EP0014279B1

EP0014279B1 - Self-priming devices for indirect domestic water heating systems and the use of such devices

Info

Publication number: EP0014279B1
Application number: EP19790300181
Authority: EP
Inventors: Thomas Robison Carruthers
Original assignee: Fleming Fabrications Ltd
Current assignee: Fleming Fabrications Ltd
Priority date: 1979-02-06
Filing date: 1979-02-06
Publication date: 1983-08-10
Also published as: EP0014279A1; DE2966041D1

Description

This invention relates to self-priming devices for indirect domestic water heating systems.
More specifically the invention provides for self-priming 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 circuits.
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 the present inven_- tion has been designed to offer a method of simplifying 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 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 ended 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 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 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 connectible 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 the first chamber is at least 4% of the volume of the water content of the primary circuit, the volume of that portion (A-B) of the second chamber between the inlet and outlet and the distal end of the tubular member is substantially equal to the volume of the first chamber and an auto-vent is located adjacent the end of the first chamber remote from the wall for venting the first chamber 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 and the auto-vent is open.
Use of a self-priming device according to the invention in an indirect domestic water heating system comprising a primary water heating circuit having at least a water heating source, and a heat exchanger, a secondary water heating circuit including a hot water storage cylinder, and a header tank for supplying cold water to said system, the heat exchanger being located in said cylinder to heat water therein by indirect heat exchange, a draw-off for domestic hot water from the cylinder and a vent to atmosphere, said self-priming device 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.
Preferred embodiments of the invention are illustrated by way of example in the accompanying drawings in which:-

Figure 1 is a sectional view of a self-priming device according to one embodiment of the invention;
Figure 2 illustrates the self-priming device of Figure 1 incorporated in an indirect domestic water heating system;
Figure 3 illustrates a self-priming device according to another embodiment of the invention incorporated in an indirect domestic water heating system;
Figure 4 is a sectional view of the self-priming device of Figure 3;
Figure 5 is a sectional view of the self-priming device of Figure 4 turned through 90°; and
Figure 6 is a partly sectional view of a vent valve.

Referring to Figure 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 11 a 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 Figure 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 16 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 outlet 24 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 self-priming 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 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% 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 Figures 3 to 5 a modified self-priming device is illustrated which is suitable for use in a gravity fed primary heating circuit as illustrated in Figure 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 36 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 A-B of the chamber 33 and as in the case of the device 1 the volume of the chamber 34 is made to be at least 4% of the total water content of the primary circuit of an indirect domestic water heating circuit in which the device is to be used.
The chamber 34 is provided with two openings 38 and 39.
A vent valve 40 of the same type as the valve 11 of the self-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 and return 42 of a heat exchanger 43 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

1. A self-priming device (1, 30) for indirect domestic water heating systems comprising a closed housing (2, 31) divided internally by a wall (3, 32) intermediate its ends to form axially disposed first and second chambers (5, 34; 4, 33), said first chamber (5, 34) being disposed below said second chamber (4, 33) when the device is in use, an open ended tubular member (6, 35) extending from said wall into the second chamber (4, 33) with its distal end adjacent the opposite end of the chamber to provide communication between the chambers, an inlet and an outlet (7, 36; 8, 37) at the end of the second chamber (4, 33) adjacent said wall (3, 32) and at least one opening (9; 38, 39) 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 (25, 36) from a domestic hot water cylinder (27, 44) and to a vent (26, 37) to atmosphere respectively and the opening or openings (9; 38, 39) in the first chamber being connectible to a heat exchanger (20, 43) in a primary water heating circuit, said heat exchanger being located in the domestic hot water cylinder (27, 44) characterised in that the volume of the first chamber (5, 34) is at least 4% of the volume of the water content of the primary circuit, the volume of that portion (A-B) of the second chamber (4, 33) between the inlet (7, 36) and outlet (8, 37) and the distal end of the tubular member (6, 35) is substantially equal to the volume of the first chamber (5, 34) and an auto-vent (11, 40) is located adjacent the end of the first chamber (5, 34) remote from the wall (3, 32) for venting the first chamber (5, 34) to atmosphere, said auto-vent being positioned to contact water in said first chamber (5, 34) and including means responsive to said water whereby when water is present in said first chamber (5, 34) the auto-vent (11, 40) is closed and when the auto-vent is exposed to air in the first chamber (5, 34) the auto-vent (11, 40) is open.

2. A device as claimed in Claim 1 characterised in that the first chamber (5) is provided with one opening (9) in the end of the chamber remote from 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 (34) is provided with two opening (38, 39) in the end of the chamber remote from the wall (32) which are connectible to the flow (42) and return (41) of a heat exchanger (43) in a primary water circuit when the device is in use.

4. A device as claimed in any of the preceding claims characterised in that the auto-vent (11 or 40) includes a water absorbent diaphragm (11 a) which closes the vent when wet and opens the vent when substantially dry and includes manually operable means (12, 12a) 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 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, 34) falls below a predetermined level.

6. Use of a self-priming device as claimed in any of the preceding claims in an indirect domestic water heating system comprising a primary water heating circuit having at least a water heating source (15), and a heat exchanger (20, 43), a secondary water heating circuit including a hot water storage cylinder (21, 44), and a header tank (22) for supplying cold water to said system, the heat exchanger being located in said cylinder (21, 44 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, 30) 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.