Part P Special Installations (Bathrooms/Outdoors) 2 — Questions and Answers
Question 1: According to BS 7671 Section 722, what additional protection is required for EV charging installations in domestic properties?
- No additional protection beyond a standard MCB
- 30mA RCD protection, and depending on the charger type, a Type A or Type B RCD (Correct answer)
- Only a time delay RCD
- Surge protection only
Correct answer: 30mA RCD protection, and depending on the charger type, a Type A or Type B RCD
EV charging installations require 30mA RCD protection. Due to the rectifier circuits in EV chargers, a Type A RCD (minimum) is required, and a Type B RCD may be necessary if the charger can produce smooth DC fault currents (unless the charger has built-in DC protection allowing a Type A to be used). AFDD protection is also recommended by Amendment 2.
Question 2: What is the minimum IP rating for electrical equipment installed outdoors in a domestic garden?
- IPX0
- IPX3
- IPX4 (splash-proof) minimum, with higher ratings where directly exposed to rain (Correct answer)
- IPX8 (submersible)
Correct answer: IPX4 (splash-proof) minimum, with higher ratings where directly exposed to rain
Outdoor electrical equipment must be rated at least IPX4 (splash-proof) for general outdoor locations. Equipment directly exposed to rain jets should be IPX5, and submersible equipment (e.g., pond pumps) must be IPX8. All outdoor circuits must have 30mA RCD protection, and cables must be suitably protected against mechanical damage, UV degradation, and moisture ingress.
Question 3: When installing an outdoor socket outlet for a domestic garden, which of the following requirements must be met?
- A standard indoor socket can be used if mounted high enough
- The socket must be rated at least IP66, protected by a 30mA RCD, and supplied by a dedicated circuit or appropriately protected spur (Correct answer)
- No RCD protection is needed for outdoor sockets
- Outdoor sockets must be supplied at extra-low voltage only
Correct answer: The socket must be rated at least IP66, protected by a 30mA RCD, and supplied by a dedicated circuit or appropriately protected spur
Outdoor socket outlets must be weatherproof (typically IP66 when the cover is closed), protected by a 30mA RCD, and ideally supplied by a dedicated circuit. The socket should be mounted at least 150mm above ground level, in a position protected from accidental damage, and the circuit must be properly earthed with adequate fault loop impedance for rapid disconnection.
Question 4: For a garden lighting circuit using 230V luminaires, what cable type is suitable for direct burial?
- Standard twin and earth (6242Y) without additional protection
- Steel wire armoured (SWA) cable or cable in suitable conduit/ducting at a minimum depth of 450mm (Correct answer)
- Any flexible cable laid on the surface
- Telephone cable
Correct answer: Steel wire armoured (SWA) cable or cable in suitable conduit/ducting at a minimum depth of 450mm
For direct burial, steel wire armoured (SWA) cable is the standard choice as it provides mechanical protection against accidental damage from gardening tools. It should be buried at a minimum depth of 450mm (600mm under roads/driveways) and route markers/warning tape placed above. Alternatively, standard cable can be used in suitable conduit or ducting at appropriate burial depth.
Question 5: What special requirements apply to the electrical installation in a domestic swimming pool or hot tub area?
- Standard domestic installation rules apply
- BS 7671 Section 702 applies: SELV lighting within Zone 0/1, no socket outlets in zones, all equipment rated for the zone, and supplementary bonding of all metalwork (Correct answer)
- Only battery-operated equipment is permitted
- A separate electricity supply is required from the DNO
Correct answer: BS 7671 Section 702 applies: SELV lighting within Zone 0/1, no socket outlets in zones, all equipment rated for the zone, and supplementary bonding of all metalwork
Swimming pool installations are covered by Section 702 of BS 7671. Zone 0 (inside the pool) permits only SELV at 12V AC/30V DC. Zone 1 (up to 2m horizontally and 2.5m vertically from the pool edge) has strict equipment limitations. All metallic parts must be supplementary bonded, and only SELV, PELV, or equipment specifically designed for use in each zone is permitted.
Question 6: When installing an outdoor circuit for a garden shed, how should the cable route be marked to warn of its presence?
- No marking is required
- Yellow/black warning tape placed approximately 150mm above the buried cable, plus cable route marker posts at changes of direction (Correct answer)
- Paint the cable route on the ground surface
- A sign on the shed is sufficient
Correct answer: Yellow/black warning tape placed approximately 150mm above the buried cable, plus cable route marker posts at changes of direction
BS 7671 requires that buried cables are adequately identified with cable route markers. This includes yellow/black warning tape placed approximately 150mm above the cable (so it is encountered before the cable during any excavation), route marker posts or plates at key points, and documentation of the cable route on the as-built drawings or electrical installation certificate.
Part P Special Installations (Bathrooms/Outdoors) 2
According to BS 7671 Section 722, what additional protection is required for EV charging installations in domestic properties?