GB2286238A - Central heating:expansion tank - Google Patents

Abstract

A venting system for the control and expansion of water in a central heating installation comprises expansion tank 1, Fig. 5, with a first expansion chamber 6, Fig. 2, connected by pipe 2 to the expansion pipe 9 of the secondary stored water of the domestic hot water cylinder 10. Pipe 2 contains a double action non-return valve 12, and is connected to the primary heating coil 11. Beneath the first expansion chamber 6 in tank 1 is expansion chamber 7, the chambers being separated by a flexible rubber diaphragm 4 which prevents the primary water from mixing with the secondary water. At the base of the chamber 7 is a boss 3 connecting this chamber to the expansion pipe 9. <IMAGE>

Description

TITLE Improvements in or relating to a Venting System for the control and Expansion of Water in a Central Heating Installation The. present invention relates to a metallic container for use in a venting system for the control and expansion of water in a central heating installation, to a said venting system incorporating the said metallic container and to a central heating installation including the said venting system.

At present there are on the market expansion vessels that are used to take the expansion of the water when heated. The use of these create a sealed system and have to be dimensioned in accordance with the volume of the water within the system, and also the pressure to which this is subjected.

These types of expansion vessels require the expansion chamber to be pre-charged with compressed air or nitrogen, and are usually supplied pre-charged from the factory. Air or nitrogen has to be added or released to meet the requirements of the head pressure of the system to which it is to be fitted.

This requires the need for skilled technicians to install and maintain at the correct pressure. The disadvantage of using this type of method is that should at any time the system have to be bled to remove air, or to recharge after a radiator has been removed for decoration or repair and then replaced, the system will lose the pressure to which it was originally set and unless rectified immediately can cause malfunction of the boiler. This can prove expensive as well as the inconvenience of not being able to operate the heating system.

There is also the use of separate feed and expansion tanks with which to feed and replenish the heating system and also to cater for the expansion of the heated water.

These must be fitted at a higher level than the highest point on the heating system so as to give a positive head of water.

All expansion tanks must be fitted with a ball valve and an overflow, they must also be protected from frost if installed in the roof space. Additional pipe-work is required to supply water from the expansion tank to the heating system and a separate expansion pipe must also be installed.

One of the greatest disadvantages of the use of this method is that as the ball valve is very seldom operative this causes the ball valve to corrode into a closed position and as the water during expansion evaporates over a period of time this can cause damage to the system because of the lack of water and air ingress through the feed pipe.

The present venting system avoids or mitigates all the aforementioned problems. The present system can be either a sealed system or a vented system and does not require a separate feed and expansion tank.

The present system is based on a venturi method of feeding water into a heating installation and at the same time creates an expansion chamber that is constantly recharged from the stored water within a secondary system.

According to one aspect of the invention there is provided a container for use in a venting system for the control and expansion o, water in a central heating insTallation, the container, being preferably metallic housing a first expansion chamber and a second expansion chamber separated from one another by a flexible and res,llent diaphragm which 7s fixed to the container in suon a way that in a medial state of the diaphragm it divides the container To provide first and second expansion chambers cf substantially equal volume, the diaphragm separating the first and secona expansion chambers being adapted vhen incorporated into a said venting system to prevent primary water from mixing with secondary water, the first chamber having a first connecting means enabling communication with a first connecting conduit to a vent and expansion conduit of secondary stored water of a domestic hot water tank or cylinder, and the second chamber having a second connecting means enabling communication with a second connecting conduit to said vent and expansion conduit.

Preferably the diaphragm is made of a rubber, e.g. butyl rubber, or other suitable elastomeric material. The metallic container may be made of steel, e.g. mild steel or stainless steel or copper. The first and/cr second connecting means may be a metallic, e.g. copper, boss connecting means.

According to a second aspect of the invention there is provided a venting system for the control and expansion of water in a central heating installation incorporating the said container of the invent ion.

Preferably the said second connecting conduit ns provided @@th a a double action non-return valve, and â oncuit leading to primary heating system is provided between The said non-return valve and Tne first expansion chamber.

According to a third aspect of the invention there @s provided a central heating installation including the venting system of the invention.

By way of example preferred forms of the invention will now be described with reference to the accompanying diagrammatic drawings, wherein: Figure 1 is a section of an empty container serving as a double expansion chamber, Figure 2 is a section of the container of Figure 1 which is filled with water, and Figures 3 to 7 are sectional circuit arrangements of various venting systems for the control and expansion of primary water in a central heating installation including the container shown in Figures 1 and 2.

Referring to the drawing a metallic container 1 serves as a double expansion chamber. The container 1 may, for instance be made of mild steel, stainless steel or copper. If made of mild steel it should be stove enamelled internally to prevent rusting. 2 is a copper boss connection To a connection pipe & connecting with expansion pipe . 10 denotes a domestic hot water cylinder. As shown in Figure 2 6 is a first expansion chamber separated from a second expansion chamber 7 by a flexible and resilient diaphragm 4 of butyl rubber.

Instead of butyl rubber another rubbery or elastomeric plastics mater-a may be used fo the diaphragm d. The edge of the diaphragm 4 is fixed to peripheral points 26,26 on a central line of the container 1. Thus in Figures 1 and 3 the diaphragm 4 is shown stretched to a top position whereas in Figures 2 and 4 to 7 it is shown in an intermediate position to divide expansion chambers 6 and 7 from one another. When the diaphragm 4 is in a stretched and generally linear state between points 26, 26 the expansion chambers 6 and 7 are of equal volume thereby allowing the diaphragm 4 to expand upwards or downwards by equal amounts. 3 is a copper boss connection to a connection pipe 5 connecting with expansion pipe 9. 11 is a heating coil of cylinder 10.

12 is a double action non-return valve in connection pipe 27 between pipe 9 and first expansion chamber 6. The non-return valve 12 should be of an approved kind, for example a type conforming To the Bye-Law 25-BS 6282.

between valve 12 and camber 6 there is fitted a pipe 28 leading to the primary heating system.

@@ is .S cold water tank and 14 is the level of the AaTe - The tank 13. 15 denotes an air vent. 16 oeno@es air bubbles in the cylinder 10. Radiators are denoted by 17 (Figure 7). 18 denotes a pump and 19 a three art valve that is used To control the flow of water in the primary system to either the coil 11 within the cylinder 10 to heat the @econdary water or to divert the primary hot water to the heating system. 20 denotes a heating flow from the hot water cylinder, 22 denotes a hot water draw off and 23 denotes a boiler or circulator.

Figure 5 shows a protected boiler or circulator 23, i.e.

within boiler or circulator 23 is fitted a pressure relief valve (not shown). Such a pressure relief valve is normally supplied and fitted by the boiler or circulator manufacturer. Figure 6 shows a primary vent pipe 25 which should be installed if a non-protected boiler or circulator 23 is installed. H denotes in Figure 4 the height between the water level 14 and the bottom of the container 1.

In Figures 5 and 6, the portion 24 represents hot water when the primary water has expanded. Portion 24 in the expansion chamber 7 is secondary stored hot water which seeps into the chamber 7 when the secondary water is pressurised from the cold water storage tank 13 above when filling the system.

Methods of operating the described and illustrated Venting systems from the control and expansion of primary water in a central heating installation will now follow.

As water -s fed from the cold water tank 13 into tne hot water cylinder 10. the water will rise within the cylinder 10 and the air contained within the cylinder 10 will pass out thiouqh the vent and expansion pipe 9.

Water will continue to rise up through the pipe 9 and will attempt to fill the second expansion chamber 7 but will be prevented from so doing by the air lock contained in the chamber 7. The air lock is air that is trapped in the chamber 7 during filling of the system. This air will be forced out during the expansion of the primary heating.system as the diaphragm 4 stretches downwards to accommodate this expansion. This air will then escape up through the pipe 9 to atmosphere. As the primary water cools and contracts the air that was contained in the chamber 7 will be replaced by secondary water from cylinder 10. It does not matter whether the chamber 7 contains air or water as in either case the pressure of the air or water will be equal to the head pressure from the cold water tank 13 above.

Water will continue to rise in the pipe 9 until it reaches the pipe 27 connecting the pipe 9 to the first expansion chamber 6. Water will pass through the double action non-return valve 12 and will continue to do so until the primary heating system is filled with water.

The pressure of water from the cold tank 13 above will ensure that the heating system is filled to the same pressure head as that of the surface 14 of the water in the cold water storage tank 13 above.

After filling, the pressure in the heating system will be equal to that of the secondary stored water as pressure is controlled by the head of water in the cold water storage tank 13.

As the water is heated in the primary heating system, the expanded volume of water will pass into the top of the first chamber 6 and this in turn will push the diaphragm downwards forcing the water or air in the second chamber 7 out and into the expansion pipe 9. If air is contained in the second chamber 7 this air will pass up and through the pipe 9 to atmosphere. If water is forced out of the chamber 7 this water will return down into the cylinder 10, as this is a very slow operation.

This method will ensure that the heating system is always at the same pressure as that of the secondary water.

Should a radiator 17 (see Figure 7) be removed and replaced this will cause a negative pressure in the heating system and the water during the secondary expansion will again refill the system. If a protected boiler or circulator 23 (see Figure 5) is fitted, that is a boiler or circulator 23 with a pressure relief valve (not shown), then there is no need to vent the heating system. Primary water will not be able to pass back into the secondary system as this is prevented by the double action non-return valve 12. If a non-protected boiler or circulator 23 (see Figure 6) is fitted without a pressure relief valve then primary vent pipe 25 should be installed. This pipe 25 is a 23 mm vent pipe connected to the downstream side of the non-return valve 12, the pipe 25 terminating above the surface 14 of the water in the cold water storage tank 13 and discharging to atmosphere.

Claims (9)

1. A container for use in a venting system for the control and expansion of water in a central heating installation 3the container, being preferably metallic, housing a first expansion chamber and a second expansion chamber separated from one another by a flexible and resilient diaphragm which is fixed to the container in such a way that in a medial state of the diaphragm it divides the container to provide first and second expansion chambers of substantially equal volume, the diaphragm separating the first and second expansion chambers being adapted when incorporated into a said venting system to prevent primary water from mixing with secondary water, the first chamber having a first connecting means enabling communication with a first connecting conduit to a vent and expansion conduit of secondary stored water of a domestic hot water tank or cylinder, and the second chamber having a second connecting means enabling communication with a second connecting conduit to said vent and expansion conduit.

2. A container according to Claim 1, wherein the diaphragm is made of rubber, e.g. butyl rubber.

3. A container according to Claim 1 or 2, constructed from steel, e.g. mild steel or stainless steel or copper.

4. A container according to Claim 1, 2 or 3, wherein the first and/or second connecting means are a metallic, e.g. copper, boss connecting means.

5. A venting system for the control and expansion of water in a central heating installation incorporating the said container and in accordance with any preceding claim.

6. A venting system according to Claim 5, wherein the said second connecting conduit is provided with a double action non-return valve, and a conduit leading to a primary heating system is provided between the said nonreturn valve and the first expansion chamber.

7. A central heating installation including the venting system according to Claim 5 or 6.

8. A container for the purpose herein set forth constructed and arranged to function as described herein and as illustrated by the drawings.

9. A venting system and a central heating system incorporating such a system as herein described and exemplified with reference to the drawings.