NO thermal actuators would be used instead of NC, so that they would be (automatically) left in open state (off) when something’s wrong (system dies) so if the failsafe thermostat kicks in, then room/house shouldn’t freeze.
For that, I want the switch/relay to have auto-off timer to put it back to open state eventually.
SELV 24V instead of mains 230V as a protective measure against electric shock at fault - it is expected, that some kid would try to, and potentially succeed in ripping out the cable.
And, zigbee because of some personal preferences, reasons.
So, summary a relay with:
wireless technology: Zigbee,
input voltage: 24V,
output: input voltage 24V (not dry-relay),
built-in functionality: auto-off on timer since turned on,
form factor: module with cable in and out - not just wires, but whole cable with sheath.
I have used a bunch of these they are OH zigbee compatible accept 24 volts to operate and you can loop that 24 volt source to your relay they have different working modes one included is on then off after a period of time . as for wiring harness and all that you likely will have to make your own cable. The link I shared is just for the zigbee board but there is also a different link for the case to put in or even device in case as well.
Thanks for replying, and info about working modes.
I already found these, and the case doesn’t seem to have enough space to loop things internally. So, not a nice surface mounted module for my use-case.
There it’d probably be a custom enclosure. And, I’m thinking also about modules, that go into back boxes.
Don’t know about Zigbee yet, but Shelly Qubino Z-Wave 2PM has a good amount of settings for built-in functionality, that include also auto-off.
For my irrigation system solenoid valves operating at 24VAC I use ESP32 with Tasmota and 5V relay extension board. I control them fromOpenHAB via MQTT. Basically ESP32 is acting in dumb mode, just relaying the commands from OpenHAB but in Tasmota you can program timers so for example my valves go to off position one hour after the on command, just in case something fails on OpenHAB or MQTT side
I’m currently trying to compose the solution out of off-the-shelf products, and see how far I can get without any custom products. And, how well will it behave regarding heating experience.
I prefer zigbee instead of wifi, because it’s a mesh network and should be more fault tolerant. And, it’s isolated from my LAN without the need to go through hassle with setting up multiple SSID/VLAN(s), firewalls, etc.
Maybe, eventually I’ll create a custom zigbee controller, that would collect temperature reports via zigbee bindings, control relays via zigbee bindings, and also have some things wired (where possible), and maybe some RS485 modbus things. And, therefore continue to function even if gateway or automation software would be down.
I have a few of these devices as well I use them to open an actuator on a vent louver and trigger a couple relays to do other things based on temp values. I liked them because they work standalone.
I will say however they are not as reliable as I had hoped and a bit finicky to configure with mqtt but they work .
I did not mention them before because they are not fully compatible with OH ZigBee binding but do work mostly ok with zigbee2mqtt also input voltage does not handle 24vac only 7-32 volt dc but you did not mention what you are using as far as ac or dc as a control circuit so it may work for you the case on these does have the ability to place a jumper on board side to use the input(supply power for device) as the common on the dry contact. What it also has a way via specially crafted mqtt publish a on command with timed off.
When setting the state to ON, it might be possible to specify an automatic shutoff after a certain amount of time. To do this add an additional property on_time to the payload which is the time in seconds the state should remain on. Additionally, an off_wait_time property can be added to the payload to specify the cooldown time in seconds when the switch will not answer to other on with timed off commands. Support depends on the switch firmware. Some devices might require both on_time and off_wait_time
