GB2265037A

GB2265037A - Control system for fire dampers

Info

Publication number: GB2265037A
Application number: GB9205599A
Authority: GB
Inventors: Peter Dyke; Alan Colin Lyall; Terence Victor Hobday
Original assignee: MOTORISED AIR PRODUCTS Ltd
Current assignee: MOTORISED AIR PRODUCTS Ltd
Priority date: 1992-03-14
Filing date: 1992-03-14
Publication date: 1993-09-15
Anticipated expiration: 2012-03-14
Also published as: GB9205599D0; GB2265037B

Abstract

A control system for a plurality of fire dampers in an installation comprises a master control unit and a plurality of slave units each associated with a respective motor driven damper for opening and closing the damper under the control of signals received from the master control unit, each slave unit being connected to the master control unit by cabling carrying a d.c. supply for the damper motor and control signals for opening and closing the damper. Each slave unit comprises a decoder (34, 36, 44) for decoding control signals from the master control unit, a relay (58) operated by the decoder for selectively connecting the damper motor (62) to the d.c. supply and a diode (66, 68) for permitting current from the d.c. supply to flow through the motor (62) in only one direction, so that reversal of the polarity of the d.c. supply cuts off the current to all the damper motors while continuing to power the decoders of the slave units. <IMAGE>

Description

CONTROL SYSTEM FOR FIRE DAMPERS Field of the invention The present invention relates to a control system for a plurality of fire dampers in an installation.

Background of the invention It is often necessary for air conditioning ducting to pass through walls and partitions required to have fire retardant properties. In such cases, it is important that the presence of the ducting should not detract from the safety afforded by the wall and in the event of a fire, the ducting should be closed to prevent heat, flames and smoke from passing through the ducting. To this end, smoke and fire dampers are known, an example being described in GB 2 244 214.

In a large building, fitted with dampers at several locations, a central control panel is required to open and close the various dampers to isolate a region in which a fire has been detected. The control panel may operate automatically in response to detection of a fire and may be fitted with a manual override for manual control.

In such a system, it is desirable to be able to shut down all the dampers at the same time in an emergency. It is known to provide motor driven dampers which are spring biassed into a closed position such that when the power supply to their motors is cut off, the dampers automatically return to their closed position. The disadvantage of cutting off the supply to all the motors, however, is that the entire electrical system is then not operational.

Object of the invention The invention seeks to provide a control system for fire dampers which allows all the dampers to be shut down at the same time, while retaining the facility to exchange data between the master control unit and the slave units.

Summary of the invention According to the present invention, there is provided a control system for a plurality of fire dampers in an installation, comprising a master control unit and a plurality of slave units each associated with a respective motor driven damper for opening and closing the damper under the control of signals received from the master control unit, each slave unit being connected to the master control unit by cabling carrying a d.c. supply for the damper motor and control signals for opening and closing the damper, wherein each slave unit comprises a decoder for decoding control signals from the master control unit, a relay operated by the decoder for selectively connecting the damper motor to the d.c. supply and a diode for permitting current from the d.c. supply to flow through the motor in only one direction, whereby reversal of the polarity of the d.c. supply cuts off the current to all the damper motors while continuing to power the decoders of the slave units.

Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block circuit diagram of a fire damper control system, and Figure 2 is a more detailed block diagram of one of the motorised damper units in Figure 1.

Detailed description of the preferred embodiment The master control unit of a fire damper control system comprises a power supply circuit 10 which is connected to a mains supply and produces a d.c. output voltage applied through a fire control circuit 12 to the two d.c. power lines shown to the right in each of the drawings. The purpose of the fire control circuit 12 is to shut down all the dampers which are controlled by slave units designated 18, 20, 22 and 24, respectively. In addition to the power supply circuit 10 and the fire control circuit 12, the master control unit comprises a control panel 14 connected by control electronics 16 to the same power lines which double as signal lines.

Each damper has an associated electric motor which acts to keep the damper open for as long as the motor is energised.

As soon as power is cut off to the motor, a strong spring in the damper causes it to shut down and limit switches in the damper signal back to the control panel 14 that the appropriate damper is shut.

In a conventional system, as soon as fire is detected, the equivalent of the fire control circuit 12 shuts off the power to the entire system. The motors of the dampers are no longer energised and it is assumed that they will shut under the action of their own springs. However, as the system power is shut off, one cannot be sure if they have all been closed and indeed there is no way of overriding the automatic control and closing some dampers while leaving others open.

In the present invention, the operation of the fire control circuit 12 is not to shut off the d.c. power supply but to reverse its polarity. The electric motors of the damper units are connected in series with diodes so that the polarity reversal prevents further current from flowing through the motors and closes off all the dampers. However, the signalling circuit remains energised and it is possible to continue to monitor at the central control panel 14 which of the dampers have closed and which are still open and the control electronics 16 allow a fire officer to control the damper units either individually or in zones depending on the location of the fire.

A slave unit is shown in more detail in Figure 2. The power for the electronic circuits of the slave unit is taken from the d.c. power / signal lines through a voltage polarity insensitive circuit, such as a full wave bridge rectifier or a change-over relay 30 or any other circuit,and a regulator 32. If a change-over relay is used, it has its energising coil connected to the power lines by way of a diode so that it is not energised when the lines have normal polarity but is energised when the polarity is reversed. When the winding is energised it reverses the connections between the regulator 32 and the power lines so that the regulator is always connected to the power lines with the correct polarity to produce the required voltages for the remaining electronic circuits to be described.

The motor 62 of the damper is connected to the power supply lines through diodes 66 and 68 which only allow current to flow through the motor when the power lines have a forward polarity. When the power line polarity is reversed by the fire control circuit 12 of Figure 1, then the motor 62 ceases to be energised and the damper closes, regardless of the position of the relay contact 60 which controls the damper when the power lines are forward biased The control signals from the control electronics 16 to the damper units are achieved by shorting the power line in a controlled manner to the network supplying the dampers.

This considerably reduces the complexity of the wiring. The signals transmitted to the slave units contain the addresses of all the units which are to be controlled as well as an instruction on whether the damper is to remain open or closed. These signals are retransmitted periodically so that the instructions to all the damper units may be regarded as being sent in time division multiplex on the same signal line.

The signal on the power line is received by all the slave units. The receiver is a simple comparator 36, the threshold of which is set to approximately half of the power line voltage to allow for voltage drops along the network due to spurious signals. The modulated signal on the signal line is passed by a capacitor 38 and a band-pass filter and amplifier 34 to the comparator 36. These circuit 34 is generally similar to those that would be found in a convention radio receiver and need not therefore be described in detail. The data signal is next passed to a decoder 44 which is connected to an address circuit 46 containing, for example, resistors, switches or other links, to enable a unique address to be manually preset in the circuit. When the data signal matches the preset address a signal is passed to gate 54 which energises a relay driver 58.The contacts 60 of the relay are then closed to allow current to flow through the motor 62 and thereby open the damper.

Two limit switches 64 are associated with the damper mechanism each of which closes in one end position of the damper. The switches 64 are connected to data inputs of an encoder 50 and together they send a two digit binary signal the encoder 50 which can have values of 10, 00 and 01 representing the fully closed, part open and fully open positions, respectively. The encoder 50 transmits back to the control electronics a signal by shorting the power line according to the address preset into the slave unit of the control electronics, the status of the damper and the incoming data. The control electronics transmits to a slave unit a signal and then listens for a finite time for a reply from the slave unit. When a reply is received and understood, the control electronics transmits to the next slave unit in the network, and so on.If no reply is received and understood, the control electronics logs 'no response' and continues. If no response is received from the same slave unit after a number of attempts, then the control electronics issues a visible and audible alarm. The controls unit also displays the status of each damper.

If a fire officer wishes to close a damper individually, then a switch on the control panel 14 associated with that damper is closed causing the control electronics 16 to send a signal to the address of the damper for closing the gate 54 and de-energising the relay driver 58. This will in turn cause the relay contact 60 to open and switch off the motor 62.

Should the decoder 44, for whatever reason, fail to receive a signal containing the address of the damper within a predetermined time then a time-out and latch circuit 56 sends a signal to the gate 54 to close the damper.

An external input to the control electronics allows for automatic fire detection and the appropriate strategy for the damper position to be implemented. The system provides information about the dampers at the central control panel at all times and allows individual the dampers to be controlled individually, either automatically or manually.

All these facilities are retained without complication to the wiring installation which only requires a single pair of wires connecting central control panel 14 to all the damper units within a zone.

Claims

1. A control system for a plurality of fire dampers in an installation, comprising a master control unit and a plurality slave units each associated with a respective motor driven damper for opening and closing the damper under the control of signals received from the master control unit, each slave unit being connected to the master control unit by cabling carrying a d.c. supply for the damper motor and control signals for opening and closing the damper, wherein each slave unit comprises a decoder for decoding control signals from the master control unit, a relay operated by the decoder for selectively connecting the damper motor to the d.c. supply and a diode for permitting current from the d.c. supply to flow through the motor in only one direction, whereby reversal of the polarity of the d.c. supply cuts off the current to all the damper motors while continuing to power the decoders of the slave units.

2. A control system as claimed in claim 1, wherein control signals are transmitted from the master control unit to the slave units via the d.c. supply lines, the control signals being actioned by shorting the power line.

3. A control system as claimed in claim 1 or 2, wherein each slave unit includes a time-out circuit for automatically closing the associated damper if no control signal is received from the master control unit within a predetermined time interval.

4. A control system constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.