CABLE SELECTION, EARTHING and PROTECTION (use BS7671:2018)

What is the symbol for 'design current' ?
1. Ib
2. In
3. Iz
4. It
What is the symbol for 'current carrying capacity' of your selected cable ?
1. Ib
2. In
3. Iz
4. It
What is the symbol for 'PROTECTIVE DEVICE RATING' in AMPS ?
1. Ib
2. In
3. Iz
4. It
What is the symbol for current after the application of 'factors' ?
1. Ib
2. In
3. Iz
4. It
Which one of the following is not a recognised 'factor' used when sizing conductors ?
1. Ci
2. Ca
3. Cg
4. Cb
What is the correction factor (rating factor) for a semi-enclosed fuse to BS 3036 ?
1. 1.75
2. 0.725
3. 0.5
4. 0.575
When calculating the size of a live conductor, if there are no 'factors' to consider - what minimum current rating MUST the cable be capable of supporting ?
1. Protective device rating
2. design current of the equipment being supplied
3. 32 amps
4. Iz
What is the function of this formula ' ? = mV/A/m ?
1. volts drop calculation
2. Total earth loop impedance calculation
3. (R1+R2) calculation
4. Ze calculation
What is the maximum disconnection time for a 230v AC circuit supplying fixed equipment not exceeding 32A, on a TT system ?
1. 0.1s
2. 0.2s
3. 0.4s
4. 5s
What is the maximum volts drop on a non-lighting circuit ?
1. 2%
2. 5%
3. 3%
4. 4%
What is the maximum volts drop on a lighting circuit ?
1. 2%
2. 3%
3. 5%
4. 4%
What is the disconnection time for a 230v AC circuit supplying sockets not exceeding 32A, on a TN system ?
1. 5 seconds
2. 0.5 seconds
3. 0.4 seconds
4. 2 seconds
What is the disconnection time for a 230v AC circuit supplying fixed equipment exceeding 32A, on a TN system ?
1. 0.4 seconds
2. 0.5 seconds
3. 5 seconds
4. 2 seconds
If a 'B' type RCBO to BSEN61009-1 - rated at 32A and 30mA, is installed in a TN system to protect a ring circuit in a detached garage, what is the maximum earth loop impedance allowed, to comply with BS7671:2018, with regard to 0.4sec disconnection time ?
1. 1.37 ohms
2. 1.5 ohms
3. 1.09 ohms
4. 1.44 ohms
How is the correct conduit size selected for installing different quantities of cables ?
1. Minimum 50% space as a general rule
2. Calculate area of conductors and deduct from conduit size
3. Select from tables in On-Site Guide by means of cable factors
4. Use a conduit selection formula
How close should the bonding connection of services pipework be to the corresponding water/gas meter in a domestic dwelling ?
1. 100mm
2. 850mm
3. 600mm
4. 350mm
What is the minimum size to be used for a extraneous bonding conductor (non PME) ?
1. 10.0 sqmm
2. 6.0 sqmm
3. 2.5 sqmm
4. 4 sqmm
What is the minimum size to be used for an exposed and unprotected supplementary bonding conductor connecting two extraneous conductive parts together??
1. 10.0 sqmm
2. 6.0 sqmm
3. 2.5 sqmm
4. 4 sqmm
What is the minimum size to be used for a protected supplementary bonding conductor connecting two extraneous conductive parts together?
1. 10.0 sqmm
2. 6.0 sqmm
3. 2.5 sqmm
4. 4 sqmm
What is the minimum c.s.a of the double-insulated 'tails' from your electricity meter to your consumers unit ?
1. 10 sqmm
2. 16 sqmm
3. 25 sqmm
4. 35 sqmm

CABLE SELECTION, EARTHING and PROTECTION (use BS7671:2018)

Cable selection, sizing, symbols, installation practices, loads, circuits - 8 questions from a bank of questions