Part P Special Installations (Bathrooms/Outdoors) — Questions and Answers
Question 1: According to BS 7671 Section 701, what is the extent of Zone 1 in a bathroom with a bath?
- The area directly above the bath tub to a height of 2.25m from the floor (Correct answer)
- The area within 0.6m horizontally from the edge of the bath
- The entire bathroom
- Only the area directly underneath the bath
Correct answer: The area directly above the bath tub to a height of 2.25m from the floor
Zone 1 in a bathroom with a bath is the area directly above the bath (or shower basin) up to a height of 2.25m from the finished floor level (or to the top of the ceiling if lower). If there is no fixed bath screen, the zone extends 1.2m horizontally from the fixed water outlet. Equipment in Zone 1 must be at least IPX4 rated and only certain items are permitted.
Question 2: What IP rating is the minimum requirement for electrical equipment installed in Zone 1 of a bathroom?
- IPX0 (no protection)
- IPX2 (drip-proof)
- IPX4 (splash-proof) (Correct answer)
- IPX7 (immersion-proof)
Correct answer: IPX4 (splash-proof)
Equipment installed in Zone 1 must have a minimum IP rating of IPX4 (protected against water splashes from all directions). If water jets are likely to be used for cleaning (e.g., in communal facilities), IPX5 is required. In Zone 2, the minimum is also IPX4. The IP rating must be appropriate for the actual conditions the equipment will be exposed to.
Question 3: Can a standard 13A socket outlet be installed in a domestic bathroom in the UK?
- Yes — anywhere in the bathroom
- Yes — but only in Zone 2 with RCD protection
- No — only shaver supply units complying with BS EN 61558-2-5 are permitted, installed at least 3m from Zone 1 (Correct answer)
- No socket outlets of any type are permitted in bathrooms
Correct answer: No — only shaver supply units complying with BS EN 61558-2-5 are permitted, installed at least 3m from Zone 1
Standard 13A socket outlets are not permitted in domestic bathrooms in the UK. Only shaver supply units incorporating an isolating transformer (complying with BS EN 61558-2-5) are permitted, and these must be installed in Zone 2 or outside the zones (at least 0.6m from Zone 1). This restriction exists because of the increased electric shock risk in wet environments.
Question 4: What type of circuit is required for an electric shower installed in a bathroom?
- It can be supplied from any convenient circuit
- A dedicated radial circuit from the consumer unit with appropriate RCD protection (Correct answer)
- The ring final circuit with a fused spur
- A lighting circuit with a 6A MCB
Correct answer: A dedicated radial circuit from the consumer unit with appropriate RCD protection
An electric shower must be supplied by its own dedicated radial circuit from the consumer unit, sized for the shower's rated load (typically 40A or 45A MCB with 10mm² cable for showers up to 10.5kW). The circuit must have 30mA RCD protection. The shower must be controlled by a double-pole isolating switch located outside the zones but accessible to the user.
Question 5: A homeowner wants to install a heated towel rail in the bathroom. What are the electrical requirements?
- It can be plugged into any socket
- It must be hardwired to a fused spur outside the zones, be Class I or Class II construction, and have appropriate IP rating for its zone location (Correct answer)
- It must be battery-operated only
- No electrical towel rails are permitted in bathrooms
Correct answer: It must be hardwired to a fused spur outside the zones, be Class I or Class II construction, and have appropriate IP rating for its zone location
An electric heated towel rail in a bathroom must be permanently connected (hardwired) via a fused connection unit, ideally located outside the zones. The towel rail itself must have an appropriate IP rating for its zone (IPX4 minimum in Zones 1 and 2) and be either Class I (earthed metal) or Class II (double insulated). The circuit must have 30mA RCD protection.
Question 6: What is the maximum height of Zone 2 in a bathroom, and what does the zone extend to?
- 2.25m high, extending 0.6m horizontally from the outer edge of Zone 1 (Correct answer)
- 3.0m high, covering the entire bathroom
- Ceiling height, extending 0.6m from Zone 1
- 2.25m high, extending 3.0m from the bath
Correct answer: 2.25m high, extending 0.6m horizontally from the outer edge of Zone 1
Zone 2 extends 0.6m horizontally from the outer edge of Zone 1, up to a height of 2.25m from the finished floor level. Beyond Zone 2 (outside zones), standard installation rules apply, though 30mA RCD protection is still required for all circuits in the bathroom location. Equipment in Zone 2 must be rated at least IPX4.
Part P Special Installations (Bathrooms/Outdoors)
According to BS 7671 Section 701, what is the extent of Zone 1 in a bathroom with a bath?