Electrical Testing Specification
Low Voltage electrical installations
Purpose Of The Electrical Testing
BS7671: 2008 (2011). (Ref 1) defines the purpose of periodic inspection & electrical testing as “to determine so far as reasonably practical whether the installation is in a satisfactory condition for continued service”. 621.2 1-4
Report Format for Electrical Testing
On completion of inspection & electrical testing, the client will be sent a copy of the Landlord Electrical Inspection Report.
Personnel Carrying out your electrical testing
Our electricians that carry out the work on site are qualified to inspect & test electrical installations & hold the City & Guilds 2391 L3 or 2394 & 2395. Copies of qualifications are held on-file & can be disclosed if requested.
Clients will be expected to disclose previous electrical test certificates, reports, design information, diagrams, drawings & other relevant information prior to work on site as required by the Electricity at Work Regulations 1989 (2).
Asbestos Register information & reports will need to be disclosed before commencement of works.
Prior to commencement of work, our Electricians will agree with clients’ representative access to equipment, areas of installation and when they can be isolated. Our electricians will accept a Permit to Work or Permit to isolate before commencing work if required.
The fixed electrical installation will be inspected & tested as agreed with the client excluding lightening protection systems, fire alarm systems, emergency lighting, data wiring/ cabling, telecoms wiring, intruder alarm systems, lift installations, HVAC systems other than the low voltage supplier to that equipment. Supply equipment will be visually inspected where it can be safely accessed but excluding high voltage installations.
Electrical Testing Limitations
- Only equipment & accessories that can be safely accessed by Engineers will be inspected & tested.
- No insulation resistance testing between live conductors.
- No equipment will be inspected & tested above 3 metres unless specifically requested & provisions for access equipment made (guidance note 3, reference 3).
- Cables concealed within trunking, conduit, within walls, floors, in roof spaces & generally within the fabric of the building, underground, to floors where proper walkways & edge protection for the purpose of safe access to electrical equipment are not present.
- Any other limitations on inspection & electrical testing to be agreed with client.
Table 3.3. Range of samples from inspection page 70 IET GN3.
|ITEM||SUGGESTED MINIMUM SAMPLE SIZE (NOTES 1,2)||TYPICAL CHECKS|
|Main switch gear external inspection||100%||Signs of damage, over heating or ageing.|
|Main switch gear internal sections and cable terminations||Ideally 100% but no less than 10%. (Note 2)||Signs of overheating, ageing check tightness of cable connections.|
|Main switch gear internal inspection of circuit breaker connections and control sections.||Ideally 100% but no less than 10%.||Signs of overheating, ageing check tightness of cable connections.|
|Final circuit distribution boards||Ideally 100% but no less than 25% (Note 4)||Signs of overheating, ageing, check of cable connections.|
|Final circuit accessories||Between 10% to 100%. (Note 3)||Damage, signs of overheating.|
|Earthling and protective bonding conductors.||100%||Presence and tightness of connections.|
- Where inspection of a sample yields poor or unacceptable results this would suggest that similar problems may exist elsewhere in the inspected items. The inspector will then need to either increase the sampling or refer back to the client: it may be that the inspector recommends that 100 per cent inspection is carried out in that area.
- 100 per cent where practicable.
- Generally , it is less appropriate to apply small sample sizing to the inspection of socket outlets compared to samples for lighting as it is more likely that user equipment will be hand held and therefore of greater potential risk from electric shock.
- Do not ‘sample samples’, resulting in a very low overall sampled installation. Samples must be representative. If it is decided to sample for example sub main cables at 10 per cent then further sampling should not be applied to the final circuit distribution boards on these circuits.
Following IET GN3. Page 75 Table 3.4 – testing to be carried out.
|Protective conductors continuity||Accessible exposed – conductive –parts of current using equipment and accessories ( notes 4 & 5)|
|Boding conductors continuity||Main bonding conductors to extraneous conductive parts.Supplementary bonding conductors.|
|Ring circuit continuity||Where there are records of previous tests, this test may not be necessary unless there may have been changes made to the ring final circuit.|
|Polarity||At the following positions;Origin of the installationDistribution boardsAccessible socket outlets
Extremity of radial circuits
|Earth fault loop impedance||At the following positions;Origin of the installationDistribution boardsAccessible socket outlets
Extremity of radial circuits
|Insulation resistance||If tests are to be made;Between live conductors and earth at main and final distribution boards (Note 6).|
|Earth electrode resistance||If tests are to be made;Test each earth rod or group of rods separately, with the test links removed and with the installation isolated from the supply source.|
|Functional testsRCDsFunctional tests of circuits breakers, isolators and switching devices||Tests are required by regulation 612.13.1, followed by operation of the integral test button.Manual operation to confirm that the devices disconnect the supply.|
- The person carrying out the electrical testing should decide which of the above tests are appropriate by using their experience and knowledge of the installation being inspected and tested and by consulting any available records. See 3.8.4 of Guidance Notes 3.
- Where sampling is applied, the percentage used is at the discretion of the inspector. See 3.8.4 of Guidance Note 3. A percentage of less than 10% is inadvisable.
- The tests need not be carried out in the order shown in the table.
- The earth fault loop impedance electrical test may be used to confirm the continuity of protective conductors at socket outlets and at accessible exposed conductive parts of current using equipment and accessories.
- Generally, accessibility may be considered to be within 3 meters from floor or where a person can stand.
- Where the circuit includes surge protective devices or other electronic devices which require a connection to earth for the functional purposes, these devices will require disconnecting to avoid influencing the test result and to avoid damaging them.
Reference 1: BS7671 2008 (2011)
Reference 2: Electricity at Work Regulations 1989 (2)
Reference 3: IET Guidance Notes 3 6th Edition