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Drill through beam, pull through conduit, or what?

How is the fan going to be controlled as run on and individually?
The fan switch will go to the fan’s switched live input, via whatever method I end up with. There are various ways it could be used, including flicking the switch on and off to get a 10 minute burst of extraction when necessary. I think the fan can be configured to not run on. I believe it also has a humidistat mode which I don’t currently use.
 
The fan switch will go to the fan’s switched live input, via whatever method I end up with. There are various ways it could be used, including flicking the switch on and off to get a 10 minute burst of extraction when necessary.
Fair enough.
I think the fan can be configured to not run on.
I've never seen a fan timer module in which the timer can be completely 'disabled' (without getting one's soldering iron out), but they invariably have a configurable run-on period, and that can usually be wound down to no more than 'a few seconds'.

If you were prepared to 'get your soldering iron out', you obviously could (referring to the circuit I included in post #6) dramatically reduce the value of (or probably completely remove) the 470 F timing capacitor (and/or, probably, remove the diode between IC1a and IC1b)
I believe it also has a humidistat mode which I don’t currently use.
That obviously would need a permanent live.
 
One option would be to remove the timer from the fan and install it near the light (instead of your proposed relay arrangement), that way only neutral and motor live required, leaving the 3rd core free for the mirror lght.
 
One option would be to remove the timer from the fan and install it near the light (instead of your proposed relay arrangement), that way only neutral and motor live required, leaving the 3rd core free for the mirror lght.
Yes, that would be the obvious option IF the OP definitely did not want the timer (or humidistat) functionality. Whilst,as I wrote, I've never seen a timer module which can be totally 'disabled' (without some 'soldering' work), removing the timer module is child's play (I've often done it, at least as a temporary measure, when a timer unit has failed or needed repair) - and obviously removes the need for two 'lives' (perm L and S/L).
 
One option would be to remove the timer from the fan and install it near the light (instead of your proposed relay arrangement), that way only neutral and motor live required, leaving the 3rd core free for the mirror lght.

That’s an interesting idea, but this fan’s control electronics seems significantly more complex than the timer designs that you’re thinking of (and that I’ve seen on other fans). For example, I think there is something like a motor speed sensor or similar that feeds back to something on the PCB; when perm live is connected, it starts the motor to do some sort of speed calibration.
 
That’s an interesting idea, but this fan’s control electronics seems significantly more complex than the timer designs that you’re thinking of (and that I’ve seen on other fans). For example, I think there is something like a motor speed sensor or similar that feeds back to something on the PCB; when perm live is connected, it starts the motor to do some sort of speed calibration.
That's pretty unusual. The timer units I've seen are all essentially the same, both physically and electronically (with just a few variants to the electronics), with just screwed-terminal blocks on the two ends of the PCB - a 3-way one for 'in' (Perm L, S/L and N) and a 2-way one for output to the motor - so, as I said, making it child's play to remove and 'bypass' the module. It sounds as if you must have a more up-market one than the various 'fairly basic' ones I've dealt with.

Most of the variations in electronics I've seen are very trivial. The one I showed was per Manrose, but many of the 'nameless' and own-brand ones I've examined are essentially identical. A slightly less trivial difference was seen in a Wickes-branded one I took out of service a decade or so ago. It used a transistor, rather than one of the gates of a CD4001 to be triggered by the S/L input, but that seemed a bit daft, since they then ended up with two of the gates of the CD4001 being unused ....

1745266673412.png
 
For a mechanical relay, half wave rectified 240 V is about 170 V RMS, which I guess is probably enough, but with some odd harmonics; I wonder if it would buzz.

My experience of the proposal: AC relays will buzz and arc

Here we go:

Ugh, well I was going to upload a 3 second video, but it seems I’m not smart enough to do that. But anyway, it buzzes very much indeed. In fact it would make quite a good door bell buzzer!

Tune in again in a few days for the next exciting installment!
 
Ugh, well I was going to upload a 3 second video, but it seems I’m not smart enough to do that. But anyway, it buzzes very much indeed. In fact it would make quite a good door bell buzzer!
As I rather expected - but probably not something that a capacitor could not deal with.
 
I’d be inclined to try experimenting with a few cap and relay variants just to get an idea how half wave rectified mains might buzz or not buzz however much you try to make it quieter or louder .
Bench test the variants and switches including mounting the relays clamped hard to wood/metal/sponge etc etc etc a bit like you might experiment to reduce transformer hum in a basic intruder alarm control panel.
Then decide to what extent you are going to include some electronics into the mix.
Once you’ve done you’ll find differing results and one might surprise you (or not).
Worth a try I think before you decide might you might or might not include in the final build.

Make a neat job of the bench test experiment and your local college or your own works department might appreciate it being donated for them to train engineers or apprentices in some of the finer arts rather than reading them in a book too.
It’ll get you a few brownie points if you’re lucky.

I like your concept of initially starting with near pure electrical solutions then maybe adding a few electronics components to arrive at your goal.

I’ve made a few boards of working examples in my time and given them away to friends and trainers because the hands on “let’s see what happens when….” Is more exciting and more memorable than book or blackboard learning.
Of course, where suitable, I have erred towards a 9v battery or even 12v examples for safety, you need to watch out a bit more for mains electrics examples. So LEDs or miniature torch lamps in the past where possible.

My best one was a few twin sockets mounted on a board and the “twin and Earth” hidden in trunking (off course it was not long lengths of Twin and Earth but the trunking concealed some low ohm resistors hidden from view to emulate longer lengths) .
Metered tests for continuity could be carried out at the OPD end and various points around the “ring final” Circuit (Sorry Flameport) and additionally a six gang switch with hidden high ohm resistors could emulate all sorts of “Insulation resistance values”. All power was from their own test meters.

It did cause some challenges both to time served an learners Electricians and Plumbers in a few cases too.
 
I’d be inclined to try experimenting with a few cap and relay variants just to get an idea how half wave rectified mains might buzz or not buzz however much you try to make it quieter or louder .
Agreed. However, I presume that in the OP's case only pretty/very 'low-powered' relays would be needed, in which case I don't imagine that much capacitance would be needed to more-or-less 'silence' the relay.

If one could find a suitable 'slow release' relay, I imagine that might also do the trick - the 'smoothing' then being magnetic, rather than capacitive.
 
Good point John
Another fairly random thought (perhaps not yet 'thought through' enough :) ) ....

... if the OP wanted to use his experience to 'play with electronics', if he fed the relay coil 'electronically' (e.g. with a transistor or SCR/triac), then a pretty tiny capacitor on the input to the driving device would probably be adequate, wouldn't it?
 
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Another fairly random thought (perhaps not yet 'thought through' enough :) ) ....
... if the OP wanted to use his experience to 'play with electronics', if he fed the relay coil 'electronically' (e.g. with a transistor or SCR/triac), then a pretty tiny capacitor on the input to the driving device would probably be adequate, wouldn't it?
In fact, thinking randomly even more, does one necessarily need the relay at all - would a triac with a small capacitor on its gate not be sufficient?
 
Yes they are all possibilities, I must admit that my Electronics is purely of a hobby basis though and it’s a few years since I was well into it .. I still think a decent or half decent cap on the supply lines with electronics fed from rectified half waves but your slow release relays could mitigate that quite a bit too.

In the days before bootstraps replaced coil transformers, mind you a Jacob’s ladder with a Cockcroft-Walton multiplier to create hundreds or thousands of volts and charge up a decent cap to hand to someone was a game well played back then ;)
 
My best one was a few twin sockets mounted on a board and the “twin and Earth” hidden in trunking (off course it was not long lengths of Twin and Earth but the trunking concealed some low ohm resistors hidden from view to emulate longer lengths) .
Metered tests for continuity could be carried out at the OPD end and various points around the “ring final” Circuit (Sorry Flameport) and additionally a six gang switch with hidden high ohm resistors could emulate all sorts of “Insulation resistance values”. All power was from their own test meters.

It did cause some challenges both to time served an learners Electricians and Plumbers in a few cases too.
That sounds like normal commercial training facilities as used by many colleges. The usual devices I've encountered are based on desk top triangular trunking and toggle switches on the vertical rear face and a row of single unswitched sockets and one end 6 terminals and a switch to represent the termination at the CU, the other version being 6 terminals and a link switch replacing each socket.

I'd be very concerned if such a system caused challenges to time served electricians
 
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