Estimation of gas usage?

[MonkeyMan]

First post so be gentle - just joined the site...

I've recently had fitted a Honeywell Evohome Control System in my house. It comprises of 10 x HR92 valves, an opentherm connector for my boiler (Viessmann Vitodens 100 System Boiler), hot water controls and a solar-compatible hot water tank (I don't yet have the solar plumbed in but plan to within the next year or so).

In my house I only use gas for my central heating and hot water - everything else is done so via electric (cooking, etc). This got me thinking that if the boiler is the only consumer of the gas, then if i knew what set point the boiler was operating at, there might be a way to infer the gas consumption for that set point and keep track of it. Following this point further, if I knew what the position was of each HR92 (ignoring hot water demand for now), then I could work out which rooms are effectively consuming gas, and summing up each would give me a proportion of consumption for each room/zone. Doing this live and constantly summing up each zone would enable analysis of each zones cost to heat.

Since I have an opentherm connector (can't remember the name) then I guess this complicates things further as I'd need to know at what rate the gas valve had also been modulated to (I presume this would effectively act as a de-rate of the boiler to a specific operating point?). Also, the hot water demand is potentially more difficult as if this is on whilst several zones are on this makes the calculations more difficult.

Is this idea a bit far fetched, or has someone else considered this before? Having a zone vs consumption/cost/time on graph would be ideal to see what areas of the home are the big consumers and where to target thermostat schedule optimisations to save money, or indeed where to focus on improving home insulation, etc.

[Toulon7559]

The realization of your idea (in my opinion) seems rather difficult.

Starts with a dependency on data available in the wireless network.
Assume that each HR92 thermostat reports to your Domoticz (with reference to page 11 of this datasheet):
- Desired (Room) Temperature
- Actual (Room) Temperature
- Valve Position => flow to radiators

From the first 2 values you can deduct whether heating is required, and knowing the volume of the room, then you could estimate how much energy is (still) nominally needed to reach the desired temperature. Which translates to required, nominal energy consumption.
By comparison with actual temperature and by numeric integration you may compile a picture for energy requirement/consumption over time.
Valve position is a derivative of required energy-consumption (and to some extend representative for actual energy input), but it has limited value, unless you know the transfer function between flow and radiator output in that room.
Instinctively I would say that with the information based on registration of difference of temperatures (and limited arithmetical effort) and a 'wet finger', you get a qualitative feeling (with some statistical background), which rooms 'spend/leak' energy and which rooms are 'conserving' energy.

Anything more elaborate is probably not more accurate (and requires a lot of effort) ........