14

Safety

 

14.1 General measures for safety

Electrical

Research has shown that voltages below 50 V a.c. do not generally cause problems. From 50 V up to 1000 V a.c. (which is termed Low Voltage), the problems will be in direct relationship to Ohms Law which states ‘the greater the voltage for a given resistance, the higher the current’. However, it must be realised this is an extremely simplistic view and the human body is quite complex but is generally considered mostly resistive. An electric shock results from the victim touching a part which is live or charged with electricity so that their body completes the electrical circuit to ground. At higher voltages, actual contact is not necessary because the current can jump appreciable distances. For a given current path through the human body, the danger to persons depends mainly on the magnitude and duration of the current flow. If recovery is not spontaneous or produced by prompt emergency treatment, the shock can prove to be fatal.

Muscular spasm may prevent the victim from letting go if they are touching a live part, the contracted chest muscles may prevent them from breathing and shouting for help and the pain and panic may cause sweating. With wet skin, the effects of the shock will be aggravated. The effect on the heart generally depends on the magnitude and duration of the shock and at what stage in the heart cycle the shock occurs. Generally, alternating currents will affect the heart to a greater extent than direct currents. At radio frequencies, burning is the main effect and fatal shock less likely.

In the United Kingdom about 50 people die each year, at work and in the home, from shocks from the normal 240 V domestic supply. In the majority of cases the victim received a shock between an exposed live part and earth. There are also a few accidents in the United Kingdom on lower voltage supplies in the range of 110/125 V and experience in countries where the supply system lies between 110 V and 120 V shows that electric shocks at these voltages can also be fatal.

Shock prevention

Electric shocks may be prevented by taking some of the following precautions, such as:

(a) using low voltages,

(b) insulating and/or enclosing live parts,

(c) preventing conducting parts, not normally live, from becoming live:

(i) by earthing and automatic disconnection,

(ii) by double insulation, and

(iii) by separating the supply from mains and earth (isolating transformer).

(d) selecting equipment suitable for the environment in which is to be used,

(e) using equipment as directed in the manufacturers’ instructions, and

(f) ensuring that the electrical equipment is tested and maintained.

Residual Current Devices

If someone receives an electric shock from a part which is live, the current flows to earth through the victim's body. RCDs can be obtained which are sensitive enough to detect this current and will trip the supply in a few milliseconds. However, it should be noted that the RCD does not prevent the person getting a shock nor does it limit the magnitude of the current, but it will limit the duration of the shock.

Most RCDs are designed for 50 Hz sinusoidal a.c. mains currents. Conventional RCDs designed for 50Hz supplies will probably not trip should an earth fault occur when used with dimmer circuits. Some manufacturers do make a much higher grade of RCD which can sense fault currents of around 30 mA at all dimmer settings above 50 V, however, it must be noted that the tripping time may vary as a result of the dimming.

Note: Never bypass any RCD if the equipment it is protecting causes it to trip – investigate why it has happened and take any necessary remedial measures.

Emergency systems

The IEE regulations requires that a means of interrupting the supply for the purpose of emergency switching shall be capable of cutting off the full load current of the relevant part of the installation. The regulations go on to state:

Where practical a device for emergency switching shall be manually operated directly interrupting the main circuit. A device such as a circuit breaker or a contactor operated by remote control shall open on de-energisation of the coil, or another technique of suitable reliability shall be employed.

The operating means (such as handle or push button) for a device for emergency switching shall be clearly identifiable and preferably coloured ‘red’. It shall be installed in a readily accessible position where the hazard might occur and where appropriate, further devices shall be provided where additional emergency switching may be needed.

The operating means of a device for emergency switching shall be of the latching type or capable of being restrained in the ‘OFF’ or ‘STOP’ position. The release of the emergency switching device shall not re-energise the equipment concerned.

The re-energising of the equipment has to be carried out by approved personnel, such as engineers or electricians, to ensure that the hazard that caused the ‘emergency’ has been dealt with correctly.

Fire extinguishers

Extinguishers come in various types:

1. water extinguishers,
2. foam extinguishers,
3. dry powder extinguishers,
4. carbon dioxide extinguishers, and
5. vaporising liquid extinguishers.

Ensure that the correct type of extinguishers are placed where they are immediately available and clearly marked to ensure that the wrong one is not used. It is essential for staff to be familiar with the colour codes of the various extinguishers and to know what it contains and how it works.

Fire lanes and evacuation procedures

Safety law is framed to preserve life rather than property and therefore the law demands a fire certificate which carries details of how to escape in the event of a fire. It also demands that the staff should be familiar with the means of escape and the escape routes, which must be clearly marked. In studio premises there will always be fairly well defined safety procedures issued by the management but when on location it is very easy to fall in the trap of putting bits of temporary scenery in the way so as to obscure possible safety routes and these should be carefully thought out prior to doing any work.

Working platforms

Scaffold platforms are a very convenient method of getting to high positions with relative safety. Having said that, the safety only comes about by following carefully all the instructions with regard to scaffolding, portable towers, etc. We are not so much concerned with permanent working scaffold platforms, but mobile platforms, which are used to gain access to a lighting grid to work with the electrical system and the luminaires. The height of a mobile scaffold tower must not be more than three times the base width, if used out of doors, or three and a half times, if used indoors. When considering the base width this must also include any outriggers which are used. The cardinal rules is that mobile scaffold platforms must not be moved whilst any person is on the platform and movement must be accomplished only by pushing or pulling at the base of the platform. A sobering thought is the statistic that about 1100 people each year suffer from accidents due to falling from scaffold platforms.

14.2 Luminaires and EN 60598-2-17 (BS4533)

The following suggestions and remarks regarding safety considerations in the design and operation of luminaires should be taken as a guide to help you through EN 60598-2-17 which is now harmonised across Europe (EEC and EFTA) and Canada accepts it as an alternative to CSA standards, however, the USA will only accept UL 1573 which is considerably different to the European standards.

The main basis of the following is EN 60598-2-17 with an overlay of good practice accumulated by the authors over many years of experience. However, it is up to the individual to determine his own interpretation of the standards because the authors cannot accept responsibility for their accuracy. It is also assumed that the reader already has a sound knowledge of good electrical practice.

A luminaire should be designed in such a way that in the event of a lamp exploding, fragments of glass or quartz 3mm in size should not escape directly in line, from a lamp, through a ventilator or other aperture. If the ventilation system is designed with a labyrinth or fitted with a mesh to prevent pieces of glass or quartz 3 mm in size coming out from a directly exploding lamp in such a way that the glass is caught within the labyrinth or by the mesh, this is accepted within the standard.

Open faced luminaires require either a safety glass with a minimum thickness of 3 mm or a safety mesh that will not permit pieces of glass or quartz 3mm in size to pass through it. Luminaires that have a single lens require a safety mesh in front of the lens of such a size as to prevent pieces of glass 25 mm passing through it, however luminaires with more than one lens do not require a mesh, but it is our opinion that it is good practice to fit one. Luminaires that have a safety glass require a safety mesh in front of it, of such a size as to prevent pieces of glass 12 mm passing through it. The glass and mesh must be captive in the luminaire. In the event of a safety glass or lens cracking, its mounting must retain the broken pieces in position. The mechanical heat test for the safety glass is carried out by placing the luminaire in the horizontal position and burning it until it reaches a stable temperature, then water at a temperature of 15°C is sprinkled onto it by hand. The unit is allowed to cool and reheated and the test is repeated three times; the glass can crack, but it must be retained in its position in the housing. Tests for halogen lamp shields require that they withstand an exploding lamp and to ensure that any hot fragments that do escape do not ignite a gauze placed under the luminaire.

The mechanical connection between the yoke and the luminaire must be locked against loosening. This is to prevent the pivots working loose, during operational use, by tilting the housing. Forms of locking may consist of either fitting a locknut or drilling and pinning the pivot shaft.

The yoke must have earth continuity to the housing if there is a risk of a single electrical fault.

The mechanical safety of the yoke requires a 10:1 safety factor on each leg of the yoke so that if one side of the yoke is disconnected from the housing the remaining leg provides a 10:1 safety factor. The test procedure is to hang the luminaire from its spigot and apply a test load to the luminaire. Since the safety factor is to 10:1, a weight of nine times the total weight of the luminaire (including all accessories) is added to the housing, making a total of 10 times the original weight. The yoke may deform under test, but it must not break. Discussions have taken place over a period of time to ascertain whether the safety factor could be reduced.

The size and type of spigot to be used can be determined from the following: Luminaires weighing up to 7.5 kg may use a 16 mm diameter spigot and it can be made of either steel or aluminium. Over 7.5 kg a 28.6 mm spigot is required and it must be manufactured from steel (aluminium is not permitted). A hybrid spigot has been developed which dimensionally suits the German DIN specification together with the British and USA standards.

A dedicated anchor point must be provided on the housing (unless it is intended for floor mounting or to be used as a hand held luminaire) whereby the safety bond can be passed over the primary means of suspension, through the yoke and terminated at the anchor point. In this way the housing will be arrested even if the yoke breaks. The test procedure is as follows. The unit will have all its accessories attached and lifted 300 mm and allowed to free fall until it is arrested by the safety bond. This procedure is repeated 30 times. During the test it is not permitted for any part of the luminaire or its accessories to become detached although they may become deformed.

Figure 14.1 Spigots

A German DIN specification exists for the size of receptacles for colour frames and barndoors. This is to ensure a good mechanical fit of component parts together with ease of interchange-ability with other manufacturers’ items of equipment. Although this is not a formal requirement it represents a very desirable feature.

If possible, luminaires should be designed to cater for the sizes quoted in these standards. The major manufacturers in Europe have already adopted these sizes.

Nominal size of colour frames – German DIN standard No. 15–560 part 38

The following dimensions (in millimetres) can be the diameter of a round colour frame or the size of a square frame: 120, 150, 160, 180, 210, 240, 270, 360, 390, 450, 480, 540.

The top latch which is normally provided for retaining the colour frame and barndoors must be self applying so that it does not rely on the operator to close it. In this way, the operator is obliged to hold the retaining clip out of the way whilst he withdraws the barndoor or colour frame. On letting go of the catch, it returns to its locked position.

PVC or other plastic cables should not be used on luminaires. This is because the cable will deform with the heat if it touches the side of the housing. The mains input cable must have a sleeve of insulation where it is clamped at the cable entry.

Any cable passing through a hole in sheet metal must be protected by a secondary sleeving to avoid mechanical damage to its insulation.

All electrical components such as switches, cables, terminal blocks, lampholders, etc. must be manufactured to the appropriate standards for the individual items concerned. Otherwise the luminaires could fail acceptance tests due to the use of unsatisfactory component parts.

The termination point of the incoming earth should be in view when the mains input terminals are exposed to enable an inspector to see that the earth is connected. The international earth symbol must be used adjacent to the incoming earth terminal. This must be punched into the metal or stuck onto it, so that it cannot be removed. The earth symbol must be a minimum of 5 mm high. Earthing washers are to be used to cut through the paint and ensure a good earth. The earthing screw is to be a minimum of 4 mm diameter with a machine cut thread, self tapping screws are not acceptable. The screw size will increase with electrical current requirements but cannot be reduced for mechanical strength reasons. The screw must be plated steel or manufactured from brass or copper.

All metal parts that can be touched on the outside of the luminaire, that could come into contact with a live part under a single fault condition, must be earthed. The lamp carriage must have a direct earth continuity wire, a scraping earth conducted along tracks is usually insufficient. Under no circumstances can push-on terminals be used for earth connections to luminaires that draw more than 3 A from the mains supply.

The terminal block should be designed so that it would allow one strand of wire to turn back from its connection by 8 mm and not touch adjacent terminals or metalwork in the luminaire. If the terminal block employed does not automatically perform this function, an insulating material must be placed under the block or used as a barrier between terminals so that isolation is achieved.

Warning labels required on the housing

The following recommended warnings are so numerous that it would require a larger housing just to display them on small luminaires. However, they are being quoted verbatim from the standards.

• Before opening disconnect all poles from the electrical supply. (The minimum height for the lettering is to be not less than 2 mm and 5 mm for graphical symbols.)
• The top of the unit must be indicated to prevent it being mounted upside down. (A broad arrow symbol may be used with the addition of the word ‘TOP’ or ‘OBEN’ in German. The minimum height of the arrow symbol is 5 mm.)
• Replace any cracked protective shield.
• To be serviced by qualified personnel.
• State the distance from the lens to a flammable surface. (When the temperature in the centre of the beam is ≤90°C with an ambient temperature of 25°C. Use the international symbol.)
• The burning angle must be stated x° above horizontal, y° below horizontal.
• Observe the lamp manufacturers recommendations.
• Maximum voltage with an a.c. or d.c. symbol.
• The maximum current.
• The maximum wattage. (State if there is more than one lamp used i.e. 4 × 1250 W.)
• The frequency of the supply (which may be in the instruction leaflet).
• The maximum case temperature in degrees Celsius. (This is defined as the hottest part of the housing that could be touched from the outside, also the maximum ambient temperature (Ta) if it is not 25°C.)
• The weight, complete with lamp and all accessories.
• The manufacturers’ name and type number. (The label must have permanent print and must be attached to the luminaire with rivets or stuck so that it cannot be removed.)

Safety instruction sheet

This must be provided with every luminaire when it is sold. The sheet must describe all the hazards involved with lamps and luminaires (see Operating & Safety Instructions).

The following should also be noted:

• Ambient temperature All luminaires should be designed to work in a maximum ambient temperature of 45°C (good practice but not a standard).

• Fuses The value of an integral fuse must be stated adjacent to the fuseholder, so that it is apparent to the operator when changing a fuse what value it should be.

• Luminaire data sheet This must be enclosed with each luminaire and include the following:

–The same information that appears on the warning labels.

–The fixing instructions of how the unit should be mounted or suspended.

–A description and location of the safety bond anchor point and how to correctly attach the safety bond.

• In addition, a description and reference numbers for the following items:

–Safety glass

–Wire guard

–Lens

–Safety bond

–A list of all lamps that can be used in the luminaire with details of their voltage, wattage, life, colour temperature and any other parameters that are relevant.

–A list of all accessories

–Recommended stands

–Spares.

Note: It is not a standard requirement to provide spares information, because the sheet will be particular to each unit. It is however, a good opportunity for the manufacturer to identify the spares at this time.

Additional requirements for discharge source

•Luminaires These require the same standards as the tungsten halogen units, plus the following:

– UV Protection Where a luminaire is not fitted with a glass lens it is recommended that a safety glass is provided to absorb the UV radiation from the lamp. The glass should have a minimum thickness of 3 mm to provide adequate mechanical strength. However, with higher wattage luminaires, an increased thickness of glass will be required to give added strength.

– UV Radiation It is prudent for a manufacturer to have an independent test certificate from a test house such as the National Physical Laboratory to determine that luminaires do not exceed any dangerous UV radiation levels or to conduct the UV tests themselves and ‘self certify’ to the appropriate standards.

• Warning on housing For UV protection, the safety glass must remain in position and be replaced if it is cracked, broken or has deep scratches.

• Door opening The lens door may be screwed closed, in which case it would not require a safety switch. In the event that the door can be opened without a tool, then a double pole mains isolation switch can be used (good practice but not a standard) which must be activated by the glass of the lens so that the unit will not work if the lens is removed or the door is open. The activator must be designed so that it cannot be operated by hand, i.e. enclosed in a tube with a push rod to prevent the operator holding the switch closed and operating the unit. Some manufacturers use a trip relay that does not re-activate until it is manually reset. The same safety requirements apply to open fronted discharge luminaires that are fitted with a safety glass.

• The following warning is required: ‘Do not open for “x” seconds after switching off’.

Note: This is due to the hot lamps having high internal pressures and seeks to avoid explosions caused by cold air blowing on the lamp. This instruction is only required on luminaires declared by the manufacturer ‘a danger when hot’, particularly xenon lamps.

Operating and safety instructions: Lamps and luminaires

Manufacturers are required to provide the following information for the safe operation of lumi-naires and their associated lamps in the entertainment industry.

It is in the interests of every person purchasing or operating luminaires to read the following typical instructions, because the manufacturer is making you aware of the possible safety problems. This will prevent you being in the unenviable position, after an accident, of the manufacturer saying ‘I told you so!’

1 Luminaires should be marked with the maximum operating current. Observe the following colour code (Europe).

Brown wire –live

Blue wire –neutral

Green/yellow wire –earth

2 When connecting the luminaire to the mains supply, ensure that it is effectively earthed, that the mains supply is at the rated voltage and that the correct polarity is observed.

3 Each circuit must be protected by rapid acting, high rupturing capacity fuse or miniature circuit breaker of suitable voltage and current rating.

4 Lamp replacement must only be carried out after the luminaire has been disconnected from the electricity supply. Allow sufficient time for the lamp to cool before removing it from the equipment. (Cooling could take as long as five minutes.)

5 Only use lamps of the recommended type and observe the maximum wattage limitation marked on the luminaire. Observe the lamp manufacturers’ recommendations relating to lamp type.

6 Insertion of the lamp into the lampholder by holding the envelope may cause mechanical breakage of the lamp and/or seal. For safety, install by holding the lamp cap or protective sleeve and use eye protection where appropriate.

7 Do not handle the quartz envelope with bare hands. Oil or grease from the skin may contaminate the surface of the envelope and in operation reduce performance and cause premature failure. If the quartz is accidentally handled, clean it before operation with a cloth moistened with alcohol or methylated spirit.

8 In certain circumstances, items made from quartz or glass may shatter. Prevent water droplets splashing onto a hot lamp as they may cause the envelope to break.

9 A suitable safety mesh or glass must be fitted to protect persons and property in the event of a lamp shattering –this is most important when lamps are used in open fronted luminaires. If the safety glass or lens should become damaged with deep scratches or chipped edges, they must be replaced.

10 The lamp shall be changed if it has become damaged or thermally deformed.

11 At the end of life, lamps should be broken in a suitable robust container or wrapped to retain quartz fragments. The gas filling has a slight toxic content and large quantities of lamps should only be broken in a well ventilated area.

12 Direct exposure to discharge and high intensity tungsten halogen lamps can cause UV irritation to the skin and eyes. The use of glass or other UV filters is advised if the lamp is used in close proximity or for a prolonged period. When reflector fittings are used to concentrate the light in open fronted luminaires, the safe exposure period will be reduced. Appropriate screening of people and surroundings must be provided.

13 The luminaire must be mounted on a firm support or stand and positioned at a safe distance from any flammable material, e.g. curtains, background paper or scenery.

14 A high amount of radiant heat is produced and high surface temperatures are developed. Avoid operation in close proximity to human skin, as burns could result.

15 Avoid improper operation of the lamp e.g. over voltage, or at burning angles not designed for the lamp type.

16 Luminaires must not be operated in explosive or flammable atmospheres or other hazardous areas.

17 All luminaires that are suspended must be fitted with a secondary independent means of support i.e. a chain or bond. Removable accessories must be retained to prevent them falling if they become dislodged.

18 A dedicated anchor point should be provided on the housing so that the safety bond can be passed around a firm support through the yoke and terminated at the anchor point on the housing.

19 The top of the unit has been indicated to prevent it being mounted upside down.

20 Special care must be taken with portable luminaires and hand held lamps. When demounting the luminaires, allow them to completely cool before standing them on a flammable surface or placing them in a carrying case.

21 For replacement parts, refer to the manufacturers’ parts list for the recommended type of safety glass, wire guard, safety suspension bond and any relevant accessories.

22 Service and repairs must only be carried out by a qualified person.

14.3 The Supply of Machinery (Safety) Regulations

For any person engaged in the lighting industry who is involved with luminaires and grid systems, these regulations have to be fully understood as they are not just recommendations but Statutory Instruments where failure to comply could lead to imprisonment and/or a heavy fine. It is also important to fully understand the implications of the Regulations for the Safe Use of Lifting Equipment (LOLER) and the Safe Use of Work Equipment (PUWER) issued by the Health and Safety Commission.

It is obviously impossible in this publication to cover the documents completely but the following is given as a brief guide. It is strongly recommended that the full regulations are obtained and studied in full.

Definition of ‘responsible person’

(a) the manufacturer of the machinery

(b) the manufacturer's authorised representative in the Community

(c) the person who first supplies the relevant machinery in the Community

Definition of Machinery

(a) an assembly of linked parts or components, at least one of which moves, including, without prejudice to the generality of the foregoing, the appropriate actuators, control and power circuits, joined together for a specific application, in particular for the processing, treatment, moving or packaging of a material;

(b) an assembly of machines, that is to say, an assembly of items of machinery as referred to in (a) above which, in order to achieve the same end, are arranged and controlled so that they function as an integral whole notwithstanding that the items of machinery may themselves be relevant machinery and accordingly severally required to comply with these Regulations; or

(c) interchangeable equipment modifying the function of a machine which is supplied for the purpose of being assembled with an item of machinery as referred to in (a) above or with a series of different items of machinery or with a tractor by the operator himself save for any such equipment which is a spare part or tool.

There are exclusions regarding certain types of machinery and the Regulations should be consulted with regard to these.

General requirements

No person shall supply relevant machinery or safety component unless the requirements of regulation 12 below are complied with in relation thereto.

Where a person –

(a) being the manufacturer of relevant machinery or relevant safety component, himself put that relevant machinery or safety component into service in the course of a business; or

(b) having imported relevant machinery or safety component from a country or territory outside the Community, himself puts that relevant machinery or safety component into service in the course of a business.

Requirements for the supply of machinery

12 The requirements of this regulation are that:

(a) the relevant machinery satisfies the relevant essential health and safety requirements;

(b) the appropriate conformity assessment procedure in respect of the relevant machinery has been carried out;

(c) the responsible person, at his election, has issued either –

(i) an EC declaration of conformity, or;

(ii) a declaration of incorporation;

(d) the CE mark has been properly affixed by the responsible person;

(e) the relevant machinery is in fact safe.

Machinery manufactured for European standards

The responsible person must:

(a) draw up and forward to an approved body a technical file;

(b) submit the technical file for verification that the standards have been correctly applied; and request that a certificate of adequacy is issued; or

(c) submit the technical file together with an example of the relevant machinery for EC type examination.

The ‘Technical File’ must include the following:

(a) An overall drawing of the machinery and control circuits

(b) Fully detailed drawings together with calculations, test results and any other data that may be required to check the conformity of the machinery with the health and safety requirements

(c) A description of methods adopted to eliminate hazards presented by the machinery

(d) A copy of the instructions for the machinery

(e) For series manufacture, the internal measures that will be implemented to ensure that all the items of machinery are in conformity with the provisions of the Machinery Directive

CE marking

For the purposes of these Regulations, the CE marking shall not be regarded as properly affixed to relevant machinery unless:

(a) that machinery –

(i) satisfies the relevant health and safety requirements; and

(ii) is safe; and

(b) the responsible person who affixes the CE marking to the relevant machinery –

(i) has carried out the appropriate conformity assessment procedure and issued an EC declaration of conformity in respect thereof;

(ii) affixes the said marking in a distinct, visible, legible and indelible manner; and

(iii) in the case of relevant machinery which is the subject of Community Directives other than the Machinery Directive, which also provide for the affixing of the CE marking, has complied with the requirements of those other Directives in respect of that machinery;

(c) No markings which

(i) are likely to deceive any person as regards the meaning and form of the CE marking; or

(ii) reduce the visibility of legibility of the CE marking shall be fixed to relevant machinery.

Modifications

Where the responsible person complies with one of the conformity assessment procedures he must inform the approved body of any modifications, even of a minor nature which he or, where the responsible person is not the manufacturer, the manufacturer has made or plans to make to the relevant machinery to which the technical file relates.

14.4 The IEE Regulations in practice

In any installation that a lighting consultant is concerned with, the electrical engineer appointed will in the main ensure that the current regulations are adopted and enforced to ensure that the system is built to any required standards. There are however, some aspects of the regulations which have to be borne in mind by the lighting consultant as well. The first of these is the selection of the equipment that meets the requirements of the permanently installed lighting system such as the dimmer racks. It is obviously no good having a piece of equipment that has a reasonable metal shell around it but leaving it possible to poke your finger through a ventilation louvre enabling you to touch a live terminal or a busbar.

There are several aspects to the safety of equipment such as this. Some of these items may seem very obvious but it's very useful to ensure that equipment meets some of the basic parameters. Any item of equipment selected must meet the requirements of the voltages present in the installation, together with the normal current consumption and additionally has to perform satisfactorily and not create any danger by the abnormal current flow during fault conditions.

IP ratings

In the case of dimmer systems, it's obvious that we have to be aware of the voltage and frequency of the mains used. Dimmer racks are defined as ‘factory built assemblies’ and the rules for these must be complied with. There are various degrees of protection required in a dimmer rack and without going into all the details, the first of these that we are concerned with is a degree of protection to IP2X. This means that the rack is protected against the entry of solid objects greater than 12 mm across and is defined as a ‘finger’ or a similar object not exceeding 80 mm in length. This can be checked by using a ‘standard test finger’. This degree of protection is required on all vertical surfaces of a dimmer rack. On the horizontal top surface however, an even greater protection is required and this is IP4X, where the top surface must be protected against the entry of solid objects greater than 1 mm. The definition refers to wire or strips of metal in thickness greater than 1 mm and solid objects exceeding 1 mm in diameter. This requirement is to protect against the dropping of small screwdrivers through slots on the top of a rack or strands of copper wire being used for the installation penetrating the slots, thus ‘shorting out’ equipment within the rack, possibly causing an electrical explosion.

IP ratings
First number	Second number
Protection against solid objects	Protection against liquids
0 No protection	0 No protection
1 Protected against solid objects over 50 mm e.g. accidental touch by hands	1 Protected against vertically falling drops of water
2 Protected against solid objects over 12 mm e.g. fingers	2 Protected against direct sprays of water up to 15° from the vertical
3 Protected against solid objects over 2.5 mm (tools and wires)	3 Protected against sprays 60° from the vertical
4 Protected against solid objects over 1 mm (tools + small wires)	4 Protected against water sprayed from all directions –limited ingress permitted
5 Protected against dust –limited ingress (no harmful deposit) permitted	5 Protected against low pressure jets of water from all directions
6 Totally protected against dust	6 Protected against strong jets of water e.g. for use on ships’ decks –limited ingress permitted
	7 Protected against the effects of immersion between 150 mm and 1 m
	8 Protected against long periods of immersion under pressure
For example, IP31 –protected against solid objects over 2.5 mm and protected against vertically falling drops of water.

The IEE regulations state that ‘where an opening larger than that permitted for IP2X or IPXXB is necessary to allow the replacement of parts’ two requirements will apply:

suitable precautions shall be taken to prevent persons from touching a live part unintentionally

and

it shall be established as far as practicable, that a person will be aware that a live part can be touched through the opening and should not be touched.

It is this particular requirement that makes the use of ‘plug in’ dimmers particularly onerous. When a ‘plug in’ dimmer is removed from a rack, quite a large space is left and terminals at the rear of the dimmer are exposed. Most dimmer racks these days have dimmers that are totally enclosed with terminals that are either very difficult to reach from the front surface of a dimmer rack or meet an IP2Xrequirement.

One of the most important regulations that concerns us with dimmer racks, is the one that states:

where it is necessary to remove a barrier or open an enclosure, or to remove a part of an enclosure, one or more of the following requirements shall be satisfied:

(i)    the removal or opening shall be possible only by use of a key or tool.

(ii)   the removal or opening shall be possible only after disconnection of the supply to the live part against which the barrier or enclosure affords protection, restoration of the supply being possible only after replacement or reclosure of the barrier or enclosure.

(iii)  an intermediate barrier shall be provided to prevent contact with a live part, such a barrier affording a degree of protection of at least IP2X or IPXXB and removable only by the use of a tool.

Item (i) is generally met on dimmer racks by a front door being fitted which is usually locked with a key, and by the fact that any rear access requires screwdrivers or special tools to remove screws or nuts. Item (ii) is met by an automatic disconnection of a supply, probably realised by having a microswitch operating a contactor for example, but this is not usually used in our installation systems although a micro switch on the lens door of a discharge luminaire is somewhat similar in operation. An example of an intermediate barrier such as quoted in (iii), would be a perspex cover such as that provided to enclose the terminals on a transformer or across terminals at the input of the rack.

Each of the pieces of equipment that we wish to install will have to have a label or other suitable means of identification to indicate what the purpose of each item is. There will be wiring going to and from any apparatus installed and this must ensure that colour codes for identification of cables meet the requirements of the country where the system is to be used. It is essential that correct colour codes are maintained so there are no misunderstandings as to their purpose.

In a lighting system we have to make many electrical connections and there are strict rules with regard to these. The most obvious one is the fact that the terminals should be large enough to make a good connection with the type of cable in use. Thus the means of connection has to take into account the following:

(i)     the material of the conductor and its insulation

(ii)    the number and shape of the wires forming the conductor

(iii)   the cross sectional area of the conductor

(iv)   the number of conductors to be connected together

(v)   the temperature attained by the terminals in normal service such that the effectiveness of the insulation of the conductors connected to them is not impaired

(vi)  where a soldered connection is used the design shall take account of creep, mechanical stress and temperature rise under fault current conditions

(vii) the provision of adequate locking arrangements in situations subject to vibration or thermal cycling.

Items (i), (ii), (iii) and (iv) cover the size of terminals including the provision of two or more parallel connections; Item (v) covers for high temperature switches where deterioration of the insulation will cause problems in practice; Item (vi) prevents the melting and breaking of soldered connections which could lead to wires floating about in cabinets; Item (vii) seeks to prevent terminals being loose either by the extremes of being cold and hot or by vibration which again could lead to wires floating about.

When using armoured cables for the input circuits to dimmer racks, there are strict rules regarding the type of cable used. One of the most important is that single core cables armoured with steel wire or tape should not be used, thus preventing any eddy currents being induced in the armour system. At the input to the dimmer rack, which is usually constructed from steel, an arrangement has to be made so that the individual conductors are not surrounded by a ferrous material thus preventing eddy (induced) currents. It's fairly obvious that any system using electrical conductors should provide a method of self cancellation to prevent harmful electromagnetic fields.

Conductors of a.c. circuits installed in ferromagnetic enclosures shall be arranged so that the conductors of all phases and the neutral conductor (if any) and the appropriate protective conductor of each circuit are contained in the same enclosure.

Every cable has to have adequate strength and be installed so that it can withstand any electromechanical forces caused by high fault currents or any other current that may occur in service. The same principle is applied to any busbar systems within dimmer racks.

As well as having regard for the regulations when we take the cables from the dimmer room to the production area and this has already been discussed but another point to be borne in mind is that any outlets either at the bottom of bars, along bars, attached to monopoles or pantographs, are all governed by regulations to ensure electrical safety is maintained.

An important element of the installation is the ambient temperatures that the racks and wiring can be subjected to, and there are rules regarding the limits and these have to be kept. The type of fusing, or protection afforded by mcbs, has to be carefully integrated with the size of cables and the loads that they are handling, although in practice the use of say a 20 A fuse on a 240 V 5 kW dimmer circuit will more than adequately protect the wiring installed which will invariably be generous in size to prevent voltage drop.

Another important element covered by regulations that we would be most concerned with is the mechanical strength of the equipment. We have to be aware of areas of high humidity, which although not usually a problem in the United Kingdom can be a problem with equipment in other countries. Much of the equipment used for entertainment will be subject to vibration, and this is another area which is governed by modern regulations.

If we could ensure a balanced distribution through our three-phase network, we wouldn't have to worry too much about the neutral conductor and it could be of a reasonable size in relation to the phase conductors. However, in many of our installations, we will have out of balance three-phase systems, therefore the neutral conductor must always have a cross sectional area appropriate to the expected value of the neutral current. In general this means the neutral conductor and the three-phase conductors are of similar size.

We are obviously concerned with the spread of fire within the systems we install, and another regulation states:

where a wiring system passes through elements of building construction, such as floors, walls, roofs, ceilings, partitions or cavity barriers, the openings remaining after passage of the wiring system shall be sealed according to the degree of fire resistance required of the element concerned (if any).

In addition

where a wiring system such as conduit, cable ducting, cable trunking, busbar or busbar trunking penetrates elements of building construction having specified fire resistance it shall be internally sealed so as to maintain the degree of fire resistance of the respective element as well as being externally sealed to maintain the required fire resistance.

The two regulations quoted cover for the instances when we go from one area to another and thus create holes in the structure. The first covers for unenclosed wiring systems where it may be just cables going from one area to another. The second regulation quoted covers for the fact that we might have trunking going through a wall and the trunking itself is sealed to the wall surround but unfortunately the internal part of the trunking allows fire to move from one area to another and this, of course, would be just as dangerous.

Additionally the regulation that covers all of the above states:

each sealing arrangement used in accordance with the regulations shall comply with the following requirements:

(i)    It should be compatible with the material of the wiring system with which it is in contact.

(ii)   It shall permit thermal movement of the wiring system without reduction of the sealing quality.

(iii)  It shall be removable without damage to existing cable where space permits future extension to be made.

(iv)   It shall resist relevant external influences to the same degree as the wiring system with which it is used.

and that

Each sealing arrangement shall be visually inspected at an appropriate time during erection to verify that it conforms to the manufacturers’ erection instructions and the details shall be recorded.

Regulation (i) above seeks to prevent harmful chemical reactions between the wiring system itself and any materials used for fireproofing, (ii) is fairly obvious that it would be no good having fireproofing that with gradual movement allowed gaps to appear. Unfortunately fire doesn't need too much of a gap to go from one area to another, (iii) covers for the situation where it would be quite easy to spray, for instance, around cables with some foam which would be fire retardant but unfortunately, if you then needed to do anything with the cables, it would be physically impossible because they'd all be glued together, and (iv) prevents the use of materials which would be less robust than the cables themselves.

Thus we have to be careful with the methods used for fire prevention because by covering for this eventuality it may make life difficult when expansion of a system is required.

During an installation temporary sealing arrangements have to be provided as appropriate and when any work is done, any sealing that has been disturbed has to be re-instated as soon as possible.

In lighting systems we have the normal mains supply cable going to the luminaires, in addition we will have low voltage multi-core cables or smaller digital signal cables provided for the control systems. This type of situation is covered by the regulations which state that we are not allowed to mix cables with various voltages present unless the insulation of all of the cables used is insulated for the highest voltage present in any of the cables or, alternative methods are adopted.

(i)    Each conductor in a multi-core cable is insulated for the highest voltage present in the cable, or is enclosed within an earthed metallic screen of a current carrying capacity equivalent to that of the largest conductor enclosed within the screen,

or

(ii)   the cables are insulated for their respective system voltage and installed in a separate compartment of a cable ducting or cable trunking system, or have an earthed metallic covering.

It is obviously extremely dangerous to pick up a conductor where we expect to find safe low voltage and in fact find mains, and the above regulations seek to prevent this happening.

The two methods are either to have good insulation of the systems so voltages can't travel from one cable to another, or conductors that are surrounded by an earthed shield where any harmful voltage will be conveyed safely away.

In practice, we generally run the mains feeds around the building separately from the control feeds, the only time where they may come into close proximity is perhaps on monopoles, pantographs or motorised barrel units where technical cables for the sound and vision system are installed in addition to the lighting circuits.

In places of entertainment and for those concerned with the production of entertainment we have a multiplicity of plugs and sockets used. These may be the normal 13 A supplies for domestic use, special sockets concerned with lighting outlets and there will invariably be provision for three-phase supplies for portable machinery. We have to be extremely careful that we don't intermix any of these socket outlets or plugs so that people are not placed in danger or machines receive voltages for which they are not designed. The main requirement for plugs and socket outlets is as follows:

(i)    It shall not be possible for any pin of a plug to make contact with any live contact of its associated socket outlet while any other pin of the plug is completely exposed.

(ii)   It shall not be possible for any pin of a plug to make contact with any live contact of any socket outlet within the same installation other than the type of socket outlet for which the plug is designed.

(iii)  Every plug and socket outlet shall be of the non-reversible type with provision for the connection of a protective conductor.

Finally but certainly not least, is the provision of devices for emergency switching. The regulations require that a means of interrupting the supply for the purpose of emergency switching shall be capable of cutting off the full load current of the relevant part of the installation.

means for emergency switching shall consist of:

(i)    A single switching device directly cutting off the incoming supply, or

(ii)   A combination of several items of equipment operated by a single action and resulting in the removal of the hazard by cutting off the appropriate supply; emergency stopping may include the retention of supply electric braking facilities.

The regulations go on to state:

where practical a device for emergency switching shall be manually operated directly interrupting the main circuit. A device such as a circuit breaker or a contactor operated by remote control shall open on de-energisation of the coil, or another technique of suitable reliability shall be employed.

The operating means (such as handle or push button) for a device for emergency switching shall be clearly identifiable and preferably coloured ‘red’. It shall be installed in a readily accessible position where the hazard might occur and where appropriate, further devices shall be provided where additional emergency switching may be needed.

The operating means of a device for emergency switching shall be of the latching type or capable of being restrained in the ‘OFF’ or ‘STOP’ position. The release of the emergency switching device shall not re-energise the equipment concerned.

Although it is possible, in a further qualified part of the regulations, to allow an automatic reset under specified conditions, we in the entertainment industry are mainly concerned with the fact that nearly all of the operatives involved with a production could de-energise the system by operating the emergency switching. The re-energising of the equipment has to be carried out by approved personnel, such as engineers or electricians concerned, to ensure that the hazard that caused the ‘emergency’ has been dealt with correctly.

14.5 Electricity at Work Regulations in practice

The Regulations are mandatory, and are enforceable by law. The intention of the Regulations is to require precaution to be taken against the risk of death or personal injury from electricity in the place of work. Whilst the Regulations cover all electrical supplies and equipment, we will restrict our coverage to portable items that can be plugged into the mains via a plug and socket. These are obviously the most vulnerable to damage and are by their description the most likely item to be handled.

The Regulations cover every portable item to be found on the premises from luminaires to kettles, from typewriters to electric drills, in fact every item fitted with a plug must be included. The wiring of the premises and permanently connected machinery and apparatus are also included, but are not being considered by us at this time. The following notes are our interpretation of some of the requirements and should not be taken as a statement of the Regulations.

The statement that all portable electrical equipment must be as far as possible electrically safe is the starting point and it really means all and every item found on the premises and does not take into account who owns it. It can be a personal radio or a rented item, it still comes under the umbrella of the Regulations. When the area safety officer calls to inspect your premises, he will ask to see the duty holder. This is any responsible person that has been nominated to keep a register of every item of electrical equipment; he will ask the duty holder for the register and expect to find certain information in it. Identify the item, the date that it was tested, the result of the test, which can only be pass or fail, action taken and the date of the next test. The period between tests can only be established by the duty holder and the operator and will depend on how often the appliance is used and the history of damage that can be sustained by the environment in which it is used. Examples could be: an electric drill being used every day, all day on a production line, in which case three-monthly tests could be deemed appropriate; equipment in frequent use and subject to transit damage could be every six months, and so on. Until a history is built up in the register no definite period can be established.

Most portable items in entertainment that are not out on rental or travelling shows, and are normally used in the same premises, could be considered to have light duty and might be considered for an annual test. Portable electrical equipment can be divided into three groups:

• Class I Requiring an earth connection to any metal part that could become live in a fault condition.
• Class II A totally insulated electrical device where no part can become live in the event of a fault condition. This type of equipment does not require an earth wire.
• Class III Low voltage equipment that has special regulations.

A typical test for Class I equipment could be a visual inspection of the cable, the plug top, the cord grip at the plug and the cord grip at the appliance and an inspection inside the plug top to determine that it is correctly wired. Any damage to these items would fail the test and the equipment would not be allowed to continue to the electrical test. The reported accidents show that 80% of electrical accidents could have been avoided by a visual inspection. If the equipment passes the visual test it will be tested electrically for earth continuity from the plug top to the frame of the appliance and the earth resistance will be recorded and must be within the Regulations’ requirements. The insulation is tested from the plug top through the earth and live conductors and must have the required resistance. Finally, a run test is conducted to determine that the equipment conforms to the Regulations in its working state. Other tests are available on some products, a high voltage test might be carried out, normally 1500 V for Class I equipment and 3000 V for Class II, but these are made at the discretion of the electrical engineer conducting the tests.

14.6 Safety checklists and inspections

Much of the equipment used in the entertainment industry is well built and a superficial examination usually would lead one to expect the equipment would work safely for long periods of time with little or nothing going wrong. However, life is not as easy as that and modern legislation requires that moving equipment such as monopoles, winches, pantographs and devices used to suspend equipment over stage areas, studio areas and particularly above audiences is regularly inspected to see no danger is present. Many items concerned with mechanical safety can be verified by visual inspection, but this is not necessarily the case with electrical equipment when the fault may lie in a piece of copper somewhere. All items of electrical equipment also have to undergo routine checks to ensure that they are not posing any hazard.

To ensure that the necessary inspections are carried out correctly, all items of equipment must be coded and numbered and a register of equipment and tests kept on the premises. When items of equipment are purchased, they must have a CE mark (including year of construction), name and address of manufacturer, designation of series or type, an identification number of the particular piece of equipment. All equipment must be accompanied by clear operating and maintenance instructions.

Routine testing (which covers many of the points of the EEC Machinery Directive) of lifting equipment has to provide checks against the following items:

1. Undue wear of any part.
2. The wire ropes used for lifting must be inspected to ensure they haven't been damaged in any way and that no strands are broken.
3. The points where wire ropes are made off to provide permanent anchor points to other parts of the structure are to be inspected to ensure they are not loose or damaged.
4. All parts of the motor assembly are firmly in place and not loose in any way.
5. All pulleys or scroll drums to be examined for undue signs of wear which would indicate possible problems with the winding of the wire ropes.
6. All diverter pulleys to be examined for signs of wear and the fact that they are free to rotate.
7. A visual inspection of the top and bottom limit system in addition to visual inspection of overload and slack wire system.
8. To apply load tests to ensure that the slack wire and overload system works correctly. In addition to traverse the unit from top to bottom to see that limit switches are operating correctly.
9. Ensure that all warning labels are present and all indicators are fully functional.
10. Ensure that the equipment is capable of being controlled from all nominated control positions, e.g. studio floor level or on the local controls at grid level.
11. All covers and guards are correctly positioned and fastened securely.

Electrical safety is covered, in the main, in the United Kingdom, by the Electricity at Work Regulations which would cover for items of equipment that are portable and in addition the latest edition of the IEE regulations pertaining to the installation of the electrical system in the building. As well as the regular checks for electrical safety under the Electricity at Work Regulations, it is also wise to check for the mechanical safety of any luminaire or other type of light source used in the entertainment industry. Most premises will, on a fairly regular basis, do some maintenance to ensure the equipment works correctly, and this obviously makes life much easier from the point of view of the electricians concerned with lighting equipment. At the time these checks for maintenance are made, it is very easy to go over some of the mechanical items to ensure that they are not damaged in any way. Testing the pan and tilt mechanism for movement and slackness might reveal problems in this area. A visual examination of a yoke for instance, would not necessarily indicate problems with the devices used to lock the yoke to the body of the luminaire. A fairly careful examination of the bodywork of any luminaire would reveal any loose parts that may be suspect and therefore in danger of falling off.

Therefore a suggested checklist for luminaires is as follows:

1. Is the yoke functioning correctly and are the pan and tilt controls, if fitted, working satisfactorily.
2. Do all locking knobs fitted correctly tighten the moving part so it can be held in the position as set.
3. Examine the spud fitted to see that it hasn't become loose from the yoke assembly.
4. Check internally for any loose parts, particularly with regard to reflectors and lamp holder assemblies.
5. Check internal wiring for any signs of wear.
6. Check all switches fitted to see that mechanically they function correctly. Although they may appear to be satisfactory from an electrical standpoint, it might be that they are not mechanically perfect. This generally avoids any arcing problems within switches, caused by springs or levers being slack.
7. Check to see that all accessories attached to the luminaire are not loose, i.e. barndoors, colour frames, etc.
8. Check all louvres which allow air flow through the luminaire for signs of damage and ensure they are working correctly to make certain that the luminaire does not get over hot. This can usually be ascertained by signs of burning on the bodywork.
9. Check to see that barndoors function correctly and are sufficiently tight to do the job needed.
10. 10 If a base or feet are provided to stand a luminaire on, ensure they haven't become damaged in any way.
11. Luminaire leads and plugs should be tested at least once a year but it's quite useful to inspect them on a more frequent basis to see that no arcing is occurring on any of the pins, which would also indicate deterioration in any of the permanent sockets fitted in the system.
12. A useful point is to listen out whilst in operation for any nasty frying noises, which would indicate lamp contacts arcing and thus a lampholder would need replacing.

Although all the foregoing seems a bit of a chore and probably most people generally say, ‘it's not my responsibility’, if most of the tests listed above are carried out, it ensures a safe working environment in which it is easier to work because all the equipment is functioning correctly.