Re: Intelligent Heating Control Software

[gordonb.7bhbi@xxxxxxxxxxx (Gordon Burditt)]

>I'd like to install a more intelligent control system for the heating in my
>house. Currently the system consists of:
>- an oil fired boiler which heats domestic hot water and water filled
>radiators. Mains gas is not available in our village.
>- a standard indirect hot water cylinder with an immersion heater which we
>only use when the boiler can't keep up with demand (usually at Christmas
>when we have a lot of visitors). The immersion heater has an X10 switch on
>it so I could have it come on at night on off peak electricity if I wanted.
>- one or two radiators in each room, fitted with thermostatic radiator
>valves
>- a two-zone 24 hour time clock with up to three on-offs per zone per day
>(one zone is the domestic hot water, the other is all of the radiators)
>- a hot water cylinder thermostat
>- a boiler thermostat
>- there is no room thermostat at present
>- when I had a loft extension done, I had them put in separate zone valves
>(3 in all) for bedrooms, living rooms and study, but these are all wired in
>parallel at present.
>
>This system has the following shortcomings:
>- the boiler is old and inefficient, and due for replacement
>- I hate thermostatic radiator valves. It seems to me that they are
>inaccurate, inconvenient, and impossible to automate
>- if the time switch says there should be room heating, but the thermostatic
>valves say it's warm enough, the boiler continuously idles at operating
>temperature, using oil needlessly.
>- I can't have higher temperatures in the morning and evening, and lower
>(but not off) in the middle of the day. I'd like to be able to do this.
>- I can only have different temperatures in different parts of the house by
>tweaking thermostatic valves.
>- I can't have heating off in the middle of the day in the bedrooms, but on
>in the living rooms.
>
>I'd like to be able to overcome all of the above, as well as add new
>features such as:
>- add one or more outdoor sensors (maybe temperature, sunshine, wind
>strength and direction) to help automatically get the temperature
>"comfortable" in all weather conditions

Seems to me you need INDOOR sensors more (and first).  Then add
the outdoor sensors.

>- ability to control the heating remotely by phone and/or internet (e.g. to
>turn the heating on an hour or two before we arrive home from holiday).
>- prioritise room heating or hot water depending on the circumstances
>- optimise the operating temperature of the boiler for best possible
>efficiency in all levels of demand

For this, it would appear that you need a computer-controllable
boiler thermostat.  Incidentally, I advise against running a
temperature sensor and a boiler control to the computer as the only
control, as a computer crash might leave the boiler on all the time,
which might eventually cause fires.  Use a controllable thermostat
which can only be set to sane values.  And have a manual OFF switch.

>What software (preferably open source) is there available to help me do
>this? Preferably I'd like something that enables me to build and experiment
>with my own control algorithms. I'd also like lots of logging so I can
>investigate the performance of various algorithms under varying conditions.

Before you worry about software, worry about the hardware.  What
can you control?  What can you sense?  Smart software won't help
much if it's blind (no sensors) or paralyzed (not enough controls).

- You can control the immersion heater.
- Hopefully you can control the boiler.
- You can control valves for hot water and the radiators.
- You can control valves for the bedrooms, living room, and study.

- Can you SENSE the state of the thermostatic valves?
- Can you SENSE the state of the boiler thermostat?
- It seems like the only feedback you have for room temperatures is
  thermostatic valves.

It seems to me that you need sensors (not necessarily thermostats)
for hot water, bedrooms, living room, and study.  You also would
like raw temperature data for logging and evaluation purposes.

Now, with temperature sensors in each zone (including the hot water),
each can indicate OK, TOO HOT, or TOO COLD.  For a first pass,
figure out for each combination of these what the best hardware
configuration is (There's 81 possible combinations of these for 4
zones and you probably can't handle all of them ideally.)  For each,
decide: boiler on/off, immersion heater on/off, valves for hot
water, bedrooms, living room, and study.

One obvious rule here is that if nothing is TOO COLD, and it looks like
it will stay that way for a while, turn off the boiler.

Later you can tweak the setup:  if, for example, the living room and study
are WAY too cold and the bedrooms are slightly too cold, turning on the
boiler and the valves for the living room and study might provide
enough spillover into the bedrooms.  You can decide that the boiler has
been on for a while and the temperature isn't going up, so you need the
immersion heater.  And you can alter target temperatures and strategies
by time, anticipating day/night outside temperature changes and
electricity rate peak/nonpeak changes.