This project allows to remotely control a heating controller.
It was designed to control a Siemens RVL470 but it should work with any heating controller whose operating mode can be manually overridden.
My heating controller - a Siemens RVL470 - is responsible to control the burner, to regulate temperature according to the required and the external temperatures. It can be configured accurately to fit your needs and your system and you should probably not change this configuration yourself.
The Siemens RVL470 also features a mode in which you can configure the hours it should heat your home (weekly program). It is quite complete and you can even configure your holiday schedule to avoid unnecessary heating.
But because I never leave my work at fixed hours I wanted more control over heating time slots. Additionally I rarely stay at home the week-end so I wanted to be able to completely turn off the heating mode.
The Siemens RVL470 provides 4 modes:
From left to right:
Standby(Heating is switched off)Automatic(Automatic changeover from NORMAL to REDUCED according to weekly program and holiday schedule)Continuous REDUCED heatingContinuous NORMAL heating
The interesting part of the RVL470 is that the operating mode can be manually overridden. The documentation informs us that if the contact H1 is bridged to the ground, then we can force a mode.
The main drawback I see in the RVL470 is that we can not directly select the mode to force. We can only bridge or not the contact H1 and the ground, so it is a simple on/off override.
What we can configure is the mode that will be forced when bridging H1 and the ground. The documentation says that operating line 172 can take values from 0 to 3. It also adds that "the RVL470 will resume the operating mode previously selected" when H1 is disconnected from the ground. So here is our plan :
We will put the RVL470 on Continuous REDUCED heating and we will configure
the mode forced on NORMAL heating.
Hence we will only need a simple electronic circuit to behave like a switch between H1 and the ground :
- the circuit receives a 1, the switch is closed, the operating mode is forced to
NORMAL heating - the circuit receives a 0, the switch is open, the operating mode is back to
Continuous REDUCED heating
The switch role will be played by a simple transistor operating in saturation mode. I choose a common NPN transistor, 2N222A. For easier debugging I also added red and green leds.
This circuit will be controlled by a Particle Photon, a cheap but powerful Wi-Fi connected micro-controller.
The Particle allows to control the heating controller remotely through Particle's cloud API, so why adding a server in the project?
Because overriding the operating mode means that the automatic mode (with clock) is no longer available. So we need a server to be responsible of the clock system. And this can be accomplished by a simple cron running on the server.
The server was planned with 3 modes (checkout its README).
This project consists of several components: