How a thermostat works on a combi boiler, two way or one way communication?

sandy700

I have a Worcester Bosch GREENSTAR CDi CLASSIC 29CDi combi boiler and a Greenstar Comfort II RF Radio Frequency Twin Channel Programmable Room Thermostat and Receiver.

I also have a raspberry pi which at present records the house temperature to a spreadsheet 24/7 via a Bluetooth sensor.

I am thinking of using the raspberry pi to intercept the data from the thermostat so that I can record when the thermostat sends data to the boiler so I know when and how often it turns on the boiler and for how long.

I know that the thermostat sends data to the boiler but does the boiler send any data to the thermostat, e.g is it a two way or just a one way communication?

Has anyone done this?

Miser1964

Passively monitoring the EMSbus for the traffic seems quite a challenge with a combination of hardware and software needed.

GitHub - emsesp/EMS-ESP32: ESP32 firmware to read and control EMS and Heatronic compatible equipment such as boilers, thermostats, solar modules, and heat pumps

Understanding the EMS Bus of Buderus / Nefit boilers - Domotic Project

Lorian

A pair of ds18b20 probes cable tied to flow and return pipes easily interfaced to will not only allow you to see when it's on and off you'll be able to see if the return is low enough for the boiler to be condensing. If you don't want to use a pi the a blue tooth thermostat and probe is only maybe a tenner or so on eBay. 

FreeBear

A couple more links...

https://github.com/kroon040/EMS-ESP-Boiler

https://domoticproject.com/calduino-connecting-arduino-ems-bus/

https://bbqkees-electronics.nl/wiki/index.html

Having spent time working with the Raspberry Pi, I'm finding the ESP32 to be even more versatile when it comes to building small interfaces. Plenty of ways to build & upload firmware - Currently using esphome as it integrates with my Home Assistant installation running on a nanoPi. Data from HA is stored in a database and then displayed using Grafana as a series of pretty graphs.

A word of caution - Once you start on the slippery slope of data recording, you go looking for other stuff around the house. Temperature, humidity, power consumption, lights on/off times.... I'm currently at 60 sets of data, and have another dozen or so sensors to hook up. Just need to finish wiring up a modbus network round the house.

Lorian said:

A pair of ds18b20 probes cable tied to flow and return pipes easily interfaced to will not only allow you to see when it's on and off you'll be able to see if the return is low enough for the boiler to be condensing. If you don't want to use a pi the a blue tooth thermostat and probe is only maybe a tenner or so on eBay. 

Stick one on the outside wall to measure external temperature, and another one inside the flue for exhaust temp. And while you're at it, one on the cold water feed pipe and DHW pipe.

sandy700

FreeBear said:

A word of caution - Once you start on the slippery slope of data recording, you go looking for other stuff around the house. Temperature, humidity, power consumption, lights on/off times.... I'm currently at 60 sets of data, and have another dozen or so sensors to hook up. Just need to finish wiring up a modbus network round the house.

I know.

I already have a couple of Switchbot  sensors, one sitting on a radiator the other sitting on top of the thermostat which have been repurposed from my greenhouse.

I already have a DS18B20 feeding a web page on my tablet which shows red when the temperature is over 21 deg C and blue when it is below that.
Whenever my wife complains about being cold I show her the red web page on my tablet

I never show her the blue page.

A pair of ds18b20 probes cable tied to flow and return pipes easily interfaced to will not only allow you to see when it's on and off you'll be able to see if the return is low enough for the boiler to be condensing. If you don't want to use a pi  a blue tooth thermostat and probe is only maybe a tenner or so on eBay. 

I had thought of that as well. I built a heated thermostatically controlled propagator for my greenhouse .using one of those and also it had automatic watering.

FreeBear

sandy700 said: I already have a DS18B20 feeding a web page on my tablet which shows red when the temperature is over 21 deg C and blue when it is below that.
Whenever my wife complains about being cold I show her the red web page on my tablet

Within the sensor read routine, do a simple (temp+1.25) calculation - The page will still show red, and you can turn the thermostat down a notch. That will save you quite a bit of money on the gas bill.

A few months on, tweak the fudge value up by say 0.5 and turn the thermostat down again. Aim to get it down to under 19°C and buy her a fluffy dressing gown and matching slippers.

sandy700

FreeBear said:

sandy700 said: I already have a DS18B20 feeding a web page on my tablet which shows red when the temperature is over 21 deg C and blue when it is below that.
Whenever my wife complains about being cold I show her the red web page on my tablet

Within the sensor read routine, do a simple (temp+1.25) calculation - The page will still show red, and you can turn the thermostat down a notch. That will save you quite a bit of money on the gas bill.

A few months on, tweak the fudge value up by say 0.5 and turn the thermostat down again. Aim to get it down to under 19°C and buy her a fluffy dressing gown and matching slippers.

That wouldn't work with my wife as she would just look at the temperature showing on the thermostat because the sensor is upstairs and she knows it is warmer upstairs than in the living room downstairs.

I tried that with our old heating I removed the knob and moved it round so that when it showed  7 (the normal setting)  it was really at 6.

That didn't work, she phoned up BG (when we used to have a service contract with them, it was warm air heating) and told them the heating was faulty, luckily I managed to move the knob back without her knowing and as the heating was due a service that's what the engineer did and nobody was none the wiser.

Now she looks at the temperature on the thermostat if she feels cold to see whether or not I have turned off/down the heating.

All I get now is it's her money as well as mine that pays the bills.