It is amazing how the company that sell the switch manage to survive

Well, do you think the diagram is from the seller not from the installation guide?

This is how the connection is supposed to be.

Most switch need to put capacitor on L1 (like in drawing) and as Fubar20 joke said that if you put the capacitor across the ceiling fan, not the light, you will see the fan speed is affected because capacitor will affect fan speed. So, avoid this.

I don't think you connect downlight that way in series, That way, the voltage is dropped by half for each downlight.

All should be in parallel, the two downlights and the capacitor

Maybe you simplified your diagram or term looping gave me different idea, but I meant connect in parallel, not series like the bottom one

You can find it today

oppss. I never seen UK smart plug, but there is pmany UK smart socket

https://shopee.sg/Ewelink-SST10-WiFi-Smart-...2483.7308901206

https://shopee.com.my/WiFi-Smart-Plug-(Mala...5564.4035291288

I look at he hole there and called it socket but the device itself are plug.... my bad

The frequency can be read here

https://en.wikipedia.org/wiki/Z-Wave

Looks like I misunderstood. I thought you got the frequency info but want to know Malaysia frequency

If they follow procedure, they need to submit any radio frequency product to SIRIM for approval since they need AP to import any radio related product. To legally import, they need product to be approved, thus I think the frequency should comply. Otherwise will not get approval. Unless they brought it in illegally , but this is legitimate business

Theoretically, zigbee is much better architecture compare to z-wave. Although both z-wave and zigbee use mesh networking, the z-wave can go up to 4 hops and limited to 232 total devices compares to no hop limit and 65k devices for zigbee. I guess the z-wave is more expensive due to less popular?

After ELCB? Why not before ELCB?

I see. The water heater one in DB. So, cannot avoid tapping after ELCB. Well I think it is RCD, not ELCB which I think will not trigger. Since you have other N nearby, then it is ok. If not just remove the heater RCD and put it near water heater. Anyway the water heater has built-in protection also usually, but people like to put additional one

That loop wire is the Live wire. Means the Fan and the light is sharing the same L wire.

The AC switch wire connect and disconnect both L and N (Double Pole Switch), unlike Fan and Light switches which only connect and disconnect only L wire. So, the Yellow one is L and the Black one is N.

My question: Is your house wiring single phase or 3-phase? The reason I ask is that because your Light L wire is Red and the AC L wire is Yellow. If 3 phase then, usually the H wire for each phase is different.

Like Fubar20 said it might trip the circuit breaker. Usually, RCD is used on each phase. Each RCD will compare the current that flows out of to load (L wire) with the current return from load (N wire). If it is not equal, then there must be leak or short, thus trip the RCD. That is why you cannot have one phase L return to another phase N.

Either use switch that requires no N or use the RF switch with receiving module at light point.

Looks like there is enough space between switches

That's good. Your house probably use 4-pole RCD or probably just normal 3-phase ELCB. This way any phase has common N

Hack the hole deeper. Not easy since you need to remove the in-wall plastic box first and put it back after hacking. Need to get longer screw to fix.

Another way is to put another mounting box next to the switch for the Sonoff and use plain switch cover. This way easy to fix in case of problem.

It has been in market quite long time ago, China made and several variations.

Bought it quite some time but never install . My fan is with light (3 light pattern control) and 3 fan speed. Looks like I can only use to remotely control the fan speed and only can on and off the light.

No need box. Put on ceiling and then don't look up

Change wall socket with smart wall socket will make it look nice than plug.

Putting another plug on smart plug adds 2 times bulge, thus possible tripping on plug.

Another bad point of having smart plug on wall socket is that now you have twice contact points; one between smart plug and the socket and the other one is the appliance plug into smart plug. This will cause more heat generated if operating high amp devices. Less efficient and more possible cause of fire.

Like what idoblu said, why need switch for water heater? Oh... you want to power it on since it takes time to heat since you are using tank type.

Well, I have tank type water heater too in Master bedroom. I find that it is not much delay. The heater inside this tank is the same power like instant one. If you turn you mixer to Hot side, it is almost like instant water heater also. Gradually during shower you can adjust accordingly.

Well, maybe you want to check from your office if you turn it off or not. Leaving it on will significantly increase electricity bill