Advice on centrifugal extractor fan fitting

ernest1990 · Feb 27, 2022

Hi all,

I've recently replaced my 4 inch centrifugal extractor fan fitting in the loft. I was hoping for some advice on if this is wired up corrrectly. The fan itself is working well.

Old fan had timer, new fan doesn't have timer.
Both fans are turned of via the pull switch in the bathroom.

I wired it up to match the old wiring:

First image attached is the old fan showing its wiring,
Second image is the new fan showing the new wiring,
Third image shows the existing switches next to the new fan (left off, right on).

With the old fan, this worked with both switches turned on. With the new fan, when both switches are on, the fan runs constantly. If I turn the left switch off and keep right on, the fans works as expected (on and off using the pull switch in bathroom).

Wanted to check if I'm good to leave this set up how it currently is regarding those left and right switches. It doesn't have any issues in how it functions. I just wasn't sure what that left switch has to do with this new fan / how I've wired this new fan up and why it causes the fan to run when switched on.

Any advice is greatly appreciated.

Thanks,
Andy.

brianmoooore · Feb 27, 2022

At a guess, the original installer (whose workmanship suggests was not a professional electrician) tried to comply with the manufacturer's instructions that the fan should be fed via a 3A fuse, and the only way he could think of doing this was to fit one in both the permanent live and the switched live.
Any reason you've started a completely new thread?
Still not convinced this is the correct fan. There's no sign of an adjuster for the overrun timer.

ernest1990 · Feb 27, 2022

brianmoooore said:
At a guess, the original installer (whose workmanship suggests was not a professional electrician) tried to comply with the manufacturer's instructions that the fan should be fed via a 3A fuse, and the only way he could think of doing this was to fit one in both the permanent live and the switched live.
Any reason you've started a completely new thread?
Still not convinced this is the correct fan. There's no sign of an adjuster for the overrun timer.

Hi thanks for your reply. The new fan doesn't have an overrun timer. I purposely went for one without it. Thanks.

brianmoooore · Feb 27, 2022

In that case you have connected it incorrectly. The permanent live should just be terminated to a loose connector block and not connected to the fan.
Why would you not want an overrun timer, especially on an inline fan, where the noise problem should be minimal.

ernest1990 · Feb 27, 2022

brianmoooore said:
In that case you have connected it incorrectly. The permanent live should just be terminated to a loose connector block and not connected to the fan.
Why would you not want an overrun timer, especially on an inline fan, where the noise problem should be minimal.

Thanks. Is this a fire hazard in it's current set up?

brianmoooore · Feb 27, 2022

This is probably a two speed fan, and without seeing the installation instructions, I can't say how it should be wired, but as things are, with the switches on, you are applying power to a stalled motor, which possibly isn't a good idea.
Disconnect the permanent live, as I said.
The other thing that stands out as wrong with the wiring is that, not only has the neutral wire not been identified with blue sleeving as required by the regs, but the black wire has been used as the neutral instead of the grey, which is contrary to convention.

ernest1990 · Feb 27, 2022

brianmoooore said:
This is probably a two speed fan, and without seeing the installation instructions, I can't say how it should be wired, but as things are, with the switches on, you are applying power to a stalled motor, which possibly isn't a good idea.
Disconnect the permanent live, as I said.
The other thing that stands out as wrong with the wiring is that, not only has the neutral wire not been identified with blue sleeving as required by the regs, but the black wire has been used as the neutral instead of the grey, which is contrary to convention.

Ok thanks for your help.

telectrix · Feb 27, 2022

from post #7.

the black wire has been used as the neutral instead of the grey, which is contrary to convention.

conventionally, i agree with not using the black as N, but if sleeved blue, any colour can be used to comply with regs. just being pedantic. nowt better to do atm.

brianmoooore · Feb 27, 2022

telectrix said:
.

conventionally, i agree with not using the black as N, but if sleeved blue, any colour can be used to comply with regs.

I'm well aware of that, but neither of the two remaining wires in use are sleeved, and, in the absence of testing, an electrician would assume neutral is live and live is neutral.
More to the point, the sloppiness of the original work suggests a DIY job.

telectrix · Feb 27, 2022

brianmoooore said:
I'm well aware of that, but neither of the two remaining wires in use are sleeved, and, in the absence of testing, an electrician would assume neutral is live and live is neutral.
More to the point, the sloppiness of the original work suggests a DIY

agree. RAF.

ernest1990 · Feb 27, 2022

When I tested it the first time after fitting there was power going into both L1 and L2, until I turned off the left switch. Could this have damaged the fan motor? It was working fine after. Thanks.