In Part 1, a friend of the automated home, Markby, begins to transform his smart home using the Shelley module, and in Part 2 he builds a smart EV charger. This time he upgraded his domestic hot water system …
We have installed Of Drayton iTRV With a 3 channel controller, a zone for accommodation, a zone for a bedroom and a third zone for hot water, you can read about it here.
While control of heating through ITRVs and visor room thermostats is in our hands, the hot water relies on a common schedule and relies on a traditional bimetallic switch in the hot water cylinder. This seems like an obvious area Drayton could offer the homeowner an advanced sensor to digitize the hot water control and give visibility to the tank temperature, but it also gives us another Shelley project.
There are some issues with the current setup. The hot water is on a fixed heating schedule, turning on the boiler in the morning and in the afternoon to heat the water If one uses a lot of hot water during the day, the phase boiler may not be long enough to provide enough heat to recover the hot water cylinder. Similarly if a lot of hot water is used in the afternoon then someone has to trigger a boost cycle.
I also have a solar iBoost that will remove surplus energy from my PV installation in an immersion heater. There are times when the tap water is leaking but the boiler water comes to heat This may be due to individual water stratification or error of the bimetallic thermostat switch. Either way I was burning fuel when it could have been avoided.
The search was for more control but not complicated or expensive and Shelley would provide the answer. Shelley add-on modules allow the addition of temperature probes or external switches. These modules are piggyback a Shelley d Or Shelley 1 p.m. And connect to the GPIO header.
We covered using Shelly devices to make a smart light or a smart EV charger and for this project I will use Shelly 1 again but this time with adding temperature to the module.
Shelley add-on module
I’ll start with the usual caution – this is an illustration of how I use Shelley devices and not a detailed tutorial. Major voltages can kill, cause serious injury or damage to property and equipment. Please ensure that you are only conducting work that you qualify for or are trained to do so and comply with local regulations.
I supplied Shelly 1 with local 240v supply to get the device. I’ve connected the previous thermostat connections to the Shelley 1’s volt-free input and output contacts. Once all major connections were made it was time to clip the add-on It has three fly cables that I will connect to three temperature probes via three Vago connectors. Spring loaded connectors were provided in the package but my addiction to Vago means I used them because they felt more powerful. To ensure a good connection and no stray strands, especially when using very fine gauge wires I regularly use bootless ferrules on stuck wires.
Once connected, the Shelly app automatically detects the presence of add-ons, and new options will be available in the Temperature Search and Device Dashboard.
In my case I have to set the temperature sensor by setting the degree Celsius, measurement unit. Then it’s time to name the sensors, in this setup it’s just top, middle and bottom. The top measured the temperature at the output of the cylinder, the middle was the position of the traditional bimetallic switch and the bottom was an extra pocket of the cylinder intended for solar. These three probes will give me a good overview of what is happening with the contents of the cylinder.
The next step was to use temperature automation to turn the relay on and off. I chose 65 degrees as the off-temperature and 40 as the on-temperature. This means I have replaced the previous thermostat with a more accurate setup and I will have more visibility of water temperature trends.
The next part of the problem was to make sure the boiler was turned on when the cylinder dropped below the minimum temperature. This will require a second shell 1 wired in the boiler ৷ I designed and built a controller that would bring to the boiler and open one of the three zone valves according to the zone that was asked to be heated. This means running wires on the zone thermostat a few years ago but now with the help of Shelley these cable runs can be replaced with Shelley devices, isn’t it wonderful!
The controller used three conventional relays but now the hot water zone relay will be replaced by a Shelley 1. Whenever this shell boiler is started the fire will start and the hot water zone valve will open. Live output from Drayton Wiser will be used as switch input in Shelley 1, replicating existing functionality.
I could also use the Direct Device to Device functionality in place of this Shelly 1. When the temperature drops below 40 degrees in the middle temperature probe, I can tell the device in the boiler to turn on the Drayton Wiser schedule regardless.
This project depicts the power of Shelley, able to connect individual devices in a precise and logical fashion. It gives us more control, comfort and energy efficiency.
Stay tuned for more smart situations with the Shelly device at the center of the solution.
Last Updated on 2021-10-04 / Affiliate Link / Image from Amazon Product Advertising API
