Bathroom fan wiring from junction box - sensible?

[topskins]

I've read over the helpful FAQs concerning wiring in an extractor fan in a bathroom, but just want to double check my thinking...

Currently I have this off my lighting circuit in my bathroom (purple being the switched live):

Now...I have a new (inline with ducting) fan that I intend to install in the loft, and (possibly) I'll have a shaver socket at some time in the dim and distant future. However, things are a bit congested in the current ceiling rose as it stands due to the downlighters already present. With this in mind, is the following sensible ?

In addition, is there any issue with the wiring in series of the halogen downlighters with the main light on the ceiling rose that I've inherited?

 

[Space cat]

Your proposed circuit would work but it's messy and it'll be a major headache for some poor mug in the future. Given that you're about to use two junction boxes, and they have to be accessible, I would start by simplifying what you've already got. Take all the wires out of the rose and put them into junction boxes instead. JB terminals are designed to take multiple wires.

I think you have too many wires, especially earth wires, for a single box so my solution would be to use two boxes side by side. Bring power into one of them, across to the other and then out from there. Use one of the boxes for the lights and the other for the fan and shaver socket. You can link the spare terminals in the boxes for switched live. Put a three pole switch in line with the fan for isolation.

 

[topskins]

Thanks for the comments Space cat.

Put a three pole switch in line with the fan for isolation.

Is this required with an SFCU? I know the lighting circuit is fused at 6A anyway, but I was following the manufacturer's (brief) instructions, and they list a fuse (I guess unnecessarily) and a "double-pole isolating switch" - I had assumed that if I'm using a DP SFCU, of which I have one spare, that this covers both bases?

Added Later

I've just noticed that the fan is double insulated, so that explains the "double pole" comment, same question applies though...

 

[Space cat]

I went looking in the Wiki for a reference to the three pole switch and I found this --

//www.diynot.com/wiki/electrics:lighting:fan

The simple circuit with the three pole switch is there but below it is something not so different from what you were going to do.

To make it work you will need a double pole switch for your lights as well but you can save on the three pole switch. I would still put in an extra JB though and get some of those wires out of your ceiling rose. You have rather a lot in there already.

There shouldn't be any problems with those halogen lights but note that they are in PARALLEL, not SERIES.

"Double insulated" means that the fan needs no earth and has no connection for one. This type of equipment is also known as "Class two" and it should have a little symbol on it consisting of two squares, one inside the other. Class one stuff needs an earth.

The need for a double pole switch has nothing to do with it being class two. You would do the same for a class one fan. Take the earth wire to your fan and isolate it in case you change the fan later.

 

[Lectrician]

I see little point using an FCU and the DP switch to be honest. It over complicates and over engineers a simple installation.

99% of fan installs do not incorporate a fuse to fuse down from 6amp, and many dont even have an isolator (not saying you should not fit one).

If the fan fails, I am sure you would easily get a replacement with ease under the warrenty regardless of how it was wired, and if you couldn't, then a standard axial fan is litterally a couple quid!

I would be more pursuaded if the fan was a ventaxia ACM 6" or similar - costing £150 odd.

 

[emgee]

I thought that isolators for extract fans were only required if the fan was in zone one of the bathroom. Is that wrong?

 

[Steve]

I thought that isolators for extract fans were only required if the fan was in zone one of the bathroom. Is that wrong?

They require an isolator, in the same way that cookers require an isolator, and sockets behind fixed appliances require an isolator. For maintenance and general safety.

 

[topskins]

They require an isolator, in the same way that cookers require an isolator, and sockets behind fixed appliances require an isolator. For maintenance and general safety.

Just to confirm though: there's no point in me getting a specific isolator here , when the DP SFCU, of which I already have one, serves the same purpose?

 

[Lectrician]

Confirmed.

 

[topskins]

Thanks all for comments, very helpful .

 

[Spark123]

I thought that isolators for extract fans were only required if the fan was in zone one of the bathroom. Is that wrong?

To mount a mains fan in zone one you'd also need to make sure it is IPX4 (or IPX5 if hosing is likely), 30mA RCD protected etc...