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

 

[Deleted member 26818]

A fault current on a part of the circuit before the RCD will take the path of least resistance i.e back to earth through the cpc and along the normal earth fault loop path and, if Zs for the circuit is within limits which it should be, take out the main breaker/fuse.

JUD the fault current won't only take the path of least resistance, it will be distributed across all paths according to their resistance.
The maximum permisable Zs values for an overcurrent device are determined to allow disconnection times to be achieved where there is a fault of negligible impedance.
Any fault which has a high resistance will not necessarily cause an overcurrent device to operate within the applicable disconnection times.
A fault may be of such a high resistance, that the current will not be enough to cause an overcurrent protective device to operate at all.
Consider a shower circuit, it might have a 50A type B MCB. The current required to cause instantaneous operation is 250A. If the current is below 70A the device will not operate. A current between 70A and 250A willl cause the device to operate anywhere between 16 minuites and some tenths of a second.
The point of using an RCD is to achieve disconnection within thousandths of a second.
Then of course there's the fact that the CPC will only provide the path of least resistance, if it is intact.
An RCD is additional protection, it is installed to provide protection in cases where an overcurrent device is not deemed to provide sufficient protection, and other forms of additional protection are not being used or not deemed acceptable.
Where cables are concealled in walls at a depth less than 50mm, an RCD will provide protection against penetration by screws or nails.
Socket-outlets require RCD protection, not to protect the socket-outlet, or the cables supplying the socket-outlets, but to protect appliances that are plugged in to the socket-outlets.
Circuits of locations containing baths or showers, and circuits in other special locations, such as on building sites, agricultural/horticultural premises require RCD protection, not just to protect appliances which may be connected to the circuit, not just to protect cables concealled in walls, but to protect in the event of any fault which may present a danger to persons.
Even where other forms of addition protection are used such as SELV in locations containing baths and showers, BS7671 still requires the LV circuit that supplies the SELV to be RCD protected.
What makes you think that BS7671 which requires an LV circuit supplying a source of SELV to be RCD protected, would then allow an LV circuit supplying an FCU to be unprotected?

 

[Octopus]

I was under the impression you'd both decided to agree to disagree!

Maybe the mods should step in!

:19:

 

[Deleted member 26818]

Murdoch, have a look at this: Young mother electrocuted by bath taps - Telegraph
The OPD didn't operate in time, in fact it didn't operate at all, as the resistance of the earth fault path was not low enough, and the woman was dead and collapsed disconnecting the earth fault path before the OPD had time to operate.
Now installing an RCD as suggested by JUD would most likely have saved the woman.
However if the earth fault had been upsream from th RCD, it wouldn't have made any difference.
This is not a simple matter such as should conductors be sleeved with the correct colour at a light switch where a competent person should be aware that any conductor at the switch could be live, this is a matter that could cause fatalities.

 

[JUD]

I was under the impression you'd both decided to agree to disagree!

Maybe the mods should step in!

:19:

I thought the info in the link to the ESC website I provided would have made mine and others cases.

If an existing circuit of a location containing a bath or shower is extended, at least the extended part of the existing circuit must be provided with RCD protection. Supplementary bonding in a bathroom or shower room must be provided unless all the requirements in the 17th Edition for the omission of supplementary bonding are met.

spin, I agree with Murdoch, let's just agree to disagree.

At the end of the day only the IET could give a definitive answer as to what is required.

 

[Deleted member 26818]

I thought the info in the link to the ESC website I provided would have made mine and others cases.



spin, I agree with Murdoch, let's just agree to disagree.

At the end of the day only the IET could give a definitive answer as to what is required.

The IET do, and it is that the the circuit requires RCD protection.
As for the ESC, they don't even recommend a code for lack of RCD protection for these circuits in their BPG for PIRs.
Heres a link to an article issued in wiring matters by the then IET Chief Engineer Mark Coles: http://electrical.------.org/wiring-matters/30/additions.cfm?type=pdf
His advice is that not only should the circuit you are working on be protected, but all other circuits, even if you haven't touched them.
I don't know, does the advice from the IET Chief engineer trump that of the ESC?

 

[ezzzekiel]

However back to the original op, the following extract taken from ESC and Niceic Guidlines

If an existing circuit of a location containing a bath or shower is extended, at least the extended part of the existing circuit must be provided with RCD protection. Supplementary bonding in a bathroom or shower room must be provided unless all the requirements in the 17th Edition for the omission of supplementary bonding are met

 

[Deleted member 26818]

However back to the original op, the following extract taken from ESC and Niceic Guidlines

If an existing circuit of a location containing a bath or shower is extended, at least the extended part of the existing circuit must be provided with RCD protection. Supplementary bonding in a bathroom or shower room must be provided unless all the requirements in the 17th Edition for the omission of supplementary bonding are met

The ESC or NICEIC do not write the Regulations.
However, if you consider that the answer you have quoted, was made in reply to a question asking how to comply with BS7671 when installing an electrical appliance such as a boiler or electric towel rail in a bathroom, the answer seems rather odd.
There is no mention of extending an existing circuit in the question, and I wonder what existing circuit do the ESC suggest be extended to supply the boiler or towel rail, the lighting circuit, or shower circuit perhaps?
Then in answer to the question: "If we reposition a pull switch in a location containing a bath or shower, would the circuit need to be RCD-protected?"
They answer :"Yes, because the work would be more than a like-for-like replacement."
So according to the ESC, if you install an electric towel rail, you can extend an existing circuit, and just provide RCD protection to the extended part of the circuit, but if you re-position an existing pull switch, you have to provide RCD protection for the whole circuit.
Then of course is what I consider their greatest faux pas, in the their best practice guide for PIRs, they do not consider the lack of RCD protection for circuits of locations containing baths and showers to be a non-compliance.

 

[ezzzekiel]

I highly respect your indepth knowledge and read a lot of your posts with great interest, but as a day to day working sparky some of your interpretations of the regulations differ greatly from mine and providing i have guidelines from other official sources then i must agree to disagree on this topic.......