GB2517552A

GB2517552A - An adjustable baffle system for a gas fire

Info

Publication number: GB2517552A
Application number: GB1410714.8A
Authority: GB
Inventors: Robert A Charmer
Original assignee: NU FLAME Ltd
Current assignee: NU FLAME Ltd
Priority date: 2013-06-14
Filing date: 2014-06-16
Publication date: 2015-02-25
Anticipated expiration: 2034-06-16
Also published as: GB201310736D0; GB2517552B; GB201410714D0

Abstract

The gas fire is ideally a simulated solid fuel fire and has a controllable baffle 10 located in a flue outlet 12. A baffle adjustor, such as a motor 26 operated by a control box 32, moves the baffle between an open and closed position to restrict/enable flow of combustion products and air through the outlet. Movement of the baffle is based on one or more parameters such as temperature measurements from a thermistor or thermocouple sensor 30. Ideally the baffle is operated so as to be open during early ignition of the fire and to gradually close as the fire heats up, thereby reducing the amount of room air lost unnecessarily to ambient via the flue. The motor is ideally located away from the baffle to protect the motor from overheating due to the heat of combustion products in the flue. Mechanical linkage using cams and/or bevel gearing is used to mechanically connect the motor to the baffle in this instance. Micro-switches may also be used. A duct having a fan is ideally provided to draw cool room air 20 over the motor to cool it when the fire is on.

Description

AN ADJUSTABLE BAFFLE SYSTEM FOR A GAS FIRE

The idea behind this system is that the chimney/flueing conditions of a gas fire can be controlled to match the flueing conditions the fire requires at thermal and flow equilibrium to ensure safe clearance of the products of combustion while optimising the fire's efficiency, and yet provide controlled and optimised ventilation of the room and property.

All properties, even double glazed properties, have ventilation gaps throughout that allow ventilation air into the property. Air, known as advantageous ventilation, typically flows in through these ventilation gaps and out through a chimney. As the chimney is heated, the thermal lift of a chimney actively draws air into the property through the ventilation openings.

The amount of air flow increases as the chimney heats up.

In order to allow safe operation of a gas fire, chimneys typically provide a far higher air flow level than is required purely for air changes and ventilation. A result of this is that an unnecessarily large amount of air can pass through the property, and warm air generated by other heat sources, such as central heating, may be needlessly lost through the chimney. Warm room air created by a central heating system which can still generate a thermal lift within a chimney, leading to the losses discussed above.

It would be beneficial, therefore, if the ventilation flowing through the property and up the chimney cou'd be controlled to ensure heat already present within the property is retained after heating, but not at the expense of ventilation which is essential for a heahhy environment.

A means whereby the air changes and ventilation can be provided and controlled yet coexist with the safe operation of a gas fire will have major benefits for rational use of energy and emissions. This will overcome a maj or issue for current housing stock with chinmeys where currendy there is little scope for improving their heating requirements without impacting on \Tentilation As insulation of properties improves, typical central heating boilers may in fact generate too great a heat output for the requirements of a typical property. By helping to retain heat generated by a gas fire, the invention may allow for the use of a gas fire for primary heating without impacting on the ventilation.

Currently, all flued gas fires are tested, according to defined standards, in order to determine their efficiency by a Flue Loss Method'. This method is based on a set size and diameter of flue and a predetermined level of spillage to allow direct comparison between different fires.

However, this does not normally match the physical chimney flow conditions into which the fire will be installed when in use. Consequently, although a direct comparison between one fire and another can be carried out under laboratory conditions (and an indication of each fire's potential may be obtained), this potential may not be realised within the properties where the fires are installed.

Gas fires, by their nature, need air for safe combustion. The ventilation gaps within a property provide the air, and the chimney provides the thermal lift with draw and means to exhaust the products of combustion from the property. However, once lit and operating under normal equilibrium' conditions, the air requirement of most gas fires is relatively small, The nature of the size variation of chimneys and their construction means that the degree of air drawn from the room can be excessive. In other words, a far higher volume of air than is required for safe combustion typically flows up the chimney. Gas fire manufacturers already provide metal plate flue restrictors for their fires to limit the volume of this so called excess air', and improve their fire's efficiency. However, since chimneys vary considerably in size and design, a restrictor cannot always be used, Listed below are some different chimney variations and where a flue restrictor is recommended: * A 9" by 9" brick or stone constructed chimney where, for single storey properties, a fire restrictor is typically not used; * A 9" by 9" brick or stone constructed chimney where, for twin storey properties, a fire restrictor is normally used; * A flexibly flue lined chinmey typically with a 5" diameter flue liner where a fire restrictor is not used; * A 5" or 7" twin waned flue system where a fire restrictor may be used dependant on the flue height; and * A pre-cast flue chimney system formed within the wall construction of the house where, regardless of height, a fire restrictor is not used.

In addition, the condition of the flue-chimney construction must be taken into account and, due to the position of the chimney terminal, wind conditions can also have an affect meaning that a fire restrictor cannot be used. Even where a restrictor can be used it can only provide one degree of control and not the variable control that is ideally required to account for different chimneys and different heat settings of the fire.

IS

There are therefore many chimney installations where there is little to no means of limiting the excess air and in turn heat that will be removed from the property. In addition, even where fires are fitted with restrictors their flow characteristics are often not in tune with the air flow that would optimise their efficiency and rational use of energy.

All gas fires are checked after their initial lighting to ensure all products of combustion are being safely drawn into the chimney. This is expected to occur within 5-10 minutes of lighting, but can be extended by a further 10 minutes if needed. If the fire does not clear its products of combustion then any restrictor can be removed and the test repeated. However, if the fire still spills after any repeat test with the restrictor removed, or if no restrictor was fitted in the first place, then the fire is deemed to have failed.

All fires will have significantly higher flue flows as the time progresses and the fire and flue heat up. In practice, neither the fire nor flue would have reached equilibrium temperature/flow conditions only 10 minutes after lighting (typically this takes about an hour), so the test provides a very large safety margin. If a tire clears its products of combustion in just 10 minutes or less, as required, then the additional flue flow generated at equilibrium will safeguard against any spillage issues such as products of combustion flowing backward down the chimney due to, for example, wind at the chimney terminal. Nonetheless, the assessment of flow characteristics only 10 minutes after the lighting the fire, rather than at equilibrium, is another reason why an unnecessary amount of excess air will typically pass from the room up the chimney.

Obviously, the air within the room is being heated by the fire during operation. Therefore, excess air drawn into the chimney has already been heated, meaning that preheated air is wasted affecting the whole efficiency of the heating system. With tall chimneys with an effective height of 3 meters or over, and especially with more efficient fires, gas fire manufactures provide a flue restrictor which is used to reduce the amount of excess air being drawn by the chimney to minimise these losses. However, these arrangements are still required to meet the required flow characteristics only 10 minutes after the lighting, so excess air flow still occurs when the fires are operating at equilibrium.

According to the present invention there is provided a flued fire as defined in the appended claim I. Not only can the system of the present invention better control the degree of heat that might be lost up the chimney, it can also actively control the ventilation, One of the features of the system may be that when the fire is operating in the low position the baffle will have holes or cut-away areas to provide sufficient open area to permit a limited air flow even when the baffle is fully closed. When the fire is turned off the baffle will remain closed to reduce the amount of warm air that will continue to flow up the chimney, thereby limiting the heat loss from a warm building, while still maintaining adequate ventilation to ensure healthy air changes of the room and property.

Further preferable features of the flued fire of the present invention are defined in the appended dependent claims 2 to 35.

A method of optimising the flueing conditions required by a flued fire as defined in the appended dependent claims 2 to 35 is defined in appended claim 36.

Further preferable method steps of optimising the flueing conditions required by a flued fire as defined in the appended dependent claims 2 to 35 is defined in appended claims 37 to 42.

In order that the invention may be more readily understood, reference will now be made, by way of example, to Figures ito 4, in which: Figure 1 shows a side view of an open-fronted gas fire indicating the locations of various components of the invention; Figure 2 shows a top view of the fire ofF igure 1; Figure 3 shows a glass-fronted gas fire indicating the locations of various components of the invention (the motor being located as shown in Figures 1 and 2); and Figure 4 shows an example of a baffle of the invention.

A first embodiment of the invention will now be described with reference to Figures 1 to 4.

An adjustable, preferably motorized, baffle iO or flue restrictor can be used to restrict the fire's outlet 12 at the optimum operating conditions (once the chimney and fire 14 have reached equilibrium) and change in line with the parameters that may affect the flow up the chimney and heat settings of the fire.

A baffle or damper system to restrict a chimney as a means of restricting the flow up the chimney is known and has been used with solid fuel appliances for many years. However, no subsequent adjustment or tuning of these baffles is typically possible, so there is no means to respond to the operation of the fire in combination with its heat settings and conditions of the chimney.

Thc adjustability could allow the baffle to be fully open on lighting of the fire, such that spillage is avoided, and then progressively close down the outlet to limit air flow 16 as less is required during operation of the fire.

It is not initially intended that the baffle system will be used to control the flow of combustion air 16 to the burner 18, but rather to limit the excess air drawn from the room as a result of the draw created by the chimney. However, the system could be used on future designs to control the flow of combustion air in tune with varying levels of heat input on gas fires.

The invention can be applied to several different flued fire types as follows: * With an open fronted fire the fire and fuel bed typically has a gas burner under the fuel effect (e.g. imitation coals, logs, twigs or pebbles) and the flame effect is open to the room such that initially the products of combustion may spill into the room but as the chimney heats up the products flow through an outlet of the fire up the chimney. Any restrictor is usually placed at the outlet, The spillage will occur at the outer most front edge of any canopy on the fire and usually the spillage of products of combustion is greater at the centre. This provides an ideal position for monitoring any spillage.

* The above also applies to so called convectors', which are open fronted fires where an air path is present around the firebox and outer case with a sealed duct that bridges the air gap typically at the back or top of the fire to provide the outlet of the fire.

* Glass Fronted fires seal off the front opening of the firebox to reduce excess air being drawn in, but have a diverter system to ensure that the combustion process can still perform safely in a blocked flue situation or in the event of a down draught. The diverter system that basically allows the products of combustion to flow into the room without being capped by the downward flow, but also inevitably allows an undesirable amount of air to be drawn out of the room during use. in this application the front inlet of the diverter is used to monitor the spillage condition of the fire.

All of these fires have an outlet that ensures all the products of combustion and excess air flow into the chimney and it is in this area that the baffle will be applied and will take the shape of this outlet.

The baffle of the invention will preferably be shaped to almost, but not completely, seal off the fire outlet. Holes 11 or cut-outs could be provided to allow the minimum flow to pass as would be required for the lowest gas flow setting of the fire will be incorporated. In addition, some degree of clearance will have to be provided to allow the baffle to pivotactuated.

The sizes of the baffle and the cut-outs or bypass holes for the lowest setting could be tailored to match the design and flow characterises of any particular tire. The baffle size would also be affected by the heat input of the fire, pure'y by nature of the volume of gas/air ratio and secondary air required.

The baffle may have a spindle 13 that passes through its centre such that it can be swivelled to either open up the fire's outlet or close it down, The spindle may pass directly through the centre of the fires outlet with bearing points at each end and may be driven by a motor 26. The best position for the motor would be up at the top of the fire, as close to the baffle system as possible, but temperature in this area may be an issue. As such, one end of the spindle may be extended and connected to a gearing system that will connect directly through 90 degrees onto another spindle that will link up with a motor positioned in a cooler region of the fire, e.g. the base, so that when the motor turns it will directly turn the vertical spindle that through the gearing will in turn rotate the spindle and the baffle in turn. Bevel gearing may be necessary to allow the motor to be positioned in the base of the fire.

The motor or stepper motor may be controlled electrically, (mains or battery) and designed to turn the required degree of rotation.

The spindle connected to the motor may have a lever or linkage system that will operate a micro switch and enable electronically the position of baffle to be predetermined, it could also have two or more micro switches capable of determining when and where the motor/actuator has progressed to and, by means of control circuitry 32, switch off the motor's electrical supply when it reaches the switch positions. These positions may correspond to the heat settings of the control system via electronic circuitry and or sofiware to provide baffle positions for fully open (fire start position), the low setting (fully closed) and any optional settings that may be considered.

The invention thus provides means of operating a baffle via a motor positioned in a suitable temperate climate which may also be positioned at a position higher up in the fire. The linkage from the motor will be shielded to protect against debris or household lint affecting the linkage.

The linkage may also pass up through a box or similar attached to the rear or side of the fire depending on where is best to position the motor with linkage relative to the fire design.

The system can make use of one or more thermistors or thermocouples 30, placed at either the front canopy edge of the fire with an open fire model or the front of the diverter, to monitor the temperature of products of combustion that will spill into the fire when first lit or if the flue flow changes affecting the temperature. The sensing temperature values could be tailored to match the flow/temperature characterises of a particular type of fire, e.g. an open fronted fire as opposed to a glass fronted fire, arid even for individual designs of fire within these categories.

Initially, all fires spill their products of combustion into the room either via the upper front edge (on an open fronted fire) or via the front of the diverter (on a glass fronted fire). As such, the temperature at this point will typically be quite high shortly afler lighting, but then fall significantly as the chimney becomes warm and the fire starts to clear its products of combustion up the chimney. However, if the flue becomes blocked or there is dovmdraught the initial high temperature may never drop or change due to the effect of these conditions.

Accordingly, a thermistor or thermocouple can be used to provide electrical signals showing indirectly how the chimney is performing, i.e. when the products are flowing up the chimney or when they are spilling. The electrical output will change and this can be used to allow a microprocessor, computer and/or circuit board to actuate the motor and baffle has required and/or prevent lighting of the fire.

It may be possible, via the electronic circuit, to provide a delay before the electrical output from the thermistor or thermocouple is monitored and the motor is operated to close the baffle.

It may be possible to adjust the baffle position if the temperature changes at the thermocouple position as the fire heats up. It will be possible to leave the baffle closed at the low flame setting and also leave it closed when the fire is turned off In the latter situation the electronic circuit could be designed to determine if the baffle is closed before initiating the fire ignition sequence.

Many options will be possible via the electronic circuits to provide the optimum performance of the fire relative to the chimney installation it has been installed into. Ultimately it will be possible to computerise the operating sequence of the fires heat up to best position the baffles rotation to optimise the efficiency of the fire.

Through apphcation of the present invention, not only can the heat output of the fire be maximised for any specific chimney but it can be designed to retain heat within the room and very important provide a balance between adequate air changes of the room, ventilation and the desired room temperature.

Although a thermistor or thermocouple system has been suggested to determine the flow characteristics, the dectrical sign&s indicating how the flow is occurring at any place on the fire can be provided by other sensors types, e.g. flow sensors and pressure transducers, either -10-alone or in combination, positioned at the outlet of the fire and/or spillage positions. Tn fact, any suitable means that can relay a signal to the electronic circuits could be used.

This same system could also be applied to a fire which incorporates a fan as a means of pressurizing the flow of combustion products 35 up a chimney with the same system used to determine the best flow being provided to optimise heat output, spillage and ventilation.

The spindle will at some point have to pass through the structure/case of the fire and at this point suitable sealing will have to be provided that will not restrictimpede the action of the motor; which will be very important if battery operation is found to be possible.

The motor and its housing will have provision for either a micro switch or numerous micro-switches to enable its rotational position to be determined or it could be a stepper motor that would allow its position to be determined. The electronic circuit and or software can be used to act on electrical signals coming from suitably positioned thermocouples, pressure or flow transducers or any means to measure temperature, pressure or flow and provide electrical outputs and these will be placed at the outlet of the fire and spillage points on the fire or the best positions to account for the fires products flow performance.

As an alternative to the geared linkage described above, the motor could be fitted with a cam that, through a linkage, can turn the baffle about its fulcrum points to the required angle of rotation. This would have the advantage of not requiring a bevel gearing system.

As an alternative to rotating, the baffle may be within a slider that moves linearly to restrict the fires outlet to the desired position. This option may provide a greater accuracy of linear movement. Drive may be provided through a cam on the motor as before.

It is possible that temperature transmitted over time through the spindle or linkage could impact on the motor, which ll have thermal limitations of around 80 centigrade, so it may be necessary to have a break in the spindle or linkage where high temperature plastic combined with insulation 15 is used to minimise thermal conduction. Providing a means of moving parts with least operational resistance in a varying environment specifically in the area of the baffle may necessitate the use of special materials that can withstand temperature, condensation and acidity.

As mentioned, the preferred position for the motor would be up at the top of the fire, as close to the baffle system as possible, but temperature in this area is an issue. To address this, the motor could be to either the left or right within an insulated box with the drive spindle coming through a clearance hole in the box. Connected to the base of the box could be a duct or tube 22, spaced away from the fire yet connected to the fire at the base and open to allow both cooling air 20 to be drawn over the motor by the rising flue pull up the chimney. This opening and duct would allow passage for the wiring 24 to the motor.

In fires incorporating a convection gap around the firebox, it is known to add a convection fan to increase the flow of air around the firebox to thereby increase the fire's efficiency. In such systems, some of this cooling air could also be directed up the duct, if required, as a means of providing a greater degree of cooling to the motor.

The sensing thermocouple could have a secondary, higher, temperature limit allowing the fire to be turned off through the existing electronic circuitry it for example, the baffle becomes stuck in a closed position due to a fault, or if the flue becomes blocked or a chimney suffers bad down draught on occasions, leading to spillage.

Incorporating a microprocessor within the electronic circuitry would allow monitoring and potentially recording of the operation of the control system and/or baffle. This would make it easier to determine whether a problem stemmed from the fire, the installation or the chimney itself Through a USB or similar connection, it may even be possible for a service engineer to connect and view the data held on a microprocessor and carry out the necessary corrective action and maintenance. Alternatively, or additionally, the data could be stored on a separate -12-handset and/or remotely, or may be uploaded or accessed remotely, to allow service or maintenance personnel to check faults without the need to visit a property.

The invention could also be applied in relation to room sealed or balanced flue' fires. These fires are totally sealed off from the room such that all combustion products are exhausted to the outside and all the air required for combustion is drav from outside rather than from the room.

As a result, spillage is not an issue in these types of products. However, the control of flow for either air supply or products of combustion could potentially be controlled with the system according to the invention. The flue systems in balanced flue fires take the form of concentric tubes where the products pass down the inner tube and the air is drawn down the outer tube.

Sometimes the inner products tube is offset vertically to allow a greater flow in the lower cooler space between the tubes. The present invention could be applied to limit the flow of products in line with the heat input variation of the fire within the products tube in much the same way again increasing efficiencies at lower settings by nature of a baffle in the products outlet side.

With this type of fire it would also be possible to apply the baffle in the in-coming air side also.

Claims

-13 -CLAIMS1. A flued fire comprising; a baffle, and baffle adjustment means, the baffle moveable between a first position and a second position, wherein, in the first position, the baffle restricts fluid flow therepast and, in the second position, the baffle enables fluid flow therepast, the baffle adj ustment means arranged to, in use, move the baffle between said first and second position in line with one or more parameters. l0
2. A flued fire of claim 1, further comprising an outlet in fluid communication with the baffle such that, in use, the flow of excess air drawn through the flued fire from the surroundings is restricted by the baffle when in the first position and not restricted by the baffle when in the second position.
3. A flued fire of claim or claim 2, wherein the first position of the baffle is a closed position and the second position of the baffle is a frilly open position.
4. A flued fire of any of the preceding claims, wherein, in use, the baffle is progressively moved from the second position to the first position such that fluid flow therepast is progressively diminished during operation of said fire.
5. A flued fire of any of the claims 2 to 4, wherein the outlet is arranged such that substantially all the products of combustion and excess air flow therethrough and into a chimney. -14-
6. A flued fire of any of claims 2 to 5, wherein the baffle is substantially shaped like the cross-section of the outlet.
7. A flued fire of any of claim 2 to 6, wherein the baffle is shaped to substantially seal the outlet when, in use, said baffle is in the first position.
8. A flued fire of any of the preceding claims, wherein the baffle comprises one or more apertures such that, in use, a minimum flow is enaNed therepast when, in use, said baffle is in the first position.
9. A flued fire of any of claims 2 to 8, wherein clearance is provided between the baffle in the first position and the outlet so as to allow movement of said baffle between the first and second positions.IS
10. A flued fire of any of the preceding claims, wherein the baffle pivots between said first and second positions.
11. A flued fire of any of the preceding claims, wherein the baffle size and shape is characterised by the volume of gas/air ratio and secondary air required.
12. A flued fire of any of the preceding claims, further comprising a spinWe positioned substantially through the centre of the baffle enabling, in use, the baffle to be swivelled from the first to the second position.

-15 -
13. A flued fire of any of the preceding claims, wherein the baffle is position proximate the uppermost portion of said fire.
14. A flued fire of any of the preceding claims, further comprising at least one micro switch arranged to enable the position of the baffle to be predetermined,
15. A flued fire of any of the preceding claims, further comprising a motor arranged to move the baffle between the first and second position.
16. A flued fire of claim 15, further comprising a cam and linkage arranged to, in use, move the baffle from the first to second position.
17. A flued fire of claim 16, further comprising gearing means connecting the motor and baffle and arranged such that the motor is located in a cool region of said fire.
18. A flued fire of claim 17, wherein said gearing means is bevel gearing.
19. A flued fire of any of claims 15 to 18, wherein motor is a stepper motor.
20. A flued fire of any of claims 15 to 19, further comprising at least one micro switch arranged to enable the position of the motor to be predetermined.
21. A flued fire of any of claims 15 to 20, further comprising a duct in fluid communication with the motor and arranged such that, in use, rising flue pull draws cooling air over the motor. -16-22. A flued fire of claim 2 I, further comprising a convection fan arranged to increase the flow of air through the duct.23. A flued fire of any of claims 15 to 22, further comprising contr& circuitry arranged to turn off the power supply to the motor when a motor position is reached.24. A flued fire of any of claims 17 to 23, further comprising heat shielding arranged around the gearing means to protect against debris and/or household lint.25. A flued fire of any of the preceding claims, further comprising temperature sensing means arranged to monitor the temperature of the products of combustion.26. A flued fire of claim 25, wherein, based on the temperate sensed, the position of the baffle may be tailored to match the desired flow characteristics of a particular fire type.27. A flued fire of any of the preceding daims, wherein the efficiency of the fire during heat up is optimised by varying the position of the baffle between the first and second position.28. A flued fire of any of the preceding claims, wherein the parameters are temperature, pressure, flow rate, baffle position and or motor position.29. A flued fire of any of the preceding claims, further comprising a fan arranged to pressurise the flow of combustion products. -17-30. A flued fire of any of the preceding claims, wherein movement of the baffle from the first position to the second position is achieved by rotation of said baffle.31. A flued fire of any of the preceding claims, wherein movement of the baffle from the first position to the second position is achieved by sliding said baffle linearly.32. A flued fire of any of the preceding claims, further comprising monitoring and or recording means to record and determine the operation of the baffle.33. A flued fire of claim 32, further comprising means to store the recorded data and or upload said data remotely.34. A flued fire of any of the preceding claims, wherein the fire is any one of an open fronted fire, a convector, a glass fronted fire or a balanced flue fire.35. A flued fire of any of the preceding claims, further comprising a burner, wherein the baffle is in fluid communication with said burner such that, in use, the flow of combustion air to the burner is limited by the baffle when in the first position and not limited by the baffle when in the second position.36. A method of optimising the flueing conditions required by a flued fire of any of the preceding claims, comprising the steps of: progressively moving the baffle from the second position to the first position as the fire heats up.-18 - 37. A method of claim 36, further comprising the step of moving the baffle into the first position when the fire is turned off 38. A method of claim 36 or 37, further comprising the step of moving the baffle into the S first position when the tire is in a low flame setting.39. A method of any of claims 36 to 38, further comprising the step of determining if the baffle is in the first position before initiating a fire ignition sequence.40. A method of any of claims 36 to 39, further comprising the step of turning off the fire when a predetermined temperature is reached.41. A flued fire substantially as herein described with reference to the accompanying drawings 42. A method of optimising the flueing conditions required by a flued fire as herein described with reference to the accompanying drawings.