This invention relates to hydronic heating systems for dwellings, offices, etc. and more particularly to radiant heating systems having one or more satellite distribution stations feeding heating loops at different water temperature and so providing multi-temperature heating loop operation.
Hydronic heating systems for heating the rooms in a dwelling, office, etc, are used widely in Europe and to a lesser extent in the United States. Water heated in a boiler is distributed to heating loops of tubing in the dwelling that carry the heat by radiation, conduction and convection to the rooms in the dwelling. A common technique provides a boiler hot water supply feeding the supply header of the distribution system for the heating loops and the boiler water return to which the system return header of the heating loops connects. The return water is heated in the boiler and sent out again to the distribution system as hot supply water, and so the water is cycled through the essentially closed system. One or more water pumps in this system keep the water flowing and valves control water flow rates through the loops depending on demand for heat.
A heating loop may include several heating elements like baseboard finned tubing or wall mounted radiators that are the principal heat exchanger of the loop, or the tubing itself may be the principal heat exchanger of the loop. In the latter case the tubing may be installed "Dry" as described in the applicant's U.S. Pat. No. 5,292,065 issued Mar. 8, 1994, entitled "Radiant Floor And Wall Hydronic Heating Systems", on top of or under the rough floor or in the wall; or is installed "Wet", embedded in cement on top of the floor. In either case, heat exchange is principally by radiation. Hence, this type of heating is called Radiant Floor Heating (RFH). Similarly, when the tubing is buried in the wall, the heating is called Radiant Wall Heating (RWH).
In such RFH and RWH systems and other hydronic heating systems using baseboard finned tubing elements or wall mounted radiators, the supply water temperature from the boiler must be controlled so that it does not exceed certain limits that are substantially lower than the usual boiler supply water temperature. There are several reasons for this: first, the temperature of radiator elements on the wall must not be so high that they are not safe to touch; second, for RFH the floor temperature must not be uncomfortable hot; and third, where the tubing is plastic, the water temperature for some plastic materials must not exceed about 140.degree. F.
In hydronic heating systems subject to such water temperature limitations, where the boiler is powered by burning fossil fuels, the boiler water supply temperature is usually well above 140.degree. F. and often at about 180.degree. F. to 200.degree. F., (for laundry and dishwashers), and so the boiler supply temperature must be stepped down before it is fed to the heating loops.
In the past, it has been the practice to mix relatively cooler boiler return water with the hot boiler supply water to "dilute" the temperature of the supply water fed to the heating loops. An electrically controlled motorized three-way mixing valve has been used in the boiler supply line that feeds the supply header for the heating loops, between the boiler supply and the heating loops supply header. The mixing valve has two inputs and one output. One input is directly from the boiler hot water supply, the other input is from the return header of the heating loops and the output is directly to the supply header of the heating loops. The mixing valve motor is electrically energized by remote reset controls that sometimes respond to outside ambient temperature, inside room temperature, boiler water temperature, supply header water temperature, etc.
In an effort to reduce expense, non-motorized three-way valves have been used in the boiler supply line. Systems using non-motorized three-way valves with supply header water temperature feedback are described in the applicant's U.S. Pat. No. 5,119,988, which issued Jun. 9, 1992, entitled: "Hydronic Heating Water Temperature Control System". That patent describes several hydronic heating systems with a non-motorized (non-electric) three-way valve having supply water temperature feedback to the valve controller. In the preferred system, the valve is a three-way diverting valve in the boiler return water line. The diverting valve has one input and two outputs and diverts water from the return line (on the way from the heating loop return header to the boiler return), to the boiler supply line that feeds the loop supply header, diluting the supply water (reducing its temperature) that is fed to the heating loop supply header.
That patent also teaches use of a non-electric thermostatic actuator head attached to the diverting valve for positioning the valve stem and controlled by a thermostatic fluid contained in the actuator, a bulb temperature sensor and a capillary tube from the bulb to the actuator. Thus, the valve is modulated by non-electric feedback of the diluted supply water temperature. The bulb sensor may be inserted into the diluted supply water or it may be clamped to the supply line next to the supply header so that it is at the temperature of water in the supply header. The thermostatic fluid in the bulb expands with temperature applying a pressure force through the capillary to the actuator head and so the valve is modulated to increase or decrease the flow of return water through the valve as necessary to maintain the temperature of the heating loop supply header water at or below a predetermined value. That value can be set by a mechanical setting on the actuator head and so an accurate reading of the supply header water temperature is made continuously and simultaneously any deviation from the setting is immediately nulled by modulating the valve.
RFH and RWH systems using embedded plastic tubing and other hydronic heating systems using wall radiators and/or baseboard finned tubing elements are some of the different kinds of heating loops. Clearly, the temperature limitation of a heating loop depends first on how and where the loop is installed, creature comfort and the materials in the loop. As the term "Kind" of loop is used herein, it means the temperature requirements and limitations of the loop and so loops of the same "Kind" have the same temperature requirements and limitations. For example: the temperature of baseboard finned tubing radiator elements can be quite high, because they are metal tubes, can be shielded and are not usually touched, even accidentally, whereas wall radiators are not shielded and must not be too hot to touch; for RFH where the tubing is beneath the floor boards, the tubing can be hotter than where the tubing is on top of the floor boards; for RWH the tubing is often covered by only thin gypsum board and so must be well below 100.degree. F.; and even the best cross-linked plastic tubing should not be exposed to water above 140.degree. F.
Where the hydronic system with a three-way thermostatically controlled diverting valve in the return line for diluting the supply water temperature (as described above) is also responsive to outdoor temperature an outdoor temperature bulb sensor, a thermostatic valve actuator attached to the valve with capillary tubes connecting the common thermostatic fluid from the bulbs to the actuator are included so that loop water temperature is increased when outdoor temperature falls. The applicant has invented such a system, which is described in his U.S. Pat. No. 5,556,027, issued Sep. 17, 1996, entitled: "Hydronic Heating Outdoor Temperature Reset Supply Water Temperature Control System".
Since the temperature of boiler supply water fed to the main distribution station is usually well above 140.degree. F. and often at about 180.degree. F. to 200.degree. F., the boiler supply water temperature may be all right for some "Kinds" of heating loops like baseboard finned copper tubing, but must be much lower for other "Kinds" of heating loops like RFH and RWH. The present application describes techniques and systems that provide several echelons of temperature ranges of loop supply water to accommodate the requirements of different "Kinds" of heating loops in a premises.
The applicant has invented a hydronic heating system with satellite distribution stations that operate at lower temperatures for multi-temperature heating loop operation. That invention is described in the applicant's U.S. Pat. No. 5,617,994, issued Apr. 8, 1997, entitled: "Hydronic Heating With Satellite Distribution Stations For Multi-Temperature Supply Water To Heating Loops". That patent describe a complete main distribution system (main station) with main supply and return headers, one or more main heating loops, a main circulation pump and a main three-way dilution control valve and feedback controls for the valve; each satellite station includes a complete satellite distribution system that has satellite supply and return headers, satellite heating loops and a satellite circulation pump; and water from the main supply header is injected into the satellite return header to add heat to the satellite station. Water flow between the main and satellite stations is balanced by a return of injected water from the satellite supply header to the main return header. Several techniques of modulating the heat flow to the satellite are disclosed in that patent application, including a modulating valve in the injection line or in the balancing return line between the main and satellite systems.
Where several such satellite stations are fed from the main station, as described in the applicant's aforementioned U.S. Pat. No. 5,617,994, heat (hot water) injection into each satellite is from the main supply header to the satellite return header and water flow is balanced by a return from the satellite supply header to the main return header. Thus, the satellites are in parallel with each other, as they all connect to the main at the same point and all return to the main at the same point, and the main and each satellite station has a complete distribution system with headers, a pump and station water temperature control.
The applicant has also invented a hydronic heating system with satellite distribution stations that operate at lower temperatures for multi-temperature heating loop operation wherein the satellite stations are in series along a main station loop from the boiler. That invention is described in the applicant's U.S. Pat. No. 5,707,004, issued Jan. 13, 1998, entitled: "Hydronic Heating With Continuous Circulation Supplying Multi-Temperature Heating Loops". That patent describe a complete main supply loop and several satellite stations is series along the main loop, each satellite station including a complete satellite distribution system and heating loops. In operation, water from the main loop is injected into the satellite pump input to add heat to the satellite station and water flow between the main loop and satellite is balanced by a return of water from the satellite pump output to the main loop.
A techniques of modulating the heat flow to the satellite in that patent, uses a three-way modulated diverting valve in the output flow from the satellite pump. That valve feeds the satellite supply header and the satellite return line to the main loop and is controlled by a thermostatic actuator that is driven by thermostatic fluid in a bulb feeding a capillary tube that connects to an actuating bellows in the actuator. The bulb is attached to the return line and so the driving fluid is at the temperature of the water flowing in the return line. When the return water temperature drops, the return water flow increases and so the supply water flow increases accordingly and so injected heat increases; and visa-versa.
The applicant herein has recognized a need for a simpler modulated thermostatic controller for the satellite station to maintain the satellite water temperature constant in the above system. Such a controller may not be required to change return water flow rate, but infrequently, and need not be required to directly control water flow from the pump output to the supply header and, preferably, does not require a thermostatic fluid bulb and capillary tube. Furthermore, it is desirable to be able to manually set the desired satellite temperature at the controller and that temperature thereafter be automatically maintained by the controller.