WO2009133543A1

WO2009133543A1 - Convection space heater

Info

Publication number: WO2009133543A1
Application number: PCT/IE2009/000023
Authority: WO
Inventors: Kevin O'dowd; Anthony Brosnan
Original assignee: K.A. Enviro Manufacturing Limited
Priority date: 2008-05-01
Filing date: 2009-05-01
Publication date: 2009-11-05
Also published as: IE20090345A1

Abstract

A space heater (1) comprises a housing (2) having vents (3) for outflow of heated air. The housing (2) has a rear plate (4) arranged for being wall-mounted, so that cool air can enter underneath and warm air exits via the vents (3). Within the housing (2) there is a tray (5) supporting a row of four fans (6), each mounted to rotate about a vertical axis to pump air axially directly from a lower riser (11) into an upper riser (12). At the upper end of the riser 12 there is a heat exchange coil 13 fed by water heating circuit pipes 16 having a volume of about 400ml. A guide 17 deflects air which rises from the coils 13 out through the vents 3. This directs the heated air away from a wall along which the heater is mounted, further contributing to efficiency. While the fans are not activated the heater has the benefit of providing a degree of continued space heating because of natural convection through the riser (11 ), the fans (6), and the upper riser (12). The pathway for such natural convection has little restriction. Electrical drive to the fans (6) is staggered so that only one received power at any time, thus achieving a very low intensity of high frequency noise from the fan motors, and also a very high electrical efficiency. Further, overall heating efficiency is very high because the heat exchanger requires only 400ml or less water of water.

Description

CONVECTION SPACE HEATER

INTRODUCTION

Field of the Invention

The invention relates to space heaters.

Prior Art Discussion

EPl 126228 describes a space heater having lower and upper risers, and radial fans mounted on a horizontal axis. US4313493 also discloses an arrangement in which air flows axially into a fan and out radially into an upper riser.

An objective of the invention is to achieve a simpler construction, and/or lower power consumption, and/or improved warm air control.

SUMMARY OF THE INVENTION

According to the invention, there is provided a space heater comprising a housing and: a lower riser, a bank of at least one fan, an upper riser; and a heat exchanger in at least one of the risers. wherein at least one fan is an axial fan, and is mounted for blowing air axially from the lower riser into the upper riser.

In one embodiment, the axis of each axia) fan extends substantially directly from the lower riser to the upper riser.

In one embodiment, there is a plurality of axial fans.

In one embodiment, the fans are arranged in a horizontal row. In one embodiment, the fans are mounted between, and delimit, the lower and upper risers.

In one embodiment, the fans are supported on a tray having apertures for axial flow of air into the fans from the lower riser.

In another embodiment, the space heater further comprises a deflector plate for directing heated air from the heater at an angle to vertical in use.

In one embodiment, the housing has a rear plate for mounting against a wall, and the guide is mounted to direct heated air upwardly and forwardly.

In another embodiment, the space heater further comprises a controller linked with the fans, with a user interface, and with a sensor and being adapted to control at least one parameter of operation of the space heater.

In one embodiment, the space heater further comprises an air temperature sensor and a heat exchanger temperature sensor, and the controller is adapted to control the fans in response to sensed air and heat exchanger temperature.

In one embodiment, the controller stores a threshold level for each of heat exchanger and air temperatures, and activates the fans if the heat exchanger level is above the heat exchanger threshold and the air temperature is below the air threshold.

In one embodiment, the heat exchanger temperature sensor is a water temperature sensor.

In one embodiment, the threshold levels are user-configurable in the controller.

In one embodiment, the controller has a wireless user interface for receiving user commands. In one embodiment, the controller is adapted to monitor power consumption of the fans and to generate a user output based on said monitoring.

In one embodiment, the space heater comprises an air filter and the controller generates an output indicating a requirement for filter cleaning if fan power consumption exceeds a threshold.

In a further embodiment, the controller is adapted to provide drive signals to the fans so that they are not simultaneously driven.

In one embodiment, the controller drives each fan with a duty cycle of one quarter or less.

In one embodiment, the controller de-multiplexes a single source drive signal to provide individual drive signal to each fan.

In one embodiment, the fans are driven by DC brushless motors.

In one embodiment, the controller provides a plurality of fan power settings and is adapted to dynamically change the fan power settings in response to sensed temperature.

DESCRIPTION OF THE INVENTION

Brief Description of the Invention

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:-

Fig. 1 is a perspective view of a space heater of the invention;

Fig. 2 is a diagrammatic cross-sectional view showing air flows in the heater; Fig. 3 is a rear perspective view with an outer housing removed, and Fig. 4 is a similar view with an inner housing removed; and

Fig. 5 is a rear perspective view of another heater in which casings are removed, showing fans and a heat exchanger.

Description of the Embodiments

Referring to Figs. 1 to 4 a space heater 1 comprises a housing 2 having vents 3 for outflow of heated air. The housing 2 has a rear plate 4 arranged for being wall- mounted, so that cool air can enter underneath and warm air exits via the vents 3, as indicated generally by the arrows A in Fig. 2.

Within the housing 2 there is a tray 5 supporting a row of four fans 6, each mounted to rotate about a vertical axis to pump air axialjy directly from a lower riser 11 into an upper riser 12, the risers being delimited by the tray 5 and the fans 6.The fans 6 have five screw fasteners mounting them on the tray 5. The edges where the tray 5 and the inner housing 15 connect to the rear plate 4 have foam padding to act as damping for the fans and to provide sound insulation.

At the upper end of the riser 12 there is a heat exchange coil 13 fed by water heating circuit pipes 16 having a volume of about 400ml. A guide 17 deflects air which rises from the coils 13 out through the vents 3. This directs the heated air away from a wall along which the heater is mounted, further contributing to efficiency.

An air filter 20 is removably mounted at the inlet of the lower riser 1 1. This may be easily removed for cleaning, such as by vacuum cleaner.

An electronic controller for the heater 1 (not shown in Figs. 1 to 4) is mounted in the lower riser 11 , and is linked to a user interface on the outside of the casing 2. The controller comprises an air temperature sensor and a water temperature sensor. The fans are driven by DC brushless 4-pole motors with a rated speed of 2800rpm and maximum power of 1.8W. Thus, for the four fans being operated together the power consumption is only 7.2 W. Another aspect of the fan drive control scheme is that the controller drives each fan with pulses which are offset so that drive is provided to only one fan at a time. The control scheme uses de-multiplexing of a single drive signal into an individual drive signal for each fan and delays these signals appropriately. The frequency of the transitions provides a one quarter duty cycle and hence even though all fans are rotating all of the time when they are activated electrical drive power is only being delivered to each fan for one quarter of the time. This control scheme has the desirable effect of (a) achieving a very low electrical power consumption (in this case only 7.2 W at the highest speed setting), and (b) reducing acoustic noise because drive is not provided to all of the fans simultaneously. Regarding the latter point, because only one fan motor is energised at any one time the high-frequency and low intensity acoustic noise generated by the motor coil is very low.

In operation, once the water sensor detects a temperature above a set point programmed into the controller (in one example 32⁰C) and the air temperature sensor is below a target temperature selected by the user on the control panel, the electronic controller turns on the power to the fans 6. Power to the fans 6 is controlled by the maximum fan speed selected by the user on the control panel. As the temperature sensed by the water sensor begins to rise the power to the fans is increased gradually until it reaches the maximum setting selected by the user. Once the air temperature sensor detects the same temperature as the set point selected by the user (for example 2O⁰C) the fans shut down. The electronic controller continues to detect both air and water temperature until any further changes cause the fans to be powered up again.

While the fans are not activated the heater has the benefit of providing a degree of continued space heating because of natural convection through the riser 11, the fans 6, and the upper riser 12. The pathway for such natural convection has little restriction. It will be appreciated that after de-activation of the fans there is a continued space heating, giving a smoother transition and in terms of space heating and prolonging the period until the fans are activated again. The controller generates a user alert when power consumption of the fans indicates that the filter needs cleaning. This is determined when the power required to activate the fans 6 exceeds an expected level for the heat exchanger temperature, thus indicating that air flow into the lower riser 1 1 is restricted.

The controller also uses wireless technology to reprogram the temperature set point and the fan speed settings, and for diagnostics/repair. The wireless interface also allows the heater to connect back to a central control unit for the heating system, switching on/off the pump which runs the zones or the actual heat source itself.

The arrangement of pipes in the heat exchanger 13 is a very simple arrangement which provides minimum resistance to the water flow which allows the heater to be integrated into old heating systems without difficulty. Due to the simple path of the heating pipes in the coil the movement of air through the coil is not constricted.

Referring to Fig. 4 the internal parts of a space heater 40 of the invention are shown. The space heater 40 comprises a wall -mounting plate 41 which, together with other housing parts defines a lower riser 42 and an upper riser 43. A tray 45 supports a line of seven fans 46_; and the rising air is heated by a heat exchanger 47 at the top end of the upper riser 43. A controller 50 is shown. A small ribbon cable connects the PCB of the controller 50 to an interface PCB located at the top right of the heater.

Tests as outlined below were carried out on the space heater of Figs. 1 to 4. The controller was set so that the water temperature needs to be at or above 32° C or above for the fans 6 operate. The controller in this embodiment allows for six different fan speeds and twelve different levels of temperature. The required levels for water temperature threshold and fan speed are set using the user interface.

Testing was carried out with the minimum water temperature setting at 32° C

- Sound level measurements were taken at a distance of one meter from the heater, aligned centrally with respect to the heater's front panel. - The water temperature was between 47° C and 50° C.

Testing began with the fan speed set to its lowest setting and the temperature was set to its highest setting. The fan speed was incremented in steps (1-6) while taking note of the power usage and noise level at each step. The results are tabulated below:

A mains cut-out test was carried out. This was done three times with the heater at two different settings (lowest & highest). Upon powering back on the heater, temperature and fan settings reverted to setting 3 (middle setting). This was the case for the two different settings (lowest & highest).

Results:

Power: At its highest setting the heater only consumed 7 Watts.

Acoustic Noise: In standby mode the heater measured 24 dBa. This is as predicted in standby mode; all fans being off. This 24 dBa can be taken as the acoustic noise present in the room. The heater at highest fan speed measured 50 dBa.

Heat Output: The heater has a heat output of 3.56 kW. It will be appreciated that the invention provides for very efficient heating. There is only a requirement for about 400ml of heated water in the heat exchanger, very much less than in a conventional radiator. Heat transfer is particularly effective because of blowing air through the heat exchanger, and yet the fans consume very little electrical power. A still further advantage is that the space heater is effective for a very low water temperature of as little as 32⁰C, much lower than the level of about 6O⁰C required in many central heating systems. In addition, the fan drive scheme allows exceptionally low power consumption, and also as low acoustic noise.

Another advantage of the space heater 1 is that there is direct flow from the lower riser 11 into the upper riser 12 in an axial flow through the fans 20. This direct flow has minimum obstruction, and so less electrical power is required for driving the fans. The direct flow path also contributes to generation of very low levels of acoustic noise.

The invention is not limited to the embodiments described but may be varied in construction and detail. For example, the heat exchanger may be located in the lower riser. The risers may be of sizes different from illustrated. For example the lower riser may be much shorter, the fans being at a lower position in the housing. The riser which accommodates the heat exchanger may be almost entirely be taken up by the heat exchanger.

Claims

1. A space heater comprising a housing and: a lower riser, a bank of at least one fan, an upper riser; and a heat exchanger in at least one of the risers, wherein at least one fan is an axial fan, and is mounted for blowing air axially from the lower riser into the upper riser.

2. A space heater as claimed in claim 1, wherein the axis of each axial fan extends substantially directly from the lower riser to the upper riser.

3. A space heater as claimed in claims 1 or 2, wherein there is a plurality of axial fans.

4. A space heater as claimed in claim 3, wherein the fans are arranged in a horizontal row.

5. A space heater as claimed in claim 4, wherein the fans are mounted between, and delimit, the lower and upper risers.

6. A space heater as claimed in claim 5, wherein the fans are supported on a tray having apertures for axial flow of air into the fans from the lower riser.

7. A space heater as claimed in any preceding claim, further comprising a deflector plate for directing heated air from the heater at an angle to vertical in use.

8. A space heater as claimed in claim 7, wherein the housing has a rear plate for mounting against a wall, and the guide is mounted to direct heated air upwardly and forwardly.

9. A space heater as claimed in any preceding claim, further comprising a controller linked with the fans, with a user interface, and with a sensor and being adapted to control at least one parameter of operation of the space heater.

10. A space heater as claimed in claim 9, further comprising an air temperature sensor and a heat exchanger temperature sensor, and the controller is adapted to control the fans in response to sensed air and heat exchanger temperature.

1 1. A space heater as claimed in claim 10, wherein the controller stores a threshold level for each of heat exchanger and air temperatures, and activates the fans if the heat exchanger level is above the heat exchanger threshold and the air temperature is below the air threshold.

12. A space heater as claimed in claims 10 or 11, wherein the heat exchanger temperature sensor is a water temperature sensor.

13. A space heater as claimed in claims 11 or 12, wherein the tlireshold levels are user-configurable in the controller.

14. A space heater as claimed in claim 13, wherein the controller has a wireless user interface for receiving user commands.

15. A space heater as claimed in any of claims 9 to 14, wherein the controller is adapted to monitor power consumption of the fans and to generate a user output based on said monitoring.

16. A space heater as claimed in claim 15, wherein the space heater comprises an air filter and the controller generates an output indicating a requirement for filter cleaning if fan power consumption exceeds a threshold.

17. A space heater as claimed in any of claims 9 to 16, wherein the controller is adapted to provide drive signals to the fans so that they are not simultaneously driven.

18. A space heater as claimed in claim 17. wherein the controller drives each fan with a duty cycle of one quarter or less.

19. A space heater as claimed in either of claims 17 or 18, wherein the controller de-multiplexes a single source drive signal to provide individual drive signal to each fan.

20. A space heater as claimed in any preceding claim, wherein the fans are driven by DC brushless motors.

21. A space heater as claimed in any preceding claim, wherein the controller provides a plurality of fan power settings and is adapted to dynamically change the fan power settings in response to sensed temperature.

22. A space heater substantially as described with reference to Figs. 1 to 4.

23. A space heater substantially as described with reference to Fig. 5.