GB2500759A

GB2500759A - Emergency lighting trigger device and override

Info

Publication number: GB2500759A
Application number: GB201301959A
Authority: GB
Inventors: Alan Daniels; Peter Warner; Angus Stone
Original assignee: P4 Ltd
Current assignee: P4 Ltd
Priority date: 2012-02-02
Filing date: 2013-02-04
Publication date: 2013-10-02
Anticipated expiration: 2033-02-04
Also published as: GB201301959D0; GB2500759B; GB201201843D0

Abstract

A normal lighting circuit 2 includes a trigger device 6 which is actuated in response to a failure in the power supply to the normal lighting circuit 2. The trigger device 6 triggers an emergency lighting system 14, bypassing at least one switch 12 in the emergency lighting system 14, and the emergency lighting 14 is illuminated regardless of whether the switch 12 is opened or closed. A second trigger device 30 may be included in the emergency lighting system 14 so that in the event of a failure in the power supply to the emergency lighting circuit 14, a switch 4 in the normal lighting circuit 2 is bypassed.

Description

Title: Emergency Lighting Trigger Device and Override

Field of the Invention

The present invention relates to a trigger device for use in lighting systems, especially emergency lighting systems, to a lighting system comprising the trigger device and to a method of controlling or operating a lighting system, especially an emergency lighting system.

Background of the Invention

Buildings, especially commercial or industrial buildings, are required to possess emergency lighting systems which can come into operation in the event of failure (e.g. due to fire or power failure) of the normal lighting system. In the UK, emergency lighting systems are specified in BS5266.

Some emergency lighting systems operate using a plurality of self-contained lights or luminaires, each associated with its own independent power source (usually a battery).

Another type of emergency lighting is operated using a central battery system, in which a central battery is used to provide electrical power to a plurality of emergency lights or luminaires. Central battery systems have a number of advantages relative to self-contained systems. For example, the operational life of a battery in a central battery system may be as much as 25 years, whilst the batteries in self-contained units need to be changed every 3 or 4 years, and much higher levels of emergency illumination can usually be created using a central battery system. Typically (but not necessarily), such central battery systems also include an inverter to convert the DC output from the battery to an AC output suitable for conventional electric light fittings, so that relatively cheap, standard light fittings can be used in the emergency lighting system. Such systems may then be termed "central inverter" systems.

Another option for emergency lighting systems is the use of a generator. Generators can be attractive because the cost is often lower than for a central inverter, but they are noisy and require ventilation when operating and must be able to start within 5

I

seconds to ensure that building occupants do not panic -this can make them rather special and hence expensive.

Emergency lighting systems, including those of the central battery-type, are known to include sub-circuit monitoring or phase failure monitoring.

Sub-circuit monitoring normally utiliscs relays to monitor the power supply to a local lighting sub-circuit. Phase failure monitoring monitors all three phases of a (three phase) AC supply, and failure of any one of the phases will normally trigger the a emergency lighting.

Summary of the invention

In a first aspect the invention provides a trigger device, actuated in response to a failure in the power supply to all or part of a normal lighting circuit, which device triggers an emergency lighting system, which emergency lighting system has at least one switch therein, and wherein the trigger device overrides said switch, such that, when the trigger device is actuated, the emergency lighting is illuminated regardless of the condition of the switch (i.e. whether the switch is open or closed).

The trigger device can be introduced in new installations but can also readily be retrofitted to existing emergency lighting systems.

Thc triggcr device will preferably bc contained within a housing, with suitable cable entry points, typically via glands in a gland plate or the like.

The trigger device will be operably connected via monitoring connections to monitor the electrical power supply to one or more normal lighting circuits or sub-circuits.

The monitoring connections will desirably monitor the power supply upstream of any switches in the normal lighting circuit or sub-circuit, so that an open switch in the normal lighting circuit or sub-circuit will not automatically actuate the trigger device.

Conveniently the trigger device will comprise one or more relays to trigger the emergency lighting. The one or more relays conveniently will act on connections across the switch in the emergency lighting circuit or sub-circuits, thereby ensuring that power is delivered to the emergency lights irrespective of whether the switch in the emergency lighting circuit or sub-circuit is open.

Suitable relays for this purpose are known to those skilled in the art and include those available from Shrack (or TE Connectivity). The relay may typically be energised a whcn thc normal lighting is in opcration and dc-cnergised whcn thcrc is a failure in the normal power supply, wherein in the energised state the relay holds open the contacts across thc cmcrgcncy lighting switch.

In another, preferred, embodiment, the monitoring' function is performed not by a relay but by an optocoupler or photocoupler. In general this involves a light source in the monitored circuit or sub-circuit, and a light sensitive component (photodetector) in the monitoring circuit, positioned so as to be operably coupled to the light source (note, this could be remotely, via an optical fibre).

The light source need not necessarily be a source of visible light. For example, a preferred light source emits predominantly infra red light. A convenient light source is an LED. A preferred light source is a infra red LED (i.e. one emitting predominantly in thc infra red part of the spcctrum).

The photodetector is preferably a photodiode or phototransistor. Thus, whilst the normal lighting circuit or sub-circuit is working, the light source operates and the photodetector detects this and causes the relay in the other, emergency, circuit to remain energised, but if the power fails and the monitored light source no longer operates, the photodetector causes the relay to drop out and activate the emergency lighting circuit or sub-circuit.

The use of a relay, or of a photocoupler, sensitive to the power supply to the normal lighting circuit, avoids the need for additional or separate phase failure or sub-circuit monitoring apparatus, although such may be included if desired. "Failure" of the power supply to the normal lighting system, sufficient to trigger the trigger device of the invention, may be total or maybe partial e.g. loss of one phase of a three phase AC supply; or an undcrvoltagc of say less than 90%, or less than 80%, or less than 70%, or less than 60% of the nominal voltage. In the UK, the nominal voltage of the normal lighting power supply will usually be 230V + 10% at 50-60Hz.

In some embodiments, the lights, luminaires or other lighting elements which are powered by the emergency lighting circuit may comprise at least one, and preferably a scvcral or many, ofthc lights, luminaires or othcr lighting elements which arc present in the normal lighting circuit or sub-circuit. Thus, the emergency lighting circuit may convcnicntly utilisc all or many of thc lights, luminaircs ctc. uscd in thc normal lighting system, in order to reduce the cost of installation. In other embodiments, the emergency lighting system comprises one or more light fittings which are separate from thc normal lighting system, or comprises only light fittings which do not form part of the normal lighting system.

The trigger device may comprise one or more indicators, preferably visual indicators, to indicate its condition. The indicator desirably includes one or more LEDs. In one embodiment an LED is illuminated when the power supply to the normal lighting circuit or sub-circuit has failed and the emergency lighting circuit is operational.

It will also be apparent that the trigger device of the present invention is able to actuate a plurality of lights, luminaircs or othcr lighting elements. Another advantage of the trigger device of the invention is that it enables the emergency lighting circuit to be switched off locally to achieve energy savings, but ensures that emergency lighting is provided when required. The switch in the emergency lighting circuit is conveniently a manually operable switch e.g. a wall switch or the like. The emergency lighting system may comprise a plurality of sub-circuits, each sub-circuit having a switch, typically a manually operable switch. In such circumstances, a corresponding plurality of trigger devices may be provided, a respective one to by-pass each of the sub-circuit switches.

In a particularly preferred embodiment, a similar, second trigger-override device may be located in the normal lighting circuit. That is, a relay may be powered by the emergency lighting circuit, upstream of the switch therein, which acts on contacts across a switch in the normal lighting circuit. Typically the second trigger/overridc device is substantially similar to the first and, when energised (typically when the emergency power source is functional), holds open the contacts across the switch in the normal lighting circuit or sub-circuit. However, should the emergency power source fail, the relay becomes de-energised and the contacts across the switch in the normal lighting circuit close, by-passing or overriding the switch. In this way, the a lights can be operated from whichever power supply is available, in the event of a failure in the other supply. The invention is especially suitable in circumstances in which two, independcnt, power supplics arc provided (typically both running from the national grid).

A preferred embodiment of the invention thus comprises two trigger devices, preferably contained within a common housing, with one trigger device functioning to actuate an emergency lighting circuit or sub-circuit, and the other trigger device functioning to actuate the normal lighting circuit or sub-circuit (if the normal lights have been switched off) in the event of a failure in the emergency power supply to that locality.

In one such embodiment, the two trigger devices are arranged within a housing side-by-side, separated from each other by insulating material, but operably coupled in the sense that each can monitor the functioning of the other circuit. Conveniently the operable coupling is achieved by means of a photocoupler, as described previously.

The invention thus also provides, in a second aspect, a lighting system, comprising at least one normal lighting circuit or sub-circuit having a switch therein, and at least one emergency lighting circuit or sub-circuit having a switch therein; a first relay responsive to a failure in the power supply to the normal lighting circuit acting to bypass or override the switch in the emergency lighting circuit or sub-circuit; and a second relay responsive to a failure in the power supply to the emergency lighting circuit and acting to by-pass or override the switch in the normal lighting circuit or sub-circuit.

Tn a third aspect, the invention provides a Hghting system, especially an emergency lighting system, comprising the trigger device of the first aspect.

In a fourth aspect of the invention provides a method of controlling or operating an emergency lighting system, the method comprising the step of installing a trigger device in accordance with the first aspect of the invention. Hi

An advantage of the trigger device of the invention is that it may be modular: one ovcrridc unit can bc fitted wherever it is nccdcd, potcntially at cach light switch. Thc system is simple and reliable so maintenance is minimised.

The terminals are chosen to allow the unit to be unplugged and easily replaced in the unlikdy event that the relay or some other component fails.

The unit can be labelled and the indicator provides some waning to maintenance engineers who might not realise the function of the unit and who might not expect two independent mains supplies to be present in one unit. No other changes are needed and no other equipment is needed, so disruption and system upgrade costs are minimised. To operate the emergency lighting only two wires need to be taken to the emergency lighting switch location, so costs are reduced. The wires are not polarity sensitive so it is unlikely to bc installed incorrectly. Sufficient isolation is provided between live supplies to maintain electrical safety and if three phase systems arc in use three override units can be used, one on each phase.

It is envisaged that there may be a need to limit the inrush current upon switching on of the emergency lights. One way of achieving this is to use a simple NTC thermistor connected in series with the normally closed contacts of the relay. When the relay releases the thermistor will limit the inrush current and then as it heats up the resistance will drop to allow ñll mains voltage to be applied to the emergency lighting load. If the circuit load or the inrush is such that the thermistor option is not practical, then two relays can be used. The first relay releases to apply a current limited mains supply to the load and then a second relay, powered from the first, operates to short out the current limiting resistance.

The two relay approach could bc replaced with a relay and a solid state switch or two solid state switches.

It will be apparent to the person skilled in the art that the present invention is best suited to situations in which the emergency lighting system (or emergency lighting circuit or sub-circuit) is energized at all times (but switched off locally by a switch), a so that the trigger device will immediately cause actuation of the emergency lighting circuit or sub-circuit) upon failure of the normal lighting.

The invention will now be described by way of illustrative examples and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of part of a normal lighting circuit and emergency lighting circuit comprising a trigger device in accordance with the invention; Figure 2 is a schematic diagram showing, in greater detail, some of the components of a trigger device in accordance with the invention in situ in an emergency lighting system; Figure 3 is a schematic illustration of parts of a normal lighting circuit and of an emergency lighting circuit, each comprising a switch and a relay/override device, such that failure of the power supply to one of the circuits automatically overrides the switch in the other of said circuits; Figure 4 is a schematic diagram of a PCB for one embodiment of a trigger device in accordance with the invention; Figure 5 is a schematic diagram of a plug-in test module which plugs into the PCB shown in Figure 4 to provide a test facility; and Figure 6 is a plan view of one embodiment of an arrangement of two trigger devices.

Detailed Description of Embodiments

Example I

Figure 1 shows a schematic representation of part of a normal lighting circuit and a part of an emergency lighting circuit, the system comprising a trigger device in accordance with the invention.

a The normal lighting system comprises a plurality of luminaires 2, and a switch 4 which can be used to switch the luminaires on or off The normal lighting system runs off a mains power supply (230V ± 10%, 50/60 Hz) from the national grid.

The emergency lighting system comprises a relay 6, which is connected to the normal lighting circuit upstream of the switch 4. The relay 6 is energised while the normal power supply is present in the normal lighting circuit. In the energised state, the relay 6 holds open contacts 8, 10 in the emergency lighting circuit, such that emergency luminaires 14 are not lit.

The emergency lighting circuit also includes a switch 12. The switch 12 is preferably a manually operable switch. Accordingly, the emergency lighting system can be deactivated (preferably manually) when not required e.g. when the normal lighting system is operational and/or when the building or the like is not in use. In this way, energy consumption is minimised and the life of the luminaires is extended.

In the event of a failure in the power supply to the normal lighting circuit, the relay 6 is de-energised, allowing the contacts 8, 10 to close. Contact 8 closes a connection in the emergency lighting circuit by-passing or overriding switch 12. Thus, even if the switch 12 is open, the emergency lighting circuit will become activated, powering emergency lighting luminaires 14. In other embodiments, one or more of luminaires 2 in the normal lighting circuit may also be powered by the emergency lighting circuit.

It is even conceivable that the emergency lighting circuit may only power luminaires 2 and may not include any "emergency only" luminaires 14.

Contact 10 closed by de-energising of relay 6 also allows power from the emergency power supply to flow to indicator light 16 (conveniently an LED), which indicates that there has been a failure in the power supply to the normal lighting circuit and that the emergency lighting system is in operation.

The emergency power supply may be, for example, a mains supply from the national grid, from a source different to that used to power the normal lighting system, such that a single national grid source failure will not disable both the normal and the a emergency lighting systems. Alternatively, the emergency power supply may comprise an independent generator, a central battery or the like. If the emergency power supply is a DC source such as a central battery, thc emergency lighting system may conveniently comprise an inverter to convert the DC source to an AC output. As shown in Figure 1, the main emergency power supply is drawn from the national grid but in the event of that too failing, a central battery/inverter combination 18 is also provided as a back-up emergency power supply.

Examyle 2 Figure 2 is a more detailed schematic illustration of the components of a trigger device in accordance with the invention. Like components in Figures 1 and 2 are denoted by common reference numerals. Thus the emergency lighting circuit comprises a switch 12, which is bypassed by the operation of relay 6, which is powered by the normal lighting circuit.

In the illustrated embodiment, relay 6 is a Shrack RTI relay (RT 314730), which is downstream of a 3K3 resistor, 20. The trigger device further comprises the following components: an X-rated 0.22RF capacitor, 22, in parallel with a IM resistor, 24; a 680R resistor, 26; a I000V KBP 207G bridge, 28; and a MARL 113-120 series LED indicator, 16.

The relay PCB is mounted on a silicon foam and housed within a powder-coated aluminium housing. The housing includes a lens and/or light pipe in one surface, to allow the indicator LED to be observed. The housing also includes e.g. two 20mm electrical conduit entry points, typically in a lower wall of the housing.

Examyle 3 Figure 3 shows parts of a preferred embodiment of a lighting system/emergency lighting system, in schematic form. The system is an enhancement of the arrangement illustrated in Figure 1 and like components are denoted by common reference numerals.

a Accordingly, a normal lighting system comprises a plurality of luminaires, 2, and a switch 4 which can be used to switch the luminaires on or off The normal lighting system runs off a mains power supply (230V ± 10%, 50/60 Hz) from the national grid.

The emergency lighting system comprises a relay 6, which is connected to the normal lighting circuit upstream of the switch 4. The relay 6 is energised while the normal power supply is present in the normal lighting circuit. In the energised state, the relay 6 holds open contacts 8, 10 in the emergency lighting circuit.

In the event of a failure in the power supply to the normal lighting circuit, the relay 6 is de-energised, allowing the contacts 8, 10 to close. Contact 8 closes a connection in the emergency lighting circuit by-passing or overriding switch 12. Thus, even if the a switch 12 is open, the emergency lighting circuit will become activated, powering emergency lighting luminaires 14. In other embodiments, one or more of luminaires 2 in the normal lighting circuit may also be powered by the emergency lighting circuit.

Contact 10 closed by dc-energising of relay 6 also allows power from the emergency s power supply to flow to indicator light 16 (conveniently an LED), which indicates that there has been a failure in the power supply to the normal lighting circuit and that the emergency lighting system is in operation.

The emergency lighting system also includes a back-up battery/inverter unit 18 to act as an auxiliary emergency power supply.

Thus far, thc system is idcntical to that dcscribed in Example 1. However, in addition a second trigger/override device is included, which comprises a second relay 30, connected to the emergency lighting circuit upstream of switch 12. The second relay is 30 is powered by an emergency power supply and is energised thereby when the emergency power supply is available. Tn the energised state, the relay 30 holds open contact 32 in the normal lighting circuit.

Should the emergency power supply go offline or fail, relay 30 is de-energised, allowing contact 32 to close, thus by-passing or overriding switch 4 in the normal lighting circuit. Accordingly, should the emergency lighting power supply fail, the switch 4 cannot be used to switch off the normal lighting luminaires 2, so that at least one of the normal and emergency lighting circuits should always be operable.

Examnle 4 Rekrring to Figure 4, a schematic diagram of one embodiment of a PCB suitable lbr a trigger device in accordance with the invention is shown.

The trigger device includes a photocoupler which comprises an infra red LED 34 ("LED 1") which, when the normal lighting circuit or sub-circuit is functioning, emits infra red light. This is detected by an infra red photodetector 36 ("Q2") in the other part of the circuit. Whilst the light is emitted by 34, the relay on the other unit remains activated, but if the LED fails completely or the emitted light intensity falls below a predetermined thseshold level, the relay drops out and the emergency lighting circuit is activated. "LED 2", denoted by reference numeral 38, is a visual indicator that the monitored supply is on.

Connection Conn 2 (reference numeral 40) is a test feature which shorts out the supply to the photocoupler photodetector 36 and the "held in" relay. When mains power is supplied to the plug-in test PCB (shown in Figure 5), the relay on that board (RL1a, reference numeral 60) operates and shorts out Conn 2, 40, which causes the main relay to drop out and activate the emergency lighting circuit or sub-circuit. In a this way, a central battery or central inverter supplying power to the emergency light circuit or sub-circuits, can be tested with all (or, if desired, just some) of the emergency lighting loads on.

A further maintenance/test feature is provided via Conn 3 (reference numeral 42). A "push to make" switch can be connected to 42 and, when operated, it connects resistor R5 (reference numeral 44) across the relay control transistor QI (reference numeral 46). If the photocoupler is on the edge of its sensitivity the operation of the switch will cause the relay to drop out and switch on the supply. If this happens the maintenance engineer knows he needs to arrange to replace the unit sometime over the following 6 months. Releasing the switch will cause the relay to operate again and the system will continue to work for some months.

LED 3 (reference numeral 48) is an indicator LED that shows the sensing relay is operated. When Qi (46) turns off, LED 48 turns off and the relay drops out.

A further feature of the PCB is related to reliability with all types of electrical load.

Small relays can be damaged by sparking (inductive loads) or by high inrush currents (capacitive loads). In the lighting industry the latter is more serious and more difficult to control. To control the inrush current RTI (reference numeral 50) is fitted. This is a Negative Temperature Coefficient thermistor that limits the current into a load to about 30A. The relay is rated at 16A and the product is rated at bA, but the effect of a capacitive load is to have an unlimited inrush current at switch on. As the thermistor heats up the resistance drops and it is rated at continuous operation of bA.

However the second relay RL2 (reference numeral 52), operates 2OmSec or so after RLI drops out to short RTI, 50, so that it is ready for a second operation and so as to limit the operating temperature.

RT2 (reference numeral 54) is a varistor which is used to reduce the effect of high pulse voltages on the circuit. The varistor conducts if the voltage is above normal peak mains voltage, so that any peak energy is dissipated in RTS, rather than allow it to damage the electronics.

Examyle 5 Rcfcrring to Figurc 6 there is shown a plan vicw of a prcfcrrcd embodiment of a device in accordance with the invention.

A housing 100 (shown with the lid removed) houses two trigger devices, indicated generally by reference numerals 102 and 104 respectively. The triggers are arranged side-by-side, but separated by a sheet of insulating material 114.

Trigger 102 contains two relays, 106a and 106b. Trigger 104 contains two relays, lOSa and 108b. A third relay, 116, is provided on a plug-in test board, similar to that illustrated schematically in Figure 5.

Trigger device 104 monitors the operation of the normal lighting circuit and is operably coupled thereto by a photocoupler, which includes optical fibre 110. Trigger device 102 monitors the operation of the emergency lighting circuit and is operably coupled thereto by a photocoupler, which includes optical fibre 112. Respective power suppliers are fed to the trigger devices by cabling entering the housing via the circular apertures 116.

Claims

Claims 1. A trigger device, actuated in response to a failure in the power supply to all or part of a normal lighting circuit, which device triggers an emergency lighting system, which emergency lighting system has at least one switch therein, and wherein the trigger device overrides said switch, such that, when the trigger device is actuated, the emergency lighting is illuminated regardless of the condition of the switch.
2. A trigger device according to claim 1, comprising a relay.
3. A trigger device according to claim 2, wherein the relay is operably connected to the normal lighting circuit and cncrgiscd thereby, and wherein failure of the power supply to all or part of the normal lighting circuit causes thc rclay to become dc-cncrgiscd which closes a contact in the emergency lighting circuit, by-passing the switch therein.
4. A trigger device according to any one of the preceding claims comprising a photocoupler.
5. A trigger device according to claim 4, wherein the normal lighting circuit comprises an LED, the light output of which is monitored by a photodiodc or other photodetector in the trigger device.
6. A trigger device according to claim 4 or 5, wherein the light source in the photocoupler is an infra red light source, preferably an infra red LED.
7. A trigger device according to any one of the preceding claims, further comprising an indicator which indicates if the emergency lighting system has been actuated.
8. A trigger device according to claim 7, wherein the indicator comprises an LED.
9. A trigger device according to any one of the preceding claims, comprising a housing which houses a relay and an indicator, and which comprises at least one conduit entry point.
10. A unit comprising two trigger devices, one of said trigger devices being in accordance with any one of the preceding claims, and the other said trigger device acting to by-pass a switch in a normal lighting circuit or sub-circuit in the event of a failure in the power supply to the emergency lighting circuit or sub-circuit.
11. A unit according to claim 10, wherein each trigger device is operably coupled to the other by a respective photocoupler.
12. A lighting system comprising the trigger device of any one of the preceding claims.
13. An emergency lighting system according to claim 12.
14. A lighting system, comprising at least one normal lighting circuit or sub-circuit having a switch therein, and at least one emergency lighting circuit or sub-circuit having a switch therein; a first relay responsive to a failure in the power supply to the normal lighting circuit and acting to by-pass or override the switch in the emergency lighting circuit or sub-circuit; and a second relay responsive to a failure in the power supply to the emergency lighting circuit and acting to by-pass or override the switch in the normal lighting circuit or sub-circuit.
15. A lighting system according to claim 14, comprising a trigger device according to any one of claims 1-9 which acts to by-pass a switch in the emergency lighting circuit or sub-circuit, and further comprising a substantially similar second trigger device which acts to by-pass a switch in the normal lighting circuit or sub-circuit.
16. A trigger device substantially as hereinbefore described and with reference to the accompanying drawings.
17. A lighting system, comprising a normal lighting circuit or sub-circuit and an emergency lighting circuit or sub-circuit, substantially as hereinbefore described and with reference to Figure 1 or Figure 3.
18. A method of controlling or operating a lighting circuit especially an emergency lighting circuit, thc method comprising thc step of installing in the circuit a trigger device in accordance with any one of claims 1-11.