GB2275099A

GB2275099A - Heating assemblies having a chimney

Info

Publication number: GB2275099A
Application number: GB9401239A
Authority: GB
Inventors: Jonathan Leslie Greenall
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-01-23
Filing date: 1994-01-24
Publication date: 1994-08-17
Anticipated expiration: 2014-01-24
Also published as: GB2275099B; GB9301337D0; GB9401239D0

Abstract

A method of controlling the quantity of heat which is carried through a chimney (3) by exhaust gases comprises the steps of using a temperature sensor (11) to measure or calculate the temperature or humidity of a part of the chimney (3), determining whether or not the temperature falls below a specified limit, and if the limit is exceeded, altering the rate of heat extraction from the flue gases by a heat exchanger (6). The method is intended to maintain chimney draught, and prevent damage due to condensation or freezing. <IMAGE>

Description

HEATING ASSEMBLIES HAVING A CHIMNEY This invention relates to heating assemblies, such as stoves and fires, which have a chimney associated with them.

Chimneys have been in common use throughout the world for hundreds of years. The great majority of houses have a chimney, and the purpose of the chimney is to exhaust the products of combustion from the stove. Chimneys are connected to many forms of heating appliance.

The principle of a chimney is that the hot exhaust gases from a heating appliance or open fire rise through the flue of the chimney because they are lighter than the colder outside air.

It is probable that early chimneys were built to vent open fires which require large quantities of air to burn properly. Considerable heat is lost through a chimney in this way. This heat is seen as being wasted.

Heating appliances have become more fuel efficient and modern appliances have less heat vented to the chimney.

This is seen generally in the art as being a good thing.

According to a first aspect of the invention I provide a method of operating a heating appliance having, or being associated with, a chimney of a flue, the method comprising measuring or calculating the temperature of a part of the chimney and operating the appliance in such a way that the temperature of the part of the chimney is a factor in how the appliance is operated.

Thus according to my invention care should be taken to ensure that the chimney is not too cold.

I have appreciated that it is not always a good thing to reduce the heat "wasted" up the chimney below a certain point. With modern stoves and fires the flue or chimney temperature can become too low, and consequently a poor draught is obtained from the chimney. Sometimes low flue gas temperature can cause condensation of the combustion products in the flue or chimney. This can result in a rapid build up of waste products of combustion, such as tar deposits.

Condensation can cause major damage to flue systems since they can seep through joint lines, for example the mortar between bricks, and causes unsightly external stains. Furthermore, the staining is not only unsightly but it also eventually causes corrision of the structure of the chimney and permanent damage. This can be very expensive to correct.

A further problem with chimneys which are too cold is that they can be damaged by water. If there is a prevailing breeze in one direction this can dry out one side of the chimney whilst leaving the other side relatively wet. This can cause uneven expansion of brickwork if there is a freezing spell, and can cause differential corrosion and erosion of a chimney. I believe it is this that causes some chimneys to bend.

In the past there have been many attempts to extract more and more heat from heating appliances, and their associated flue systems. For example flue pipes are known to be cooled by water filled heat exchangers, and fans have been used to cool flue pipes and to increase the heat output by heat exchanging to the room in which the appliance is situated, to reduce heat loss through the flue of the chimney. I believe that the heat which goes up the chimney is not "wasted", but can serve a useful purpose of keeping the chimney hot so as to ensure that the effects of combustion product condensation, and weather damage to the chimney, are reduced, and to ensure that there is a proper temperature difference over the height of the chimney so that there is a good rise of air, or flue draught, and that the appliance burns correctly.

Other features of the present invention are that it is preferable not to let the temperature of the part of the chimney being monitored, or the temperature calculated for the part of a chimney, fall below a predetermined level. Preferably the temperature of said part of the chimney or the flue is kept at an even temperature, within a predetermined range.

Preferably the temperature of the part of the chimney or the flue is monitored continuously or periodically, and a signal or signals indicative of the temperature of said part of the chimney or the flue are fed to a controller. Preferably the temperature control of the said part of the chimney or flue is achieved by varying the heat extracted from the exhaust flue gases as they go up the chimney or the flue. Preferably the method comprises altering the rate of heat extraction from the flue or exhaust gases by a heat exchanger.

Preferably the part of the chimney or the flue at which the temperature sensor is provided is at or near the top of the chimney or the flue. Temperature measurement is preferably achieved by electrical means.

According to a second aspect of the invention I provide a heating installation comprising a heating appliance and a chimney or a flue associated with the appliance, the installation also having chimney heat control means, a temperature sensor adapted to sense the temperature of a region of the chimney or the flue, and a controller adapted to control the chimney heat control means, the temperature sensor providing signals to the controller indicative of the temperature of the region of the chimney or the flue and the controller controlling the operation of the chimney heat control means so as to control the temperature of the chimney or the flue.

Preferably the chimney heat control means comprises means for varying the amount of heat in the combustion gases which go up the chimney or the flue.

Preferably the chimney heat control means comprises a heat exchanger, most preferably a heat exchanger which also serves to heat the room of the appliance, or heats water to provide hot water. The controller preferably controls the proportion of the heat of the flue gases which go up the chimney or the flue.

The temperature sensor is preferably provided towards or at the top of the chimney or the flue, but may be provided simply above the roof, or in the loft space.

There may be a second temperature sensor provided to sense the temperature of the outside air.

According to a third aspect of the invention I provide a kit comprising a controller and temperature sensor, the controller being adapted to control the operation of chimney heat control means of a heating installation, and the temperature sensor being adapted to provide signals indicative of the temperature of a region of a chimney of a heating installation to the controller, the arrangement being such that, in use, the controller operates a heating appliance in a manner which is dependent, at least in part upon the temperature signals.

According to a fourth aspect of the invention I provide a method of protecting a chimney or a flue comprising the steps of monitoring conditions, properties or states in or adjacent the chimney or the flue to determine if the conditions, properties or states are within specified limits and adjusting the operating characteristics of the chimney or the flue if the conditions, properties or states are beyond the specified limits.

The conditions, properties or states may be humidity, air flow rate, temperature, or emissions content of the exhaust gases including particulate or other material transport of the exhaust gases, CO content, or CO2 content. Of course other properties associated with chimney exhaust gases may be monitored.

The operating characteristics of the chimney which may be altered may be air flow rate from an appliance, exhaust gas temperature or emissions content of the exhaust gases.

An embodiment of the invention will now be described by example only with reference to the accompanying drawings. The drawing shows schematically a heating assembly 1 provided in a house. The heating assembly comprises a heating appliance 2 and a chimney 3 extending upwards from the heating appliance, through a roof space 4, through a roof 5, and above the roof.

The heating appliance 2 has heat exchange means 6 which comprises a system of ducts (not shown) for transferring hot air to a number of air outlet grills 7. The grills 7 are provided in the room in which the appliance is provided, and may also be provided in other rooms, for example rooms adjacent to that room. The heat exchange means 6 may also comprise a system of pipes for heating hot water, either to be used for heating radiators in the house, or to provide a hot water supply for domestic use, or both. The heat exchange means 6 also includes a fan (or in the case of water a pump) for forced convection of the heat transfer fluid.

A controller 8 is provided in the room. The controller 8 has an on/off switch 9 and a variable room heat control dial 10.

A temperature sensor 11 is provided at the top of the chimney 3 and passes signals indicative of the temperature to the controller 8 via wires 12. The temperature sensor 11 is, for example, a thermocouple.

The temperature sensor 11 monitors the temperature of the brickwork of the chimney 3 at a region at the top of the chimney. Signals indicative of this temperature are passed to the controller 8. The controller is manually set by the occupant of the room to provide more or less heat to the room via the heat exchanger 6 by manipulation of the variable room heat control dial 10. However, the amount of heat which the controller allows to be transferred to the room is also constrained by the temperature of the chimney 3. The controller has a pre-recorded minimum temperature below which the temperature of the region of the chimney in the vicinity of the temperature sensor 11 should not be allowed to fall.Thus whilst the amount of heat transferred to the room is under the control of the user the electronic controller 8 will not allow the user to transfer too much heat to the room - an eye will be kept upon the temperature of the chimney. The controller 8 thus sets a maximum proportion of the heat of the flue gases which can be transferred out of the flue gases by the heat exchange means, or put another way ensures that a minimum amount of heat still goes up the chimney to keep it warm.

The minimum amount of heat required to go up the chimney can of course be exceeded if the user turns the dial 10 down.

The minimum amount of heat that is allowed to go up the chimney by the controller 8 may depend upon other factors as well as the temperature indicated by sensor 11. For example, it may depend upon the wind speed of the air passing past the chimney. A sensor may be provided in light of this and provide suitable signals to the controller 8. Another factor may be the temperature of the outside air. Again, a sensor indicative of this may be provided which provides suitable signals to the controller 8.

If a house, or nearby houses, have a plurality of chimneys then not all of the chimneys need be provided with separate temperature sensors 11. It could be possible simply to assume that the temperature of two chimneys in the same region would be much the same and provide a single sensor. For example, when there are two flues in a common chimney brickwork structure, which is often used where heating appliances of different houses are back to back on a common adjoining wall, a single sensor may provide signals to separate controllers for both heating appliances.

A temperature sensor 11 may measure the temperature of the external surface of the brickwork of the chimney, the temperature of a deeper region of the brickwork, for example in the region of the aperture of the flue, or may even measure the temperature of the gases in the flue.

The temperature sensor may be provided at a position other than at the top of the chimney. For example it could be provided in the roof space 4. An extrapolation between the temperature in the roof space 4 and the temperature of the chimney outside of the building could be made.

Another way in which the invention could be performed is to set up a system similar to that shown in the drawing initially in order to ascertain what is the minimum setting for the controller 8, perhaps build in an allowance to take into account the fact that the system may be used on worse days than the day upon which it is set up (set in minimum proportional heat transfer of the chimney somewhat higher than that actually calculated - as a safety margin), and the sensor 11 can then be removed. Thus the invention may be used only to set up the controller 8 initially. Once the controller 8 knows its minimum allowed setting the temperature sensor can in this scenario be removed.

However, it will be appreciated that I prefer to have the temperature sensor monitoring the temperature of the chimney continuously, or periodically, as a regular check on the performance of the system.

Control of the heating appliance of the preferred embodiment is based on monitoring the chimney or flue gas temperature at the top of the flue, either by direct measurement at that point, or by way of calculation based on pre-recorded calculated information. A consequence of this is that flue temperatures can be kept more constant than in previous methods of operating a heating appliance, and consequently flue draughts, and burning speeds of the fire, are regulated better.

One preferred way of setting up the system is to ensure that maximum heat is transferred to the home consistent with keeping the flue termination temperature at or above the predetermined level designed to prevent condensation.

Claims

1. A method of operating a heating appliance having, or being associated with, a chimney or a flue, the method comprising measuring or calculating the temperature of a part of the chimney and operating the appliance in such a way that the temperature of the part of the chimney is a factor in how the appliance is operated.

2. A method according to claim 1, in which the temperature of said part of the chimney or the flue is kept at an even temperature, within a predetermined range.

3. A method according to claim 1 or claim 2, in which the temperature of the part of the chimney or the flue is monitored continuously.

4. A method according to claim 1 or claim 2, in which the temperature of the part of the chimney or the flue is monitored periodically.

5. A method according to any preceding claim, in which a signal or signals indicative of the temperature of said part of the chimney or the flue are fed to a controller.

6. A method according to any preceding claim, in which the temperature control of the said part of the chimney or flue is achieved by varying the heat extracted from the exhaust flue gases as they go up the chimney or the flue.

7. A method according to any preceding claim, in which the method comprises altering the rate of heat extraction from the flue or exhaust gases by a heat exchanger.

8. A method according to any preceding claim, in which the part of the chimney or the flue at which the temperature sensor is provided is at or near the top of the chimney or the flue.

9. A method according to any preceding claim, in which temperature measurement is achieved by electrical means.

10. A method substantially as described herein with reference to the drawing.

11. A heating installation comprising a heating appliance and a chimney or a flue associated with the appliance, the installation also having chimney heat control means, a temperature sensor adapted to sense the temperature of a region of the chimney or the flue, and a controller adapted to control the chimney heat control means, the temperature sensor providing signals to the controller indicative of the temperature of the region of the chimney or the flue and the controller controlling the operation of the chimney heat control means so as to control the temperature of the chimney or the flue.

12. A heating installation according to claim 11, in which the chimney heat control means comprises means for varying the amount of heat in the combustion gases which go up the chimney or the flue.

13. A heating installation according to claim 11 or claim 12, in which the chimney heat control means comprises a heat exchanger.

14. A heating installation according to any one of claims 11 to 13 has which a heat exchanger which also serves to heat the room of the appliance, or heats water to provide hot water.

15. A heating installation according to any one of claim 11 to 14, in which the controller controls the proportion of the heat of the flue gases which go up the chimney or the flue.

16. A heating installation according to any of claims 11 to 15, in which the temperature sensor is provided towards or at the top of the chimney or the flue.

17. A heating installation according to any one of claims 11 to 16, in which a second temperature sensor is provided to sense the temperature of the outside air.

18. A heating installation substantially as described herein with reference to the drawing.

19. A kit comprising a controller and temperature sensor, the controller being adapted to control the operation of chimney heat control means of a heating installation, and the temperature sensor being adapted to provide signals indicative of the temperature of a region of a chimney of a heating installation to the controller, the arrangement being such that, in use, the controller operates a heating appliance in a manner which is dependent, at least in part upon the temperature signals.

20. A kit substantially as described herein.

21. A method of protecting a chimney or a flue comprising the steps of monitoring conditions, properties or states in or adjacent the chimney or the flue to determine if the conditions, properties or states are within specified limits and adjusting the operating characteristics of the chimney or flue if the conditions, properties or states are beyond the specified limits.

22. A method of protecting a chimney substantially as described herein.