GB2220469A - Discharging condensate from gas boilers - Google Patents

Abstract

Apparatus is provided for discharging condensate from a condensing type gas-fired appliance to a drain pipe, the apparatus comprising a tank 20 for receiving and collecting condensate discharged under gravity from the appliance and syphon means 21 adapted to commence discharge of the condensate from the tank to the drain pipe only when the collected condensate has risen to a predetermined uppermost level and to continue discharge of the condensate thereafter only until the collected condensate has fallen to a predetermined lowermost level. The lowermost chamber 27 of the tank is surmounted by a chamber 30 of smaller cross-sectional area. This causes the liquid in the upper chamber to rise relatively quickly and so to accelerate the establishment of a syphoning action. Syphoning action is promoted by restrictor 39 in tube 21. <IMAGE>

Description

"APPARATUS FOR DISCHARGING CONDENSATE FROM A CONDENSING TYPE GAS-FIRED APPLIANCE" The present invention relates to-apparatus for discharging condensate from a condensing type gas-fired appliance such as a gas-fired boiler.

During operation of a condensing type gas-fired boiler, water vapour contained in the exhaust gas is caused to condense out from the exhaust gas on the walls of the boiler heat exchanger.

In conventional boilers of this type the condensate water is discharged under gravity to a receptacle such as a U shaped collector pipe. This leads to a drainage point which may be in the form of a downwardly sloping drain -pipe which discharges its contents into a soil stack or open gulley. In use the condensate trickles continuously along the drain pipe to the drain while condensate is being collected.

In sub-zero temperature conditions the trickle of condensate may freeze leading to a blockage forming in the drain pipe.

It is therefore an object of the present invention to provide apparatus enabling the condensate to be discharged in such a way that the likelihood of the condensate freezing in the drain pipe in sub-zero temperature conditions is greatly reduced.

According therefore to the present invention we provide apparatus for discharging condensate from a condensing type gas-fired appliance to a drainage point, the apparatus comprising a tank for receiving and collecting condensate discharged under gravity from the appliance, the tank having a lowermost chamber surmounted by an uppermost chamber communicating therewith, the uppermost chamber having a smaller cross-sectional area than the lowermost chamber, a drain pipe serving as the drainage point for the condensate and condensate discharge means adapted to commence discharge of the condensate from the tank to the drain pipe only when the collected condensate has risen to a predetermined level within the uppermost tank chamber and to continue discharge thereafter only until the condensate has fallen to a predetermined level within the lowermost chamber.

In this way the condensate can be discharged in a concentrated surge at discrete intervals instead of a continuous trickle.

As a surge provides a greater volume flow of water and heat content in unit time than does a trickle there is a reduction in the risk of the water freezing in the drain pipe.

The preferred form of condensate discharge means comprises syphon means as this is the simplest and cheapest form of discharge device involving no moving parts. The syphon passage may incorporate a restrictor to promote the syphon action.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a conventional drainage system for discharging condensate from a condensing boiler, Figure 2 is a diagrammatic view of a first embodiment of the invention, and Figure 3 is a diagrammatic view of a second embodiment of the invention.

Referring to the drawings, Figure 1 discloses the bottom half of a condensing boiler 1 comprising a sump 2 for collecting condensate discharging downwardly from the heat exchanger (not shown) in the top half of the boiler and a drainage duct 3 for receiving the condensate discharging downwardly from the sump 2 for discharge to a soil stack (not shown) e.g. a drain.

The duct section adjoining the sump 2 is in the form of a U 4 which extends through a side wall 5 of the boiler casing 6 and terminates in a downwardly sloping drain pipe 7 which discharges the condensate to a drain.

In use, condensate is continuously discharged to the sump 2 and then enters the duct 3 before being discharged from the pipe 7 in the form of a continuous trickle.

Referring to Figure 2, here the duct 3 shown in Figure 1 has been replaced by a tank 20 incorporating a syphon tube 21. The sump 2 terminates in a vertically downwardly extending discharge pipe 22 which terminates within the tank 20.

The tank 20 is formed with a main compartment 23 into which the pipe 22 extends and an adjoining sub-compartment 24 separated from the main compartment 23 by an internal wall 25. The upper ends of both compartments are closed by a wall 26 through which the pipe 22 extends and from which the wall 25 is spaced.

The main compartment 23 comprises a lowermost chamber 27 formed by the base 28 of the tank, a vertical side wall 29, two further spaced vertical side walls arranged in the plane of the paper and adjoining the side wall 29 and the internal wall 25 which as shown extends upwardly from the base 28. The main compartment 23 also forms an uppermost chamber 30 surmounting the lowermost chamber 27 and formed by a vertical side wall 31, the two adjacent vertical side walls common to those of the uppermost chamber and the internal wall 25. The side wall 31 is located inwardly of the side wall 29, there being a horizontal wall 32 which adjoins the walls 29 and 31. Thus the uppermost chamber is of reduced cross-sectional area compared to that of the lowermost chamber for purposes to be described.

The sub-compartment 24 is formed by the base 28, the internal wall 25, the vertical side walls common to the main compartment and a further vertical side wall 33 from which there extends outwardly a downwardly sloping drain pipe 34.

The syphon tube 21 is in the form of an inverted U having one arm 35 located in the main compartment 23 and another arm 36 having a generally vertical portion 37 located in the sub-compartment 24 and a downwardly sloping end portion 38 located in the drain pipe 32, the tube 21 extending through an aperture in the internal wall 25.

The bend in the tube 21 is arranged to be level with the uppermost chamber 30 for a purpose to be described. The internal diameter of the arm 36 is restricted at 39 by means of a restrictor member and this tends to promote the syphon action.

In use, condensate entering the sump 2 is discharged to the lowermost chamber 27 of the compartment 23. As the level of condensate within the chamber 27 rises the condensate enters the arm 35 of the syphon tube 21.

Eventually the level of condensate reaches the uppermost chamber 30 and flows over the bend in the syphon tube 21 to effect the syphoning action previously described. This action continues until the level of liquid falls to a point in the lowermost chamber enabling air to enter the lowermost end 40 of the arm 35 to discontinue the syphoning action. The reduced cross-sectional area of the uppermost chamber 30 compared to the lowermost chamber 27 causes the liquid level in uppermost chamber 27 to rise more rapidly than that in the uppermost chamber 30 so as to accelerate the rise of the liquid level in the arm 35 of the syphon tube 21 towards and over the bend.

In order to ensure the access of air to the lowermost end 40 of the tube 21 the top wall 26 of the tank 20 is provided with an air vent 41.

The space between the side wall 25 and the top wall 26 forms an overflow 42 for liquid in the uppermost chamber 30.

Referring to Figure 3 where parts similar to those shown in Figure 2 bear similar reference numerals, here the sump 2 has been completely dispensed with and the condensate is arranged to discharge directly from the heat exchanger shown schematically by 50 into a collector tank 51. In this case the collector tank 51 has three compartments 52, 53 and 54.

The first compartment 52 which is arranged to receive the condensate has an opening 55 in its uppermost end and is otherwise formed by a base 56, a vertical outer wall 57, lying in the plane of the paper and two spaced vertical outer side walls (not shown) also common to the other compartments and a vertical inner wall 58 also common to the second compartment 53.

The inner wall 58 adjoins an outer top wall 59 at its uppermost end, which top wall 59 has a portion 60 which slopes downwardly towards the opening 55 and serves as a drip tray to receive condensate from the heat exchanger 50 for supply to the first compartment 52. As shown the internal wall 58 terminates short of the base 56 to form an opening 61 to permit the condensate to enter the second compartment 53.

The second compartment 53 is formed by the base 56, the internal wall 58, the two vertical side walls previously mentioned, a further internal wall 25 common to the third compartment and an inner top wall 70 which adjoins the internal wall 58 at one end and, at the other end adjoins the top wall 59 at a point where the sloping portion 60 levels off to horizontal portion 71.

The second compartment 53 forms a lowermost chamber 72 into which one arm 35 of the syphon tube 21 extends and an uppermost chamber 73 surmounting the lowermost chamber 72.

The lowermost chamber 72 is formed between the internal walls 58 and 25, the two vertical side walls common to the other compartments and a first part 74 of the inner top wall 70, which part 74 slopes in the same sense as the drip tray 60 and adjoins at one end the internal wall 58.

The uppermost chamber 73 is formed between the vertical side walls common to the other compartments, the internal side wall 25 and a second part 75 of the inner top wall 70, which part 75 adjoins the part 74 at one end and the outer top wall 59 at the junction between parts 60 and 71.

The uppermost chamber 73 thus has a reduced crosssectional area in comparison to the lowermost chamber 72 for reasons which have already been explained in the description accompanying Figure 4.

The third compartment is formed by the base 56, the internal wall 25, the two vertical outer side walls and the remaining outer wall 76.

The wall 76 has a lower vertical portion 77 adjoining the base 56, an upper verticl portion 78 disposed inwardly of the portion 77, and adjoining the outer top wall 59 at the junction between the parts 60 and 71 and an intermediate portion 79 adjoining the portions 77 and 78.

The portion 78 is co-planar with the internal wall 25 from which it is spaced to form an overflow opening 80.

Extending outwardly from the portion 77 of the wall 76 and sloping downwardly is a drain pipe 34. The other arm 37 of the syphon tube 21 has an end portion 38 located within the drain pipe 34. The bend in the syphon tube 21 is located level with the uppermost chamber 73 for the same reasons as previously explained in the description accompanying Figure 4.

The syphon tube 21 operates in the same manner as previously described commencing discharge when the level of the liquid in the uppermost chamber 73 has reached a predetermined uppermost level and terminating discharge when the liquid level in the lowermost chamber 72 has reached a predetermined lowermost level.

The portion 78 of the wall 76 is provided with an air vent 81 to ensure that the tank is vented to atmosphere to enable the siphoning action to be terminated when the liquid has fallen to a level co-terminous with the lowermost end 39 of the syphon arm 35.

Claims (4)

1. Apparatus for discharging condensate from a condensing type gas-fired appliance to a drainage point, the apparatus comprising a tank for receiving and collecting condensate discharged under gravity from the appliance, the tank having a lowermost chamber surmounted by an uppermost chamber communicating therewith, the uppermost chamber having a smaller cross-sectional area than the lowermost chamber, a drain pipe serving as the drainage point for the condensate and condensate discharge means adapted to commence discharge of the condensate from the tank to the drain pipe only when the collected condensate has risen to a predetermined level within the uppermost tank chamber and to continue discharge thereafter only until the condensate has fallen to a predetermined level within the lowermost chamber.

2. Apparatus as claimed in claim 1 in which the condensate discharge means comprises syphon means.

3. Apparatus substantially as hereinbefore described with reference to either Figure 2 or Figure 3.

4. A condensing type gas-fired heating appliance incorporating the apparatus as claimed in any of claims 1 to 3.