fan in bathroom

[dayrider3883]

I have installed a fan from the lighting switch to bathroom do i need to use a spur for the fan or can i go direct

 

[dayrider3883]

but how can you take both lives into a 3 amp fuse

 

[Octopus]

Back to my point, which is by using a FCU RCD and using this to supply the lights, fan and sometimes a shaver point the RCD is protecting all the circuits of the location i.e. in the said bathroom. PLUS there is a single point of isolation too.

There are too many homes around that don't have RCD's so IMHO my solution is certainly in the spirit of the regulation.

Got my Elecsa annual coming up so I might well ask him for his interpretation!

 

[Deleted member 26818]

Good point, I thought you just had to make additions on older installations comply such as RCD sockets etc..and you were not obliged to upgrade the whole circuit?

You must ensure that the addition or alteration complies with BS7671.
BS7671 only requires circuits of special locations to be RCD protected.
On other circuits, RCD requirements only apply to the socket-outlets and cables concealled in walls.
As such you can extend such circuits by for instance surface mounting any new cables, and using RCD socket-outlets. Leaving the existing part of the circuit without RCD protection.
However with circuits of special locations, the requirement is to provide protection for the circuit, by only protecting the extended part of such a circuit, you will not have met the requirements of BS7671.

 

[Deleted member 26818]

but how can you take both lives into a 3 amp fuse

You don't, you take one live to the fuse, and two lives from the fuse.

 

[Octopus]

You don't, you take one live to the fuse, and two lives from the fuse.

Or fit the FCU before it gets to the light and then everything after it is fused down!

 

[Deleted member 26818]

Back to my point, which is by using a FCU RCD and using this to supply the lights, fan and sometimes a shaver point the RCD is protecting all the circuits of the location i.e. in the said bathroom. PLUS there is a single point of isolation too.

There are too many homes around that don't have RCD's so IMHO my solution is certainly in the spirit of the regulation.

Got my Elecsa annual coming up so I might well ask him for his interpretation!

Wherever RCDs are placed in a position other than at the origin of a circuit, there is danger that an earth fault between the origin of the circuit and the RCD will bypass the RCD.
Whilst such a situation may not be considered a particular danger in normall circuits, where special locations are concerned, it is considered a particular danger.
As such BS7671 requires circuit protection for special locations, rather than RCD protection just for cables or equipment.

 

[JUD]

Yes it's a common misconception, although I believe that it's deliberate attempt to circumvent the Regulations, as using an RCD FCU is often a lot easier than providing RCD protection for the whole circuit.
701.411.3.3 Requires: "Aditional protection shall be provided for all circuits of the location, by the use of one or more RCDs having the characteristics specified in Regulation 415.1.1."
Which translated means all circuits supplying a location containing a bath or shower shall have 30mA RCD protection.
They've re-worded the Regulation in the amendment to only refer to LV circuits. We were hoping that this re-wording would have allowed the use of SELV equipment without the supply circuit having to be RCD protected, if the source of SELV was outside of the location. Unfortunately such is not the case. RCD protection is still required for the LV part of a SELV circuit, even though it will be as much use as a chocolate tea pot.

My interpretation is that if you supply the bathroom lighting from an RCD FCU attached to the original lighting circuit then this creates a new circuit starting at the FCU as that is now the protective device for that circuit.

As it also incorporates an RCD then IMO it complies with all relevant regs.

 

[Deleted member 26818]

My interpretation is that if you supply the bathroom lighting from an RCD FCU attached to the original lighting circuit then this creates a new circuit starting at the FCU as that is now the protective device for that circuit.

As it also incorporates an RCD then IMO it complies with all relevant regs.

Appendix 15 whilst only being informative, indicates that circuits start and in the case of RFCs finish at DBs.
It also indicates the FCUs are items of equipment supplied by final circuits, or devices used to provide overcurrent protection where the current carrying-capacity of a conductor is reduced.
There is no Regulation in BS7671 that suggests the origin of a circuit would be at an FCU.

 

[Octopus]

"All circuits of the location" could be interpreted as "the circuits in the location", not those adjacent to, under or over.


Tin hat on!

 

[JUD]

The origin of a circuit is at an overcurrent protective device. In this case that overcurrent protective device is the FCU.

Haven't you ever wondered why the regs give max Zs values for 3 and 13A BS 1362 fuses.

You are mistaking the origin of a circuit with the origin of an installation.

 

[Deleted member 26818]

The origin of a circuit is at an overcurrent protective device. In this case that overcurrent protective device is the FCU.

Haven't you ever wondered why the regs give max Zs values for 3 and 13A BS 1362 fuses.

You are mistaking the origin of a circuit with the origin of an installation.

According to BS7671, the origin of a circuit is not neccessarily at the overcurrent device.
Regulations 433.2.2 434.2.1 indicate that devices can be installed along the run of a conductor, within 3m.
Whilst the definition of a circuit in Part 2: "Circuit. An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)."
Indicates that a circuit is protected by the same protective device, it does not indicate that the protective device is the origin of the circuit.
However the definition aside, the fact remains that Appendix 15 informs us that the origin of a circuit is at a DB, not at an FCU.

 

[JUD]

According to BS7671, the origin of a circuit is not neccessarily at the overcurrent device.
Regulations 433.2.2 434.2.1 indicate that devices can be installed along the run of a conductor, within 3m.
Whilst the definition of a circuit in Part 2: "Circuit. An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)."
Indicates that a circuit is protected by the same protective device, it does not indicate that the protective device is the origin of the circuit.
However the definition aside, the fact remains that Appendix 15 informs us that the origin of a circuit is at a DB, not at an FCU.

Nor does it state that the protective device has to be at a DB. Appendix 15 is not a regulation but more of an example of typical socket-outlet circuits.

In the case of the bathroom in the OP the assembly of electrical equipment is the light and the fan which will be supplied from the same origin (the FCU) and be protected against overcurrent by the same protective device (again the FCU)

This is why Zs info is provided for BS 1362 fuses. Because the light and fan in the bathroom are supplied by the 3A FCU their max Zs becomes 16.4Ω instead of say 7.67Ω as with a Type B BS 60898 breaker.

 

[ezzzekiel]

Wouldn't comply with BS7671, as the whole circuit requires RCD protection, not just the part that enters the Bathroom.

another usual argument, or just the addition you are responsible for

 

[marks1]

i have to agree with jud on this one. If you have an RCD FCU supplying the lights and the fan in the special location then you are complying with the regs. You don't have to protect the lighting circuit that isn't in the special location eg in the bedroom. However If there is a shower circuit in the special location that isn't rcd protected then this would also need upgrading to current regs even if you are not working on that circuit. That is what i interperate as "all circuits of the location"

 

[Deleted member 26818]

I am well aware that the definition of a circuit does not state that the protective device has to be at a DB.
I quoted the Definition to point out that a OPD is not considered to be the origin of a circuit.
Appendix 15 is not an example of typical socket-outlet circuits.
It sets out options for the design of ring and radial final circuits for houshold and similar premises in accordance with Regulation 433.1, using socket-outlets and fused connection units.
I accept that an FCU meets the requirements of an OPD as far as the definition of a circuit is concerned.
However the particular circuits we are discussing, are final circuits, and the requirements for final circuits are not just restricted to the definition of a circuit in Part 2 and those of Regulation 433.1.
Regulation 314.4 states: Where an installation comprises more than one final circuit, each final circuit shall be connected to a separate way in a distribution board. The wiring of each final circuit shall be electrically separate from that of every other final circuit, so as to prevent the indirect energizing of a final circuit intended to be isolated."
Now unles you are suggesting that the FCU, the light, the fan and associated wiring are not a final circuit, or that an FCU is a distribution board; how can having the origin of a circuit being an FCU meet the requirements of Regulation 314.4?