I’m trying to figure out the right relay and wiring for a fan isolator switch that sits above the bathroom door (outside).
The current functionality is that, when the isolator switch is on, the bathroom light switch turns on the fan when the light is on. When the light switch is turned off, the fan turns off after 15 minutes, so I assume its drawing power continuously.
If the isolator switch is off, then the fan has no power.
I want to keep this exact functionality, just that I want to add an additional relay between the isolator and the fan, so I can turn on/off the fan remotely, almost like a 2nd isolator switch.
It should still receive and send power to the fan so it can run off its timer when the light turns off, except if the isolator or the relay are turned off.
I don’t 100% understand all the ports on a relay such as how they exactly create a circuit, but I really want to its just I can’t seem to find the right explanation.
Can someone please help with what kind of relay would do the job and the wiring involved.
If your device connects to mains electricity (AC power) there is danger of electrocution if not installed properly. If you don’t know how to install it, please call an electrician.
Beware: certain countries prohibit installation without a licensed electrician present
Remember: SAFETY FIRST. It is not worth the risk to yourself, your family and your home if you don’t know exactly what you are doing. Never tinker or try to flash a device using the serial programming interface while it is connected to MAINS ELECTRICITY (AC power).
That’s understandable - thanks! I have already some experience with replacing some 2 gang and 2-3 way switches with smart switches by Tapo I think 220s? Also wired up a relay on a 1 gang 2 way switch which works great.
Either one to be honest, whichever way would be better. Ideally I want the relay between the isolator and the fan, so I can cut power to the relay and fan using the isolator, but if I keep it on, I want to control the fan with the relay and the light switch.
Current circuit goes:
Light Switch - > Isolator Switch - > Fan
This has a live, a switched live and a neutral.
I am thinking of going:
Light Switch - > Isolator Switch - > Relay - > Fan
The way the fan currently works with the isolator switch in ON is:
Fan turns on when light switch is turned on
Fan continues for ~15 minutes after light switch is turned off
I assume the live is passing power through to the fan the whole time so the timer can work for the 15 minutes and then it closes.
When the light switch is on, the switched live connects the circuit again and prompts the fan.
I just want to add a relay to be able to turn off the fan, even if the light switch or isolator are on.
So, I want to essentially leave the isolator on all the time.
It is positioned very high above the door frame and I have no problem turning it off as I am over 190cm, but my wife is 160 and she has to jump up to reach it or call me. At night this can be annoying (also the fan is really really loud, but I can’t replace it as this is a rented property)
I want the light switch to control the fan as it does now, but I also want to have the ability to turn the fan on/off with a remote button, I have a bunch of those, regardless if the light is on or not.
For the diagram, I pass in a neutral to shelly, a live and leave the switched live going to the fan?
And I assume the L being shorted into I(nput), is so that when the shelly is switched, it goes to the fan, otherwise it is closed off from O(utput)
Correct.
You can’t really use the “switched live” as relay output because of the timer delay.
So you use Shelly just to cut Line to fan. Depending on how the delay circuit is done, just brief off-on might be enough to reset the delay timer. Otherwise keep it off for half an hour.
What you could do is connect “switched live” also to Shelly input SW to trigger some automation. For example:
You switch light on>> Shelly gets the trigger and turn on fan L.
You switch the light off>> Shelly gets the trigger and if it’s night, turns off fan L, if daytime leaves the fan L on for half an hour.
Wait, if I keep switched live and neutral to the fan, doesn’t that mean that the light will turn the fan on every time, even if shelly is set to off, because there is a complete circuit from the switch that bypasses shelly?
Can be but probably not. Depends on the circuit, I expect there is a relay triggered by light switch with delay. Just disconnect the fan L wire from the switch and try.
Shellys relay is dry contact, you could switch neutral as well, but I prefer Live if I can choose.
Or if complete time control is desired, (for example leave the fan on for an hour after shower) you can just disconnect the trigger wire going to fan(brown) from isolator and connect it together with L wire from Shelly output O.
Successfully wired up the light to the fan, I actually took out the isolator to save space in the end, but essentially it is the same wiring that Karosm recommended.
Unfortunately this doesn’t let me control the relay with the Switched Live from the light for whatever reason, but I also tried getting the input from the SW as well, by shorting that instead, which actually made it doable, but could only have the fan on while the light was on, which isn’t ideal, so I went back to the above.
Anyway, happy with it and have automations setup to turn on/off together with light as well as other bits like humidity sensor related and timings.
I tried a bunch of different approaches to be honest, I went with skipping the outgoing switched, but it seems the fan needs a signal from that one to start, even though it pulls the voltage from live.
I tried putting both Fan Live and Switched in the O on the shelly, Live on the L and Light’s switched on the SW, that ended up the same.
I tried a few of ChatGPT’s ideas, but I have a feeling that it might understand electrical currents a bit less than me which is confusing, because it tells me one thing after I gave a very detailed description of the current wiring, and that thing is the exact opposite of what actually works. at one point it told me to short the neutral with the shorted SW and a Live???
So I think with a bit of automation now I am fairly happy.
DANGER OF ELECTROCUTION 
, you got pass forward, but not not with the final result: