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Iee wiring regulation 17th edition. please provide the chapter and section etc. for any statement that insists that a low voltage (12v) fan must be fitted, if used in zone 1..

I refer to 411.7.1
"Installation of FELV and PELV only where circuit contains equipment such as transformers, relays, remote control switches which is insufficiently insulated"
Just to let you know that the regulations do not contain the words, extractor, air, fan. Only the word Ventilation.
The relevant page 167. Section 701.5 provides most of what is relevant.
Page 166 states "where SELV or PELV is used" it does not say that it is required.
and again:
702.55.4 states "Low Voltage is permitted"
It does not say it is required.
I think the regulation is stating that IPx4 for zone 1 can be fitted with 240v (with 30mA RCD), but if fitted with Low Voltage (as a preference) there is more concern that the transformer and the feed to the transformer needs to be outside the zones and fitted with isolation switch and also with 30mA RCD.
Can you please confirm. Please include specific Chapter and section references. Thank you

4 Answers from MyBuilder Electricians

Best Answer

Regulation Group 701.32 divides locations containing baths or showers into three precisely-dimensioned zones designated zone 0, zone 1, and zone 2. The zones are determined taking account of horizontal or inclined ceilings, walls with or without windows, doors, fixed partitions, ceilings and floors, where these effectively limit the extent of a zone.
Where the dimensions of fixed partitions are smaller than the dimensions of the relevant zones, for example, partitions having a height lower than 2.25 m, the minimum distance in the horizontal and vertical planes needs to be taken into account.- there is a diagram in BS7671 that illustrates this.

Regulation 701.411.3.3 requires additional protection against electric shock to be provided for all circuits in the bathroom (i.e. the use of an RCD) - see regulation Regulation 415.1.1 for the specific RCD details.

A SELV fan may be used in locations containing a bath or shower, subject to the following conditions:
• the transformer is installed outside zones 0, 1 and 2 (see Regulations 701.512.3, 701.55(iii) for zone 0, and 701.55(iv) for zone 1),
• that basic protection against electric shock is provided for equipment in zones 0, 1 and 2 by basic insulation complying with Regulation 416.1, or by barriers or enclosures affording a degree of protection of at least IP2X or IPXXB (see Regulation 701.414.4.5 ),
• the nominal voltage of current-using equipment protected by SELV in zone 0 must not exceed 12 V a.c. rms or 30 V ripple-free d.c. (seeRegulation 701.55(iii)),
• the nominal voltage of any switch of SELV circuits installed in zone 1 must not exceed 12 V a.c. rms or 30 V ripple-free d.c. (Regulation 701.512.3 )
• the nominal voltage of current-using equipment in zone 1 protected by SELV does not exceed 25 V a.c. rms or 60 V ripple-free d.c. (Regulation 701.55(iv)

In summary you have various options and fitting an SELV fan is not mandatory.


Answered 27th Oct 2011

regulation 701.55 concerns the current using equiptment suitable for use in zone o a special location. i e a bath or a shower and includes ventilation, regards Terry.


Answered 26th Oct 2011

Hi, if you look in the regs book and look at the zones it will tell you what voltage you can have in them zones, you can have 240v in zone 1 but equipment must be fixed, permanently connected and suitable for zone 1 according to the manufacture's instructions, if you put in low-voltage you will need to put transformer out of bathroom and you will need to be RCD protected if 240v, and both will need isolation switches

hope that helps



Answered 26th Oct 2011

Manufacturers installation documentation will confirm if the LV equipment is permitted to be installed in Zone 1.
Mains equipment is permitted providing it is permanently connected, additionally protected (30mA RCD) and designed/manufactured to be accommodate the expected environmental conditions in that zone.
Usually, this designed equipment would have reinforced internal insulation/shielding as well as being additionally enclosed.

Check manufacturers literature


Answered 12th Sep 2019

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