Electrical FAQs

Which is safer, Alternating Current (AC), or Direct Current (DC)?

Alternating Current (AC) and Direct Current (DC) have slightly different effects on the human body, but both are dangerous above a certain voltage. The risk of injury changes according to the frequency of the AC, and it is common for DC to have an AC component (called ripple). Someone with special equipment can measure this, but the effect on a particular person is very difficult to predict as it depends upon a large number of factors. As a consequence you should always avoid contact with high voltage electrical conductors, regardless of the type of electrical current they are carrying.

More detailed technical information on electrical injury is given in the standard BS PD 6519 "Guide to the effects of current on human beings and livestock - Part 1: General aspects.'

[Back to top]

Everyone gets a ‘belt’ from electricity every now and then, don’t they?

No, not if they are careful and follow the simple rules to securely isolate electrical equipment, and check it is dead before they start work. If you have received an electric shock but were not injured, then you are lucky. Next time a slight change in events may lead to a very different result. No one is immune to an injury from electricity.

See electrical injuries and read the downloadable HSE leaflet Electrical Safety and You  (Electrical Safety and You is available in Welsh), or the HSE bookletElectricity at work – safe working practices.

[Back to top]

How do I know if my electrical equipment is safe?

You can find out if your electrical equipment is safe by carrying out suitable checks, such as inspection and/or testing. The level of inspection and/or testing should depend upon the risks. A simple visual inspection is likely to be sufficient for equipment used in a clean dry environment. In addition, equipment that is more likely to become damaged or is operated in a harsh environment, is likely to require more demanding electrical tests. 

Checks should be carried out often enough that there is little chance the equipment will become unsafe before the next check. It is good practice to make a decision on how often each piece of equipment should be checked, write down the decision, make sure the check is carried out, and write down the results. You should change how often you carry out checks according to the number and severity of faults found.

The best way to find out if specialised equipment is safe, is to have it inspected and tested by a person with specific competence on the type of equipment. This may be the original manufacturer or his authorised service and repair agent. A reputable servicing company that deals with the type of equipment should also be competent to check its safety.

Read the free downloadable HSE leaflet Electrical Safety and You  or select another publication from the resources web page.

[Back to top]

How do I know if my electrical installation is safe?

The best way to find out if your electrical installation is safe is to have it inspected and tested by a person who has the competence to do so, such as an Electrical Contractors Association (ECA) National Association for Professional Inspectors & Testers (NAPIT) National Inspection Council for Electrical Installation Contracting (NICEIC) , or The Electrical Contractors' Association of Scotland (SELECT) approved electrical contractor. These can be found in the Yellow Pages.

It is possible to do simple checks on your installation using an electrical socket tester. This is a device that can be plugged into a socket outlet, and can identify if there is a wiring fault. However, be aware that many types of socket tester cannot detect certain types of fault, and could indicate the socket is safe when it is not. Read the information provided by HSE on Electrical Socket Testers.

[Back to top]

How do I know if someone is competent to do electrical work?

A person can demonstrate competence to perform electrical work if he or she has successfully completed an assessed training course that has included the type of work being considered, run by an accredited training organisation, and has been able to demonstrate an ability to understand electrical theory and put this into practice.

A successfully completed electrical apprenticeship, with some post apprenticeship experience is a good way of demonstrating competence for general electrical work. More specialised work such as maintenance of high voltage switchgear or control system modification is almost certainly likely to require additional training and experience.

Issues of competence are covered in the Memorandum of guidance on the Electricity at Work Regulations, the HSE booklet Electricity at work – Safe working practices, and other publications listed on the resources web page.

[Back to top]

Can I do my own electrical work?

You can do your own electrical work if you are competent to do so. Simple tasks such as wiring a plug are within the grasp of many people, but more complex tasks such as modifying an electrical installation may not be.

It is particularly important that anyone who undertakes electrical work is able to satisfy the requirements of the Health and Safety at Work etc Act 1974 and the Electricity at Work Regulations 1989.

For work on electrical installations below 1000 volts ac you should be able to work within the guidelines set out in BS7671 ‘Requirements for electrical installations. IEE Wiring Regulations. Seventeenth edition’. Other work should be carried out according to the guidelines set out in the relevant industry standard.

Those who wish to undertake electrical testing work would normally be expected to have more knowledge and to be able to demonstrate competence through the successful completion of a suitable training course.

More complex electrical tasks such as motor repair or maintenance of radio frequency heating equipment should only be carried out by someone who has been trained to do them.

Issues of competence are covered in the Memorandum of guidance on the Electricity at Work Regulations, the priced HSE booklet Electricity at work – Safe working practices, and other publications listed on the resources web page.

[Back to top]

When should I use a residual current device?

It is advisable to use a residual current device (RCD) whenever possible but particularly in wet or damp locations such as outdoors. An RCD rated at no more than 30mA limits the energy in a particular type of electric shock and can save your life. However, an RCD cannot protect you from every type of electric shock, so you should still make sure that circuits are securely isolated before you work on them.

It is best to use an RCD that is incorporated into the switchboard of your installation. This means that all circuits fed from that RCD are protected by the RCD. An RCD that is incorporated into an ordinary mains socket, or plugged into it, will protect anything that is attached to that socket, but it is possible that equipment may be plugged into another, unprotected, socket.

RCDs should be regularly tested by pressing the ‘test’ button, and by making sure that the RCD trips. Faulty or inoperative RCDs should be removed from use.

RCDs rated above 30mA provide very limited protection against harm from an electric shock. See information on RCDs.

If you are using electrical equipment in particularly harsh conditions it is worthselecting lower voltage equipment powered by a transformer with an output centre tapped to earth, or powered by a battery. Additional precautions may also be required depending on the specific location, BS7671:2001 Requirements for electrical installations, IEE Wiring Regulations, Seventeenth edition, Section 7, offers guidance on this.

[Back to top]

How often should I test my electrical equipment?

'Electrical equipment should be visually checked to spot early signs of damage or deterioration. Equipment should be more thoroughly tested by a competent person often enough that there is little chance that the equipment will become dangerous between tests. Equipment that is used in a harsh environment should be tested more frequently than equipment that is less likely to become damaged or unsafe.

It is good practice to assess how often equipment being used for work purposes should be tested, write down your findings, make sure the testing is carried out, and write down the results of the tests.

Read the downloadable HSE leaflet Electrical Safety and You  or select another publication from the resources web page.

[Back to top]

How often should I get my electrical installation tested?

Electrical installations should be tested often enough that there is little chance of deterioration leading to danger. Any part of an installation that has become obviously defective between tests should be de-energised until the fault can be fixed.

You should have your electrical installation inspected and tested by a person who has the competence to do so, such as an Electrical Contractors Association (ECA) National Association for Professional Inspectors & Testers (NAPIT) National Inspection Council for Electrical Installation Contracting (NICEIC) , or The Electrical Contractors' Association of Scotland (SELECT)  approved electrical contractor. These can be found in the Yellow Pages.

It is possible to do simple checks on your installation using an electrical socket tester. This is a device that can be plugged into a socket outlet, and can identify if there is a wiring fault. However, be aware that many types of socket tester cannot detect certain types of fault, and could indicate the socket is safe when it is not. Read the information provided by HSE on Electrical Socket Testers.

[Back to top]

Who should I talk to about electrical safety?

In the first instance a competent electrical contractor should be able to give advice on electrical safety, and should also be able to direct you to a suitable electrical engineer for advice about specialist areas. If you cannot get satisfactory answers,HSE can be contacted in a number of ways.

[Back to top]

When should I report an electrical accident to HSE?

You should report any work related accident that comes under the requirements of the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) 1995.

In general, an electrical accident is reportable if:

  • the person dies as a result of their injuries, OR
  • the person suffers a major injury, OR
  • as a result of the injury the person is away from work for more than 3 days, or cannot undertake their full range of normal duties for more than 3 days, OR
  • a person receives an electric shock or burn where the person loses consciousness, or requires resuscitation, or admission to hospital for more than 24 hours, OR
  • plant or equipment came into contact with overhead power lines, OR
  • there is an electrical short circuit or overload that causes a fire or explosion.

There is more information on when you should report an accident or dangerous occurrence to HSE.

[Back to top]

What should I do if I think someone is working unsafely?

If you think someone is working unsafely you should ask him or her to stop immediately and tell a manager. If you are still unhappy about how someone is working, you should Notify HSE.

[Back to top]

What voltages are dangerous?

A wide range of voltages can be dangerous for different reasons. A very low voltage (such as that produced by a single torch battery) can produce a spark powerful enough to ignite an explosive atmosphere. Batteries (such as those in motor vehicles) can also overheat or explode if they are shorted.

If a person comes into contact with a voltage above about 50 volts, they can receive a range of injuries including those directly resulting from the electrical shock (stopped breathing, heart, etc), and indirect effects resulting from loss of control (such as falling from a height or coming into contact with moving machinery). The chance of being injured by an electric shock increases where it is damp or where there is a lot of metalwork.

Electrical or thermal burns can also occur from the flow of electrical current or hot surfaces. See the information on electrical injuries.

[Back to top]

When is it safe to work on live electrical equipment?

It is never absolutely safe to work on live electrical equipment. There are few circumstances where it is necessary to work live, and this must only be done after it has been determined that it is unreasonable for the work to be done dead. Even if working live can be justified, many precautions are needed to make sure that the risk is reduced ‘so far as is reasonably practicable’. Read HSE booklet Electricity at work – safe working practices for more details.

Electrical Safety Council have produced a free practical guide on safe isolation procedures 

[Back to top]

How do I make my electrical equipment safe to work on?

You can be reasonably sure that your electrical equipment is safe to work on if all sources of energy (electrical, mechanical, gas, pneumatic, hydraulic, pressure etc) have been securely isolated and any stored energy has been released from the equipment. You should always follow the procedure for doing this described in the instructions provided by the manufacturer of the equipment, and any local safety rules. If you cannot find the instructions, contact the manufacturer and get them to send you instructions before you start work.

Equipment containing dangerous chemicals or other substances may have to be decontaminated before it is safe to work on. You should ask a competent person what to do.

It is important that there is no chance that a source of energy can be deliberately or inadvertently re-connected to the equipment whilst it is being worked on. This can be achieved by applying a lock to each isolation device, and the person doing the maintenance should have all the keys to these locks in his or her possession. Warning notices should be posted at the points of isolation.

If work is to be carried out on, or near, exposed conductors, the conductors should be proven dead, using appropriate test equipment, before work commences.

Electrical Safety Council have produced a free practical guide on safe isolation procedures 

Information on secure isolation

[Back to top]

Who has the responsibility to make sure everyone works safely?

It is the responsibility of everyone to make sure that work is safely undertaken. Managers have a responsibility to provide the resources, instruction and training necessary to enable their workers to work safely and so that others are not endangered by the work activity. Workers have a responsibility to make sure they keep themselves, and others safe.

[Back to top]

What should I do if I think I have seen an unsafe electrical installation or equipment?

If you think you have an unsafe electrical installation you should first warn everyone to stay away from it, and, if it is safe to do so, switch it off. You should then contact a competent person such as an Electrical Contractors Association (ECA) National Association for Professional Inspectors & Testers (NAPIT) National Inspection Council for Electrical Installation Contracting (NICEIC) , or The Electrical Contractors' Association of Scotland (SELECT)  approved electrical contractor who will be able to advise you how to make your installation safe.

If the installation you think is unsafe is not owned by you or under your control, you should attempt to find out who does own it, and contact them. Electrical distribution poles, pylons and equipment should have a contact telephone number attached to them.

If you cannot find out who owns or controls an electrical installation you think is unsafe, you should contact your local authority or HSE.

[Back to top]