DIY Doctor

Help with wiring extractor fan pls!

Postby hairyjockman » Tue Apr 07, 2020 4:56 pm

Hi all. Just fitted a small toilet in my garage and now have fitted an Xpelair extractor fan but cannot seem to get working - any help folks? Standard 24ov UK house and I was attempting to wire to the light so it only works when switched on. Thought it would be a simple 2 wire 2 minute job....I've attached a pic of the diagram and its a new fan unit.
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Postby Mr White » Tue Apr 07, 2020 8:35 pm

You have wired it across the switch.
It should be wired across the light.
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Postby hairyjockman » Thu Apr 09, 2020 7:12 am

Thanks for reply mr W. However, a simple reply has given me more questions than answers LOL! As a mechanic used to 12/24 systems and only occassionaly replacing or fitting sockets in a house the answer threw me a wobbly.
What difference does tapping the spur in the line at the switch or the light end make? surely the power is constant and running the whole length of that section anyway?
As this is a timer unit I was hoping the timer could bypass the permanant live to eliminate the run-on after switched on but have a feed that would allow the timer to work when switched on using the feed to the fan unit - ie so it could be set to run for x minutes when light is activated.
If this cannot be done can the unit still function with 2 wires but without a permanant live as the timer would then not be reqd. If yes then where and to what do the red/black wires go? Red to Live/brown Black to Neutral/blue tapped in where?
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Postby Mr White » Thu Apr 09, 2020 9:32 am

I was always taught "If I tell you something, you will never learn"

Look at your own drawing.
You have a cable running from the switch to the light (This is correct)
You have then connected the supply to the new fan across the switch.

Let me ask you this.
Q) What happens when you operate the switch?
A) The potential differance between the two wires is removed.

Now do you see why the fan can not go where you put it.

Regarding can you have the over run timer work, or not, depending on your choice at the time, the answer is no, as it would need more switches, one to operate the timer and fan, and one to operate only the fan.

TIP: Diagrams are not worried about voltage.
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