Electricity: circuit makers and breakers – Fluid pressure – Flow-responsive type
Reexamination Certificate
2001-01-24
2003-04-22
Luebke, Renee (Department: 2833)
Electricity: circuit makers and breakers
Fluid pressure
Flow-responsive type
C200S08400B
Reexamination Certificate
active
06552283
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to tankless water heaters, and, more particularly, the present invention relates to a flow switch that functions to turn the electronic controls of a water heater on and off.
BACKGROUND OF THE INVENTION
Every household and many businesses require hot water for everyday use. These hot water consumers typically rely on conventional storage water heaters to store and constantly heat water for production upon demand.
A variety of fuel options are available for conventional storage water heaters, including electricity, natural gas, oil, and propane. Ranging in size from 20 to 80 gallons (75.7 to 302.8 liters), storage water heaters remain the most popular type for residential heating needs in the United States. A storage heater operates by releasing hot water from the top of the tank when the hot water tap is turned on. To replace that hot water, cold water enters the bottom of the tank, ensuring that the tank is always full.
Because the water is constantly heated in the tank, energy can be wasted even when no faucet is on. This is called standby heat loss. It is possible to completely eliminate standby heat losses from the tank and reduce energy consumption 20% to 30% with demand (tankless) water heaters, which do not have storage tanks. Cold water travels through a pipe into the unit, and either a gas burner or an electric element heats the water only when needed.
Tankless water heaters save energy because they do not need to constantly heat water in a large storage tank. To achieve this, tankless water heaters instantaneously heat water as it is passing from the consumer's water supply to the outlet (e.g. faucet or showerhead). The tankless water heater, therefore, needs to “know” when hot water is in demand in order to function properly. Flow switches are used to signal the tankless water heater that the consumer desires hot water. Briefly, when a consumer turns on a faucet or a dishwasher, any hot-water-requiring device, water flows from the water supply through the tankless water heater system. This flow of water causes the flow switch to activate the heating element (e.g. gas or electric) of the tankless water heater.
Previous attempts have been made to provide effective flow switches for use in tankless water heaters such as are described in U.S. Pat. No. 4,900,896 to Maus ('896 patent); U.S. Pat. No. 5,091,612 to Van Fossen ('612 patent); U.S. Pat. No. 5,408,578 to Bolivar ('578 patent); and U.S. Pat. No. 5,479,558 to White, Jr. et al. ('558 patent); all of which are incorporated herein by reference.
The '896 patent describes a continuous flow water heater which has a sealed chamber containing an electrical heating element and a diaphragm having an orifice through which water must flow upon a demand for hot water. The center of the diaphragm translates axially in response to the water flow and moves an internal magnet, which influences an external magnet to throw a flow switch. A heat sink made from a material exhibiting high thermal conductivity extends from within the sealed chamber to a position in heat exchanging relationship with a thermostat, the contacts of which are closed unless the water exceeds a set value. The flow switch and thermostat are in series with a source of electricity and the heating element such that the heating element is only energized if there is water flow through the heater and if the exiting water does not exceed a selected temperature. The sealed chamber is contained within a housing made of heat-resistant plastic. A plurality of opposed pairs of longitudinally extending grooves are formed in the housing, and a mounting bracket is provided for detachably snapping into one of the pairs of grooves to allow the heater to be mounted in a variety of different orientations.
The '612 patent describes a flow switch adapted to be attached to a pipe is designed to trip a switch at a preset flow rate. The switch employs a bending metal blade which deflects in the flow stream to move a magnet attached to the downstream side of the blade relative to a reed switch or Hall-effect switch. The switching device is preferably mounted in a slot on a printed circuit board to enable selection of a range of available trip points.
The '578 patent describes a continuous flow water heater assembly requiring no storage tank and including an entrance chamber having a flow control switch mounted therein adapted to be activated upon a positive flow of water through the system wherein the water flows from the entrance chamber to a plurality of heating elements each of which are at least partially segregated by virtue of their being removably mounted within separate heating chambers. The heating chambers are attached in fluid communication to one another by a plurality, at least two, ports which are of proportionately different sizes such that water will be passed between the first and second heating chambers in a proportionately different amounts through the different sized ports. Water is thereby effectively distributed between the heating elements so as to prevent exposure of the heating elements when activated and thereby eliminating either of the heating elements from being exposed to air and thereby subject to burnout.
The '558 patent describes a very compact tankless water heater delivers heat in proportion to demand. A flow responsive valve energizing an electrical control system is purely flow responsive, even to minute flow, and consumes no power when dormant. An uncomplicated electronic control system is connected to power by the flow switch, and is substantially de-energized when dormant. Most electronic components of the control system are mounted on the flat front wall of the pressure vessel. Thus, overall dimensions are minimized, cool water serves as a heat sink, and heat generated by electronic controls is captured for heating purposes. In particular, triacs controlling the heating elements are cooled, thus prolonging their life. A preferred embodiment of the novel heater has a maximum electrical consumption of 22 kilowatts, with equivalent heat output, and has overall external dimensions of 24 inches in height, 5.5 inches in width, and 4 inches in depth (61 cm in height, 14 cm in width, and 10 cm in depth). An outlet pipe fitting extending above adds approximately 2 inches (5 cm) to the overall height, enabling the water heater to be installed in a typical building interior wall or partition.
Many of the above-described inventions employ flow switches that are mechanical in nature. Mechanical flow switches are at risk of breakdown and can be rendered ineffective by particulate matter in the fluid flow. In addition, many of these flow switches are manufactured of material subject to corrosion and decay. For example, the '896 patent relies on a diaphragm to sense water flow, thereby actuating a system of magnets whereby the flow switch is activated. The '612 patent, although employing magnetic principles, relies on a metal blade to sense flow through the pipe. The '578 patent uses a magnetic flow switch that slides along the interior of a narrow pipe in response to fluid flow. This type of flow switch would be rendered inoperable by particulate matter prohibiting such movement. Similarly, the '558 patent relies on water flow to move a plunger which in turn causes a level arm to activate a circuit. As with the '578 patent, particulate matter in the flow can lodge itself between the plunger and the pipe wall, thereby “sticking” the plunger in the open position even once the flow has subsided.
Consequently, there is a need in the art for a tankless water heater flow switch that is resistant to corrosive materials.
There is a further need in the art for a tankless water heater flow switch that reduces the likelihood of performance breakdown as a result of particulate matter buildup.
There is a further need in the art for a tankless water heater flow switch that provides consistent control performance regardless of the flow rate.
SUMMA
Brooks Michael
Cabrera Carlos
Lott & Friedland, P.A.
Luebke Renee
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