Paper 6 Flashcards
State three test lead conditions which are necessary to ensure compliance with GS 38
Max 4mm tip
Finger guards
Fused
b) List five reasons why a periodic inspection and test may be requested by a client
Time duration since last periodic Change of use Change of occupier Following damage, fire or flood Requested by insurance company or licensing authority Any suitable alternative
c) List five items of information or conditions that, if not available or obvious, may require an inspector to carry out more detailed inspection of an installation.
Maximum demand, allowing for diversity Number and type of live conductors of the source Earthing arrangements (system) Nominal voltage Nature of current and frequency PFC Ze Service head protective device, rating and type Etc. any from item 2.3 of GN3
d) Periodic inspection and testing may not be necessary if certain conditions are met
622.2 if the installation is under an effective management system, periodic inspection may be replaced by an adequate program of continuous monitoring and maintenance
Figure 1 , enclosed, shows a typical steel-wire armoured cable termination into a metallic
junction box. Describe five items that would be verified by inspection, and for each item give details as to why the item is inspected, together with the human sense to be used.
S A D C O W S
- Correct polarity and identification, visual inspection to ensure no reversals,
- Existence of the cpc/fly lead, visual inspection required because the armoring is the cpc.
- Conductor connections electrically and mechanically sound, touch used to ensure no loose connections
- Glands tight and correctly installed, touch to check connection is tight and cpc connection is continuous
- Check for corrosion visual check to ensure enclosure and connections are suitable for continued use.
- Check for signs of overheating, visual check for evidence of burning – brown marks or soft/sagging insulation also Smell for burning, to ensure the circuit/connection is not being overloaded
A 30 mA RCD is installed to provide additional protection for a final circuit containing a number of socket-outlets.
a) Explain why the RCD instrument tests should be carried out prior to operation of the test button.
If the RCd is not manually tested for a while it can become sticky which would prevent if from operating under a 30ma fault current. The mechanical test button can unstick a sticky RCD making it operate more easily under the 30ma test. Thus making the RCD appear to be in better condition than it really is.
State the instrument and tests that are used to test an RCD and maximum disconnection times.
RCD testing to be undertaken using an RCD tester, the following needs to be tested for both half cycles
½ times test, tested at 15mA must not operate for 2000ms
1 times test, tested at 30mA, BS type RCD’s must operate within 200ms – BS EN type RCD’s must operate within 300ms
5 times test, tested at 150mA, must operate within 40ms
c) Determine the maximum permissible value of earth fault loop impedance for a 30ma RCD
Maz Zs = 50v / I∆n
= 50 / 0.03 = 1667Ω
d) State two conditions that must be met that would allow removal of the RCD providing additional protection to the final circuit.
If the sockets are under the supervision of skilled or instructed persons.
If the sockets are identified by a durable label for specific use only
Under what circumstances is it not reasonable to use sampling.
If there is evidence that the installation is in bad condition. If there are non compliance’s on the sampled circuits the sample size must be increased. If further non compliances are found the entire installation must be inspected and tested.
c) Explain why dismantling of this installation should be reduced, as far as is reasonably practical.
If equipment and enclosures are opened there is a risk faults may be introduced that were not already there. If conductors are disconnected or moved for testing there is a risk they will not be reinstated correctly
Explain the correct procedure to be followed where a number of defects are discovered which are potentially dangerous and require urgent remedial action
Where a C1 code is identified, immediate danger, this should be made safe before continuing the inspection, and the customer should be notified in writing without delay. Where a C2 potentially dangerous defect is identified, the details of the C2 would be listed in the OBSERVATIONS section of the report and the customer should be advised of required repairs in a covering letter to be completed as soon as practicable. Both of the above would result in the electrical installation condition report identifying the installation as UNsatisfactory
