As per the title: From which load cable does an aqara double-relay switch drains power to operate?
If not from booth, will it be safe to have a load cable (L1) to a non smart bulb and, importantly, a load cable (L2) to smart bulb (with no current whatsoever when in off state)?
What are you trying to achieve with turning off the smart bulb? Ideally, smart bulbs should be always on, and you should just remotely turn off the light. Turning it on and off randomly will hurt your zigbee mesh network, unless it’s a wifi bulb… Eve then, using the hard-off is stupid, cuz you lose the functionality.
Switch should draw load from L, but since it’s no-neutral, it needs either L1 or L2 populated to close the circuit. I don’t think there’s anything about having to connect both, or one specific output, so it should use whichever of outputs to close the circuit. I don’t think anyone tested it. TBF, if you want a smart bulb, I would even consider just bridging the cables to have it always-on and use a single-rocker switch.
All smart bulbs in the house are, obviously, always on in their respective wall switches (none of them smart, just old dumb ones).
This is was option, for two main reasons:
a) quick reverse to non smart house, if I want to rent or sold the house and take with me all the bulbs, hubs, etc. The system is implemented in such a way that I can reverse it all back to full, or partial, dumb mode.
That’s why I never get smart hardware that’s no easily removal, for that reason or for upgradability.
b) I want a physical dumb switch ready to be off if I need to mess with a particular fixture wiring instead of switching of the breaker for that zone.
In order to keep the dumb switches I concealed them under pictures and photo frames so no one will turn the smart bulbs off inadvertently, in facto, outsiders won’t even know where switches are located.
But there’s one particular 2-gang switch that has an inconvenience, 1 gang switches the hall bulb, and the other the external bulb which is part of the condominium in a shared fixture and therefore I’m not allowed to apply any modifications. Unfortunately that fixture can’t accommodate a smarbulb, or at at least one with sufficient lumens for the task. Besides being economically inefficient to buy a smarbulb for the sake of just wanting it to be on or off.
So, what do I want?
So, I cannot conceal it like the other dumb switches I have in the house, because I still need the second gang.
And, I’d be more comfortable knowing that there’s no power being drained in the remote possibility of having to hard power off the smartbulb (besides flickering and other abnormalities that can damage the bulb electronics).
So, having said that, it’d be solved if the H2 switch drained power from only one of the load cables, say for eg. L1 and not L2, in that case, I’d wire the dumb bulb to L1 and the smart bulb to L2.
That’s what I’m trying to accomplish.
That’s a bit peculiar problem you’re having, then. Solving this with your typical no-neutral switch would be tricky, because I’m pretty sure they’re designed to close the circuit with either of the Ls, or even both at the same time.
If you want one of the lights to be always on with ability to turn it off only for when you want to change the bulb etc, you could install a shelly 1pm behind the light, where you have a neutral line and hard-wire it to L behind the wall switch. Then, for the light you want to operate with a physical switch just use a single rocker without neutral. That way you won’t have to worry about the trickle current to the smart bulb, and you can turn it off with your smart home system.
Well, in the meantime I’ve ordered the H2 
, because of Black Friday, in fact, while I was searching for answers, I already lost precious time for ordering in time for tomorrow deliveries, I’ll have to wait for next week
So, fait accompli, I think I’ll just leave it simple, and untie one of the channels to the smart bulb relay and leave it on in the app. And convince myself to use the breaker for servicing that light wiring when needed. As it’s not such a deal-breaker to actually invest more time and gear.
For what I’ve read it’s possible to do just that (untie one or both relays) in ZigBee mode.
The wall switch will then control the other light, and the remaining 3 buttons I’ll automate the alarm system and other stuff useful to operate when entering and exiting the house.
Thanks for the replies 
I would be careful about this statement with no-neutral version. I have the old one (H1?) with no-neutral, but only a 1-gang, 2 gang ones I have are all with neutrals, and the no-neutral one has limited functionality. My 1-gang no-neutral is missing OppleSwitchCluster where the couple/decouple is located. I’m pretty sure the same will be with 2-gang switches, but maybe the newer version has it.
The post surprised me by delivering the package this morning
I’ve mounted the switch and was able to do everything I wanted.
Didn’t test if it works with solely either with the first or the second Load cables, though.
I installed it (without neutral wire) and in the setup chose ZigBee (it comes with Thread protocol by default), the app than downloads and installs ZigBee firmware into the switch, so far so good.
In app we can decouple any one, or both, the buttons from it’s respective relays. In case anyone wonders: it’s not possible to couple both relays to a single button, as per the firmware design, but…
… we can, indeed, re-route the “coupling” via Hub, this is, pressing a button that sends a command to the Hub to open or close a relay, which in turn sends it back to the switch unit.
So, in my case, I decouple the Button 1 from it’s relay, then set up an automation (called it Hard Power) to operate the Relay 1.
That automation is by default disabled in the app. (If servicing is needed, I just have to enable that automation).
So, as the relay is by default opened, the LED indicator is on, which is a plus, as in the event of a bulb failure, I instantly know if it’s the bulb or if is a power cut to that bulb.
Then, I set up an automation (called it Soft Power) to that button to operate the smartbulb with an IF condition:
If Hard power is disabled,
then turn on/off smartbulb.
In that way when I manually enable Hard Power automation, the button acts as a relay opener, otherwise it acts as simple smartbulb wireless switch.
And since the LED is only lit if the relay is opened, than I know when power is cut from the bulb.
Now, the condominium light of my flat is “smart” (and “turning off” forgetting proof) and linked to the doorbell as well, while maintaining safety operation of the smartbulb inside, all in the same switch.
