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

 

[telectrix]

i'm sitting on the fence on this one. both arguments hold water. maybe an adjudicator is required here. Widdler?

 

[Deleted member 26818]

i'm sitting on the fence on this one. both arguments hold water. maybe an adjudicator is required here. Widdler?

Carefull, you don't get splinters.

 

[telectrix]

it's a metal fence, electrified on a timer to get me up in the mornings.

 

[Octopus]

What really annoys me continually about these nice ambiguous regs in BS7671 is the fact that we professionals don't always agree on them and Joe Public hasn't got a clue - which makes our lives very difficult!!!!!!!!!!

 

[telectrix]

not difficult, just interesting.

 

[Grommit]

New builds are so much easier these days.

Live pair into a dual accessory box (mounted outside the bathroom) with one pair from the light, one pair from the pull switch and one 3 core from the fan back to the dual accessory box.

Live pair into the FCU (fused down to 3 amp), load pair out to the fan isolator with the light pair/switch pair/fan 3 core terminated into the fan isolator. No connector blocks, neat and tidy, job done. Simple.

The light remains on in the bathroom for maintenance to the fan when the fan isolator is off.

Isolate the load side of the FCU by removing the 3 amp fuse from the FCU for maintenance to the bathroom light/bathroom pull switch without the need to isolate any other lighting points connected to the the circuit supplying the bathroom lighting.

 

[JUD]

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?

Regulation 314.4 isn't what we're discussing here. That is separation of final circuits.

Nowhere have I said that an FCU is a distribution board. The supply side of the FCU is connected to a final circuit that is fed from a distribution board.

What I'm saying is that the cable coming off the load side of an FCU is it's own circuit with the BS 1362 fuse as it's protective device.

Let me ask you this. On a schedule of test results what would you enter as the protective device for the lights and fan in the bathroom. You couldn't put the one at the distribution board as that is not the primary protective device for that wiring. Therefore you would have to enter it as a separate circuit and the protective device would be BS 1362.

 

[ezzzekiel]

Rcd fcu for your part of the works job done

 

[Deleted member 26818]

Regulation 314.4 isn't what we're discussing here. That is separation of final circuits.

Nowhere have I said that an FCU is a distribution board. The supply side of the FCU is connected to a final circuit that is fed from a distribution board.

What I'm saying is that the cable coming off the load side of an FCU is it's own circuit with the BS 1362 fuse as it's protective device.

Let me ask you this. On a schedule of test results what would you enter as the protective device for the lights and fan in the bathroom. You couldn't put the one at the distribution board as that is not the primary protective device for that wiring. Therefore you would have to enter it as a separate circuit and the protective device would be BS 1362.

We are discussing 314.4.
314.4 requires that where there is more than one final circuit, each final circuit must be supplied from a separate way at a distribution board.
If 'the cable coming off the load side of an FCU is it's own circuit', then what kind of a circuit is it?
If it is a final circuit, then it does not comply with BS7671, as it is not supplied from a separate way at a distribution board.
If it is a distribution circuit, then it must be supplying either a DB or switch gear.
Is it supplying a DB or switchgear, or is it some other kind of circuit which is not defined in BS7671?
When we test continuity of RFC conductors, we are required to record the highest measured value of R1+R2. The measurements are taken at each point on the RFC including any spurs, and the highest reading recorded.
We do not record the highest value measured on the RFC, and then list spurs as separate circuits and record their values separately.
As for your question, I would treat the whole circuit as one circuit, I would not attempt to separate the lighting circuit into two circuits, one for the lights and another for the bathroom light and fan.
As such I would list the lighting circuit protective device as the protective device.

 

[Deleted member 26818]

Rcd fcu for your part of the works job done

You can do that ezzzekiel, but I would expect it to be noted as a departure on any certification, and I would further expect you to ensure that it provides the same degree of safety as would be achieved by compliance with the Regulations.

 

[D Skelton]

The extractor fan doesn't neccessarily need an isolator.

Please read:

Bathroom extractor fans and 3 pole isolation, a source of much controversy

 

[Geordie Spark]

The extractor fan doesn't neccessarily need an isolator.

Please read:

Bathroom extractor fans and 3 pole isolation, a source of much controversy

An excellent & VERY useful post.

Thank you.

 

[JUD]

We are discussing 314.4.
314.4 requires that where there is more than one final circuit, each final circuit must be supplied from a separate way at a distribution board.
If 'the cable coming off the load side of an FCU is it's own circuit', then what kind of a circuit is it?
If it is a final circuit, then it does not comply with BS7671, as it is not supplied from a separate way at a distribution board.
If it is a distribution circuit, then it must be supplying either a DB or switch gear.
Is it supplying a DB or switchgear, or is it some other kind of circuit which is not defined in BS7671?
When we test continuity of RFC conductors, we are required to record the highest measured value of R1+R2. The measurements are taken at each point on the RFC including any spurs, and the highest reading recorded.
We do not record the highest value measured on the RFC, and then list spurs as separate circuits and record their values separately.
As for your question, I would treat the whole circuit as one circuit, I would not attempt to separate the lighting circuit into two circuits, one for the lights and another for the bathroom light and fan.
As such I would list the lighting circuit protective device as the protective device.

This is the third time I've asked this and you haven't even mentioned it.

WHY, if you can't have a circuit using a BS 1362 fuse, do they provide Zs values for them in the regs. I've never seen a distribution board with 3A and 13A plug-top fuses in them.

 

[ezzzekiel]

You can do that ezzzekiel, but I would expect it to be noted as a departure on any certification, and I would further expect you to ensure that it provides the same degree of safety as would be achieved by compliance with the Regulations.

Just as well I deal with the nic then

 

[Deleted member 26818]

This is the third time I've asked this and you haven't even mentioned it.

WHY, if you can't have a circuit using a BS 1362 fuse, do they provide Zs values for them in the regs. I've never seen a distribution board with 3A and 13A plug-top fuses in them.

It may well be the third time that you've asked the question, I'm still struggling to see it's relevance.
I'm not aware of any Regulation prohibiting the use of a BS1362 fuse in a circuit.
As far as I'm concerned, there are many instances where the use of a BS1362 fuse is quite acceptable, in fact Appendix 15 indicates that devices which use such fuses may be supplied through both ring and radial circuits. For instance where the current carrying-capacity of a conductor is reduced, when spuring off of a circuit.
Judging from your arguments, it appears that you accept that RCD protection must be provided for the whole circuit if that circuit is of a location containing a bath or shower.
Your argument appears to be whether the origin of the circuit is as the information contained in Appendix 15 indicates at a DB; or as you contend, at an FCU.
As I posted earlier, I accept that an FCU meets the requirements of an overcurrent protective device as per the definition of a circuit in Part 2.
However Regulation 314.4 requires that final circuits be conected to a separate way at a distribution board and unless I'm mistaken, an FCU is not a DB.
Do you have an argument that allows us to disregard Regulation 314.4?