New extractor fan installation

flembot · Post by **flembot** » Tue Aug 17, 2021 11:12 pm

Hi everyone. Our extractor fan of 14 years has finally given up the ghost. Need to fit a new one.

Have ordered and received a Envirovent Silent 100. Only snag is the fact that the old fan was 12v and the new one is 230v.
I have went into the loft to look at the existing wiring and taken some photos. I would really appreciate some advice on how to wire this fan.
Presumably I will need to disconnect the transformer of the old fan and connect this new fan directly from the mains cable? I did similar years ago when I changed all of our lights from MR16 low voltage spots to GU10 spots. However perhaps with extractor fan it is slightly more complicated?

Can anyone explain what I need to do to get this wired up? Can I just jack up the mains cable to the fan bypassing the transformer or is there a bit more to it?

PS the bathroom light switch outside the bathroom has two switches on it. One is for the lights and the other is for the fan.

Loft space - the one at the back is the one being replaced. Both of these fans were fitted during extension project 2007

: loft space; IMG_1435.JPEG (245.65 KiB) Viewed 2019 times

This is the transformer

: transformer model; IMG_1441.JPEG (216.03 KiB) Viewed 2019 times

The current wiring configuration

: Wiring 1; IMG_1439.JPEG (176.92 KiB) Viewed 2019 times

: Wiring 2; IMG_1440.JPEG (270.31 KiB) Viewed 2019 times

New fan wiring

: New fan wiring; IMG_1433.JPEG (192.55 KiB) Viewed 2019 times

aeromech3 · Post by **aeromech3** » Wed Aug 18, 2021 1:05 pm

Well I was waiting for one of the Electrical wizards whom might spot the easy path! Yes it should be relatively easy, if you had chosen the same unit which is still available as both that and the Silent 100 you have now have timers hence the Ls terminal; this means they need a permanent live (danger) and a switched live. You told us the fan has a separate switch but we don't know how it is wired; if the old fan continued on for a time after this switch was off then the permanent live was at the transformer and as you have two brown wires into the old transformer this is possible, But, without a competent person and a multi meter we do not know because both could be switch live and the fan will run but only when selected. I could not find a wiring diagram for the 412T to see what the brown to red terminal was ie L or Ls.

Neelix · Post by **Neelix** » Wed Aug 18, 2021 1:43 pm

You need to ensure continuity of the cpc from the fuseboard to the fan

aeromech3 · Post by **aeromech3** » Wed Aug 18, 2021 2:05 pm

Neelix :The Envirovent Silent 100 are manufactured with double electrical insulation (Class II) and therefore they do not need an earth connection.

flembot · Post by **flembot** » Wed Aug 18, 2021 2:50 pm

Hi thanks for the replies

Yes I have chosen the same unit - ie. this unit has a run on timer just like the previous fan

Light switch - I could get a photo of how this is wired later when I get home. It is a 2 way switch. One switch turns on the bathroom light and has no effect on the fan. The other switch triggers the fan. When this switch is then turned off the fan will continue to run until its run on timer (in the transformer) stops it. Not sure if that helps. If you need a photo as how its wired I can get one later.

Have a feeling one of the brown wires is live and the other would be our switch live. :dunno:

Neelix · Post by **Neelix** » Wed Aug 18, 2021 4:21 pm

aeromech3 wrote: ↑Wed Aug 18, 2021 2:05 pm Neelix :The Envirovent Silent 100 are manufactured with double electrical insulation (Class II) and therefore they do not need an earth connection.

The fan might not but BS 7671 states that a continuous CPC be present at each point on every 230 v circuit

flembot · Post by **flembot** » Wed Aug 18, 2021 5:51 pm

Happy to get a bit of four core cable (ie Live, Neutral, Switch Live and Earth) to run the whole way to the fan. If that is what you mean?

Other than that do I take it that one of those brown cables going into the transformer is the switch live that I need?

aeromech3 · Post by **aeromech3** » Wed Aug 18, 2021 6:36 pm

A competent person, working on the wires going into the old transformer, would need to be sure they are electrically isolated; throwing a switch or breaker does not guarantee that and a check with a meter would be normal as there is a permanent live which for all we know might come from a different circuit to the switched live, as it is, the blue neutral enters separately and might be borrowed!
If all that is possible, it would not matter if either brown was connected to the L and Ls because if it was the wrong way the fan would run continuously, if so then after isolating and checking again, the browns could be switched.

flembot · Post by **flembot** » Thu Aug 19, 2021 10:14 am

aeromech3 wrote: ↑Wed Aug 18, 2021 6:36 pm A competent person, working on the wires going into the old transformer, would need to be sure they are electrically isolated; throwing a switch or breaker does not guarantee that and a check with a meter would be normal as there is a permanent live which for all we know might come from a different circuit to the switched live, as it is, the blue neutral enters separately and might be borrowed!
If all that is possible, it would not matter if either brown was connected to the L and Ls because if it was the wrong way the fan would run continuously, if so then after isolating and checking again, the browns could be switched.

A voltage tester like this one? https://www.amazon.co.uk/dp/B07SL4NSS1/ ... TF8&psc=1

Also - once I determine the wires and can remove the transformer. What is the best thing I should be using to couple them together to connect to the extractor fan?

I'll also need a length of flex 4 core cable I presume, yes? Like this? https://www.tlc-direct.co.uk/Products/CA0dot75F4B.html

Thanks

Someone-Else · Post by **Someone-Else** » Thu Aug 19, 2021 2:16 pm

Just asking...........
Why remove the transformer? why not throw the whole box and fan away, they are not needed by the new fan, while you are at it, why not rewire it so that there are no joints?

aeromech3 · Post by **aeromech3** » Thu Aug 19, 2021 2:54 pm

Won't the 3 wires you remove from the defunct transformer reach to the new fan connection terminals when it is installed above the ceiling, the terminals should be under the small cover near your thumb in the picture?
Mostly the Electricians on this Forum would not recommend a voltage tester, like you link to, they would, as S-E states in his text use a multi meter; you could find many uses for one, like checking batteries etc and S.fix # 75337 is cheap enough and there is even a video.
Remember you are checking for no A/C voltage V~ and that means you have isolated correctly; however I always check the meter is working against a safe known voltage point when on mine the range would be 600 V~.
As a side note, many on here have recommended WAGO connectors, I only recently purchased some; S.fix do them but large qty whereas Toolstation do small amounts, I am converted now and made some 25 piece purchases on ebay for my future jobs.

flembot · Post by **flembot** » Thu Aug 19, 2021 3:33 pm

Someone-Else wrote: ↑Thu Aug 19, 2021 2:16 pm Just asking...........
Why remove the transformer? why not throw the whole box and fan away, they are not needed by the new fan, while you are at it, why not rewire it so that there are no joints?

Well I would be removing the transformer for that very reason - not required by the new fan.
What do you mean when you say throw the whole box and fan away? I would be removing the old fan anyway to install the new one.

Rewire it so that there are no joints - apologies but re-wire what?

flembot · Post by **flembot** » Thu Aug 19, 2021 3:53 pm

aeromech3 wrote: ↑Thu Aug 19, 2021 2:54 pm Won't the 3 wires you remove from the defunct transformer reach to the new fan connection terminals when it is installed above the ceiling, the terminals should be under the small cover near your thumb in the picture?

Do you know what - you are probably right - they would reach. But it would mean me squeezing those two grey electrical cables down through the hole and into the fan housing - it might be a bit tight and fiddly.

What do you think?

Neelix · Post by **Neelix** » Thu Aug 19, 2021 4:02 pm

Buy a new 12v fan …..

aeromech3 · Post by **aeromech3** » Thu Aug 19, 2021 5:26 pm

Yes flembot, no consolation, but I have complained to Xpelair about the measly connector blocks and space for cabling in their units; its something an electrician has to deal with; if you need to join wires then 3 double WAGO connectors 221-412, one for each of the L, Ls, N wires. T.station 10 pack # 50675.