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From the helpline We continue with our series of answers to some of the more frequently asked questions put to our Technical Helpline.

QUESTION ANSWER

Is it permissible to install a wall-mounted extractor fan having a rated voltage of 230 V within zone 1 of a room containing a bath (or shower)?

QUESTION

How many points should be recorded for a twin socket-outlet, in the box titled ‘Number of points served’ which forms part of the Schedule of Circuit Details for the Installation? Yes. Ventilation equipment is included in the list of fixed and permanently connected current-using equipment that may be installed in zone 1 of a location containing a bath or shower, provided it has a degree of ingress protection to at least IPX4 and is suitable for installation in zone 1 according to the manufacturer’s instructions (Regulation Group 701.5 refers).

ANSWER

Where the fixed wiring is terminated at a particular point, regardless of whether the termination is for connection of an accessory having single or multiple outlets or an item of current-using equipment, the number of points served is one.

QUESTION

Are there any specifi c requirements to consider when designing a circuit to supply a hot tub? ANSWER

It is clear that the user of a hot tub is at a greater risk of death due to, for example, reduced body impedance and being in contact with the general mass of Earth. BS 7671 does not provide specific requirements for electrical installations associated with hot tubs. However, it is reasonable for the contractor to apply engineering judgement and to class hot tubs as either a bath or basin depending on its location.

For example, where a hot tub is in an indoor location, such as a garden shed or cabin it might be reasonable to apply the full requirements of Section 701 (Locations containing a bath or shower) or where a hot tub is located outdoors in the open air the full requirements of Section 702 (Swimming pools and other basins) might be applied.

It would be wise for the contractor to liaise with the hot tub installer prior to the installation of the circuit to ensure that the manufacturer’s instructions have been adequately considered as well as the recommendations, where relevant, of BS EN 60335-2-60 (Household and similar electrical appliances. Safety. Particular requirements for whirlpool baths and whirlpool spas) (Regulation 110.1.3 refers).

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QUESTION

Can I use a socket-outlet to BS 1363-2 within an a.c. charging point as the point of connection for an electric vehicle?

QUESTION

Where the opening for a buried cable to enter a domestic dwelling is formed below ground level, does BS 7671 specify any certain requirements?

QUESTION

Is it permitted to install a main protective bonding conductor for the gas installation pipework within the sleeve containing the gas pipe where that sleeve passes through the external wall to an external meter box? ANSWER

Socket-outlets to BS 1363-2 may be incorporated in an a.c. charging point provided the manufacturer approves the socket-outlet’s suitability for such use. Where this is not the case, a suitable socket-outlet or connector should be selected from Regulation 722.55.201.

It should be noted that the vehicle manufacturers’ instructions should be followed when determining the type of socket-outlet to be used in a.c. charging points (Regulation 722.55.201 refers).

ANSWER

No. However, openings below ground, as for any opening formed, should be formed in accordance with the relevant guidance issued by the governments in the United Kingdom (UK) jurisdictions in the form of Approved Documents (England and Wales), Technical Handbooks (Scotland) and Technical Booklets (Northern Ireland), to ensure the requirements of the building regulations are satisfied.

An overview of government guidance for the UK typically recommends that openings below ground level are permitted for the passage of services provided they are limited to a maximum area of 0.1 m2 at not less than 2 m centres apart.

Also, where an opening is formed below ground level, care should be taken to avoid damage to the provisions provided to resist moisture entering the dwelling, such as the damp proof membrane.

Where doubt exists regarding openings the local Building Control Department should be contacted.

ANSWER

Yes, although BS 7671 does not actually say so. Technical Bulletin TB 102 produced by Gas Safe Register (which registered gas engineers can view/download from the technical area of Gas Safe’s website) advises that, for low-pressure gas meter installations* (pressure not exceeding 75 mbar on the inlet to the meter), the bonding conductor may be run within a sleeve that contains the gas pipe with the connection being on the outlet of the meter but within an external meter box.

The important point here though is that routing the bonding conductor in this manner must not interfere with the sealing of the sleeve, whose purpose is to prevent any escape of gas within the meter box from entering the dwelling. * Domestic gas installation may also be supplied with gas at medium pressure (75 mbar up to 2 bar - this fact will be highlighted by notices within the meter box), whereby the use of a rear entry sleeve for either gas pipework or a bonding conductor is strictly prohibited.