Part P Bathroom Zone Regulations 3 — Questions and Answers
Question 1: What is a shower zone and how does it differ from a fixed bath zone?
- A shower zone (without a tray) extends to 1.2 m radius from the shower head and 2.25 m height; a fixed bath zone follows the plan dimensions of the bath (Correct answer)
- Shower zones are identical to bath zones
- Shower zones only apply to walk-in showers
- Shower zones are only defined for power showers
Correct answer: A shower zone (without a tray) extends to 1.2 m radius from the shower head and 2.25 m height; a fixed bath zone follows the plan dimensions of the bath
For a shower without a tray, BS 7671 Section 701 defines Zone 1 as a cylinder of 1.2 m radius from the shower outlet and 2.25 m height; Zone 2 extends a further 0.6 m from the Zone 1 boundary.
Question 2: Can a luminaire (light fitting) be installed in Zone 1 of a bathroom?
- Yes, if it has a minimum IP rating of IPX4 and is suitable for use in Zone 1 (or higher-rated SELV luminaire) (Correct answer)
- No luminaires may be installed in any bathroom zone
- Only battery-powered luminaires are permitted in Zone 1
- Only recessed downlights regardless of IP rating
Correct answer: Yes, if it has a minimum IP rating of IPX4 and is suitable for use in Zone 1 (or higher-rated SELV luminaire)
Luminaires rated at least IPX4 may be installed in Zone 1; they must be appropriate for the zone, with no user-serviceable lamp without a tool, and connections within the fitting must be adequately protected.
Question 3: Are heating appliances permitted in bathroom zones?
- Yes — specifically designed electric towel rails, fixed heaters and under-floor heating designed and rated for the relevant zone are permitted (Correct answer)
- No electrical heating of any kind is permitted in bathroom zones
- Only gas-fired heating is permitted in bathrooms
- Only central heating radiators fed by hot water are permitted
Correct answer: Yes — specifically designed electric towel rails, fixed heaters and under-floor heating designed and rated for the relevant zone are permitted
Fixed electrical heating (towel rails, panel heaters, under-floor heating) is permitted in bathroom zones provided the equipment is specifically designed and rated for the zone (correct IP rating and thermal suitability).
Question 4: What RCD protection is required for circuits supplying bathroom zones?
- All circuits supplying equipment in bathroom zones must be protected by a 30 mA RCD (Correct answer)
- RCD protection is not required in bathrooms if the equipment has a high IP rating
- Only circuits in Zone 0 require RCD protection
- 50 mA RCD is permitted for bathroom circuits
Correct answer: All circuits supplying equipment in bathroom zones must be protected by a 30 mA RCD
BS 7671 requires all circuits that supply equipment within bathroom zones to be protected by a 30 mA RCD, providing additional protection against electric shock, recognising the increased shock risk in wet environments.
Question 5: Can a consumer unit be installed inside a bathroom?
- No — consumer units must not be installed in rooms containing a bath or shower, as they contain live parts that are not adequately protected against water ingress (Correct answer)
- Yes, if the consumer unit has an IP44 rating
- Yes, if it is inside a locked enclosure
- Yes, if it is more than 2.25 m above floor level
Correct answer: No — consumer units must not be installed in rooms containing a bath or shower, as they contain live parts that are not adequately protected against water ingress
BS 7671 Section 701 prohibits the installation of consumer units (distribution boards) in rooms containing baths or showers, due to the risk from water ingress and the presence of unprotected live parts.
Question 6: What is the significance of 'simultaneously accessible' parts in relation to bathroom supplementary bonding?
- Parts are simultaneously accessible if they can be touched by a person at the same time; bonding ensures they are at the same potential, preventing shock current between them (Correct answer)
- It means parts that are adjacent to each other
- It means parts that are on the same electrical circuit
- It means parts that can be seen from any position in the bathroom
Correct answer: Parts are simultaneously accessible if they can be touched by a person at the same time; bonding ensures they are at the same potential, preventing shock current between them
The concept of simultaneous accessibility is fundamental to supplementary bonding; if a person can touch two conductive parts at the same time (e.g., a metal bath tap and a radiator), they could be shocked by a potential difference between them during a fault.
Part P Bathroom Zone Regulations 3
What is a shower zone and how does it differ from a fixed bath zone?