GB2516687A

GB2516687A - Ventilation Unit

Info

Publication number: GB2516687A
Application number: GB1313591.8A
Authority: GB
Inventors: Matthew James William Reaney
Original assignee: Polypipe Ltd
Current assignee: Polypipe Ltd
Priority date: 2013-07-30
Filing date: 2013-07-30
Publication date: 2015-02-04
Also published as: GB201313591D0

Abstract

A ventilation unit 14 comprises a housing 30 having a base 30c forming a longitudinal first plane of the housing, an inlet 16 in a first side of the housing and an outlet 18 in a second side of the housing. A fan 44 drives air from the inlet to the outlet and is inclined at an angle with respect to the first plane. The fan can be oriented offset relative to the housing outlet. The housing can be detached to a mounting member 28 such that, on detachment thereof, the housing and fan separate from the mounting member whilst the mounting member remains in position on a building. A sound absorbing member 62 can also be provided between the fan outlet and the housing outlet. The fan may be a backward curved centrifugal fan in a scroll casing. An inclined plate 50 may direct the air from the inlet to the outlet and comprises a bevelled aperture 52. The mounting member comprises grooves, indentations or slots (39a, 39b fig 2) to support duct connectors 40, 42. A plurality of turning vanes (68, fig 7b) comprising ridges (70) and channels (72) direct the air leaving the fan.

Description

Ventilation unit The present invention relates to a ventilation unit for a ventilation system, and in particular but not exclusively to a ventilation unit for a mechanical extract ventilation system.

Building regulations specify the functional requirements for the design and construction of buildings, to ensure the health and safety of people in and around buildings. For example, Part F of the England and Wales Building Regulations, which relates to indoor aft quality, stipulates various requirements for ensuring efficient and effective ventilation. This is required to avoid the continued presence of moist air, which would otherwise lead to a build-up of condensation and mould, in turn leading to structural damage to the building and/or an adverse effect on the health of the occupants.

Ventilation systems for buildings are of course well known. Of note, mechanical extract ventilation (MEV) systems provide continuous extraction of polluted ci damp aft from wet rooms', e.g. kitchen, bathroom, utility room etc., in a dwelling or building. Such systems may be centralized (cMEV), with a single or multiple entry points and a single exit point, or decentralized. In the case of a centralized system, ducting leads from the wet room(s) to an MEV unit containing a continuously running fan, enabling polluted air to be extracted and expelled externally of the building via the exit point.

Although such known systems are able to provide ventilation efficiently and effectively, they are often large and bulky, which limits theft suitability for use in some locations.

Known systems can also be difficult to access for the purpose of maintenance! repair or replacement. Furthermore, known systems utilize powerful fans to convey polluted air from the wet rooms for extraction to the outside of the building, which are often noisy. Aspects and embodiments of the piesent invention have been devised with the foiegoing in mind, and aim to impiove upon existing ventilation units and systems.

According to a first aspect of the invention, there is provided a ventilation unit for a ventilation system, the unit comprising a housing having a base defining a longitudinal fiist plane of the housing, an inlet in a fiist side of the housing, an outlet in a second side of the housing, and a fan for driving a fluid from the inlet to the outlet, the fan comprising a fan inlet and a fan outlet, and wherein the fan is inclined at an angle with respect to the first plane.

The fan may be inclined with respect to the first plane at any angle. Preferably, the base of the fan is inclined at said angle with respect to the first plane. Preferably the angle is substantially between 00 and 21°, or substantially between 5° and 16°, or substantially between 7° and 14°, or substantially between 9° and 12°, or substantially between 10° and 11°. Most preferably the angle is substantially 10.5°. Tilting the fan advantageously reduces the housing depth required to accommodate the fan, compared with the depth that would be required if the fan inlet was oriented parallel to the housing inlet. Orienting the fan flat in relation to the housing plane would provide the greatest reduction in the depth of the housing required, but this may not allow sufficient airflow to be drawn into the fan efficiently. As such, tilting the fan at a small angle provides the maximum possible inlet area, maintaining sufficient body depth for support and structure but also reducing the depth of housing required.

Inclining the fan at 10.5° is particularly useful and beneficial, although it will be appreciated that providing the fan at an angle slightly less or slightly more than this will still provide the advantage. For example, the fan can be provided at an angle substantially between 10° and 11° degrees or substantially between 9° and 12°. It is possible to provide the fan at a smaller angle, substantially between 0° and 9° although it will be appreciated that some efficiency will be lost and an inclination above 0° is generally required in order to achieve airflow. It will also be appreciated that the fan could be provided at a greater angle, e.g. substantially between 12 and 15°, substantially between 15 and 25° or more, e.g. substantially between 25° and 90°, if the height of the housing is not constrained.

According to a second aspect of the invention, there is provided a ventilation unit for a ventilation system, the unit comprising a housing having a base defining a longitudinal first plane of the housing, an inlet in a first side of the housing, an outlet in a second side of the housing, and a fan for driving a fluid from the inlet to the outlet, the fan comprising a fan inlet and a fan outlet, and wherein the fan is oriented within the first plane with the fan outlet offset relative to the housing outlet. Conveniently, the unit inlet and unit outlet are provided at opposite ends of the longitudinal plane of the housing.

The fan outlet may be offset relative to the housing outlet at any angle between Q0 and 90°. Piefeiably the angle is substantially between 100 and 80°, or substantially between 200 and 700. More preferably, the angle is substantially between 30° and 60°.

Even more preferably the angle is substantially between 4Q° and 500. Even more preferably, the angle is substantially between 42° and 48°. Most preferably, the angle is substantially 45°. The angle can be chosen depending upon space and efficiency requilements. 45° or similar, e.g. 42-48° or 4O5O0, has been found to be optimal in balancing space saving requirements and redirecting the airflow to improve efficiency.

Offsetting the fan outlet relative to the longitudinal direction of the housing advantageously allows the fan to be oriented such that its smallest dimension can be positioned laterally in the housing, which enables the width of the housing to be minimized. This can be particularly beneficial where space is restricted and, for example, enables the unit to be mounted between joists or other supporting stiuctures of a building. Offsetting the fan additionally directs the airflow output from the fan more centrally towards the housing outlet, thus improving efficiency of the ventilation unit.

Accoiding to a third aspect of the invention, there is piovided a ventilation unit for a ventilation system, the unit comprising a mounting member for mounting the unit to a building and a housing member comprising an inlet, an outlet and a fan, the fan comprising a fan inlet and a fan outlet for driving a fluid from the inlet to the outlet, and wherein the housing member is detachably attachable to the mounting member such that, on detachment thereof, the housing and fan separate from the mounting member whilst the mounting member remains in position on the building.

Advantageously, the housing is easily removable from the mounting member (lid), which remains attached to the building, allowing maintenance, repair or replacement.

The fan, and other components contained within the housing, e.g. electronic circuitry etc., are conveniently removable with the housing further facilitating access thereto.

In an embodiment, the ventilation unit comprises attachment means for detachably attaching the mounting member to the housing. One or more fasteners may be provided on the mounting member and/or the housing in order to attach the mounting member to the housing. More preferably, the attachment means comprises one or more fasteners provided on or in the mounting member that are retained by the mounting member on detachment of the housing from the mounting member. In an embodiment, the fastener may comprise a nut and bolt or a screw. An aperture may be provided in the mounting member, and a corresponding aperture may be provided in the housing, through which the bolt can extend. The nut is preferably attachable to the bolt at a base or underside of the housing. A recess may be provided in the housing to accommodate the bolt. This advantageously ensures the nut and bolt do not protrude from the housing to again ensure the extent of the ventilation unit is minimized. A washer, e.g. a repair washer, can also be used with the nut and bolt.

According to a fourth aspect of the invention, there is provided a ventilation unit for a ventilation system, the unit comprising a housing having an inlet and an outlet, a fan for driving a fluid from the inlet to the outlet, the fan comprising a fan inlet and a fan outlet, and a sound absorbing member provided between the fan outlet and the housing outlet. Advantageously, the provision of a sound absorbing element assists in absorbing noise generated by the running of the fan, to minimize noise pollution in the building in which the ventilation unit is located.

In an embodiment, the sound absorbing element partially blocks the fan outlet. The sound absorber therefore achieves absorption of sound as it creates an obstruction in the airflow path from the fan. Preferably, the sound absorber is formed integrally with the housing.

In an embodiment, the fan comprises a scroll casing that terminates at the fan outlet.

The scroll casing forms an airflow passage around the fan, and terminates in a scroll exit. The sound absorber may partially block the scroll exit and/or fan outlet.

Preferably, the sound absorber is a baffle that partially extends across the fan outlet.

Preferably, the sound absorber comprises a ridge. The ridge may be configured such that the height thereof decreases laterally across the fan outlet and in a direction towards the outer edge of the fan scroll casing. Preferably, the ridge begins on a side of the housing which is opposite the fan outlet. The starting height may be substantially equal to that of the height of the housing, but could be less, e.g. approximately 90%, 80%, 75% or 50% of the height of the housing. The height of the ridge decreases into a lower portion located toward said opposite wall of the housing, with the profile resembling a curve that flattens towards the opposite wall. The decrease may approximately correspond to an exponential decrease. Alternatively the height may decrease substantially linearly.

The ridge may be configured such that the height thereof decreases in a direction from the fan towards the unit outlet. The ridge may be configured to decline towards the unit exit, again with a curve that flattens towards the exit. Alternatively, the decline could be substantially linear. The sound absorber extends generally concentrically with respect to the rotational centre of the fan, through an arc of approximately 600, but this could be substantially between 55 and 65°, or 50 and 70°.

Preferably, the fan is a centrifugal fan and, more preferably, the fan is a backward curved centrifugal impeller fan. Such fans advantageously provide high centrifugal performance with relatively low running noise which, in combination with the provision of a sound absorbing element, ensures noise pollution is kept to a minimum.

The previously described aspects and embodiments may be used alone or in any combination. The following embodiments and advantages are also presented with reference to any or all of the aspects and embodiments described above: The ventilation module is preferably a mechanical extract ventilation (MEV) unit and, more preferably, a centralized mechanical extract ventilation (cMEV) unit, and even more preferably a cMEV unit having a single inlet and outlet. The ventilation system is operational to convey a fluid, preferably air.

Preferably, the fan is a centrifugal fan, and more preferably a backward curved centrifugal impeller fan. The fan may be provided in a scroll casing. The geometry of centrifugal fans advantageously lends itself to shallow ventilation unit installations but, additionally, the ventilation unit and components thereof have been carefully designed and tested in order to ensure good performance is still achieved.

The ventilation unit may further comprise an airflow directing member for directing airflow from the housing inlet to the fan inlet. The airflow directing member may comprise a plate or panel locatable on the fan. The airflow directing member preferably comprises an opening or aperture substantially corresponding to the fan inlet. The aperture may be bevelled towards its centre. Preferably, the fan plate is inclined from a base of the housing at or near the inlet end thereof, in a direction towards the outlet thereof, to assist in directing airflow to the fan. The plate thus acts as a division between the inlet side and the outlet side of the ventilation unit, preventing airflow from the inlet side of the housing to the outlet side of the housing, except through the fan.

The housing is preferably elongate and may be rectangular in shape. The housing may be formed by moulding, e.g. from expanded polypropylene. This advantageously keeps the mass of the unit low, and such material is also easy and inexpensive to manufacture, install and maintain.

In an embodiment, the ventilation unit comprises an inlet duct connector provided at or near the housing inlet and an outlet duct connector provided at or near the housing outlet. The duct connectors are configured for connection to ducting of the ventilation system. In an embodiment! the housing is configured to receive the duct connectors and, in a preferred embodiment, the housing and duct connectors are sized so that there is an interference fit therebetween. During installation of the ventilation system, the duct connectors can be permanently connected to the ducting of the ventilation system. When removal of the housing is required, therefore, the housing is removable from the ducting connectors.

The mounting member may comprise one or more structures for supporting the duct connectors in the housing. The mounting member preferably comprises a groove, indentation or slot located extending adjacent and parallel to the duct connector when located in the housing underneath. More preferably, a groove, indentation or slot is provided on each side of the duct connector when located in the housing underneath.

The added structure/contouring of the mounting member both helps support and locate the duct connectors, and adds rigidity and strength to the mounting member.

The mounting member may comprise one or more means for securing the mounting member to a building. Preferably, the mounting member comprises apertures through which fasteners, e.g. screws, can be inserted for affixing the mounting member to a building. The mounting member is preferably formed from an Acrylonitrile Butadiene Styrene (ABS) sheet.

In an embodiment, one or more airflow directing features are provided for directing airflow from the fan towards the unit outlet. The one or more airflow directing features may comprise one or more turning vanes. Preferably, a plurality or a series of turning vanes are provided. More preferably, the turning vanes comprise a plurality or series of ridges and channels leading from the fan outlet to the housing outlet. The airflow directing features may also be integrally formed in the housing.

Aspects and embodiments of the invention thus provide a compact ventilation unit that can, for example, fit within standard joist pitches in buildings. Due to the preferred choice of fan, and especially in aspects and embodiments employing inclining the fan relative to the longitudinal plane of the housing, the depth of the ventilation unit can be kept to a minimum, typically less than 127mm (Sinches). The compactness of the unit advantageously ensures that, when installed in a building, it is also aesthetically unobtrusive.

Aspects and embodiments of the invention also provide a ventilation unit with a small number of component parts. In particular, integrally torming features within the housing helps minimize the number of separate parts required.

Embodiments of the invention will now be described with reference to the Figures of the accompanying drawings in which: Figure 1 shows a schematic view of a building with a mechanical extract ventilation unit and system; Figure 2 is an isometric view of a ventilation unit according to the present invention; Figure 3 is an exploded isometric view of the ventilation unit of Figure 2; Figure 4 is another exploded isometric view of the ventilation unit of Figure 2, showing the airflow path therethrough; Figure ba shows a top plan view of the mounting member of the ventilation unit of Figure 2 and Figure Sb is a cross sectional view along line A-A therethrough; Figure 6a is an isometric rear view of the ventilation unit of Figure 2 with the mounting member removed and Figure 6b is an enlarged view of a portion thereof; Figure 7a is the same isometric rear view of the ventilation unit as in Figure 6a and Figure 7b is an enlarged view of another portion thereof; Figure 8 is a top plan view of the ventilation unit of Figure 2 with the mounting member removed; and Figure 9 is an exploded side view of the mounting member, duct connectors and housing of the ventilation unit of Figure 2.

Figure 1 shows an exemplary building 10 and a ventilation system 12 installed therein.

Any ventilation system can be used, although it is particularly advantageous to use a centralized mechanical extract system (cMEV) 12. The ventilation system 12 comprises a central cMEV unit 14. The ventilation unit 14 has a single entry or inlet 16 and a single exit or outlet 18. The outlet 18 is connected by ducting 19 to a vent 20 located in a wall or the roof of the building 10. The vent 20 enables air to be expelled to the exterior of the building 10. The inlet 16 receives polluted air from a branched ducting system 22 that extracts polluted air from various wet rooms located around the building. This can be achieved using known means, e.g. adjustable extract air valves or fixed inlet grilles 24. The ventilation system 12 thus provides for simultaneous ventilation of a plurality of wet rooms in a building via multiple extract points 24 located in those rooms. In an alternative embodiment, the branched duct system 22 could be replaced with a single duct system leading from a single room or a radial type system comprising multiple lengths of a single smaller bore duct running individually from each room to a manifold that combines the flows together into a single duct for connection to the unit 14. The ventilation unit 14 is conveniently located in a loft or roof space of a building, but could be located elsewhere if required.

The ventilation unit 14 comprises a fan 44 (not visible in Figure 1) to draw polluted air from the wet rooms into the ventilation unit 14 and to exhaust it to the external vent 20.

As the operation of the fan 44 would cause a negative pressure within the system, each wet room is also provided with an air inlet vent 26, e.g. a trickle ventilator in the window frame, through which fresh air from outside the building 10 can be drawn in order to balance the pressure. This can be achieved as a result of the negative pressure and through operation of the fan 44, or additional fans can be provided to forcibly draw air into the wet rooms. The fan 44 is designed to run continuously, and may be controllable to do so at a present number of speeds, e.g. one, two, three or more. The ventilation unit 14 may also be provided with conventional boost functionality.

Aspects and embodiments of the invention could be utilized in any building! including residential dwellings, but are paiticularly useful in communal living areas e.g. student accommodation clusters and residential care homes.

Figure 2 shows a cMEV ventilation unit 14 that can be utilized in the ventilation system 12 of Figure 1. The unit 14 complises a lid or mounting membei 28 and a base oi housing member 30. In the embodiment shown, the unit 14, and thus the lid 28 and housing 30 are elongate and rectangular in shape. In the following description, reference to the longitudinal direction of the unit 14 refers to the length thereof. The width of the unit extends transversely with respect thereto, and the unit has a depth peipendicular to the plane defined by the length and the width (the longitudinal plane).

The housing has a base 30c which thus lies in/parallel to the longitudinal plane. In alternative embodiments, not shown, the unit 14 could be a different shape, e.g. square oi circular/spherical.

The mounting member 28 is configured for attachment in or to a building 10. Apertures 32 are provided in the lid 28 for attaching the lid 28 to a ceiling oi other support in the building 10, e.g. with sciews, bolts or other fasteners. Other conventional fixing means could also be employed, e.g. by bonding the lid 28 to the building 10 or strapping the unit 14 to supporting building members.

The lid 28 is piovided with additional apeitures 34. The housing 30 complises corresponding apertures 36. In the embodiment shown, the apertures 36 extend through the full depth of the sidewalls 30a, 30b of the housing 30. Fixing means, e.g. a nut and bolt, and optionally a washei, (not visible in Figure 2) are used to attach the housing 30 to the lid 28 via the corresponding apertures 34, 36 provided therein. The bolt is insertable into the lid aperture 34, through the housing aperture 36 and a washer e.g. a repair washer and a nut, e.g. a dome nut, secures the components 28, 30 together. Recesses 38 are provided within the base 30c of the housing 30 to accommodate the nuts so they do not protiude therefrom.

Two pairs of laterally oriented slots 39a, 39b are provided in the lid 28. These add structure, and thus rigidity, to the lid 28, and also serve as location means for duct connectors (which will be described in further detail below) located underneath the lid 28, adjacent and between the slots 39a and 39b.

It is convenient to vacuum form the mounting member 28 from an Acrylonitrile Butadiene Styrene (or ABS) sheet, and for the housing member 30 to be formed of moulded expanded polypropylene. Such materials are both easy to work with in terms of the design and manufacture of the components, and are lightweight and inexpensive. It will, however be appreciated that other materials and other processes e.g. injection moulding can be used.

Figure 3 shows an exploded view of the ventilation unit 14. The entry point or inlet 16 is provided at a first end of the unit 14, and the exit point or outlet 18 is provided at a second, opposite end thereof. A first or inlet duct connector 40 is located at or in the vicinity of the unit inlet 16. A second or outlet duct connector 42 is located at or in the vicinity of the unit outlet 18, for connection to the ductwork 19 that leads to the exhaust vent 20. During installation of the ventilation system 12, the duct connectors 40, 42 are permanently bonded or sealed to the ductwork 19, 22 of the ducting system 12 in a conventional manner.

A fan 44 is provided within the housing 30. The fan is preferably a backward curved centrifugal impeller fan 44. The fan has an inlet 47 and an outlet or discharge 48. As is conventional with this type of fan, the inlet 47 is perpendicular to the outlet 48. The inlet 47 of the fan 44 is parallel to the axis I-I shown in Figure 4, as will be discussed below. The fan 44 could simply be provided in the housing 30 although, in the embodiment shown, the fan 44 is provided in a scroll casing 46. The scroll casing 46 has a spiral or seashell-type' configuration for directing the air flow from the inlet 47 towards the outlet 48. This configuration provides a space the cross sectional area of which increases towards the fan outlet 48, allowing air travelling therethrough to expand.

A fan inlet plate 50 is located above the fan 44. The inlet plate 50 is conveniently formed by vacuum forming an ABS sheet, although other materials and other processes can be utilized. The inlet plate 50 comprises a flat central section, with an aperture 52 provided therein. The aperture 52 is sized to substantially match that of the fan inlet 47. The plate 50 comprises a beveled portion leading from the plate 50 to the aperture 52, this forming an inlet ring for the fan 44. The longitudinal ends of the inlet plate 50 are sloped such that they taper in a direction away from the central portion to the edges at each end of the plate 50. The plate 50 thus acts as a division between the inlet side 16 and the outlet side 18 of the ventilation unit 14, preventing airflow from the inlet side 16 of the housing 30 to the outlet side 18 of the housing 30.

except through the fan 44.

The inlet plate 50 is secured to the housing 30. In the embodiment shown, apertures 54 are provided near the edge of the inlet plate 50 on the inlet side thereof, and corresponding apertures 56 are provided on a portion 57 of the housing 30. This portion 57 of the housing 30 is formed at the inlet side 16 of the housing 30, and extends upwardly from the base 30c of the housing 30 toward the fan 44. The apertures 56 are located along the inclined portion 57, at a height above the base 30c of the housing 30. The plate 50 is locatable on the inclined housing portion 57 and securable thereto e.g. by a screw, bolt or other suitable fixing means utilizing the apertures 56. Each corner of the edge on the inlet side of the fan plate 50 is contoured with a cut-out 58 shaped to sit adjacent an abutment 60 provided on the housing 30.

Each corner of the edge on the outlet side of the fan plate 50 is also contoured with a cut-out 58 shaped to sit adjacent an abutment 60 provided on another raised portion 61 of the housing 30. The raised portions of the housing 57, 61 can be integrally formed with the housing 30, or provided separately therein. When positioned in the housing 30, the inlet plate 50 covers the fan 44, with the aperture 52 leaving the fan inlet 47 exposed, and the plate 50 presents a surface that is inclined from the inlet side 16 upwardly toward the outlet side 18. The fan inlet plate 50 is shown in position within the housing 30 in Figure 4. The alignment of the plate 50 with respect to the fan -i.e. with the plate 50 parallel to the inclination of the fan 44 within the housing 30 (described below) -is very important, since the inlet ring must be parallel to the fan 44 in order for the fan 44 to operate correctly and provide optimal performance.

Figure 4 shows the plate 50 fixed to and in the unit housing 30. It can be seen that the plate 50 and configuration of the housing 30 present a continuous surface rising from the base 30c of the housing 30 up to the ceiling thereof (i.e. the underside of the lid 28). When fitted, the lid 28 clamps the upper end of the plate 50 down against the supports 61 in the housing 30.

Figure 4 also shows arrows depicting the flow path for air being drawn into the ventilation unit 14 by the fan 44. Air enters the unit 14 from ducting 22 (not shown here, but culminating in the duct connector 40) at the inlet 16. The fan inlet plate 50 directs the incoming air up the sloped surface theieof and into the apeiture 52 towaids the fan inlet 47. The air is thus drawn into an enclosed space defined by the housing 30, the plate 50 and the lid 28, and this, and the beveled surface 52 of the plate 50, aid in directing incoming air to the fan inlet 47.

It is desirable and convenient, in embodiments of the invention, to use a backward curved impeller centrifugal fan. An external rotor EC (electronically commutated) motor (not shown) can be used to drive the fan 44, although it will be appreciated that any other known fan drive can be utilized. Backward cuived centrifugal fans are vety convenient foi medium airflow, high piessure applications such as overcoming the resistance of a duct system. Other fans, e.g. forward curved centrifugal fans or mixed flow fans could also be utilized.

Although not visible in the Figures. the fan 44 comprises an impeller having a drive shaft that rotates about an axis I-I and a series of blades mounted thereabouts. The fan inlet 47 is also located along this axis. As the fan 44 rotates, aft enters the impeller which tomes au radially outwardly into the scroll casing 46 in a direction peipendicular to the axis I-I due to centrifugal motion. As shown in Figure 4, and also in Figure 5b, the impeller axis I-I of the fan 44, is provided at an angle a relative to the normal (depicted by axis N-N). A cross section through the housing 30 and the fan 44 is also shown in Figuie 5b. Here it can be seen that the base 44a of the fan 44 is inclined by the same angle a. This defines a plane F-F extending at the angle a relative to the longitudinal plane X-X of the housing 30 (i.e. 0° with respect to the horizontal as shown in Figure 5b). The base 44a of the fan 44 extends in/is paiallel to the plane F-F.

It can be seen from the figures, and especially Figure 5b, that the depth of the fan 44 constitutes its smallest dimension. As such, when designing the ventilation unit 14 to be as compact as possible, it is beneficial to mount the fan 44 in the housing 30 as flat as possible. However, mounting the fan 44 flat (i.e. with plane F-F parallel to plane X-X) would not easily or efficiently permit air to enter the fan 44 via inlet 47, which is located perpendicularly thereto. It is, therefore, necessary to balance the two requirements. It has been tound that inclining the fan 44 at an angle ci of substantially 10.5° provides the maximum possible fan inlet area whilst keeping the depth of the housing 30 minimal.

Although inclining the fan 44 at 10.5° is particularly useful and beneficial, for the reasons provided above, it will be appreciated that providing the fan 44 at an angle slightly less or slightly more than this will still provide the advantage. It will also be appreciated that the fan 44 could be provided at a greater angle if the height of the housing is not constrained and/or if high fan efficiency is not critical. For example, the angle can be substantially within the range 0°-21°, or substantially between 5° and 16°, or substantially between 7° and 14°, or substantially between 9° and 12°, or substantially between 100 and 11°.

Referring now to Figure 6a, there is shown a rear isometric view of the unit 14 without the lid 28 or rear duct connector 42. Air exiting the fan 44 will do so via the scroll casing 46, to the fan exit 48, to then be vented therefrom at the housing exit 18. A sound absorber 62 is provided, to absorb some of the inevitable airborne noise that will be generated by the fan 44. In the embodiment shown, the sound absorber 62 is pre-formed integrally with the housing 30, although it will be appreciated that a separate sound absorber could instead be provided. The sound absorber 62 sits across part of the exit of the scroll 46, to create a baffle or obstruction in the airflow path. The scroll casing 46 forms an airflow passage around the fan 44, between the outer wall of the scroll casing 46 on a first side 30a of the housing and the impeller, and terminates in the fan outlet 48.

The sound absorber 62 comprises an elevated portion or ridge 64 that begins on the side 30b of the housing 30, which is opposite the fan outlet 48 which is located adjacent the opposite side 30a of the housing 30. In the embodiment shown, the starting height is substantially equal to that of the height of the housing 30, but it could alternatively be less, e.g. approximately 90%, 80%, 75% or 50% of the height of the housing 30. The height of the baffle 62 decreases into a lower portion 66 located toward the opposite wall 30a of the housing 30, with the profile resembling a curve that flattens towards the opposite wall 30a. The decrease may approximately correspond to an exponential decrease. Alternatively the height may decrease substantially linearly. The baffle 62 is also configured to decline towards the unit exit 18, again with a curve that flattens towards the exit 18. Alternatively, the decline could be substantially linear. The side profile of the baffle 62 can also be seen in Figure 5b.

The baffle 62 extends generally concentrically with respect to the rotational centre of the fan 44, through an arc of approximately 600, but this could be between 55 and 65°, or 50 and 70°. Figure 6b shows an enlarged view of the sound absorber 62 in the region marked in Figure 6a.

The sound absorber 62 beneficially absorbs noise emanating from the fan 44 (which is running constantly). The baffle 62 has been designed to ensure that the effect on the airflow is not detrimental to the overall performance of the fan 44, which could occur due to the positioning of the baffle 62 across part of the exit of the scroll 46.

Figure 7a is the same as Figure 6a, and again shows shown a rear isometric view of the unit 14 without the lid 28 or rear duct connector 42. Airflow directing features 68 are provided integrally formed in the housing 30, for directing air exiting from the fan 44 to the unit exit 18. Alternatively, a separate airflow directing component could be provided. In the embodiment shown, the airflow directing or turning features 68 comprise a series of ridges or ripples 70 provided in the housing 30 at the end of the fan scroll 46. As previously indicated, rotation of the fan impeller causes air to be expelled radially therefrom and into the scroll casing 46. The curvature of the scroll casing 46, and the channels 72 defined between the ridges 70 act to direct the air towards the exit 18 with the aim that it will exit in a direction parallel to the longitudinal axis X-X of the housing 30, so reducing turbulence and noise generation. The turning vanes 68 can more easily be seen in Figure 7b, which is an enlarged portion of the region marked in Figure 7a.

Referring now to Figure 8, a top plan view of the ventilation unit 14 is presented, partially cut away to reveal the components inside. Included in this Figure is the "ideal positioning" 144 for the fan 44 in the longitudinal plane of the housing 30. Although the exit 18 from the ventilation unit 14 lies parallel to the longitudinal axis X-X of the housing 30, the ideal orientation for the fan outlet 48 is along an axis R-R positioned at an angle 3=45° thereto. Air enters the fan 44 parallel to the shaft axis I-I, and movement of the impeller blades increases the pressure of the air and accelerates it radially into the fan scroll casing 46 via centrifugal motion, and changing its direction by 90°. Air thus exits the fan 44 in a direction parallel to the axis R-R as shown in Figure 8. To achieve this operation, centrifugal fan casings are necessarily geometrically asymmetric. Embodiments of the invention utilize this asymmetry to minimize the lateral size of the housing 30 required by aligning the minimum dimension of the fan 44 in the direction of the lateral width of the housing 30.

It has been found that, with the fan 44 rotated by an angle 13 approximately equal to 45° with respect to the longitudinal axis X-X of the housing 30, it is still possible for the fan 44 to expel air from the unit exit 18 in the X-direction without compromising too much on tan output and performance. This differs from conventional arrangements, where the fan exit 48 is provided in-line with the outlet of the ventilation system. It is to be noted that the air turning vanes 68 also assist in realigning the airflow to ensure air exits the unit 14 in the desired direction (along the X-X axis).

It is a further advantage that rotating the fan 44 by 45° helps to centralize the airflow with respect to the unit outlet 18. Otherwise, if the fan 44 were not rotated, the fan outlet 48 would direct air down one side of the housing 30 only, due to the asymmetric arrangement of the fan 44 (as can be seen in Figure 8). Rotating the fan 44 by 45° relative to the axis X-X is optimum and convenient in order to achieve the greatest reduction in lateral size of the fan 44 (and thus the housing 30) and to centralize the airflow output. However, it will be appreciated that rotating the fan 44 by any angle between 0° and 90° is possible depending on the geometry of the particular fan being utilized and the airflow required or desired. The fan 44 may be offset relative to the housing outlet at any angle between 0° and 90°. For example, the angle may be substantially between 10° and 80°, or substantially between 20° and 70°, or substantially between 30° and 60°, or substantially between 40° and 50°, or substantially between 42° and 48°.

To further improve the performance of the fan 44, the area covered by the fan scroll 46 is increased, compared with known fan scrolls. Conventionally, the fan scroll would exit at 45° from the direction of the airflow at point 46a shown in Figure 8. The airflow towards the exit 18 is thus quite restricted. Therefore, in order to minimize airflow losses, the scroll has been manipulated and the exit point brought to position 46a', the scroll including the part 46b shaded grey in Figure 8, this also corresponding to the position of the baffle 62.

The result of the arrangement described provides the advantage of having virtually all of the true geometry required of a fan scroll with only slight losses arising from turbulence/resistance from utilizing turning vanes being heavily outweighed by the near completeness of the scroll.

Figure 9 is an exploded side view showing the mounting member 28, the duct connectors 40,42 and the housing 30. In the event of access to the unit 14, e.g. when maintenance or repair is required, or at the end of the lifetime of the unit 14, the nuts can be removed to release the housing 30 from the lid 28 (which will remain fixed in/to the building via the fixings 32. The bolts remain captive in the lid 28 due to their insertion into the upper side thereof. The duct connectors 40, 42, due to their bond to the ductwork 22 of the ventilation system, also remain in position adjacent the lid 28, and slide out of the housing 30. As such the housing 30, containing all of the electrical components including the fan 44, is easily removable without the need to disturb the rest of the ventilation system 12 or remove the fixings from the unit mounting surface 28. Once ready to replace, the housing 30 can simply be offered up to the lid 28, the bolts re-inserted into the apertures 36 and, when the bolts have extended fully therethrough, the nuts can be re-applied to again secure the housing 30 in position.

This is in contrast to known products where, for example, the ventilation unit is often spherical with multiple outlets and ducting is connected to a spigot on the exterior of a ventilation unit. Such units are thus bulky and, in order to gain access to the unit, it would be necessary to disconnect the spigot -which might not even be possible.

The lid 28 thus performs several functions: it acts as a closure for the housing 30, to contain and comprise the components therein; it acts in defining the air inlet path; it serves as a mounting bracket for attaching the ventilation unit 14 to a ceiling or like support in a building; it provides a bearing surface against and to which the housing body 30 can be attached; and it clamps the upper part of the fan inlet plate 50 in position.

Aspects and embodiments of the invention thus provide a compact ventilation unit that can, for example, fit within standard joist pitches in buildings. Due to the preferred choice of fan, and especially in aspects and embodiments employing inclining the fan relative to the longitudinal plane of the housing, the depth of the ventilation unit can be kept to a minimum, typically less than 127mm (5inches).

Aspects and embodiments of the invention have been described comprising a single inlet 16 and a singlet outlet 18, which is convenient foi the aim of pioviding a compact unit 14. However, it is would also be possible to provide a unit having a plurality of inlets and/or outlets if size constraints are of less importance.

Claims

CLAIMS: 1. A ventilation unit for a ventilation system, the unit comprising a housin9 having a base defining a longitudinal first plane of the housing, an inlet in a first side of the housing, an outlet in a second side of the housing, and a fan for driving a fluid from the inlet to the outlet, the fan comprising a fan inlet and a fan outlet, and wherein the fan is inclined at an angle with respect to the first plane.
2. The ventilation unit of claim 1, wherein the fan is inclined with respect to the first plane at an angle substantially between Q° and 25°, or substantially between 12° and 15°, or substantially between 9° and 12°, or substantially between 100 and 11°, or is substantially 10.5°.
3. A ventilation unit for a ventilation system, the unit comprising a housing having a base defining a longitudinal fiist plane of the housing, an inlet in a first side of the housing, an outlet in a second side of the housing, and a fan for driving a fluid from the inlet to the outlet, the fan comprising a fan inlet and a fan outlet, and wherein the fan is oriented within the fiist plane with the fan outlet offset relative to the housing outlet.
4. The ventilation unit according to claim 3, wherein the fan is offset relative to the housing outlet at any angle between 00 and 900, or substantially between 100 and 800, or substantially between 200 and 700, or substantially between 3Q0 and 60°, or substantially between 400 and 530, or substantially between 42° and 48°, or is substantially 45°.
5. A ventilation unit for a ventilation system, the unit comprising a mounting member for mounting the unit to a building and a housing member complising an inlet, an outlet and a fan comprising a fan inlet and a fan outlet for driving a fluid from the inlet to the outlet, and wherein the housin9 member is detachably attachable to the mounting member such that, on detachment thereof, the housing and fan separate from the mounting member whilst the mounting membei lemains in position on the building.
6. The ventilation unit of claim 5, comprising attachment means for detachably attaching the mounting member to the housing.
7. The ventilation unit of claim 6, wherein the attachment means comprise one or more fasteners provided on the mounting member andloi the housing.
8. The ventilation unit of claim 7, wherein one or more fasteners are provided on or in the mounting membei that aie ietained by the mounting member on detachment of the housing from the mounting member.
9. The ventilation unit of claim 8, wherein the fastener is a nut and bolt or a screw.
10. The ventilation unit of claim 9, wherein an aperture is provided in the mounting member, and a coiiesponding apeiture is provided in the housing, through which the bolt can extend from the mounting membei into the housing.
11. The ventilation unit of claim 10, wherein the housing further comprises a recess to accommodate the bolt.
12. A ventilation unit for a ventilation system, the unit comprising a housing having an inlet and an outlet, a fan for driving a fluid from the inlet to the outlet, the fan comprising a fan inlet and a fan outlet, and a sound absorbing member provided between the fan outlet and the housing outlet.
13. The ventilation unit of claim 12, wherein the sound absorber is formed integrally with the housing.
14. The ventilation unit of claim 13, wherein the sound absorbing element partially extends acioss the fan outlet and/or unit outlet.
15. The ventilation unit of claim 14, whelein the sound absorber comprises a ridge.
16. The ventilation unit of claim 15, wherein the ridge is configured such that the height thereof decreases laterally across the tan outlet and/or unit outlet.
17. The ventilation unit of claim 15 or 16, wheiein the iidge is configuied such that the height thereof decreases in a diiection fiom the fan towards the unit outlet.
18. The ventilation unit of any preceding claim, wherein the ventilation unit is a mechanical extract ventilation (MEV) unit and or a centralized mechanical extract ventilation (cMEV) module having a single inlet and outlet.
19. The ventilation unit of any preceding claim, wherein the fan is a centrifugal fan.
20. The ventilation unit of claim 19, wherein the fan is a backward curved centrifugal impeller fan.
21. The ventilation unit of any preceding claim, wherein the fan is provided in a scioll casing.
22. The ventilation unit of any preceding claim, further comprising one or more airflow directing members for directing airflow from the housing inlet into the fan inlet.
23. The ventilation unit of claim 22, wherein the airflow directing member comprises a plate or panel locatable on the fan.
24. The ventilation unit of claim 22 or 23, wherein the airflow directing member comprises an opening or aperture substantially corresponding to the size of the fan inlet.
25. The ventilation unit of claim 24, wherein the aperture is bevelled towards its centre.
26. The ventilation unit of claim 25, wherein the fan plate is inclined from a base of the housing at the end thereof nearest the unit inlet, in a direction towards the end thereof nearest the unit outlet, to assist in directing airflow to the fan.
27. The ventilation unit of any preceding claim, wherein the housing is elongate, or is rectangular in shape.
28. The ventilation unit of any preceding claim, wherein the housing is moulded, or is moulded expanded polypropylene.
29. The ventilation unit of any preceding claim, wherein the ventilation unit comprises an inlet duct connector provided at the housing inlet and an outlet duct connector provided at the housing outlet.
30. The ventilation unit of claim 29, wherein the duct connectors are configured for connection to ducting of said ventilation system.
31. The ventilation unit of claim 29 or 30, wherein the housing is configured to receive the duct connectors.
32. The ventilation unit of claim 31 wherein the housing and duct connectors are sized so that there is an interference fit therebetween.
33. The ventilation system of any of claims 29 to 32, comprising a mounting member for attaching the unit to a building, wherein the mounting member comprises one or more structures for supporting the duct connectors in the housing.
34. The ventilation system of claim 33, wherein said structures comprises a groove, indentation or slot located extending adjacent and parallel to the duct connector when located in the housing underneath.
35. The ventilation system of claim 34, wherein a groove, indentation or slot is provided on each side of the duct connector when located in the housing underneath.
36. The ventilation system of any preceding claim, wherein the mounting member comprises one or more means for securing the mounting member to a building.
37. The ventilation system of claim 36, wherein the mounting member comprises one or more apertures for receiving a fastener for affixing the mounting member to a building.
38. The ventilation system of any preceding claim, comprising a mounting member for attaching the unit to a building and wherein the mounting member is formed from an Acrylonitrile Butadiene Styrene (ABS) sheet.
39. The ventilation system of any preceding claim, further one or more airflow directing features for directing airflow from the fan towards the unit outlet.
40. The ventilation system of claim 39, wherein the one or more airflow directing features comprise one or more turning vanes, or a plurality or a series of turning vanes.
41. The ventilation system of claim 40, wherein the turning vanes comprise a plurality or series ot ridges and channels leading from the fan outlet to the housing outlet.
42. The ventilation unit of any of claims 39 to 41, wherein the airflow directing features are integrally formed in the housing.
43. A ventilation unit substantially as hereinbefore described with reference to any one or all of the Figures of the accompanying drawings.