Improvements in water supply systems

Abstract

 A water flow control assembly comprises a pump (11) installable in a mains water supply line (10), a sensor (14) for measuring the rate of flow of water in the supply line and a control (13) for adjusting the speed of the pump when the pump is in operation in response to flow rate measured by the sensor. The control acts to limit the speed of the pump so that the flow rate does not exceed a predetermined value.

Description

[0001] This invention relates to water supply systems and in particular, though not exclusively to systems for boosting domestic mains water supplies.

[0002] A number of households suffer from low mains water pressure, particularly at periods of high demand, giving rise to low flow rates. A way of resolving this problem is to boost the pressure by means of a pump. However, Water Authorities tend not to allow extraction of water by means of a pump above a certain flow rate. A typical solution, therefore, is to install a pump in the supply line with a restrictor to limit the output. This arrangement has the disadvantage, however, that flow is restricted under all supply pressure conditions.

[0003] The present invention provides a water flow control assembly comprising a pump installable in a mains water supply line, first sensing means for measuring the rate of flow of water in the supply line, and control means for adjusting the speed of the pump when the pump is in operation in response to flow rate measured by said first sensing means, wherein the control means acts to limit the speed of the pump so that the flow rate does not exceed a predetermined value.

[0004] By way of example, embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic illustration of a flow control assembly according to the invention installed in a mains water supply line.

[0005] The flow control assembly seen in Figure 1 comprises a pump 11, a flow transducer 12 and control unit 13. The pump 11 and flow transducer 12 are installed in a mains water supply line 10, with the flow transducer conveniently situated downstream of the pump. The flow transducer 12 measures the rate of flow of water in the supply line 10. The signal from the flow transducer 12 is fed to the control unit 13.

[0006] When the pump 11 is in operation, the rate of flow of water down the supply line 10 is proportional to the speed of the pump. The control unit 13 is arranged to control the speed of the pump 11 in response to the flow rate measured by the flow transducer 12. In particular, the speed of the pump 11 is controlled to ensure that the boost that it gives to the mains supply pressure does not result in an over-extraction of water. In the UK currently, flow rates of up to 12 litres per minute are allowable in pump-assisted extraction.

[0007] A pressure sensor 14 situated upstream of the pump 11 measures the pressure of the water supply to the pump, ie. the prevailing mains pressure in the supply line 10. The signal from the pressure sensor 14 is fed to the control unit 13. The control unit 13 is arranged to allow the pump 11 to operate when the signal from the pressure sensor 14 indicates that the mains pressure has fallen below a certain value, which will be set typically at around 2 or 3 bar. The pump 11 may or may not operate to boost the flow, depending on the demand.

[0008] Whenever the mains supply pressure is at or above the set value, the signal from the pressure sensor 14 indicates this to the control unit 13, which in turn acts to inhibit operation of the pump 11. When the pump 11 is not in operation, water is nevertheless able to flow through it and along the supply line 10 under normal mains pressure. In this condition, the limit on the water extraction rate does not apply.

[0009] In a modified arrangement, a by-pass may be provided in the supply line 10 to go around the pump 11. This would have the advantage of allowing water to flow freely around the by-pass when the pump is not in operation, rather than having to flow through the pump itself. In this modified arrangement, the by-pass would preferably incorporate a non-return valve in order to prevent backflow of water when the pump is in operation.

[0010] It will be appreciated that any suitable variable speed pump may be used in the assemblies described above. The pump speed control may be stepped or smoothly variable.

[0011] Conveniently, the elements of the assemblies described above may be constructed as an integral unit so that they can be easily installed. Advantageously, the assemblies can be pre-set in the factory so as to avoid the need for calibration or adjustment after installation. This also has the advantage of preventing the possibility of subsequent tampering.

[0012] In an alternative arrangement, the pump itself may be used to measure the rate of flow of water in the supply line 10. In this arrangement, the pump that is used is an impeller type pump driven by a brushless, electronically controlled motor. Such motors have permanent magnet rotors and use electronic commutation. That is, built-in electronic sensors are used to detect the rotational position of the rotor and feed signals back to electronically control the energy supply to the motor and hence control the motor speed.

[0013] In this arrangement, the pump impeller is able to rotate whether or not it is being driven by the motor. In this sense, the impeller acts like a turbine and the flow through the pump is thus directly proportional to the rotational speed of the impeller. Since the impeller is mounted on the same shaft as the rotor of the motor, the signals from the built-in electronic sensors in the motor are an indication not only of the rotor speed, but also of the impeller speed. Thus, these signals can be used as a measure of the flow rate through the pump, ie through the supply line. This has the advantage of doing away with the need for the separate flow transducer 12 of the earlier described arrangements.

[0014] As regards ensuring that the flow rate through the pump does not exceed the predetermined limit when the pump is operational (ie when it is being driven by the motor), this can be achieved by suitable control of the electronic control system within the motor.

Claims

1. A water flow control assembly comprising a pump installable in a mains water supply line, first sensing means for measuring the rate of flow of water in the supply line, and control means for adjusting the speed of the pump when the pump is in operation in response to flow rate measured by said first sensing means, wherein the control means acts to limit the speed of the pump so that the flow rate does not exceed a predetermined value.

2. A flow control assembly as claimed in claim 1 and further comprising a second sensing means for measuring the pressure of the water in the mains supply line going into the pump.

3. A flow control assembly as claimed in claim 2 wherein the control means is arranged to inhibit operation of the pump other than when the water pressure measured by said second sensing means falls below a predetermined value.

4. A flow control assembly as claimed in any preceding claim and further comprising a by-pass in the supply line to go around the pump.

5. A flow control assembly as claimed in claim 4 wherein said by-pass comprises a non-return valve to prevent backflow of water.

6. A flow control assembly as claimed in any preceding claim wherein said first sensing means is situated in the supply line downstream of the pump.

7. A flow control assembly as claimed in any one of claims 1 to 5 wherein the pump is an impeller type pump and said first sensing means comprises means for sensing the rotational speed of the pump impeller.

8. A flow control assembly as claimed in claim 7 wherein the pump is one that is driven by an electronically controlled motor and the signals from the in-built electronic control sensors in the motor are used as a measure of the rotational speed of the pump impeller.

9. A flow control assembly as claimed in any preceding claim wherein the assembly is constructed to be installable as a self-contained unit.

10. A flow control assembly as claimed in claim 9 wherein the calibration of the control means can be pre-set prior to installation of the assembly.

11. A domestic water supply incorporating a flow control assembly as claimed in any preceding claim.

Drawing