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Power supply for all applications from the mains will be warranted. Nevertheless, failures of the mains may occur.
If by failure of the mains voltage human life or material assets are endangered, then an emergency lighting system may be installed.
Emergency lighting is an additional illumination being automatically switched on in case of failure or dimming of the general lighting. For this, additional investment in electrical devices, cables and installation materials will be required.
The power supply for minor emergency lighting systems is made by direct current originating from accumulators. In normal operation the accumulators are being charged by the mains via charging rectifiers.
For emergency current supply of industrial shops, agricultural breeding and hatching plants, protection rooms or operation theatres the capacity of accumulators is too low.
The emergency current in such instances will be supplied by emergency power generating sets with a Diesel engine. These have an almost unlimited application and may be suited to the required wattage and voltage.
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Emergency lighting systems may be fed by accumulators or emergency power generating sets. Accumulators are accommodated in battery rooms and supply direct current, standby generation sets mostly three-phase current. Emergency lighting systems are divided into panic lighting and special lighting! |
The panic lighting illuminates rooms and evacuation paths. In case of danger it will enable escape from the corresponding location without accident and danger. Its mean illuminance will be less than that of the general lighting. In average it will be 1 - 3% of the general lighting’s illuminance. Depending on the type of rooms, this is fixed in regulations. Examples for application of panic lighting are:
Meeting rooms, escape ways, stairways and doors in dimmed rooms of public buildings, out-patient departments, shopping centers, multi-storey dwelling houses, museums, restaurants, schools, production rooms.
Contrary to panic lighting, special lighting will render it possible to continue processes the interruption of which would endanger human life, domestic stock or important plants. The illuminance of special lighting may be up to 100% of the general lighting’s illuminance.
Application fields of special lighting are e.g.:
Operation theatres in hospitals, control stations in industrial plants, information centres in mail traffic and telecommunications.
The emergency lighting is switched on or prepared for operation by one actuation at the emergency lighting main distribution. In case of mains failure or decrease of the mains voltage below a value of 80% it will switch automatically if the standby circuit arrangement is employed.
In case of the emergency lighting’s permanent circuit arrangement same operates in parallel with the general lighting. Change-over from general to emergency lighting takes place automatically. The change-over is being indicated by optical or acoustic signals at an appropriate place, e.g. at the subdistributions of the emergency lighting system.
Fig. 6.1. Mode of action of a
permanent circuit arrangement
1 general lighting circuit, 2 emergency lighting circuit
Fig. 6.2. Actual operating diagram of
a standby circuit on failure of the mains
1 general lighting circuit, 2 emergency lighting circuit
Emergency power generating sets will be put into operation by an automatic starter after a short time delay. If the Diesel engine does not start after the first starting trial the starting procedure will be repeated until the Diesel set runs or is put out of commission after making a certain number of starting trials in vain. For this reason regular test runs, e.g. weekly ones, are to be performed with emergency power generating sets for keeping them always in operating condition.
After the mains voltage has returned, lighting will again be taken over by the general lighting system through repeated change-over. In this way accumulator systems will be prevented from discharging themselves until exhausted.
An example for emergency lighting dependent on the general lighting is shown in fig. 6.3.
Fig. 6.3. Dependent emergency
lighting
This type of emergency lighting will be installed in such rooms which are rarely entered by persons, but which must be lighted also in case of emergency. The particularity in this type of emergency lighting is the actuation of the general lighting and emergency lighting by one and the same switch.
When the general lighting is switched off, the emergency will not be put into operation either in case of mains failure. Only if after switching on the general lighting this illumination should fail, the emergency lighting will be switched on automatically. Depending on the degree of danger to human beings and material assets switching-on delays are maintained. This serves to avoid unnecessary switching-on of the emergency lighting in case of short-time failures of the mains or great variations in the voltage of the mains. Some switching-on time delays of emergency lighting systems are summarized in table 6.1.
Table 6.1. Turn-on delays in emergency lighting systems
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Turn-on delay |
Examples for application |
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0.5 seconds |
meeting rooms, cinemas, department stores, hotels, operation theatres, control rooms, pedestrian tunnels |
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30 seconds |
shelters, reception halls, staircases, normal ward units in hospitals, big garages, open plan offices |
For some emergency lighting systems there may be further special requirements. For instance, it holds that
- lamps for emergency lighting must not be operated via lighting dimmers,- the special lighting in operation theatres of medical institutions must also be switched on automatically if the lighting at the place of operation fails due to rupture of the incandescent lamps filament or other defects,
- in systems, for which a master switch is provided (a.o. in explosion-prone rooms) the emergency light is operated by a separate switch.
For installation of emergency lighting systems a lot of principles in designing of the emergency lighting system are to be considered. The designer will have to include these principles into his working documents for the erection staff. These are first of all
- the installation materials to be used,- the choice of the type of installation and the arrangement of the emergency system’s lighting fittings,
- the arrangement of the emergency lighting system’s circuits.
The distributions of the emergency lightings will be arranged according to fire sections. If the emergency lighting distribution in one fire section should fail due to fire, it will be warranted thereby that the emergency lighting continues to function in other fire sections.
For avoiding unauthorized interferences in emergency lighting distributions, those distributions must be locked. To make work easier when carrying out maintenance and repair work a general wiring diagram in all-pole representation is to be exhibited at the emergency lighting system’s main distribution. The installation plans of the emergency lighting system are to be permanently up-dated.
The general wiring diagram is to include the following information:
- description of the distribution in detail up to the last distribution fuse,
- current type and supply voltage,
- type and capacity of the emergency power plant,
- designation of the outgoing circuits,
- rated current of the fuses,
- number of lighting fittings,
- capacity of the individual circuits,
- cross sections and materials of the conductors,
- the protective measure applied against too high a contact voltage.
A number of demands are put to the installation of emergency lighting lamps mentioned in the following:
- Emergency lighting lamps may be accommodated together with general lighting lamps in one lighting fitting.- For being able to discern emergency lighting lamps from general lighting lamps the lamp bases of emergency lighting lamps will be painted red.
- As already described in section 6.1., the panic lighting is to warrant safe escape from dangerous areas. Max. 12 lamps may be connected to one circuit, loading the circuit up to 6 A. In that case a 10 A fuse will have to be used.
- The lamps of the panic lighting along the escape ways are alternately to be connected to two circuits. This will secure continued illumination of the escape ways on failure of one emergency lighting circuit.
- For panic lighting only lighting fittings of a max capacity of 60 W are to be installed. However, these lighting fittings are to be equipped with lamps of max. 40 W only.
- Adjacent to each emergency lighting fitting a pictogram is to be exhibited in a well visible place.
- The pictogram is to contain the following information:
· distribution,
· circuit,
· lamp’s capacity,
· number of the lighting fitting in the circuit.
- Within a system the lighting fittings are to be marked uniformly.- The emergency lighting fittings within one circuit are to be numbered in succession.
- For being able to discern junction boxes of the general lighting circuit from junction boxes of the emergency lighting circuit without doubt, the interior of the latter will be marked by green paint. It will not serve the purpose to mark the covers. After repair work they may be mixed up.
- Installing switches in circuits of the panic lighting is not permitted. In the most unfavourable case the emergency lighting may become ineffective on failure of the mains supply thereby!
- On emergency lighting systems selected protective measures against too high a contact voltage will have to be applied, since the emergency lighting system will have to continue to operate in case of failure. Such protective measures are the protective conductor system or protective insulation. Neutralization or protective earthing are unsuitable on the other hand. This is important insofar, as on failure of the mains the emergency lighting will be the only illumination still working.
In emergency lighting systems up to 250 V no protective measure against too high a contact voltage will be required!
Fig. 6.4. Marking of emergency
lighting fittings
1 designation of emergency lighting distribution, 2 number of circuit, 3 lamp wattage, 4 number of lighting fitting in the circuit, 5 bordering of pictogram (green)
For operating emergency lighting systems, rated voltages have been established. They may be taken from table 6.2.
Table 6.2. Nominal voltages of emergency power plants
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Nominal voltage |
Application |
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12 V |
In systems up to 200 W for consumer’s installations only |
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24 V |
For lamps in operation theatres only |
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60 V |
For industrial control, not for emergency power plants serving for emergency lighting only |
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110 V |
Power distribution systems or remote controlled stations |
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220 V |
Preferred voltage enabling a simple and economic construction of emergency lighting systems. Standard lighting fittings, switches, fuses, motors etc. can be used |
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380 V |
Application for special lighting only since consumer’s installations with great capacity are being operated |
The emergency lighting system will be installed in accordance with the installation type of the general lighting system. In industrial plants lines of the emergency lighting may be installed bunched together with other lines too. In all other emergency lighting systems the lines of the emergency lighting are to be installed in a distance of 50 mm minimum from all other lines.
In buildings like cinemas, theatres, shopping centres, exhibition halls and rooms, hotels, restaurants and shelters only with copper conductors having a cross section of min. 1.5 mm2 are permissible. This holds also for explosion-prone rooms which are generally to be installed in the damp-proof version.
Fig. 6.5. Separated general and
emergency lighting in a
corridor
Emergency lighting is an illumination to be installed at additional investment, turning automatically on in case of the general lighting’s failure or too high an undervoltage. Supply of emergency current may take place by batteries or emergency power generating sets.
Emergency lighting systems are classified into panic lighting and special lighting.
The emergency lighting system may be operated as standby circuit or as a permanent circuit. It will also be possible to operate the emergency lighting as an illumination dependent on the switching condition of the general lighting.
The lighting fittings of the emergency lighting are being equipped with lamps of max. 40 W capacity.
The lighting fittings in the emergency lighting circuit are to be marked. They will obtain a designating pictogram containing the distribution, number of circuit, capacity of lamps and number of lighting fittings in the circuit.
Switches are not to be installed in circuits of panic lighting. In emergency lighting systems protective measures against too high a contact voltage are required from a supply voltage of 250 V upwards only.
If protective measures against too high a contact voltage are to be applied, such protective measures are being chosen which will warrant further function of the emergency lighting also on occurrence of a fault to frame.
Circuits along escape routes are divided in such a way as to install the lamps of one circuit alternating with the lamps of the other circuit. Therefore, on failure of one emergency lighting circuit, the escape route will still be illuminated.
In industrial plants lines of the emergency lighting may be installed together with lines of other circuits.
In all other emergency lighting systems a distance of at least 50 mm between the emergency lighting’s lines and further line systems must be kept.
In public buildings, protection rooms and explosion-prone rooms copper will have to be exclusively used for conductor material.
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