EP1936291B1

EP1936291B1 - Ventilation system

Info

Publication number: EP1936291B1
Application number: EP20070254926
Authority: EP
Inventors: Colin Biggs
Original assignee: Nuaire Ltd
Current assignee: Nuaire Ltd
Priority date: 2006-12-20
Filing date: 2007-12-18
Publication date: 2012-08-29
Anticipated expiration: 2027-12-18
Also published as: GB0625581D0; EP1936291A2; EP1936291A3

Description

The present invention relates to a ventilation system, according to the preamble of claim 1, such a system is known, for instance, from WO 2005/050026 .
Ventilation systems are often provided with at least two fan units, one to act as a lead or 'duty fan' and the other as an idle or 'standby' fan, ready for operation should the duty fan fail. Conventionally, such a ventilation system comprises two complete fan units located together in a common enclosure, one of the fans arranged to operate continuously until failure, at which point the other fan starts and takes over the ventilating operation.
Such functionality is known as '100% duty and standby operation' and is commonly specified in the UK and elsewhere for toilet extract ventilation systems, for smoke transfer ventilation systems, extract and stairwell pressurisation systems and also for critical process ventilation systems.
In the event of duty fan failure, the standby fan may be turned on by manual control, but more commonly, is turned on automatically by a duty fan failure detection system, linked to the standby fan's control circuit.
Other control enhancements are commonly found, for example, 'duty sharing', whereby each fan in turn periodically assumes the role of the duty fan, thus equalising wear and ensuring that both fans are regularly exercised.
To achieve 100% operation from both fans, it is necessary to arrange the system so that either: 1) two identical fans are used, and the air entry and discharge paths are similar for both in terms of resistance to airflow, or 2) the two fans are dissimilar, so that each component is rated to achieve the same delivered air flow rate for the unit as a whole.
Currently, there are a number of known systems available on the market.
Referring to Figure 1, there is illustrated a known ventilation system 1 comprising a housing 2 having an air inlet port 3 at one end 2a and an air outlet port 4 at an opposite end 2b. The housing 1 contains a first fan 4 and a second fan 5. The first fan 5 and the second fan 6 are identical and are arranged side by side in parallel between the air inlet port 3 and the air outlet port 4.
The first fan 5 and the second fan 6 are provided with respective non - return shutter or damper arrangements 5a and 6a, each configurable in an open position to enable air to flow through the respective fans 5 and 6 and in a closed position to prevent air flowing thorough the respective fans 5 and 6.
In use, the shutter associated with the duty fan is open (the first fan 5 in Figure 1) and the shutter associated with the standby fan is closed (the second fan 6 in Figure 1). The duty fan 5 causes air to flow into the housing 1 through the air inlet 3 and out from the housing through the air outlet 4. The closed non -return shutter 6a of the standby fan 6 prevents the backflow of air through the standby fan 6, an effect that would de-rate the performance of the duty fan 5.
Typically, the fans 5 and 6 are centrifugal fans, although they may also be axial flow fans, provided that they can overcome the air flow resistance presented by the system's layout.
In such systems, the fans are arranged side by side, so that the air entry and exit paths for both are similar. A disadvantage of such systems is that the width (w) of the housing is at least twice that of an individual fan, and often as much as three times as wide. This is necessary to allow for a reasonable clearance around the fans' inlet areas. Additionally, the length (L) of the housing may also be significantly greater than that of an individual fan to make provision for efficient guiding of incoming air and to incorporate the non-return shutters or dampers 5a, 6a. Simply reducing the size of the housing 1 can cause significant penalties in terms of performance, noise and required fan power.
Figure 2 illustrates an alternative known ventilation system 20. The system 20 comprises a housing 21 having an air inlet port 22 at one end 21 a and an air outlet port 23 at an opposite end 21b. The housing 21 contains a first fan 24 and a second fan 25 arranged in series between the air inlet port 22 and the air outlet port 23.
In use, one of the fans 24 and 25 acts as the duty fan and the other of the fans 24 and 25 acts as the standby fan. The duty fan causes air to flow into the housing 21 through the air inlet 22 and out from the housing through the air outlet 23, the airflow path running sequential through both of the fans 24 and 25.
This fans in series arrangement is more compact than the fans in parallel arrangement, but has the disadvantage that the duty fan has an additional air resistance load imposed on it by the idling resistance of the standby fan. This additional load can severely limit the overall performance and energy efficiency of the system.
The series arrangement is most commonly applied to axial flow fans, since by the nature of their construction, the standby fan offers a relatively low resistance to air flow. Centrifugal fans tend to have blading and other components arranged such that their idling resistance is relatively large.
The majority of Run and Standby ventilation systems are used for toilet ventilation systems or other systems that are generally complex. These systems, for reasons of economy and occupant comfort, are typically ducted systems of high aerodynamic resistance. The use of centrifugal fans is often preferred in such ducted systems due to 1) their efficient and quiet operation against higher resistance and 2) their relative insensitivity to poor inlet and discharge conditions (compared to axial flow fans), as caused by limited space in which to arrange the fan layout. The fans in series arrangement for Run and Standby unit design is preferable due to its relative compactness, but hitherto this has been unachievable with centrifugal fan designs requiring efficient operation.
Embodiments of the present invention aim to at least alleviate the above described problems.
According to the present invention there is provided a ventilation system according to claim 1.
Advantageously, having an airflow path that bypasses whichever of the fan arrangements is idle, reduces the airflow resistance of the housing for whichever of the fan arrangements is active. In addition, closing the airflow path that bypasses whichever of the fan arrangements is active, prevents the back flowing of air past the active fan arrangement.
An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic perspective view of a prior art ventilation system already described above;
Figure 2 is a perspective view of another prior art ventilation system already been described above; and
Figures 3a and 3b are plan cut away views of a ventilation system embodying the present invention.

Referring now to Figures 3a and 3b there is shown a ventilation system 30 comprising a fan chamber or housing 31 of generally rectangular cross section, comprising an air inlet 32 at a first end 31a and an air outlet 33 at an opposite second end 31b. The housing 31 is typically formed from sheet metal, for example aluminium. In use, the air inlet 32 is connected to incoming duct work (not shown) and the air outlet 33 is connected to outgoing duct work (not shown) and the ventilating system 30 is used to ventilate one or more enclosed areas of a building, for example a lavatory.
A first fan arrangement 34 and a second fan arrangement 35 are mounted within the housing 31 in series with each other and spaced apart along a longitudinal axis of the housing 31, with the first fan arrangement 34 located upstream of the second fan arrangement 35. The width of the housing 31 is about twice that of the first fan arrangement 34 and the second fan arrangement 35 and thus the housing 31 and fan arrangements 34 and 35 together define channels (c) running either side of the fans 34 and 35.
In a preferred embodiment each of the fan arrangements 34 and 35 comprises a single fan in a protective casing or shroud (not shown), although it will be appreciated that each of the fan arrangements 34 and 35 may comprise multiple fans arranged in series or parallel.
The housing 31 further contains a first air - flow control arrangement 36 and a second air flow control arrangement 37. The first air - flow control arrangement 36 is configurable between a closed configuration illustrated in Figure 3a, and an open configuration illustrated in Figure 3b. In the closed configuration, air-flow through the channels defined by the first fan arrangement 34 and the housing 31 is substantially prevented, whilst in the open configuration air-flow through these channels is allowed.
Similarly, the second air - flow control arrangement 37 is also configurable between a closed configuration illustrated in Figure 3b, and an open configuration illustrated in Figure 3a. In the closed configuration, air-flow through the channels defined by the second fan arrangement 35 and the housing 31 is substantially prevented, whilst in the open configuration air-flow through these channels is allowed.
In operation, one of the first 34 and second 35 fan arrangements acts as a duty fan arrangement whilst the other acts as a standby fan arrangement. A system controller 38 is connected to the first 34 and second 35 fan arrangements and to the first 36 and second 37 air-flow control arrangements and controls the first 36 and second 37 air-flow control arrangements such that the first air-flow control arrangement 36 is closed and the second air-flow control arrangement 37 is open when the first fan arrangement 34 acts as the duty fan (Figure 3a), and the first air-flow control arrangement 36 is open and the second air-flow control arrangement 37 is closed when the second fan arrangement 35 acts as the duty fan (Figure 3b).
Such a system provides several advantages, in particular, the air-flow path through the housing 31 is not entirely channelled through which ever of the fan arrangements 34 and 35 is idle. Instead, as illustrated in Figure 3a, when the first fan arrangement 34 is the duty fan, airflow enters the housing 31 through the inlet 32, passes partly through the standby second fan arrangement 35 and partly through the channels defined by the second fan arrangement 35 and the housing 31, entirely through the duty first fan arrangement 34 and out through the outlet 33. As illustrated in Figure 3b, when the second fan arrangement 35 is the duty fan, airflow enters the housing 31 through the inlet 32, passes entirely through the duty second fan arrangement 35, partly through the standby first fan arrangement 34 and partly through the channels defined by the first fan arrangement 34 and the housing 31 and out through the outlet 33.
The cross sectional areas of the channels are selected such that the airflow resistance presented by the channels when open is much lower than the airflow resistance presented by the standby fan. Therefore, as illustrated by the arrows in Figures 3a and 3b, a greater proportion of airflow passes through the channels than through the standby fan.
Advantageously, when in the closed configuration, the air- flow control arrangements 36 and 37 also prevent the backflow of air in the system.
In a preferred embodiment, the first 34 and second 35 fan arrangements comprise centrifugal fans, this approach enabling the system to be constructed with a much smaller equipment area than has been possible to date. It will be appreciated however that it is not essential feature of the invention that the fans are centrifugal fans, and that other fan types may be used in embodiments of the invention, for example, mixed flow fans, cross flow fans and axial flow fans.
As illustrated in Figures 3a and 3b, in a preferred embodiment, the first 36 and second 37 air - flow control arrangements each comprises a respective metal plate 36a, 37a that spans the entire cross sectional area of the housing 31. The first fan 34 has its discharge orifice mounted through an aperture formed centrally in the metal plate 36a and likewise the second fan 35 has its discharge orifice mounted through an aperture formed centrally in the metal plate 37a. Each plate 36a and 37a further comprises a respective pair of apertures 36b, 37b with an aperture of each pair formed either side of the respective fans 34 and 35. Each of the first 36 and second 37 air - flow control arrangements further comprises a respective pair of shutters 36c, 37c for opening and closing the respective pair of apertures 36b, 37b, to allow or to prevent air flow flowing around the fan arrangements 34 and 35.
A motor arrangement 39 controlled by the controller 38 is provided to open and close the pairs of shutters 36d and 37d. The shutters may be in the form of flaps as shown in Figures 3a and 3b, but alternatives may be used, for example, motorized grilles may be used to open and close the apertures 36b and 37b. Any suitable motor arrangement may be used to open and close the shutters, for example, linear or rotary motors, or the shutter operating mechanism may be fan pressure operated with gravity or spring closure.
The controller 38 is arranged to monitor for malfunction of the duty fan and if a malfunction is detected, to close the duty fan down and to activate the standby fan to act as the new duty fan. The controller 38 also changes the configuration of the first 36 and second 37 air - flow control arrangements from that illustrated in Figure 3a to that illustrated in Figure 3b or vice versa, depending upon which of the fan arrangements 34 and 35 is the new duty fan.
The controller 38 may also be arranged to periodically change which of the first 34 and second 35 fan arrangements is acting as the duty fan and to configure the first 36 and second 37 air - flow control arrangements accordingly.
Having thus described the present invention by reference to a preferred embodiment it is to be well understood that the embodiment in question is exemplary only and that modifications and variations such as will occur to those possessed of appropriate knowledge and skills may be made without departure from the scope of the claims. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims.
The singular reference of an element does not exclude the plural reference of such elements.

Claims

A ventilation system (30) comprising:
a housing (31) comprising an air inlet (32) and an air outlet (33), a first fan arrangement (34) and a second fan arrangement (35) arranged in series within the housing (31) causing air to flow through the housing (31) from the inlet (32) to the outlet (33), a controller (38) causing one of the first fan arrangement (34) and the second fan arrangement (35) to act as an active duty fan arrangement (35) whilst the other acts as an idle standby fan arrangement, and characterized in that the system furthermore comprising an airflow control system (36,37) selectively configuring first and second different airflow paths through the housing (31) in dependence upon which of the first fan arrangement (31) and second fan arrangement (35) acts as the duty fan arrangement, wherein each of the different airflow paths is arranged such that substantially all of the airflow passes through the duty fan arrangement and at least a portion of the airflow bypasses the idle fan arrangement.
A ventilation system according to claim 1 wherein the airflow control system (36,37) is configurable in a first configuration for when the first fan arrangement (34) is active and the second fan arrangement (35) is idle and in a second configuration for when the first fan arrangement (34) is idle and the second fan arrangement (35) is active, in the first configuration a first airflow path by-passing the first fan arrangement (31) being substantially closed and a second airflow path by-passing the second fan arrangement (35) being open and in the second configuration the first airflow path being open and the second airflow path being substantially closed.
A ventilation system according to claim 1 or 2, the system further comprising:
a control arrangement (36,37) for selecting to configure the airflow control system in the first configuration or the second configuration in dependence upon which of the first and second fan arrangements is active.
A ventilation system according to any preceding claim, wherein, the first path comprises at least one channel and the airflow control system (36,37) comprises a first closure arrangement for closing the at least one channel for the first configuration and opening the at least one channel for the second configuration.
A ventilation system according to claim 4, wherein, the second path comprises at least one channel and the airflow control system (36,37) comprises a second closure arrangement for opening the at least one channel for the first configuration and closing the at least one channel for the second configuration.
A ventilation system according to claim 4 or 5 wherein either the first or second closure arrangements comprises at least on shutter (36c,37c).
A ventilation system according to claim 6 wherein the at least one shutter (36c,37c) is motorised for moving between an open and a closed position.
A ventilation system according to any preceding claim wherein the first and second fan arrangements (34,35) comprise centrifugal fans.
A ventilation system according to claim 4 wherein the at least one channel is defined by the first fan arrangement (34) and the housing (31).
A ventilation system according to claim 4 wherein the at least one channel is defined by the second fan arrangement (35) and the housing (31).