Procedures for work on Fixed Electrical Installations Toolbox Talk 1: Electrical Isolations

Main Points: Hazards and risks associated with work on electrical systems Procedures for carrying out electrical isolations Procedure for padlocking off and posting of caution notices on isolations

On average, 20 people are killed in the UK every year by electrical accidents whilst at work - most of these accidents are preventable. The Electricity at Work Regulations 1989 requires precautions to be taken against the risk of death or personal injury from electricity in work activities. The purpose of these procedures is to put in place a system of control measures to prevent injury to University Staff and contractors from the hazards and risks associated with work on electrical systems at the University.

HAZARDS AND RISKS ASSOCIATED WITH WORK ON ELECTRICAL SYSTEMS Electric shock Electric arcing Fire Electrical explosions

Electric Shock occurs when a person makes contact with a live conductor while simultaneously in contact with an earthed object or another live conductor at a lower potential and current passes through the body. The effects of electric shock include: Muscular contractions causing involuntary gripping of the live source and being unable to let go. Cardiac arrest. Electric burns Momentary loss of control or balance Factors in the surrounding environment that can increase the likelihood of electric shock include wet or damp conditions or areas where there is a high proportion of earthed metal in cramped surroundings.

PROCEDURES FOR CARRYING OUT ELECTRICAL ISOLATIONS Note: The Senior Electrician/Chargehand Electrician must be contacted prior to any work being carried out if the distribution board or consumer unit is found to be unsafe to work on (e.g. covers missing leaving live parts exposed). 1. Identify the circuit to be isolated (refer to circuit charts or use a fuse finder if charts are poor or do not exist). 2. To isolate the circuit carry out one of the following: a) Switch off circuit breaker or isolator and lock off OR b) Remove the fuse and carrier. Apply locking device to the fuse carriage and lock off. Note: Fuses that have been removed must be retained by the person responsible for the isolation and not left lying on distribution board shelves or rooms. If neither of the above is possible contact the Senior Electrician/Chargehand Electrician (Maintenance) prior to carrying out any work.

Post caution tags on the circuit breaker OR on the lock in the fuse carrier. Note: Taping over fuse carriages or posting caution tags on the distribution board door is NOT acceptable. The caution tag must state the person carrying out the isolation and the reason for the isolation.

To test the circuit to prove that it is dead the following must be done: Note: Authorised equipment MUST be used (see section 4.0). (i)If using a multimeter ensure that the correct function (voltage testing) has been selected. Note: All multi-meters issued to staff will be a type that will not give rise to danger if inadvertently put to an incorrect setting. (ii) Prove the test meter by applying the leads to the test unit.

(iii) Apply the testing leads to the electrical equipment to be worked on in this order: Each phase & earth Each phase & neutral Each phase to phase Neutral to earth (if the neutral has been disconnected) Prove the test meter again by applying the leads to the test unit. Note: In the case of testing that a socket has been isolated a Martindale plug in tester may be used. The plug in tester must be proved on a live socket before and after the check on the socket that is being proved dead.

Question: Which of the following is an acceptable isolation for an electrical contractor: a) Switch off the circuit breaker/isolate and post a caution on the door b) Remove the fuse and put some tape over the holder c) Switch off circuit breaker and apply a maintenance padlock before handing over the isolation to a contractor d) Switch off circuit and apply a maintenance padlock and contractors padlock (if contractor to work on circuit)

Procedure for the electrical isolation of a motor or pump 1.Switch off the isolator serving the motor. 2. If it cannot be confirmed that the isolator is a 2 pole isolator (for single phase) or 4-pole type isolator (for 3 phase), then open the isolator cover to check that the neutral link has been physically separated. If the neutral link has not been physically separated, drop the neutral link (this is assuming the isolator has a neutral which can be dropped). Note: should any covers be broken or missing exposing live parts the Senior Electrician/Chargehand Electrician (Maintenance) MUST be contacted before the works proceed. 3. Lock off and post caution tag. 4. Remove cover of the motor and prove that power supply to the motor is dead. De-isolation of motor Re-connect the neutral link prior to the de-isolation being carried out. After carrying out a de-isolation check that the motor is operating in the right direction by momentary switching the motor on. Note: The above test should be satisfactory for most applications. In rare cases where phase rotation tests are required (i.e. tests which are carried out with covers removed and there are exposed live parts where there is a foreseeable risk of danger) then the procedures listed for “Work on or near live conductors which may foreseeably give rise to danger” will apply.

Procedure for the isolation of main switches on incoming low voltage switchboards In addition to the isolation and locking off of the main switch the following must be carried out: 1) Uninterrupted Power Supply (UPS) to be shut down and isolated: Procedure for shutting down the UPS system listed in the operating manual to be followed. Switch off and isolate the power supply from the UPS. Lock off and post caution tag. Switch off and isolate the power supply to the UPS on the main LV board. Lock off and post caution tag.

2) Standby generator to be isolated and locked off: Push stop buttons (external and internal) Turn selector switch from ‘auto’ to ‘stop’/off Switch main circuit breaker to off position Disconnect battery tails Senior Maintenance Electrician/Chargehand Electrician to apply personal padlock and caution tag. Senior Maintenance Electrician/Chargehand Electrician to remove key and place in lockout box.

De-isolations Tests required prior to the system being de-isolated Systems or equipment which have been worked on must not be de-isolated until copies of the tests required by BS7671: 2008 (the IEE Wiring Regulations 17th Edition) have been supplied to the person carrying out the de-isolation. Re-connection of the neutral conductor In cases where the neutral conductor has been disconnected (e.g. in an older type isolator), the neutral conductor must be re-connected prior to the de-isolation being carried out.

Neutral conductors on older circuits On older circuits the dangerous practice of borrowing neutrals may have been carried out. A borrowed neutral which has been used in another circuit could be live when disconnected (or become live if the other circuit is switched off at the time of disconnection but subsequently re-energised). For disconnectionAgainst disconnection the neutral conductor the circuit to be worked will be isolated from any source of potential power a neutral which has been borrowed can become live once it is disconnected - risk of electrocution fire if a neutral conductor which was disconnected on a 3-phase board is not reconnected when the board is reenergised

Neutral conductors on older circuits (continued) For this reason work involving older boards will need to be considered on a case by case basis, however the following guidelines will apply: Staff should be aware that on older circuits borrowed neutrals could be an issue. Neutrals should be treated as being potentially "live". Tests should be carried out between neutral and earth for any voltage if the neutral is disconnected. Note: the test will only work if the other circuit is energised at the time the neutral is disconnected. ALL neutrals which have been disconnected should be terminated into separate terminal blocks. They should be treated as being potentially ‘live’ when being reconnected.

Neutral link in place Neutral link dropped

PROCEDURES FOR PADLOCKING AND POSTING OF CAUTION NOTICES ON ISOLATIONS Padlocks used by Estates Section staff Estates Section staff are only permitted to use padlocks that have been approved by the Senior Maintenance Electrician/ Chargehand Electrician. All padlocks used by Estates Section staff will have unique keys with no duplicate keys being held.

Work on low voltage installations (general) The padlocks of all persons (including contractors) working on the low voltage installation must be applied at each point of isolation. The Estates electrician carrying out the isolation must apply a caution notice at each point of isolation. The padlock of the Estates electrician carrying out the isolation must be the first padlock applied to the isolation and the last padlock removed prior to de-isolation. Work on mechanical equipment Where isolations are required to enable work to be carried out on an item of mechanical equipment (e.g. pump), the padlocks of all engineers working on the job must also be applied at each point of isolation.

What is wrong in this picture?

Isolations where multiple padlocks cannot be applied On some small lighting and power circuits it may not be possible to apply multiple padlocks at the point of isolation. In this case the padlock of the Estates Electrician will be applied, the key for the padlock must then be put in the lockout box and the padlocks of all those involved in the works (including contractors) applied to the lockout box. The lockout box must then be taken to nearest electrical workshop. The Estates Section electrician must apply a caution notice at the point of isolation. Lockout box for use when multiple padlocks cannot be applied to a circuit. Put key for maintenance padlock on circuit breaker into box......then apply contractors and maintenance padlocks to box.

Isolations where it is not possible to apply a padlock Where it is not possible to apply a padlock (e.g. older type switchboards with fuse carriers which cannot be locked off), the Senior Electrician or Chargehand Electrician must be contacted. The phase cable to the fuse carriage must be disconnected, the end taped and a caution tag applied to the end of the cable - taping over fuse carriage holders and leaving the circuit cables connected is NOT acceptable. Note: this work must be done with the switchboard dead and securely isolated. The fuse carrier should then be put back into the board without the fuse, this will ensure that the live parts of the board are covered.

Question: What is wrong in these two photos?

Question: 1.Where multiple padlocks cannot be applied for an isolation for Projects work which of the following should be done: a)Apply a maintenance padlock to the circuit then handover to the contractor. b) Apply the contractors padlock to the circuit then handover to the contractor. c) Apply a maintenance padlock to the circuit, put the key into a lockout box, then apply both maintenance and the contractors padlock to the locked box. WRONG CORRECT

Removal of padlocks in the absence of the owner The removal of padlocks will only be permitted in exceptional circumstances (i.e. the consequences for the University of not removing the padlock are operationally or financially unacceptable). The removal of a padlock MUST be authorised by an Assistant Estates Director.

PROJECTS ISOLATION REQUEST FORM - GUIDANCE ON COMPLETION FOR AN ELECTRICAL ISOLATION The only Projects staff who are authorised to complete a request for an electrical isolation are the M&E Project Engineers. If any other staff (e.g. Building Clerks of Works) require an electrical isolation it must be referred to one of the M&E Project Engineers. Maintenance staff will normally isolate electrical services on behalf of Projects. On some occasions it may be more efficient for one of the M&E Project Engineers to carry out the isolation themselves. In this case a Projects Isolation Request Form will still need to be completed by this person. An individual form is required for each area to be electrically isolated (i.e. electrical isolations for two completely separate areas require two separate forms). Requests for isolation of other services (e.g. fire alarm, water etc) must not be put on the same form. Forms must not be faxed.

SECTION 1 OF FORM Parts 1-6 The M&E Project Engineer requesting the electrical isolation, or carrying out the isolation, must complete parts 1 to 6 of the form. The information in parts 1 to 6 must contain sufficient detail for the isolation to be carried out (location, circuit board number, circuit number etc). Maintenance staff carrying out isolations must only isolate the electrical services listed on the form. If additional services require isolation a new form must be completed. Part 7 The isolation may not proceed until: - The Clerk of Works (Maintenance) has checked Parts 1-6 of the form and signed Part 7 of the white and yellow copy of the form. Note: If the Clerk of Works (Maintenance) is unavailable then the Senior Electrical Engineer, Chargehand Electrician or Assistant Estates Director (Maintenance) should carry out the checks and sign this part of the form. - The Building Clerk of Works responsible for the area has signed part 7 of the form.

SECTION 2 OF FORM Part 1 This must be completed by the Senior Electrical Engineer or Chargehand Electrician confirming that the electrical isolation may proceed. Permission for the isolation should not be granted if the information in Parts 1 to 7 of the form are either incomplete or do not contain sufficient information. Part 3 Part 3 must be completed by the electrical contractor who will actually be carrying out the work. The isolation must only be carried out if there is an electrical contractor there to accept it.

SECTION 3 OF THE FORM Part 1 Electrical de-isolations MUST NOT be carried out until copies of the dead tests for the work required by BS7671: 2008 (IEE Wiring Regulations 17th Edition) have been forwarded to the person who will carry out the de-isolation. FILING OF PROJECTS ISOLATION REQUEST FORMS The Projects representative must collect each of the copies of the form and file these together in file H PRO ISO kept in the Estates office.

Questions: 1.Who can accept an electrical isolation? a)A building Clerk of Works b) An electrical contractor c) The principal contractor (building) for the works WRONG CORRECT WRONG

Question 2. Who can complete a request for an electrical isolation? a)A building Clerk of Works b)The Clerk of Works (projects) c) M&E Project Engineers d) Project Managers WRONG CORRECT WRONG