Thermostat without rewiring (Tuya/Grid connect switch)

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deadlyllama

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#275858 14-Sep-2020 10:56

I've got a DETA grid connect (i.e. Tuya) switch turning built in heaters in a very large room off and on. The switch is near the switchboard which is not in the same room or even sharing a wall.

Is there a way I could get a wireless temperature sensor set up to turn the heaters on/off like a thermostat, and if so what should I buy?

I can if necessary reflash my Tuya switch to Tasmota and set up one of the open source home automation systems but if I can keep my current setup with the Tuya stuff that makes it easier for other people to deal with.

CokemonZ

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#2563563 14-Sep-2020 10:59

Grid Connect has temp sensors. Note - you need the hub as well.

You can use the Tuya app to setup automation to do what you're looking for.

You can also get them cheaper from Aliexpress, as the sensors aren't mains powered.

https://www.bunnings.co.nz/arlec-grid-connect-smart-home-sensor-kit_p0148570

openmedia

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#2563788 14-Sep-2020 14:25

I'm using

Home Assistant
Brilliant power switches flashed with Tasmota
Xiaomi BTLE Temp sensors

I can use the virtual thermostat in Home Assistant to manage the heaters, and none of the data is headed off into the cloud.

Generally known online as OpenMedia, now working for Red Hat APAC as a Technology Evangelist and Portfolio Architect. Still playing with MythTV and digital media on the side.

richms

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#2564023 14-Sep-2020 20:04

I wouldnt trust anything wifi based to regulate temperature like that.

Richard rich.ms

deadlyllama

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#2567485 18-Sep-2020 13:46

Is it possible to get the Grid connect/tuya sensors to act like a "normal" switched heater with thermostat? I.e. the heaters are on if both the switch is on and the room temperature is below the setpoint.

Currently the heaters are turned on and a countdown timer started so they turn off after 3 hours, and there's a schedule to turn them on from 8am-12pm on Sundays.

This is for a small suburban church, it helps if what I set up isn't too complicated for someone else to maintain. Hence my preference to use the bundled Gridconnect app. The cloud means that someone else maintains the server...

It sounds like if I reflash with Tasmota and install home assistant on our NAS this is definitely possible. If I go that route I'd get Zigbee sensors rather than the Arlec BTLE, .

CokemonZ

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#2568003 19-Sep-2020 12:34

Grid connect is a rebranded version of the tuya app, and uses the same cloud service.

Based on what you have described it is likely the scenario would work.

It's fairly simple.
Between time x and y
If temperature is below x
Turn on switch
At time y turn off switch.

CokemonZ

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#2568004 19-Sep-2020 12:39

Sorry had another play.

It works like this.

At time x
If sensor y reads less than temperature y
Turn on switch

At time z turn off switch

That is very easy to setup, and works.

You may not even need the temperature sensor, you could use the weather in the app. If the weather forecast says it is less than 20 at this time turn on switch.

Handle9

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#2568053 19-Sep-2020 15:47

deadlyllama:

Is it possible to get the Grid connect/tuya sensors to act like a "normal" switched heater with thermostat? I.e. the heaters are on if both the switch is on and the room temperature is below the setpoint.

Currently the heaters are turned on and a countdown timer started so they turn off after 3 hours, and there's a schedule to turn them on from 8am-12pm on Sundays.

This is for a small suburban church, it helps if what I set up isn't too complicated for someone else to maintain. Hence my preference to use the bundled Gridconnect app. The cloud means that someone else maintains the server...

It sounds like if I reflash with Tasmota and install home assistant on our NAS this is definitely possible. If I go that route I'd get Zigbee sensors rather than the Arlec BTLE, .

If you go this way you need to make sure you have hysteresis in your control otherwise you will have horrible chatter and you are very vulnerable to sensors with short time constants. 2 degrees is the normal hysteresis for electric heater or conventional heat pump control. You can off set this however you like above or below setpoint.

e.g. If your setpoint is 22 degrees you only switch the heaters on when the room gets to 21 degrees and you switch them off when the room gets to 23 degrees.

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deadlyllama

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#2568343 19-Sep-2020 21:16

OK, sounds like I need Home Assistant. Step 1, work out why it doesn't start after installing it on the Synology (it's an old DS215j).

michaelmurfy

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#2568347 19-Sep-2020 21:28

deadlyllama:

OK, sounds like I need Home Assistant. Step 1, work out why it doesn't start after installing it on the Synology (it's an old DS215j).

That NAS only has 512mb of ram. Home Assistant needs way more than that. You need to get a Raspberry Pi 4 (with at-least 2gb of ram) or the likes.

But any Tuya Smartlife product will work with Gridconnect. It is the same thing, just rebranded.

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Handle9

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#2568349 19-Sep-2020 21:31

michaelmurfy:
deadlyllama:

OK, sounds like I need Home Assistant. Step 1, work out why it doesn't start after installing it on the Synology (it's an old DS215j).

That NAS only has 512mb of ram. Home Assistant needs way more than that. You need to get a Raspberry Pi 4 (with at-least 2gb of ram) or the likes.

But any Tuya Smartlife product will work with Gridconnect. It is the same thing, just rebranded.

A Pi 3 is totally adequate for Home Assistant.

CokemonZ

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#2568369 19-Sep-2020 22:29

Agreed. You can do what you need in the grid connect app.
Anything else is overcomplicating this specific situation.

deadlyllama

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#2569063 21-Sep-2020 11:23

CokemonZ: Agreed. You can do what you need in the grid connect app.
Anything else is overcomplicating this specific situation.

For stuff on a timer, sure, but if someone wants a button to push that will make the heaters stay on for the next three hours, as long as the temperature is below 18 degrees, with some hysteresis ... it sounds like a no?

CokemonZ

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#2569113 21-Sep-2020 11:45

deadlyllama:

CokemonZ: Agreed. You can do what you need in the grid connect app.
Anything else is overcomplicating this specific situation.

For stuff on a timer, sure, but if someone wants a button to push that will make the heaters stay on for the next three hours, as long as the temperature is below 18 degrees, with some hysteresis ... it sounds like a no?

You can setup two things out of the box which get you close:

1: turn off switch if temperature gets above x

No matter what that will just turn off the switch

2: When switch is set to on, set delay 3 hours. At 3 hours turn off.

Out of the box supported, just a smart with state change.

There are no if statements on the tuya app, so hysteresis is probably difficult with the other criteria.

Possible on a simple schedule by the looks.

You might be better off looking at a heatermate - they now have a wifi one. www.heatermate.com.au

In my personal view and experience anything homebrew that you need to maintain like this is risky. I don't know what your hourly rate is, but putting in a hard wired temperature sensor could be cheaper than 4 - 5 hours maintenance over the next 12 months.

deadlyllama

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#2708383 17-May-2021 12:52

So I'm looking at this again and thought I'd google for "grid connect thermostat" and my own thread came up which is never a good sign.

CokemonZ:

...

In my personal view and experience anything homebrew that you need to maintain like this is risky. I don't know what your hourly rate is, but putting in a hard wired temperature sensor could be cheaper than 4 - 5 hours maintenance over the next 12 months.

Yeah. I'd rather not do a homebrew but it's looking like the best option. The sensor would have to be some distance from the current switch. My hourly rate is not what it was, as I'm the minister at the church in question - it doesn't pay nearly as well as my previous IT career :) Plus this project looks like fun.

In the intervening year I've discovered the existence of the Lilygo products. I could go homebrew with no hardware development. Just grab a T-Watcher, add a 1-wire temperature probe (with correct plug already attached).

Then the job becomes: write some micropython - make the display show setpoint, current temperature, and use the buttons for on/off, setpoint up, setpoint down. The messiest bit will be calling the Tuya API to control the switch.

By leaving the switch that turns the heaters on/off as it is, and just controlling it via the Tuya API, if the thermostat fails people can go into my office and turn the heaters on and off manually.