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Topic Title: Flat rewire
Topic Summary: Bathroom fan
Created On: 11 January 2013 08:22 PM
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 11 January 2013 08:22 PM
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tillie

Posts: 789
Joined: 03 May 2006

Hi , I am just finishing a flat I rewired before Christmas.

I have returned to connect two extract fans which have been installed by the glaziers whilst fitting new glass.

The kitchen fan I wired so you turn on manually.

The bathroom fan I wired for a fan with an overrun.

The glass company who fitted the fans have installed a standard fan with no timer.

The problem I have is that the flex from the fan has been run in behind the new tiling over to my switch with no way of getting out without damaging the new tiles.

So my question is does a bathroom fan need an overrun timer.

I have looked through ADF ( table 52 ) and it just states that an internal room with no openable windows should have a fan with a 15 min overrun.

This bathroom does have an openable window so do I need an overrun , I think not.

And secondly and more importantly should I ( we ) be doing all the flow rate tests that I am reading about in the document ?

Advice appreciated.

Regards
 11 January 2013 08:47 PM
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daveparry1

Posts: 6202
Joined: 04 July 2007

I don't think it does have to have an over run capability and I certainly wouldn't be bothering about flow-rate tests, just check the makers figures re the displacement. You say it's a flat, might be a different matter if it were commercial, eg offices etc.

Dave.
 12 January 2013 01:29 AM
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kirchoffs

Posts: 180
Joined: 08 February 2010

You could fit a remote timer outside the bathroom if you can get to the cable. I've used the Greenwood ones . Click on link below.

https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQezOUVsY_extXCun1b0iqIaHENE0wBx7wIxGq7lH8tE1zENE9tVQ

Regards Dominic
 12 January 2013 07:46 AM
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leckie

Posts: 1863
Joined: 21 November 2008

You do not need an overrun if the window opens, so no problem there.

I wouldn't worry about the flow rate as long as the fan can extract at a min of 15L/sec, might be a bit more of a concern if it were a ducted system but not for a window fan.

I was watching a building inspector, private outfit acting as the NHBC, testing the flow rate of the extract fan to a site we did. The site agent warned me that this guy was an absolute stickler and was refusing to sign off jobs if the flow rate of the fans was not up to scratch. He undid his briefcase and removed his calibrated test equipment. It was a sheet of A4 paper; he held it up to the fan and said that if the fan couldn't hold the paper up he would fail the fan! Unbelievable!

Edited: 12 January 2013 at 04:23 PM by leckie
 12 January 2013 08:50 AM
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daveparry1

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As you say Leckie, unbelievable although maybe a slightly stiffer test than the sheet of loo paper that I often use!

Dave.
 12 January 2013 09:31 AM
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SKElectrical

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Originally posted by: tillie




The bathroom fan I wired for a fan with an overrun.


The glass company who fitted the fans have installed a standard fan with no timer.



The problem I have is that the flex from the fan has been run in behind the new tiling over to my switch with no way of getting out without damaging the new tiles.


I don't quite follow you.
Are you saying that you did wire to the fan with both perm live and switched live?
Are you also saying that the glass company ALSO wired for a fan (with just a switched live)?

If there is both a sw live and perm live at the fan then I would advise you to swap the fan for one with over run, as it's poor practise to install a standard fan in a bathroom.
As for isolation switch - really not important unless it is an ensuite.

If it is wired in flex, you could consider using the cpc as a perm live (if double insulated).
Other options could be to change the sw live to perm and install a humidistat fan, or pir fan - all seem better options than just a standard fan.
 12 January 2013 12:33 PM
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redtoblackblewtopieces

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Using cpc of flex which would be green/yellow in colour and against regs to use other wise, cores of any colour can be oversheathed green/yellow and connected to earth but not other way around its in the regs and I think one electrician got in serious trouble doing this on a tankstat cable
Kevin

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Safety through a Standard
Compliance by Approved Documents
 12 January 2013 12:45 PM
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redtoblackblewtopieces

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514.4.2
Kevin

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Safety through a Standard
Compliance by Approved Documents
 12 January 2013 04:29 PM
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leckie

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Sk
Why would an isolator only be required for an en-suite?

Why is a standard fan in a room with a window poor practice? It complies with building regs.

On no account ever use a cpc as anything other than a cpc. Potentially extremely dangerous and has cause at least one death that I know of.
 12 January 2013 07:19 PM
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tillie

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Hi , I wired the fan with a sw live and perm live over to a 4 pole fan isolator.

The glaziers supplied the fans which were prewired with 2 core flex.

They ran the flex up to my isolator and left it in the back of the box.

In the meantime the bathroom has been tiled and the flex is now behind the tiles.

I always install fans with overrun timers in bathrooms because I thought you had to.

Now rather than having to smash out two tiles I am thinking of leaving the fan in place and Part F appears to say that I am allowed to do so.

As for installing isolators on fans I thought this was a must if there was no other means of light ie window in the room concerned.

I always do install isolators on fans with overrun timers.but is there a definitive reg.

Regards
 12 January 2013 09:57 PM
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leckie

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Don't touch any tiles, you don't need to, leave it as it is. It complies.

What is the isolator for on this piece of equipment?
Probably just for maintenance, for cleaning for example. Therefore the isolator needs to be under the control of the person carrying out the maintenance. This would mean local to the fan or lockable if outside the room.
 12 January 2013 10:20 PM
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rocknroll

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The clue here is intermittent, in a domestic situation an intermittent fan is deemed to be under occupant control, the purpose of switching on to disperse pollutants and steam and then off again, whilst it is recommended that where there is a room without or does not have an opening window the fan should be controlled by the light switch and have an overun time, if the owner wants a seperate switch and no overun thats their choice as they control it.

In testing such as air quality and air tightness intermittent fans are switched off and do not figure in the test providing they are fitted properly, ie sealed around the fan and the aperture does not compromise the envelope.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 12 January 2013 10:23 PM
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SKElectrical

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yes I knew my post would rattle a few cages..

I have never wired the with the intention of using the green/yellow as a live (but I have swapped equipment like for like that does utilise the green yellow as a live conductor - such as a pir, or fan).
doing this on a tankstat cable
- That is a different kettle of fish altogether.

Until recently I thought it very poor, but in hindsight it really is no big deal especially if it's double insulated - sometimes you have to use your own judgement. In addition, I would not use brown tape, but brown sleeving, and I would also mark up with permanent marker pen. It remains imperfect practise.

Isolators for ensuites only? Well as a rule I don't wire for isolators be it for fans or showers - there isn't much point... except for an ensuite where cust can switch isolator to 'off ' if they deem the fan too noisy at night time.

Why is a standard fan in a room with a window poor practice? It complies with building regs.

Just because it complies with building regs doesn't make it good practise. Why on earth settle for the minimum standard.

I note all departures from the wiring regs on the EIC.

Domestically, I only install silent fans with a minimum of overrun / humidistsat
or preferably (and dearer)
ceiling fans ducted outside;
both options including back draft shutter, and triangular cowel with silent shutter.
 12 January 2013 10:35 PM
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leckie

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So you are prepared to connect perm live on a pir switch using a g/y cpc? You must be potty. What about when the class 2 fitting is replaced with a class1 and someone is electrocuted?
 12 January 2013 10:43 PM
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SKElectrical

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the earthing arrangement of the light fitting wouldn't be affected by the scenario I am talking about.
Again, the gr/yell wire would have clear coloured identification...
and just because some spark can't be ar**d getting their testers out, isn't my problem.
I'm talking about a short run of flex (1 metre max) surface clipped with junction box all in clear view.
 12 January 2013 10:46 PM
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leckie

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Sorry but that is rough. If its only 1m swap it.
 12 January 2013 10:55 PM
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SKElectrical

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I hate to hijack the original post, so this is my last comment on this.
If you think im driving to the wholesalers to replace a 30cm bit of flex - think again buddy boy!

Just want to re-iterate I install 4 core flex on a new installs.
 12 January 2013 11:06 PM
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leckie

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Well the op was about a fan installed in a room with a window. The fan was pre-wired by others in flex with a sw line and neutral. This was buried under tiles.
The guy didn't want to chop out tiles and make a mess.

He has been advised, quite correctly that he did not need to.

You advised him to swap the fan, even though he doesn't need to, and if necessary use the cpc of a flex for a perm line. Even though you haven't seen the install, so you don't know how long the flex is that has been installed by others. It might be 6m for all you know.

You then said that you wouldn't bother with an isolator, even though there would be a perm live if he took your advice, to the fan.

The mind boggles.
 12 January 2013 11:27 PM
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SKElectrical

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I don't settle for bog-standard nor do my customers.
I actually gave the OP different options - some compromised wiring standards to a degree but all provided better solutions for the customer - the OP can decide which if any best suits.
With modern building practices, condensation is the biggest problem facing householders. The fan installed is not suitable, and the building regulation that says it is, is not worth the paper it's written on.
If you want to install bog-standard pendants, bog-standard fans, bog-standard flood lights, bog-standard doorbells, and bog-standard consumer units, go right ahead, afterall the regs may say they're okay. I won't.
 12 January 2013 11:39 PM
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leckie

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IET » Wiring and the regulations » Flat rewire

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