On Mon, 18 Feb 2019 at 10:38, Adam John Trickett via Hampshire <
hampshire@???> wrote:
> Bonjour !
>
> I have finally found a use for a Raspberry Pi...! Since moving to France
> we
> have ended up with a house with stupid electrically heated oil filled
> radiators. They are not properly controlled and quite inefficient, at best
> you
> can control them on a thermostat but there is no clock...
>
> It seems obvious that all I need is a thermometer, a mains relay a
> Raspberry
> Pi and some some software to create a time controlled thermostat that I
> can SSH
> into...!
>
> So I think I need
> a box
> a AC/DC transformer for the Pi
> a mains relay
> a digital thermometer
> an override switch
> something to mount the relay and transformer on
> WiFi Pi or WiFi module for Pi depending on model
>
> I think this is technically easy to do, but the biggest constraint seems
> to be
> that the overall box needs to be small and "wife friendly"...
>
>
I built a similar thing to this in the past.
Only difference was I was controlling the on-off to the house boiler, and
not individual radiators.
The easiest waterproof temperature sensors to integrate are ones based on
the DS18B20.
You can get them quite cheaply on ebay. e.g. See attached picture.
I used an arduino and a relay driver board to switch the mains on/off.
The controller software I used was openHAB.
www.openhab.org
Its open source, and there is an app for a phone so you can control it all
from your smartphone, or via a web browser.
I programmed the arduino to go into fail safe more when the openHAB server
was down.
The fail safe was, radiators on, but never above temperate 22C
The arduino would also start up in fail safe mode, until it detected
openHAB server.
I placed temperature sensors around the house, and used them to decide when
to turn the heading on.
After doing all this, I think the most useful thing was me being able to
look at the temp of the hot water and know immediately when it was hot
enough to have a shower. I could then use this to program the system to
turn on at just the right time, so that the shower was hot at exactly the
time I needed it to be in the morning.
The system could predict, based on the current temperature, how long it
would take to get to 50C. (shower temp)
So, on cold nights, it would start heating earlier.
I also did some reading, and heating the water to only 50C was not entirely
perfect. You have to heat it to 60C sometimes to kill bad things like
Legionnaires.
So, I saved energy by only heating to 60C occasionally, and leaving it at
50C most of the time.
For me, I only needed the relays next to the central boiler. You are
needing a relay and temp sensor in each room.
I would probably put DS18B20 on the end of the cat5 cable in each room and
then use a smart plug switch control, such as the image attached.
And then have a central controller, such as a RPI to control it all.
I think you can get some smart plug switches with DS18B20 sensors in them,
so that might simplify the wiring.
Kind Regards
James
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