SELF-PRIMING DEVICES FOR INDIRECT DOMESTIC WATER HEATING SYSTEMS AND THE USE OF SUCH DEVICES

Abstract: Self-priming devices for indirect domestic water heating systems which have a primary heating circuit including a heat exchanger (20) which heats domestic water in a secondary circuit, both circuits being fed with cold water from a common source. The self-priming device (1) has axially disposed upper and lower chambers, the upper chamber (4) being connected in the secondary circuit and the lower chamber (5) being connected in the primary circuit. The device acts as expansion and contraction chambers for both circuits and isolates the water in the primary circuit from the water in the secondary circuit during operation of the system. An auto vent valve (11) is provided adjacent the bottom of the lower chamber (5) to provide for inital filling of the primary circuit and for replenish­ ing the primary circuit from time to time through the secon­ dary circuit. The volume of the lower chamber (5) is at least 4 to 4.5% of the total water content of the primary circuit.

Description: t'Self-priming devices for indirect domestic water heating systems" This invention relates to self-priming devices for indirect domestic water heating systems. KOre specifically the invention provides for selfpriming devices which can be incorporated in existing domestic water heating systems to convert the system into an indirect water heating system which may or may not include a pumped or gravity fed central heating system. An indirect domestic water heating system is a system whereby domestic water in a storage cylinder is heated by means of a heat exchanger located in the storage cylinder. Water in a primary heating circuit is heated in a boiler or the like and is passed through the heat exchanger, the heat exchanger transferring heat from the primary water to the secondary water without the primary and secondary waters mixing. The primary water may be in a central heating system and may be gravity fed or pumped. Feed water for the primary and secondary circuits are supplied from a common source such as a storage tank but care must be taken to ensure that the primary water after it has entered the primary circuit does not enter and mix with the secondary water. The self-priming device of the present invention provides for isolating the circuits. The water in the primary circuit is separated from the water in the secondary circuit by a self-priming device according to the invention which acts as an expansion and contraction chamber for both circuits0 The self-priming device is connected externally of the domestic hot water cylinder to the heat exchanger inlet in a primary circuit and to a vent in a secondary circuit. It is known from our British Patent Specifications Nos. 1,421,532 and 1,421,533 to provide a compensator device between the primary¯water circuit and the secondary water circuit to isolate the circuits from each other during operation of the heating system when cold water is supplied to both circuits from a common source. It has been found that the compensator devices of the prior specifications have the disadvantage that the lower chamber is filled with primary water during operation and during the initial heat up period the primary water in the lower chamber expands into the upper chamber and mixes with the secondary water in the upper chamber The self-priming device of the present invention provides for automatic venting of the primary circuit which obviates the disadvantage of the prior constructions and provides for a more efficient system. The self-priming device of te present invention has been designed to offer a method of tImplifying the design and reducing the cost of indirect domestic water heating systems and also ensures that the primary and secondary waters are isolated from each other as heating and cooling occurs and ensures automatic topping up of the primary circuit should leakage or evaporation losses occur. A self-priming device for indirect domestic water heating system comprises a closed housing divided internally by a wall intermediate its ends to form axially disposed first and second chambers, an open ended tubular member extending from said wall into the second chamber to adjacent the opposite end of the chamber to provide communication between the chambers, an inlet and an outlet at the end of the second chamber adjacent said wall and at least one opening at the end of the first chamber remote from said wall, said inlet and outlet being so arranged as to be connectible to an outlet from a domestic hot water cylinder and a vent to atmosphere and the opening or openings in the first chamber being connectible to a primary water heating circuit which includes a heat exchanger located in the domestic hot water cylinder, the volume of the first chamber being at least 4 to 4.5 of the volume of the water content of the primary circuit, the volume of the portion of the second chamber between the inlet and outlet and the end of the tubular member being substantially equal to the volume of the first chamber, and an auto vent device located adjacent the end of the first chamber remote from said wall. Preferred embodiments of the invention are illustrated by way of example in the accompanying drawings in which: Fig. 1 is a sectional view of a self-priming device according to one embodiment of the invention; Fig. 2 illustrates the self-priming device of Fig. 1 incorporated in an indirect domestic water heating system; Fig. 3 illustrates a self-priming device according to another embodiment of the invention incorporated in an indirect domestic water heating system; Fig. 4 is a sectional view of the self-priming device along the line Y-Y of Fig. 3; Fig. 5 is a sectional view of the self-priming device along the line X-X of Fig. 3; and Fig. 6 is a partly sectional view of a vent valve. Referring to Fig. 1 of the drawings a self-priming device indicated generally at 1 comprises a tubular housing 2 closed at both ends and divided internally intermediate its ends by a wall 3 to form a chamber 4 and a chamber 5. A tubular member 6 open at both ends extends from the wall 3 into the chamber 4 to provide communication between the two chambers. An inlet 7 and an outlet 8 is provided at the end of the chamber 4 adjacent the wall 3 and an opening 9 is provided in the bottom 10 of the chamber 5 remote from the wall 3. An auto vent device 11 is provided in the wall 3 of the chamber 5 at the lower end of the chamber remote from the wall 3. The auto vent device 11 is automatically actuated and may be in the form of a valve having absorbent diaphragm washers ila which swell when wet to close the valve and when dry contract to provide a passage through the valve. A manually actuated screw threaded member 12 is also provided for manual operation of the valve and a screw threaded member 12a provides for setting the valve to open a predetermined amount when dry or substantially dry. It is essential that the auto vent device is located at the lower end of the chamber 5 so that the chamber 5 is filled with air when the device is in operation thus providing an air seal between the primary and secondary water to keep them apart. The volume of the lower chamber 5 is arranged to be at least equal to the volume of the portion A-B of the upper chamber 4. Referring to Fig. 2 of the drawings the self-priming device 1 is incorporated in a pumped primary circuit of an indirect domestic hot water heating system in which the opening 9 is connected to the flow side of a primary water heating system which includes a boiler or water heating source 15 and flow pipes for conducting heated water round a circuit and return pipes 17 for returning the water to the boiler 15. A space heating unit 18 or radiators (not shown) may be incorporated in the circuit in known manner. A pump 19 shown in the return side of the primary circuit may be incorporated in the flow side of the circuit. A heat exchanger 20 is connected to the flow and return circuits in the primary circuit and provides for indirectly heating a secondary circuit comprising domestic hot water in a hot water storage cylinder 21 which is supplied with cold water from a header tank 22 through a pipe 23 connected to the lower end of the cylinder 21. An outlet 24 for domestic hot water supply and a vent pipe 25 are connected to the upper end of the cylinder 21. The outle ?4 and vent 25 may have a common outlet from the cylinder as illustrated or the outlet and vent may be separate. The vent 25 is connected to the inlet 7 of the selfpriming device and the outlet 8 of the self-priming device is vented to atmosphere through a pipe 26. The vent valve 11 is manually operated to vent the primary circuit so that the circuit can be filled with cold water from the secondary circuit. When the primary circuit is filled, i.e. to a level just below the vent valve 11 the valve is manually closed thus allowing the valve to actuate automatically the lower chamber 5 or 34 being full of air providing a seal between the primary and secondary waters. When the primary circuit is filled with water the boiler 15 heats the water in the primary circuit which is circulated by the pump 19. Water circulating through the heat exchanger heats the water in the secondary circuit and the self-priming device provides for keeping the primary and secondary water separate by providing a volume of air in the chambers between the primary water and the secondary water and also acts as an expansion and contraction chamber for both circuits. The air in the chambers is provided by air released from the heated water. The volume of the lower chamber of the self-priming device is made to represent at least 4 to 4.5 of the total water content of the primary circuit. The self-priming device above described is particularly suitable for a pumped primary circuit but it can also be used in a gravity system. Referring to Figs. 3 to 5 a modified self-priminr device is illustrated which is suitable for use in a gravity fed primary heating circuit as illustrated in Fig. 3. The modified self-priming device indicated generally at 30 comprises a housing 31 closed at both ends and internally divided intermediate its ends by a wall 32 to form two chambers 33 and 34. An open ended tubular member 35 extends upwardly from the wall 32 into the chamber 33 to provide for communication between the chambers and the chamber 33 is provided with an inlet 35 and outlet 37 corresponding to the inlet 7 and outlet 8 of the self-priming device 1. The volume of the chamber 34 is at least equal to the volume of the portion h-B of the chamber 33 and as in the case of the device 1 the volume of the chamber 34 is msde to be at least 4 to 4.5 of the total water content of the primary circuit of an indirect domestic water heating circuit in which the device is to be used. TYe chamber 3 is provided with two openings 38 and 390 A vent valve 40 of the same type as the valve 11 of the sel-priming device 1 is also provided at the lower end of the chamber 34. The openings 38 and 39 are connected to the flow 41 anci return 42 of a heat exchanger t3 in a primary water heating circuit, the heat exchanger being located in a domestic hot water cylinder 44 to heat water in a secondary circuit for domestic use. The inlet 36 is connected to a draw-off for domestic hot water from the cylinder and to a vent to atmosphere. The vent valve 11 or 40 may be replaced by an automatic float air vent valve wherein a float member is housed in a chamber to actuate a vent valve when water in the chamber falls below a predetermined level. The valve is also manually operable.

Claims: CLAIt3 1. A self-priming device for indirect domestic water heating systems comprising a closed housing divided internally by a wall intermediate its ends to form axially disposed first and second chamber, said first chamber being disposed below said second chamber when the device is in use, an open eroded tubular > member extending from said wall into the second chamber with its distal end adjacent the opposite end of the chamber to provide communication between the chambers, an inlet anci an outlet at the end of the second chamber adjacent said wall and at least one opening at the end of the first chamber remote from said wall and when the device is in use said inlet and outlet being connectible to an outlet from a domestic hot water cylinder and to a vent to atmosphere respectively and the opening or openings in the first chamber being connectlble to a heat exchanger in a primary water heating circuit, said heat exchanger being located in the domestic hot water cylinder characterised in that the volume of that portion (A-B) of the second chamber (4) between the inlet (7) and outlet (8) and the distal end of the tubular member (6) is substantially equal to the volume of the first chamber (5) and an autovent (11) is located adjacent the end of the first chamber (5) remote from the wall (3) for venting the first chamber (5) to atmosphere, said auto-vent being positioned to contact water in said first chamber and including means responsive to said water whereby when water is present in said first chamber the auto-vent is closed and when the auto-vent is exposed to air in the first chamber the autovent is open. 2. A device as claimed in claims 1 characterised in that the first chamber (5) is provide¯. with one opening (j ir: the end of the chamber remote fro the wall (3) for connection to a primary water heating circuit when the device is in use. 3. A device as claimed in claim 1 characterised in that the first chamber (5) is provided with two openings (3 & 39) in the end of the chamber remote from the wall (3) which are connectible to the flow (42) and eturn (41) of a heat exchanger in a primary water circa b when the device is in use. 4. A device as claimed in an: of the preceding claims characterised in that the au=-vent (11 or 40) includes a water absorbent diaphragm (aha) which closes the vent when wet and opens the vent when substantially dry and includes manually operable means (12,P2a) for opening and closing the vent, 5. A self-priming device as claimed in any of claims 1 to 3 characterised in that the auto-vent (11 or 40) comprises an automatic float air vent valve having a float member housed in a chamber to actuate a vent valve when water in the chamber (5) falls below a predetermined level. 6. A self-priming device as claimed in any of the preceding claims in an indirect domestic water heating system characterised by a primary water heating circuit comprising at least a water heating source (15), and a heat exchanger (20), a secondary water heating circuit including a hot water storage cylinder (21), and a header tank for supplying cold water to said system, the heat exchanger being located in said cylinder (21) to heat water therein by indirect heat exchange, a draw-off (24 or 37) for domestic hot water from the cylinder and a vent (26) to atmosphere, said self-priming device (1) being connected between the primary and secondary water circuit to keep the primary water separate from the secondary water when the system is in operation. CLAIMS 1. A. self-priming device for indirect domestic water heating systems comprising a closed housing divided internally by a wall intermediate to its ends to form axially disposed first and second chambers, an open ended tubular member extending from said wall. intro the second chamber to adjacent the opposite end of the chamber to provide communication between the chambers, an inlet and an outlet at the end of the second chamber adjacent said wall and at least one. opening at the end of the first chamber remote from said wall said inlet and outlet being so arranged as to be connectible to an outlet from a domestic hot water cylinder and to a vent to atmosphere and the opening or openings in the first chamber being connectible to a primary water heating circuit which includes a heat exchanger located in the domestic hot water cylinder, the volume of the first chamber being at least 4 to 4.5% of the volume of the water content of the primary circuit, the volume of the portion of the second chamber between the inlet and outlets and the end of the tubular member being substantially equal to the volume of the first chamber, and an auto vent device located adjacent the end of the first chamber remote from said wall. 2. A self-priming device as claimed in Claim 1, in which the first chamber has one opening at the end of the chamber remote from the wall said opening being connectible to the flow side of a primary water hefting circuit. 3. A self-priming device as claimed in Claim 2, in which the vent valve includes a water absorbent diaphragm which closes the valve when wet and opens the valve when substantially dry. 4. A self-priming device as claimed in Claim 3 wherein the vent valve is an auto-vent. 5. h self-priming device as claimed in any of the preceding claims in an indirect domestic water heating system having primary and secondary water heating circuits, said primary circuit including at least a water heating source and 2 heat exchanger, said secondary circuit including a hot water storage cylinder, a header tank for cold water for the cylinder, a draw off for domestic hot water from the cylinder and a vent to atmosphere, said heat exchanger being located in the cylinder to heat the domestic hot water and said self-priming device being connected between the primary and secondary circuits to keep the primary water separate from the secondary water when the primary water is heated.

Inventors: CARRUTHERS, THOMAS ROBISON
Applicants: FLEMING FABRICATIONS LIMITED
Application year: 1979
Main classification: F24D3
IPC codes: F24D3