installing smart switches - upstairs/downstairs

[sinbrad]

You have the right idea in my book. Having got 'L' to the second smart switch, you also need a neutral to it, to connect the other end of your virtual load to, namely the capacitor. I'm hoping your two blacks in the choc block are actually a neutral and that will work.

How do I know they are neutral?

 

[Avo Mk8]

How do I know they are neutral?

Test equipment. Multimeter? Continuity check (power off) between the black wires and relevant consumer unit neutral.
If your volt stick checker has never indicated a voltage on said wires during all your experimenting, I would say there's a good chance they are neutral. Much as nobody likes guesswork, it would be safe (because of the few mA current involved) to connect the capacitor to the black wires to check if the configuration does work.

 

[brianmoooore]

Almost definitely the two blacks in the fastfix box are neutrals. One T&E is L and N directly or indirectly from the CU, the other T&E is SwL and N to the lamp, and the 3&E is to the other switch.
Why do you need two smart switches to control one light? If it's a smart switch, surely it can be controlled from anywhere.

 

[sinbrad]

Almost definitely the two blacks in the fastfix box are neutrals. One T&E is L and N directly or indirectly from the CU, the other T&E is SwL and N to the lamp, and the 3&E is to the other switch.
Why do you need two smart switches to control one light? If it's a smart switch, surely it can be controlled from anywhere.

Yes, that is correct regarding the smart switches but there are people in the house that still want the manual element so there is still the requirement for two smart switches. Eventually all switches will be replaced with smart switches

 

[sinbrad]

Well, stumbled at the final hurdle. Got both smart switches powered up and paired to the smart life app but I am unable to pair them together as there is no setup guide to do this. I have reached out to the manufacturer but little hope there. On amazon it does state multi-way via smart life app but that's it, no instructions or anything included and a search on google etc throws up a blank. Oh well, it was an interesting project and thanks for all the input

 

[Avo Mk8]

Well, stumbled at the final hurdle. Got both smart switches powered up and paired to the smart life app but I am unable to pair them together as there is no setup guide to do this. I have reached out to the manufacturer but little hope there. On amazon it does state multi-way via smart life app but that's it, no instructions or anything included and a search on google etc throws up a blank. Oh well, it was an interesting project and thanks for all the input

Sorry to hear that. Don't give up!
There are probably some words of wisdom out there somewhere on how to get the app to do the job.
Failing that, I'm sure there are other smart switches that will do what you need.
What you've done so far is the right way to do it, just seems the app is a bit impenetrable!