode is still functional, and
(2) if the voltage potential measured is not greater than the first predetermined magnitude, re-measure the voltage potential sensed between the electrically conductive hollow sheath structure and the liquid storage vessel, compare the voltage potential that is re-measured to a predetermined second magnitude, and then provide at least one indication of a degree of necessity of replacing the sacrificial anode based on the comparison of the voltage potential that is re-measured and the predetermined second magnitude.

8. The electric heating element of claim 6 , wherein the sensing portion of the protection apparatus includes a resistor and a voltage measuring device operative to sense a voltage potential between the electrically conductive hollow sheath structure and the liquid storage vessel.

9. The electric heating element of claim 5 , wherein the protection apparatus includes apparatus for selectively impressing a voltage on the electrically conductive hollow sheath structure from an external voltage source, and the protection apparatus functions to provide impressed current cathodic protection to the liquid storage vessel without utilization in the liquid storage vessel of a separate anode structure for such function.

10. The electric heating element of claim 5 , wherein the protection apparatus further includes the control portion is operative to in the absence of an impressed voltage on the electrically conductive hollow sheath structure, output a signal indicative of a dry firing condition of the electric heating element if a voltage potential measured between the electrically conductive hollow sheath structure and the liquid storage vessel is not above a predetermined value thereof.

11. An electric heating element for insertion into a liquid storage vessel of a liquid heating apparatus through a mounting opening in a wall portion of the liquid storage vessel, the electric heating element comprising:
a mounting portion connectable in the mounting opening to the liquid storage vessel;
an electrically conductive hollow sheath structure comprising an outer end secured to the mounting portion, and an inner end spaced apart from the outer end and being insertable through the mounting opening into the interior of the liquid storage vessel;
an electric heating filament extending through the interior of the electrically conductive hollow sheath structure and being electrically isolated therefrom;
an insulating structure associated with the outer end of the electrically conductive hollow sheath structure and operative to electrically isolate the outer end of the electrically conductive hollow sheath structure from the liquid storage vessel when the electrically conductive hollow sheath structure is installed in the liquid storage vessel;
a first connection structure, coupled to the electric heating filament, through which electrical heating current can flow to the electric heating filament;
a second connection structure, electrically isolated from the first connection structure, through which an electrical current may be impressed on the electrically conductive hollow sheath structure; and
a control portion configured to sequentially (1) measure a voltage between the liquid storage vessel and the electrically conductive hollow sheath structure, (2) record a magnitude of the voltage measured if the voltage measured is above a predetermined value, (3) apply the voltage that may be impressed to the electrically conductive hollow sheath structure equal in magnitude to the magnitude of the voltage recorded plus a predetermined additional impressed voltage, and (4) terminate the voltage that is applied to the electrically conductive hollow sheath structure, and restart the sequence.

12. The electric heating element of claim 11 wherein:
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Assignees

• Rheem Mfg Co

Inventors

• Boros Jozef
• Chaudhry Raheel A
• Hong Yan
• Trant Troy E

Classifications

• G05B23/0235

  based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold · CPC title

• F24H9/2021

  Storage heaters · CPC title

• F24H9/45 Primary

  for preventing galvanic corrosion, e.g. cathodic or electrolytic means · CPC title

• F24H1/202

  with resistances · CPC title

• C23F2213/21

  combining at least two types of anodic or cathodic protection · CPC title