Continuity - confirmed :
During any verification process to confirm the soundness ofan electrical installation - whether it be a new installation, an alteration oraddition, or whether examining the condition of an existing installation - thecontinuity of conductors has to be confirmed.
The requirements of Regulation - 612.2.1 and Regulation - 612.2.2 of BS7671:2011: regarding the continuity ofprotective conductors are generally well understood. However, the implicationsof not testing the line and neutral conductors for continuity are often notfully appreciated.
Why do we carry outcontinuity-tests :
Firstly, it is to ensure that any earthing system is acontinuous and a low resistance path to allow the passage of fault currents ofsufficient magnitude to operate the protective device during fault conditionswithin the required disconnection time.
Secondly, confirmation of the “ zero ” potential between metal parts, both extraneousand exposed-conductive-parts, within an installation to reduce the effects ofelectric shock for the user of the electrical installation.
Thirdly, that the conductors, including all line and neutralconductors, are connected in the correct sequence for safety and foroperational purposes.
Polarity,
Although not directly part of continuity testing, doesfacilitate the confirmation that conductors are continuous and connected in thecorrect sequence.
Earth fault loop impedance testing is part of the ( Verification processof the continuity of the conductors ) , although this test on its owndoes not prove that all conductors are continuous.
One of the areas that are oftenoverlooked is the continuity of neutral conductors. ( Apartfrom ring final circuit continuity testing ) , there is no requirement in BS 7671 toverify the continuity of neutral conductors. Nor is there any facility in thecertificates to record neutral continuity.
( ring final circuit continuitytesting ) Generic schedule of test-results . p.402 . Ring-final-circuit-continuity - L . N . CPC .
2394: Condition of circuit-accessories -621.2. (iii) confirmation that the installation is notdamaged or deteriorated so as to impair-safety . PIR .
- Operation of main-switches- function - check . 612.13.2.
Equipment . such as switchgear and controlgear assemblies .drivers . control and interlocks . shall be subjected to a functional-test . to show that it is properlymounted . adjusted and installed in accordance with the relevant requirementsof these Regulations .
- Manual operation of circuit-breakers. & RCDs to provide disconnection - 612.13.2.