Manual Extractor Fan Wiring

brettuk · Post by **brettuk** » Tue Feb 11, 2020 8:24 pm

Hey,

Hot on the heels of my success wiring up a relay up to the timed extractor fan and light in the downstairs toilet, I thought I'd try and do the same for the utility room which has a manually operated fan and light (not timed or linked)

Opening everything up, I'm not seeing what I expected to see, I expected to see everything come off the ceiling rose, wired similar to a timed extractor fan linked to the light but instead with just the Switched Live from the Fan switch going via the rose to the fan, without touching the lighting. That's not what I'm seeing.

I'll attach the pictures below, but I'm seeing a switch configuration which to my laymans eyes looks like it has a neutral in the switch, and then there is a direct 3 way and earth cable which goes to the extractor fan, bypassing the rose entirely. This seems completely different to the rest of the house wiring (where there definately ISN'T a neutral at the switches), and if there was a neutral at the switch I'd expect to see them coupled together not going into a switch, but the switch appears to have a N terminal looking at the pictures. Am I completely misunderstanding this switch configuration or am I really seeing this?

Also I'm a bit confused with the light wiring, from the rose it seems as though the yellow with red sleeve is connected to another cable (possibly the other switch, as the 2nd switch for the light doesn't seem to be wired via the switch as I'd usually expect), and the blue with red sleeve is the cable used for switched live.. there's also another point where the light can be controlled (note not the fan).

So if I'm understanding this right, I could install the relay in the switch, as it has a neutral there, and control the load going out on the RED cable (for the fan) and the BLUE with RED sleeving for the light?

The fan is the right hand side switch (the one closest to the camera) the light is the furthest switch. The yellow cable both behind the switch and behind the fan isn't hooked up - as there's no need for permie live at the fan I suppose

Someone-Else · Post by **Someone-Else** » Tue Feb 11, 2020 8:34 pm

You are looking at a double pole grid switch.

A normal switch breaks one wire, usually the live. (So as you rightly said if there was a neutral you would see both connected together in a choc block)
A double pole switch breaks two wires at the same time.

Grid switch is a way of configuring switches (on a grid funnily enough) so you can have almost what ever you want or need. I have a grid switch with no switches but two neon indicators.

The 3 core and earth from the switch to the fan, i would guess is there for future use, so if a fan with timer over run is ever used, the 3rd wire can start the timer.

brettuk · Post by **brettuk** » Tue Feb 11, 2020 8:49 pm

Thanks for the reply, that's interesting. Are both those switches double pole grid switches?

Someone-Else · Post by **Someone-Else** » Tue Feb 11, 2020 9:09 pm

They are definitely grid switches. (Since if one is a grid switch the other must also be a grid switch)
As for both being double pole, maybe can't tell from the angle of the switches. (need to see the complete back)

brettuk · Post by **brettuk** » Tue Feb 11, 2020 9:34 pm

Had another look, pretty sure it isn't - and I think from looking at the other switch, that the other switch is the switch that connects to the light, and this switch is the "end" switch, that completes the circuit.

I want to install a Shelly 2.5, which I'm going to have to put behind the 2 Pole switch so I can control the fan, so it's going to need to be on the "end" switch.

The Shelly takes in a L, N, a SW1 (switched live), a SW2, and outputs on 1 and 2

In this diagram i've wired up the light to 01 output, and because I've outputted it onto the L2, even though it's on the end switch, if I so wish I should be able to switch the light on via the relay no matter the position of either switch (am I correct in that?), the Common will be linked up to SW1, so if either switch is ON, the relay will know that the switches are ON, and if either switch has triggered OFF the relay will know it's OFF.

I've then wired up the fan switch to SW2 and output to 02.

Will this diagram work? It's not ideal, but I have to put the relay where I can control both loads.

Someone-Else · Post by **Someone-Else** » Tue Feb 11, 2020 9:50 pm

I have no experience of a shelly 2.5, so I can not comment.

brettuk · Post by **brettuk** » Tue Feb 11, 2020 9:56 pm

It's just a simple relay really. Take the shelly out of the equation, if I provide a live to l2 it will always keep the light on no matter the status of the switches right? And the common will be live if the switches provide an on state, and off if it doesn't.

brettuk · Post by **brettuk** » Wed Feb 12, 2020 1:38 am

Didn't work, which makes total sense thinking about it! The light would never go off

Unfortunately the position I need to be in to control the light isn't the same position as I need to be in to control the fan. So I'm using a shelly 1 to control the fan (works perfectly), and I'll install a separate shelly 1 to control the light.