Wiring a continuous extract fan

[Scoob72]

Getting a sparkie in to do this, but I'm curious as to how it's done....especially as far as my budget is concerned. I need to add a continuous extract fan into my cellar (running at low speed 24x7), but the only lighting circuit nearby that it can connect to is a an 'extension' off the main lighting circuit. It's just 2 core and earth from the main lighting circuit (upstairs), straight into a ceiling rose, powering the single bulb. There is no onward run of cable to another light.
Can this type of circuit support a continuously running fan. The light is off most of the time. Or is this going to be a more complex/expensive wiring job than I hope for?

Thx

 

[Iggifer]

It depends, does a cable from this light then go to a switch? If so its super simple.

If there is one cable that goes to the rose total, it might be a bit trickier, but you could always pick up a supply from a socket circuit.

The circuit should be fine to run a fan 24/7, a faulty fan in a friends bathroom was on for about 6 months before it got replaced, depends what else you have on the circuit tbf

Why must the fan be on 24/7? Damp?

 

[Scoob72]

Thanks for the reply. No, there's no cable from this light to a switch. It seems like the cable from this switch comes down from somewhere above....which is why I'm concerned it might be an expensive job. There is one working double socket in the cellar.....could that be used to provide power? And yep, the reason is damp. I need to get some continuous ventilation into the cellar.

 

[Iggifer]

You could spur off a socket to a fused spur and feed it from there.

Fans use very little power, a few hundred watts at most.

I would however, consider scrapping that plan, and look into getting a dehumidifier. I used to live in a damp flat, and picked one up on a screwfix deal and it changed my life (the flat already had 2 extract fans)

It would literally suck litres of water out of the air a day, and washing that used to take 3 or 4 days to dry, dried in hours.

The choice is yours of course

 

[Taylortwocities]

Fans use very little power, a few hundred watts at most.

Eh? are you turning into Winston? 20-30 watts might be more like it!

 

[Scoob72]

I had a proper damp survey done and they recommended continuous ventilation rather than running a dehumidifier, mainly because there is already some ventilation via air bricks. Running a dehumidifier would just extract moisture out of air pulled into the cellar.

Anyway, I've just had another look at the wiring and it doesn't seem to be quite what I originally thought. The wire which I thought ran up through the cellar ceiling to another lighting circuit in fact seems to run to the consumer unit and is its own circuit. If that's correct does it just mean the extractor fan can be wired directly off that lighting mains? i.e. cheap and simple to do?

 

[flameport]

If it's a separate circuit for the cellar light, then fan can be connected to it. Probably could be connected even if it wasn't separate.

What exactly is the point of this fan - all cellars are damp, due to them being underground. A fan will not change that.

 

[JohnW2]

Fans use very little power, a few hundred watts at most.

Eh? are you turning into Winston? 20-30 watts might be more like it!

In context, I'm not so sure about that. We obvious don't know the size of the cellar we're talking about, but I'm sure that a piddly little 'bathroom extractor fan' would have virtually no noticeable effect in my cellar, so we might be talking about something much meatier.

Kind Regards, John

 

[Iggifer]

Exactly what I was thinking, honest guv

 

[JohnD]

the latest generation of ducted fans are quieter and more powerful, and use less electricity.

For example, this one is about twice the power of a typical bathroom fan
https://www.tlc-direct.co.uk/Products/SLTD160.html

A larger fan will be quieter than a small one of the same throughput.
https://www.tlc-direct.co.uk/Products/SLTD500SILENT.html

Personally I would start by looking at holes, ducts or airbricks on two or more sides of the building. Natural airflow is silent and free.