A valve assembly for plants providing both heating and domestic hot water

Abstract: A valve assembly for a combined plants adapted for providing both heating and sanitary hot water comprising a gas-fired boiler (1), a heat exchanger (2), a water/water heat exchanger (17) that can be included through a three-way valve (4) in the circuit of the heating water, at least one radiator (R), and a pump (P) for circulating the heating water, such assembly being formed by two sub-assemblies or valve units. The first unit (I) comprises an integral metal block in which there are formed or mounted said three-way valve (4), a pipe fitting (3) for the connection with the main heat exchanger (2), a fitting (5) for the connection with the radiator (R), an outlet fitting (9) for the domestic water, two pipe fittings (22,23) for the connection with the water/water heat exchanger (17), a pressure switch (15) and a by-pass valve (16) with an associated outlet fitting (10). The second unit (II) comprises an integral metal block in which there are formed or mounted a pressure difference device (14), a pipe fitting (6) for the connection with the radiator (R), an inlet fitting (8) for the domestic water, an outlet fitting (7) towards the pump (P), two fittings (32,33) for the connection with said water/water heat exchanger (17).

Description: The present invention concerns a valve assembly adapted for being used in combined plants for providing both heating and sanitary hot water, i.e. residential plants wherein the same heat source, particularly a wall gas-fired boiler, is used for heating both the water for the heat radiating elements (radiators) for heating the rooms, and the sanitary or domestic hot water for various purposes (EP-A-0 466 010). The known plants of this type although advantageous from the costs and environment viewpoint, have a number of drawbacks, and more precisely require piping, valves and various components that are often connected in non-standard manner and lead to cumbersome and complicated arrangements, and in case also irrational, that are difficult to be assembled and ackward for any possible maintenance intervention. This situation negatively affects also the cost and the reliability level of the plants. The object of the present invention is that of overcoming the above mentioned shortcomings and limitations and more precisely of providing a valve arrangement or assembly for realizing plants of the above mentioned type, which is extremely compact, easy to be connected to the remaining of the plant, that allows an easy and simplified maintenance, and has quite limited costs, both for its construction and installation. According to the invention, such objects are achieved through a valve assembly for combined plants adapted for providing both heating and sanitary hot water and comprising a gas-fired boiler, a main heat exchanger, a water/water heat exchanger that can be included in the circuit of the heating water by means of a three-way valve, at least one radiator, and a pump for circulating the heating water, characterized in that said valve assembly comprises two sub-assemblies or valve units, the first unit comprising an integral metal block in which there are formed or mounted said three-way valve, a pipe fitting for the connection with said main heat exchanger, a pipe fitting for the connection with said at least one radiator, a pipe fitting for the outlet of the domestic hot water, two pipe fittings for the connection with said water/water heat exchanger, said integral metal block further housing a pressure switch and a by-pass valve with an associated outlet fitting; said second unit comprising an integral metal block in which there are formed or mounted a pressure difference device, a pipe fitting for the connection with said at least one radiator, a pipe fitting for the inlet of the domestic water, an outlet pipe fitting to said pump, two pipe fittings for the connection with said water/water heat exchanger. Additional advantageous features are the objects of the dependent claims. The assembly according to the invention has a reduced size and provides for original solutions. More particularly it is equipped with an advantageous device exploiting the pressure difference for controlling a three-way valve in lieu of the known arrangements, e. g. provided with a Venturi tube. Such novel pressure difference device can further include a flow rate regulator, if necessary and without any modification thereof. The assembly of the invention incorporates a pressure switch, a by-pass valve and a number of pipe fittings and sections already designed for accomplishing functions of the system so that the installation of this latter is very simple and advantageous. The invention will now be described with reference to the attached drawings illustrating preferred but non-limiting embodiments thereof, in which: Fig. 1 schematically illustrates the construction of the valve assembly according to the present invention; Fig. 2 is a front view of the valve assembly according to the invention; Fig. 3 is a top view of the assembly of Fig. 2; Fig. 4 is a side view of the assembly of Fig. 2; Fig. 5 illustrates the structure of the unit I; Fig. 6 is a cross section along line B-B in Fig. 5; Fig. 7 is a cross section along line C-C in Fig. 5; Fig. 8 is a cross section along line A-A in Fig. 5; Fig. 9 illustrates the structure of the unit II; Fig. 10 is a cross section along line B-B in Fig. 9; Fig. 11 is a cross section along line A-A in Fig. 9; Fig. 12 is a cross section along line C-C in Fig. 9; Fig. 13 illustrates the structure of the pressure difference device according to the invention; and Fig.s 14 and 15 schematically illustrate two alternative constructions of the valve assembly according to the present invention. Fig. 1 is a diagram illustrating the construction of the valve assembly according to the invention in a residential heating plant also capable of producing domestic hot water, i. e. a plant capable of heating water circulating in a closed circuit which includes heat radiating elements, and of supplying upon request domestic hot water for various uses, by employing the same heat source, more particularly a gas-fired boiler. Specific and/or preferred embodiments of the assembly and of the components thereof are shown in Fig.s 2 to 4 and 5 to 12, respectively. Through a (main) finned heat exchanger 2 the gas-fired boiler 1 heats the water circulated within a heating circuit by a pump P. The heated water passes through a three-way valve 4 which usually delivers the water to the radiators or radiating elements schematically represented by one element R, through the heating delivery pipe 5 and returns via the return pipe 6 to the pump P. Upon a request of domestic hot water, the three-way valve 4 closes the passage 5 to the radiators and supplies the hot water to a second water/water heat exchanger 17 (e.g. of the plate type) where the domestic hot water from the pipe 8 (that is from the water system) and which is delivered through the output pipe 9 to the taps for erogating the hot water, one of them being schematically indicated by RE in the Figure. The valve assembly according to the invention is shown in Fig.s 2 to 4 and substantially comprises two sub-assemblies or valve units made up as two blocks I and II. The construction of block I or delivery distributor is illustrated in details in Fig.s 5 to 8. As shown in Fig. 1 in the rectangular dashed frame labeled with I, and also with reference to Fig.s 2 to 4, the first unit I comprises a three-way valve 4, a spigot or pipe fitting 3 for the connection with the main heat exchanger 2, a spigot or pipe fitting 5 for the connection with the radiator R, an input spigot or pipe fitting 9 for the sanitary water, and two spigots or pipe fittings 22, 23 connecting the unit with said water/water heat exchanger 17. The three-way valve 4 in the left part of unit I is actuated by a diaphragm valve 12 which is fitted into a properly threaded seat 38 of the unit. It comprises a housing 120 within which a diaphragm 121 is movable with an associated pushing head or pan 122 which drives a rod 123 which in turn is connected to the stem of the valve 4. Such valve 4 in turn houses two valve bodies 42 and 43 axially urged by a return spring 44 in the housing 40 of the valve 4. The inner space of the control valve 12 is divided into two chambers, each provided with a supply duct 124 and 125, respectively for low and high pressure, the further connections of which will be illustrated later on with reference to pressure difference device 14. A further return spring 126 is preloaded in such a manner as to overcome the force of the spring 44 in the three-way valve. An axially located rod or spindle 127 is connected at one end with the pan 122 while its other end protrudes upwards from the valve housing for actuating a microswitch 128 enabling the start of the pump P upon a request of domestic hot water in periods when the boiler is not burning. In the assembly according to the invention the ignition of the burner is caused by a second microswitch 155 actuated by a pressure switch 15 as described later on. As can better be seen in Fig. 5, the valve 12 is fitted to the unit 1 by screwing it over the pipe fitting 38 and can easily be dismounted for the maintenance and in case the replacement of parts thereof. A conceptually similar arrangement with a three-way valve and a diaphragm control valve is disclosed the EP-A-0 466 010 to which reference is made for further details. A port or opening 30 is provided in the first unit I in correspondence with the pipe fitting 3 and allows for the introduction of a temperature probe, typically a (not shown) thermistor. To an additional pipe fitting 48 of the three-way valve 4 there are connected a by-pass valve 16 and a pressure switch 15 actuated by a pressure difference for opening the burner-enabling microswitch 155 in case the water level within the heating system is low and/or the pressure is null (due to a blocked pump). Such arrangement advantageously prevents the burner from being ignited in the above mentioned circumstances which in the known systems could cause drawing poca water at very high temperature (with the risk of scalds) before the intervention of the protection termostato provided for in such systems. Referring also to Figures 5 to 8, and particularly to Fig. 6, such pressure switch device 15 comprises a chamber 150 formed near the fixture housing the by-pass valve (illustrated later on), and divided into two portions by a diaphragm 151. One of such portions being connected through a passage 165 with the three-way valve, and the other portion being connected through a passage 164 to a point before the pump P, i.e. to a lower pressure area. A pan 152 urged by a coil spring 154 and provided with a stem or spindle 153 protruding from the chamber 150 for actuating the microswitch 155 abuts against the diaphragm 151. When water is present in the system, the water is pressurized by the pump P on the side of the valve 4, with the other side being at a lower pressure, and the so formed pressure difference acts on the diaphragm 151 that actuates the safety microswitch 155. The pipe fitting 48 is further connected to the by-pass valve 16, also illustrated in Fig. 6, which comprises a threaded metal duct 166 engaging the thread 161 of the pipe fitting 160 and carries a valve body 162 provided with longitudinal passages and urged by a coil spring 163. When the pressure difference between the delivery and the return pipes reaches a (high) predetermined level, e.g. due to large frictional losses in the radiators, the by-pass valve opens and a portion of the water is recirculated through the by-pass pipe section 10A provided for supplying a certain amount of water to the main heat exchanger 2 under any circumstances. The above by-pass valve is for example of the type disclosed in the Italian Utility Model application No. MI91U 000577 filed on June 25, 1991 and entitled "By-pass valve for hydraulic plants" to which reference is made for further details. Unit I further provides two pipe fittings 22 and 23 for the connection with the water/water heat exchanger 17, for the inlet of the heating water and the outlet of the domestic heated water, respectively. The second unit or valve sub-assembly II is shown as framed by a dashed line in Fig. 1. The construction of such block II, also called primary return distributor, is illustrated in details in Figures 9 to 12. It comprises the following components that are formed or mounted as an integral component. A device 14 activated by a pressure difference is housed in the main duct 60 for the domestic water (see Fig. 10) that will be illustrated with more details later, a pipe fitting 6 for the connection to the radiator(s) R, an inlet pipe fitting 8 for the domestic water, an outlet pipe fitting 7 to the pump, and two pipe fittings 32, 33 for the connection to said water/water heat exchanger 17. As can be seen in Fig. 13, the device 14 comprises a threaded locking ring 140 (which fits the duct 60), a valve body 141 having an orifice 145 and located at one end of a coil spring 146, and a spacer 147 formed as a cage of plastic material crimped or otherwise fixed to the ring in order to act like a spring stop. Upon the opening of the tap RE for drawing domestic hot water, the water coming from the water inlet tube 8 and directed to the plate-type heat exchanger 17 via the pipe 143, initially passes an orifice 145 in the valve body 141 as long as its flow rate is less than a predetermined value, e.g. 2 liters/min. When the draw of domestic hot water increases, the force of the spring 146 is overcome and water can pass also around the valve body 141. Thus the by-pass device is opened at a predetermined pressure level which is determined by the spring characteristics. When the water flows, the value of the pressure in the water system is available in the pipe section 142, whereas the value of the pressure drop is made available outside the valve 14 by the pipe section 144. These two sections are connected with the pipe fittings 125 and 124, respectively, of the diaphragm valve 12. As it is clearly seen in Fig. 13, the pressure difference device 14 is dimensioned for housing a flow rate regulator 80 (a so called Mannesmann valve) that keeps the flow rate constant even if the pressure varies. Such known valve employs a rubber seal of the O ring type that is deformed in accordance with the pressure and therefore progressively narrows the passage when the pressure increases. Such regulator is useful for keeping the flow rate constant, as requested, even when the local pressure of the water is rather high and the tap fully opened, thus avoiding a situation in which water not heated enough is supplied to the user. In case the pressure of the water system is low, the regulator is not used, that is such a regulator is not fitted in the device since it causes a remarkable pressure drop. In the pressure difference device there are further incorporate a metal ring 81 for fastening the regulator 80, and a metal mesh cylindrical filter 82, with a plug 61 closing the duct 60 at the right end. According to the invention, the replacement of the regulator, e.g. when this latter becomes clogged due to limestone or ageing, is quite simple. The cost of the regulator is very low and the replacement thereof very quick, the more so when compared with present devices equipped with an associated nut or additional components. Moreover the protection filter formed as a metal mesh is housed in the body of the device without requiring additional components. As can better be seen in Fig. 10, a tap 21 for the feedwater makeup of the heating system is fitted into a seat formed at an angle on the pipe fitting 8, and laterally to the duct 60 housing the pressure difference device, there is formed a duct 65 which is longitudinally divided and houses at one end a check valve 13 comprising a threaded plug 67 and an axially located coil spring 68 with this later carrying at its other end a valve body 69 equipped with an O rig 70. The above arrangement realizes a check valve 13 incorporated in the group of the invention, so that the water for filling the circuit and coming from the water system via the filling tap 21 must overcome the spring force in order to open the communication passage. This way it is prevented the risk that the heating water can accidentally reach the domestic water circuit (usually containing drinkable water) in case the pressure in the water system is too low, or when there is no water in the system, e.g. after a draining for a maintenance or repairing operation. In accordance with another embodiment of the invention which is illustrated with some components carried ouside in Fig. 10, the group further includes a tap for draining the heating system. According to such embodiment the plug 67 is axially bored and communicating with the inside of duct 65 via a passage 83, and contains a closing plunger actuated by an outer knob 80. In the second group several different components necessary for its proper working are formed or mounted as clearly shown in Figures 2 to 4. More precisely a pipe fitting 51 for a pressure gauge is formed near the pipe fitting 7, and a fitting 11 for an expansion tank 71 adapted to accomodate the water dilatation is realized near the former. Moreover on the pipe fitting 6 for the heating water return there is provided a fitting 18 for mounting a safety valve (not shown). Between the units I and II there is located a highly effective plate-type heat exchanger 17 of known design featuring very low flow resistance and a size that is small and can be varied during the manufacturing thereof in accordance with the requested flow rate. In the known plants problems are encountered in realizing the connections to the water/water heat exchanger due to the reduced distances therefrom and to the small size of the heat exchanger. This render the production complicate requiring a high manufacturing accuracy which further renders troublesome the maintenance since the components are difficult to access by wrenches and other tools. The manner by which the plate-type heat exchanger and the two units are connected together is shown in Fig. 4 for the first unit, that is for the heating hot water inlet and the domestic hot water outlet. More precisely the first connection is carried out through a pipe fitting 22 engaging a tightening nut 29 to be screwed on a threaded pipe fitting 24 of the plate-type heat exchanger 17, while for the oulet of the domestic hot water there is provided a smooth pipe fitting 23 receiving a smooth pipe fitting 27 of the heat exchanger, equipped with a seal ring (e.g. an O ring) 28 received in a groove. A similar arrangement is provided for the second unit that realizes the outlet connection for the heating hot water and the inlet connection for the domestic water (pipe fittings 32 and 33 in Fig. 11). The tightening the upper nuts causes a tie rod action that brings about also the connection of the lower smooth fittings, with the seal being ensured by the seal rings. Thanks to the above mentioned action, for releasing the heat exchanger there is required the loosening of two nuts only (or their tightening for the assembling therof). Fig. 14 schematically illustrate an embodiment of the present invention which is particularly useful for a vertical mounting, whereas the embodiment shown in Fig. 15 is particularly preferred when the pipe fittings 5, 6 and 8, 9 are horizontal. The same numeral references of Figures 2 and 3 have been used in both Figures 14 and 15 for indicating equal or substantially equivalent parts.

Claims: A valve assembly for combined plants adapted for providing both heating and sanitary hot water and comprising a gas-fired boiler (1), a main heat exchanger (2), a water/water heat exchanger (17) that can be included in the circuit of the heating water by means of a three-way valve (4), at least one radiator (R), and a pump (P) for circulating the heating water, characterized in that said valve assembly comprises two sub-assemblies or valve units, the first unit (I) comprising an integral metal block in which there are formed or mounted said three-way valve (4), a pipe fitting (3) for the connection with said main heat exchanger (2), a pipe fitting (5) for the connection with said at least one radiator (R), a pipe fitting (9) for the outlet of the domestic hot water, two pipe fittings (22, 23) for the connection with said water/water heat exchanger (17), said integral metal block further housing a pressure switch (15) and a by-pass valve (16) with an associated outlet fitting (10); said second unit (II) comprising an integral metal block in which there are formed or mounted a pressure difference device (14), a pipe fitting (6) for the connection with said at least one radiator (R), a pipe fitting (8) for the inlet of the domestic water, an outlet pipe fitting (7) to said pump (P), two pipe fittings (32, 33) for the connection with said water/water heat exchanger (17). A valve assembly as claimed in claim 1, characterized in that on said first unit (I) there is mounted a diaphragm valve (12) equipped with a rod (123) for actuating said three-way valve (4), the chamber (120) of said valve being divided by said diaphragm (121) into two portions that are supplied via two pipe fittings (124, 115) adapted to be connected to points of said second unit (II) between which a pressure difference exists, said diaphragm valve (12) further comprising a return spring (126) stronger than the spring (44) provided in said three-way valve (4), and a further rod (127) for actuating a microswitch (128) enabling the start of said pump (P). A valve assembly as claimed in claim 1 or 2, characterized in that said pressure switch (15) comprises a chamber (150) formed near the pipe fitting (160) housing the by-pass valve (16), that said chamber is divided into two portions by a diaphragm (151), one of said portions being connected through a first passage (165) to said three-way valve (4), and the other portion being connected through a second passage (164) to a point before said pump (P), said pressure switch (15) further comprising a pan (152) urged by a spring (154) and provided with a stem (153) actuating a second microswitch (155) controlling the ignition of the gas burner. A valve assembly as claimed in claim 3, characterized in that said by-pass valve (16) comprises a metal threaded duct (166) engaging the thread (161) of said duct (160) and carrying a valve body (162) having longitudinal passages and being urged by a return spring (163). A valve assembly as claimed in claim 4, characterized in that said it further provides a connecting pipe section (10A) between said by-pass valve (16) in the first unit (I) and the outlet pipe fitting (7) towards the pump (P) in the second unit (II). A valve assembly as claimed in the preceding claims, characterized in that said pressure difference device (14) comprises a threaded locking ring 140 which fits the duct 60, a valve body (141) having an orifice (145) and located at one end of a coil spring (146) and axially movable within said duct (60), a spacer (147) and a plug (61) for closing the end of said duct (60). A valve assembly as claimed in claim 6, characterized in that said pressure difference device (14) houses a flow regulator (80) of the so called Mannesmann valve type, that maintains the flow rate constant when the pressure varies, a metal ring (81) for fastening the regulator (80), and a metal mesh cylindrical filter (82). A valve assembly as claimed in claim 1, characterized in that said second unit (II) comprises a tap (21) for the waterfeed makeup of the heating circuit. A valve assembly as claimed in claim 8, characterized in that it comprises a duct (65) which is longitudinally divided and houses at one end a check valve (13) comprising a threaded plug (67) and a coil spring (68) axially located thereon, said spring (68) carrying at its other end a valve body (69) equipped with an O rig (70), and in that said plug (67) is axially bored and communicating with the inside of said duct (65) via a passage (83), and contains a closure plunger actuated by an outer knob (80) for draining the heating circuit. A valve assembly as claimed in the preceding claims, characterized in that said second unit (II) comprised a pipe fitting (51) for a pressure gauge, a pipe fitting (11) for an expansion tank, and a pipe fitting (18) for a safety valve in the return pipe (6) for the heating water.

Inventors: FUGAZZA GIUSEPPE, FUGAZZA, GIUSEPPE
Applicants: FUGAS SRL, FUGAS S.R.L.
Application year: 1993
Main classification: F24D19
IPC codes: F24H9, F24D3, F24D19