2365 Level 3 practice questions

Question 1 · Unit 301

A PV string inverter develops a fault and shows no output on a sunny day. Before any d.c. work, the installer must remember that the array is:

1. AStill live whenever light falls on it
2. BEarthed and therefore dead
3. COnly live at night
4. DSafe because the inverter has failed

Question 2 · Unit 301

Upgrading loft insulation before installing a heat pump is recommended so that the:

1. AHeat pump can be smaller and run more efficiently
2. BFlow temperature must be increased
3. CRadiators can be made smaller
4. DElectrical supply can be reduced to 110 V

Question 3 · Unit 301

A 6 kWp PV array generates an estimated 5,400 kWh in a year. Its specific yield is:

1. A32,400 kWh/kWp
2. B900 kWh/kWp
3. C1.1 kWh/kWp
4. D450 kWh/kWp

Question 4 · Unit 301

A PV array of 16 modules each rated 410 W has a peak output of:

1. A25.6 kW
2. B6.56 kW
3. C0.41 kW
4. D4.10 kW

Question 5 · Unit 302

Three 60 µF capacitors connected in parallel give a total capacitance of:

1. A60 µF
2. B20 µF
3. C180 µF
4. D540 µF

Question 6 · Unit 302

A load draws 12 kW at 0.6 power factor. After correction to 0.95, the apparent power changes from 20 kVA to about:

1. A7.2 kVA
2. B20 kVA
3. C31.6 kVA
4. D12.6 kVA

Question 7 · Unit 302

A transformer is 96% efficient and delivers 4.8 kW to its load. Its input power is approximately:

1. A5.0 kW
2. B9.6 kW
3. C4.8 kW
4. D4.6 kW

Question 8 · Unit 302

A lamp provides 800 lux at 1 m. By the inverse-square law, the illuminance at 2 m is:

1. A1600 lux
2. B400 lux
3. C200 lux
4. D800 lux

Question 9 · Unit 303

A two-person job involves fault finding near exposed busbars in a distribution board. The safest approach is to:

1. ARely on rubber-soled work boots alone
2. BRemove the main earth connection first
3. CWork it live in order to save time
4. DIsolate, lock off and prove dead before access

Question 10 · Unit 303

A cooker circuit reads near-zero resistance between line and neutral when isolated and disconnected from the appliance. This indicates:

1. AA high-resistance joint
2. BA short circuit in the fixed wiring
3. CCorrect insulation resistance
4. DA healthy open circuit

Question 11 · Unit 303

On a radial circuit with a suspected break, testing continuity from the board to the midpoint accessory tells the electrician whether the fault is:

1. AIn the first or the second half of the circuit
2. BWithin the protective device
3. CAn overload condition
4. DCaused entirely by a simple reversed polarity fault

Question 12 · Unit 303

After rectifying a fault that involved a damaged section of cable, best practice is to:

1. AIgnore it if the circuit works
2. BTape over the damage and re-energise
3. CLeave the damaged cable in place and simply increase the device rating
4. DReplace the damaged length rather than rely on a temporary repair

Question 13 · Unit 304

For the R1+R2 test, the line and cpc are linked at the board and resistance is measured at each point. A reading that climbs steadily toward the circuit's far end indicates:

1. AA dead short circuit right at the board end of the run
2. BSimple reversed polarity
3. CA faulty test instrument always
4. DNormal behaviour as conductor length increases

Question 14 · Unit 304

During an EICR, a circuit with no earth fault protection where it is now required (e.g. cables in walls without RCD) is typically coded:

1. AC3 improvement only
2. BSatisfactory, no action
3. CC2 (potentially dangerous)
4. DNo code required

Question 15 · Unit 304

At handover, demonstrating the operation of the RCD test button to the client is good practice because it:

1. AShows them how to perform the recommended periodic user test
2. BIncreases the circuit rating
3. CAutomatically calibrates the RCD's residual trip current setting
4. DReplaces formal testing

Question 16 · Unit 304

The part of BS 7671 that sets out the requirements for inspection and testing is:

1. APart 7
2. BPart 1
3. CPart 6
4. DPart 4

Question 17 · Unit 305

A designer is told the supply is 230 V TN-C-S with a Ze of 0.35 Ω and a PFC of 1.6 kA. These figures are used to:

1. AChoose the internal wall paint colour scheme
2. BSet the required lighting lux level
3. CVerify disconnection times and breaking capacity
4. DSize the incoming water pipe run

Question 18 · Unit 305

A 230 V circuit has a design current of 18 A and a cable with tabulated capacity 24 A after derating. A suitable device satisfying Ib ≤ In ≤ Iz is:

1. A32 A
2. B16 A
3. C6 A
4. D20 A

Question 19 · Unit 305

Selectivity between a 100 A upstream fuse and a 32 A downstream MCB is desirable so that a fault on the final circuit:

1. AAlways blows the 100 A upstream main fuse first
2. BHas no effect on either of the devices
3. CDisconnects the whole building supply
4. DTrips only the 32 A device, keeping others supplied

Question 20 · Unit 305

A design that is fully documented with calculations and assumptions benefits later work because it:

1. ALets future changes be checked against the design
2. BPrevents any future modification at all
3. CRemoves the need for any certification at all
4. DReplaces the need for any testing