Inspection, Testing and Certification Flashcards
What must the resistance be for a main earth on a services pipe?
0.05 or below
What are 3 examples of extraneous parts?
Main water pipe
Central heating systems
Exposed metal building structure
What is an extraneous conductive part?
A conductive part liable to introduce potential into the installation, not part of the electrical installation. Connected to the MET
What is an exposed conductive part?
conductive part of equipment, which can be touched, and which is not normally live, but which can become live when basic insulation fails. Part of the electrical installation
What are 3 examples of exposed conductive parts?
A metal consumer unit cover
Metal casing on a toaster
Metal socket face
What is step 1 of continuity of a ring final circuit?
Line to line (R¹)
Neutral to Neutral (Rn)
Cpc to Cpc (R²)
What is step 2 of continuity for ring final circuits?
(R¹+Rn) ÷ 4 (check that r¹ and Rn are at the bottom of each socket)
What is step 3 of continuity for ring final circuits?
(R¹+R²) ÷ 4
R2 = when there is no cpc conductor
How do you test a radial circuit?
Place live wire in earth bar, and test:
Radial - 1 conductor in protective device
Ring - 2 conductors in protective device
How do you test polarity?
Test volt meter between L + E (should light up)
Test volt meter between L + N (should light up)
Test volt meter between N + E (should NOT)
What cpc size should supplementary bonding be?
4mm²
What is IPF?
Fault current - for earth faults
What is PFC?
Prospective short-circuit current (overload and short circuits)
What 3 things can effect instrument accuracy?
- The state of the battery
- The deterioration of leads
- The ambient temperature
What voltage is tested for insulation resistance on SELV + PELV circuits?
250v DC
