Data processing: generic control systems or specific application – Specific application – apparatus or process – Mechanical control system
Reexamination Certificate
2002-06-19
2004-03-16
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Mechanical control system
C237S00800C, C236S04600F
Reexamination Certificate
active
06708083
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a fossil fuel-fired home heating or cooling system that consumes minimal electrical power for operation and control.
BACKGROUND OF THE INVENTION
The AC relay-based control scheme for home heating systems has not changed substantially since the early 1930s. Since 1945, major developments in home heating systems have consisted of adding additional components and safety mechanisms such as stack dampers and flame sensors. However, the control scheme has not been updated.
Heating systems typically have control schemes wherein most of the components in the heating system are activated or deactivated by closing or opening AC relay contacts. These electromagnetic switches close or open when the circuit supplying power to the magnetic coils within them are energized or de-energized. In gas-fired hydronic systems, the boiler control circuit coordinates the operation of the circulator pump, stack damper and gas valve. The zone valves, thermostats and boiler control circuits in these systems typically operate on non-lethal 24V AC power, which is obtained from 110/120V AC household power using a transformer.
In recent years, development in home heating systems has focused on improving the Annual Fuel Use Efficiency of the boiler or furnace, which considers only consumption of fossil fuel and not the electrical energy used by components in the system. Electric power demand of fuel-burning heating systems has consequently increased, such that today, a typical system consumes 20W on standby, as much as 2 kW during main burner ignition and 250-550W during normal hydronic boiler or hot-air furnace operation. Due to its high electricity demand, when utility power goes off, the typical heating system can operate only if an expensive back-up power system has been installed. Moreover, when building heating systems fail during the winter, the effects can be harmful to the health and safety of building occupants and the integrity of the building plumbing systems. To date, there has been no move to redesign the control system to try to reduce the electric power consumption of home heating system controls in order to address these problems with the prior art.
Additionally, there is no easy way to troubleshoot faults in conventional home heating systems. For example, if the blocked vent switch on the stack damper in a gas-fired heating system opens, the gas valve will close, but the stack damper will stay open and the circulator pump will stay on. Diagnosis of this problem is complicated because no error messages or indications are displayed anywhere in the system. Thus, conventional heating systems suffer from poor error detection capabilities.
U.S. Pat. No. 6,237,855 (Stickney et al.) describes a system for controlling a hydronic heating system with a DC power source. This system uses DC power as the primary source of electricity by having DC relays and separate DC pumps for each zone. But this system also uses DC-AC inverters and DC-DC converters, which have significant electrical losses associated with them. Thus, even though this system uses DC power, it does not redesign the control system so as to use microprocessors to control the heating system operation, to further reduce power consumption, or to provide enhanced system diagnostics.
Various microprocessor-based control systems have been developed for heating systems. Microprocessor-based systems described in U.S. Pat. Nos. 4,381,075 (Cargill et al.), and 4,844,335 (McKinley et al.) compare the temperature of the water in the boiler and the temperature of outside air to control the boiler water temperature. These systems concentrate on controlling the temperature of the boiler water but not the other control circuits in the system.
The microprocessor-based system described in U.S. Pat. No. 5,318,104 (Shah et al.) further utilizes a microprocessor-based controller for comparing the set temperature and the actual temperature for controlling the cycling of the heating/cooling plant. The microprocessor activates the heating/cooling plant based on which zone in the system requires the most heat/cooling (the zone of greatest thermal error).
The electronic boiler control unit described in U.S. Pat. No. 5,779,143 (Michaud et al.) combines several controls in one circuit, thus requiring no external wiring. The microprocessor for this hydronic heating system changes boiler water temperature in relation to the outside air temperature as well as the current boiler water temperature and operates zone valves based on a priority heating zone. Again, this system improves the seasonal efficiency of the boiler, but does not alter the control circuits for the other components in the system.
Finally, U.S. Pat. No. 5,515,297 (Bunting) describes a monitoring and diagnostic apparatus for an oil-only burner system, with three sensors that are able to detect and display errors in the operation of the burner thermostat, burner ignition transformer, and stack vent outside temperature. A microprocessor records and displays the data the three sensors measure for diagnosis of the operational history over a pre-selected time interval.
However, to date, no commercially available microprocessor-based control system for a home heating system has been designed to operate independently from the electric utility grid (AC power) by using DC power. In addition, no heating system incorporates the detection and display of errors in the heating system when they occur. Furthermore, no control system for a home heating system is capable of communicating with an external computer for purposes of data storage or error diagnosis.
Zone valves are used in hydronic heating and cooling systems to deliver hot or cold water to a particular area, or zone, of the entire area served by a heating or cooling system. Typically, the zone valve receives a contact closure signal from a thermostat, which causes the valve to open. Conventionally, a heat motor or an electric motor is turned on, and stays on to hold the valve open. The valve typically opens by driving an elastomeric diaphragm or ball away from a seat against a spring, or by holding a rotary valve, like a ball valve, open against a spring. When the thermostat contacts open, the motor circuit opens and the valve is returned to the closed position by a mechanical restorative device, typically a spring-return mechanism. Power must therefore be supplied to the valve whenever it has to be opened, making zone valves highly electrical energy inefficient. A typical valve is powered by a 24 volt AC power supply.
U.S. Pat. Nos. 5,131,623 and 5,540,414 (Giordani et al.) describe a zone valve where a motor driven actuator rotates a ball valve 90 degrees from closed to open position. When the motor is de-energized, the valve is returned to its normally closed position by a spring.
U.S. Pat. No. 6,186,471 (Genga et al.) describes a zone valve with a motor driven actuator that rotates a valve from a first position to a second position, such that the motor is only rotated when the valve changes position. At least one of the positions is a fail-safe position to which the valve will return if there is a loss of electrical power. As the valve turns, a sensor, as opposed to a mechanical switch, detects when the valve has reached a desired position and the motor is de-energized. However, the position of the valve is not known a priori without using the actuator to rotate the valve. The actuator provides a capacitive energy storage element that powers the motor in case of power failure.
Consequently, a need exists for a valve wherein (i) a motor turns the valve, and (ii) power to the motor is controlled using a sensing system that detects the position of the valve, and (iii) the position of the valve can be determined without rotating the valve. Such a scheme would be beneficial in enabling the development of remote indicators that detect and display the state of each zone valve in a heating system. In addition, if the state of each zone valve is known when power returns, then there is no need for a
Cheever Erik A.
Houser Ari N.
Orthlieb Frederick L.
Parlikar Tushar Anil
Conte Lisa Burgin
Dilworth Paxson LLP
Lee Douglas S.
McConathy Evelyn H.
Picard Leo
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