fused connection units

[Big_Spark]

pipme, you state that the spur is fed from the lighting circuit, so in effect the actual fused spur is not required, but until the introduction of 3 pole isolators, it was common practice to use a Switched fused spur to act as a local Isolator for the fan. This would allow the fan to be isolated and worked upon without the inconvenience of removing the supply to all the relevent lighting on the same circuit. It also introduced a level of safety that ensured the circuit could not be re-energised by a third party without the Electricians knowledge.

However, since the introduction of 3 pole isolators for local isolation purposes there has been no need or requirement to fit a fused spur to the circuit that feeds the fan.

In order to feed a timed fan from the lighting circuit you simply need 3 core and Earth to give the supply you require.

Red should be used to denote permanent live, and this would be connected to the "loop" lives in the cieling rose/batten lampholder base.

Yellow should be sleeved red and this will connect to the live feed from the switch to the live of cieling rose/batten lampholder base.

The Blue should be used as the neutral and the uninsulated core should be sleeved in green/yellow sleeving and used for the Earth.

Between the cieling rose/batten lampholder and the fan, you should introduce the 3 pole Isolator. This can be located where-ever you like, although I would suggest within 300mm of the fan if moisture will not be a problem.

The supply from the Isolator to the fan will be simple, The Neutral will go to the Neutral terminal, the switched supply will go to a terminal marked as such, or possibly L1, whilst the red permanent live will feed a terminal marked as such or simply L. This is the general consensus, but I would suggest that you read the fan manufacturers instruction to ensure they have followed this convention, some do not on every model.

 

[pipme]

Hi,
Thanks FWL_Engineer.
Unfortunately my bathroom lighting has not been wired using the rose loop method, but appears an amalgam of that and junction box method.
Installed as I have mentioned by an electrician.
I have been thinking, and to satisfy the one appliance per FCU rule, (I could have argued that the bathroom light was actually a large indicator of probable power to the fan and hence the FCU was just supplying the fan.... poor joke) I will utilise a spare pullcord switch dedicated to the fan only, this being supplied from 2 pole FCU on landing high. I shall, following your advice, mount the 3 pole isolator at safe airy position in loft near fan .... enabling as you pointed out .... isolation of the fan to enable cleaning etc.
I think this layout will be very easy to analyse by a visual of the cabling in the future.
My concern has been driven by the scorching and burnt out resistor I found on the old fan circuit board ... my warning I percieved .... nothing seemed amiss in the normal operation of the fan ....... so for me, safety first, cost second for this out of sight kit, and perhaps exceeding the regultary requirement in doing so.
We once had an extra pullcord switch for extraction in a previous house, on one hand bit of a pain, on the other gives some control of fan ... not needed for every visit to bathroom. So has benefit in conservation of heat etc
Hope this meets some approval.

P.
ps. Thought I stayed up late !!!

 

[il78]

FWL

What would you like me to justify? Why you should use FCU's for circuits in bathroom.
As a spark you cant, it should be designed properly but this does not make it unsafe. The poster asked if they could and your reply was that FCU's should never be used....But why?.....because its your personal preference.

Any-one that is willing to answer questions on a forum must accept that other people will disagree and must able to accept criticism . But you cant!
I dont look for holes in peoples replies, I just dont understand where they are coming from, so I ask....This one was not "pretty obvious"

The cut & paste thing......I thought that was funny, and it made the point...

And I did justify my reasonings in the post above (1-5), you have your way and I have mine........

Regards,

Ian

 

[Extrasolar]

Just to add my two pence worth if it's worth anything at all. My extractor fan in the bathroom has a pull cord switch on it. It isn't a timed version nor does it have a switched live, you just turn it on and off as you need.

It is connected to an FCU protected by a 3amp fuse which is fed from the rose in the bathroom.

Pretty much the basic fan installation I suppose.

 

[Big_Spark]

Ian, what I was aking you to justify was why you disagree.

Please don't make assumptions about my reactions, I do accept that people will disagree with me, perhaps you should re-read my post in which I justify my position, I clearly state this is a PERSONAL view and that otheres, including yourself, ma disagree.

Your post implies that you believe me to be new to the idea of posting on forums, that could not be farther from the truth as I have actually been a moderator of a forum that had many thousands of members and several hundred active posters on a daily basis..thankfuly I was not alone in this task.

I have been using the internet since 1991 and using this type of bulletin board for almost 7 years.

 

[il78]

You should never run shaver points or fans in bathroom from a ring main spur or a radial circuit for other purposes.

This remark was made by you, I have not edited it in my own favour

This implies that it is against regulations or considered as dangerous. Granted you mentioned that its personal preference but later on in the discussion, which I would never argue with because we all have our own personal reasonings.

As for justifying my reasonings for installing FCU's to circuits within a bathroom, well there shouldn't be, but you already knew the answer, if the installation has been designed correctly in the first place, but you may limited access to the lighting circuit, the customer wants a fuse spur, its cost effective.....

I appreciate your opinions more than others on this forum, and maybe why I look for discrepancies in your comments, either that or I just dont like you
Nobody take this to heart, I like you all really.....

 

[Big_Spark]

Ian, it matters not to me whether you like me or not, it is important to me that those that are attempting to undertake electrical work that they have no experience or training for recieve the best possible advice, whether that be from you, Breezer, Ban myself or anyone else.

I cannot help the way you chose to read my comment, I accept that it could have implied that the regs would not allow this, this was certainly not my intent, but i do stand by my comments on this subject.

HOWEVER, I 100% agree that a properly designed installation should never find an installer, professional or otherwise, in a position of making this judgement call.

As I stated, the IEE, whilst not banning this practise, do not condone it either, for many of the reasons I used to justify my position..so I suppose we will simply have to agree to disagree on this point.

No great shakes.

 

[pipme]

hi,
Extrasolar ..... I had hoped to see my old fan installation as a conventional, if that's the word, set up ... read some books looking for loop-in rose or Junction box system.
Found the live bathroom lighting feed going to the supply side of light pullcord sw. being used as a junction as well as switch, there being 3 lives and associated earths, ( the 3rd taking perm live eventually for fan to a junct box several meters distant ) this junct box recieved the single core neutral 2 cables supplying that, a tap into existing circuit. See my prob as an amateur ? This junct box has neutral, sw live, live, earth ... to feed the fan ... circuit has :- no 3 amp fuse, no 2 poleFCU, no 3 pole isolator ..... this was installed by a sparky.... Anyone think he did a good job? Not on the cheap, as part of an otherwise excellent bathroom instal project by plumbing firm .. several years ago.

The circuit was a little difficult for the likes of myself to analyse .. not conforming to the standard types I had read up about. .... Confident about direct replacement ... More reticent about redesign .... Sure now that the my job will be more 'professional' and safer than the old set-up.

I felt the need to retain timed type fan, teenagers prefer a sauna, leave bathroom, shut door (sometimes !) and forget !!

DIYnot forums good fun, nice to read the odd squabble over a point of preference .... interesting to pick-up accidental mis-communications too .... just shows it aint easy. Be nice if we were allowed to post pictures directly ... guess would be awkward with different sized image files tending to clog the site....

Thanks all.
P

 

[breezer]

Be nice if we were allowed to post pictures directly ... guess would be awkward with different sized image files tending to clog the site....

Thanks all.
P

sorry to say this but you can post images directly to this forum, see here

 

[pipme]

Hi,

Yes, saw that.
Was thinking more like directly into the text area ... here for example.
Cheers,
P

 

[breezer]

like

this?

 

[pipme]

Hi,

Yep, just like that !! excellent !

Who cuts your grass then Breeze ? I see no sheds !!

I am still amazed no-one has picked up on the duct extractor fan manufacturer requiring 3 amp fuse protection and how to accomplish this when using the bathroom light switch for the timed over-run fan .... you cannot protect the sw Live AND permanent live after the switch ... no 3 pole fcu available. If you do so before the switch then you also protect the light also, not recommended. (tho' could claim it is just a big warning light for fan !)
So to hell with it .... easy way out for me, separate pullswitch for fan supplied by 2pole fcu (can then sw off to change fuse if necessary). ... 3pole Isolater in loft near fan .... Job done ... Satisfactory ????

Perhaps inelegant ... safe tho' ????

P.

 

[ban-all-sheds]

I am still amazed no-one has picked up on the duct extractor fan manufacturer requiring 3 amp fuse protection and how to accomplish this when using the bathroom light switch for the timed over-run fan .... you cannot protect the sw Live AND permanent live after the switch ... no 3 pole fcu available.

Would it be unduly cynical of me to wonder if the m'fac has made this requirement deliberately, knowing that it'll be hard to do, knowing therefore that people won't do it, thus giving them a handy get-out from warranty claims?

If you do so before the switch then you also protect the light also, not recommended.

Why not? A 100W light draws 435mA - how much does your fan draw?

.... easy way out for me, separate pullswitch for fan supplied by 2pole fcu (can then sw off to change fuse if necessary). ... 3pole Isolater in loft near fan .... Job done ... Satisfactory ????

Perhaps inelegant ... safe tho' ????

P.

Yup - safe. Problem is that people might forget to turn the fan on, which is why they are conventionally wired into the light. If you want it on the light and you want the 3A fusing and you do not want to fuse the light as well, then there is nothing wrong with taking the permanent live and switched live through 2 unswitched FCUs. Or if you used a dual (not 2-gang) box like one of these:

then you could neatly mount a 2-module grid plate with 2 fuse modules and the isolation switch next to each other.

Other makes of accessories and other suppliers are available.

 

[Big_Spark]

Rather nice solution there Ban, Never seen it done but it is certainly workable, my only thought on this would be whether this would fall outside of what the NICEIC or IEE find acceptable.

Perhaps Il78, as an NIC Tester will be able to shed light on this for us.

I do like it in theory, and can certainly see no problem with it.

 

[pipme]

Hi,
Like the pix ...

" Why not? A 100W light draws 435mA - how much does your fan draw? "

Rated at 40 watt !! Given 3 amp fuse, does this allow the thermal overload to do its stuff before the fuse blows, in the event of a problem ?

My bathroom has window, so is not required to have extract fan ... convienience really.
No problem with extra cord pull sw, neon telltale would be useful, with timed fan !! hmmm is it on or off ?
Imagine say I have a fire and there is some stuff left over, along comes old FWL employed p'raps by my Insurance company as an inspector... ah, ha says he, Manufacturer states fuse at 3 amp .... No fusing here except 6 amp lighting fuse at main, that is 100% greater..... I'd be left with a fire damaged roof (at best) and possibly no insurance !!
A strict man of the book may also not be pleased with lights and fan off same FCU.
Grid plates etc are new to me, so am off to read up.
P