I have read about weather compensation, but fail to see how it will change the fuel used enough to be worth while, assuming that the existing set up is already using analogue control.
Boiler weather compensation uses an outdoor temperature sensor to automatically adjust the temperature of the water sent to your radiators (the flow temperature). When it is cold outside, it turns the radiator water hotter; when the weather is mild, it turns the water cooler.
How It Works
• Outdoor Sensor: A small sensor mounted outside your home measures the real-time air temperature.
• Heating Curve: The boiler uses a preset mathematical curve to match outdoor temperatures to ideal radiator water temperatures.
• Continuous Modulation: Instead of blasting water at maximum heat until the house is hot and then turning off, the boiler runs gently and continuously at a lower, steady level.
The point is however, this happens anyway. The return water temperature to the boiler tells the boiler what temperature the output water needs to be.
This is done to ensure the return water is cool enough to ensure the latent heat is extracted from the flue gases, so the boiler is modulated.
The problem arises where the boiler is turned off and back on by an external control, each time that happens, the boiler reverts to full output, so either an electrical modulation control, or a water modulation control is required to keep return water cool enough.
But if the boiler can sense the outside temperature then it has another way to know how hot the output water needs to be.
However, what ever method is used, the boiler needs to be the correct size for the home.
The boiler needs to do two things, one is to maintain the homes temperature which clearly depends on how well insulated the home is, and two to reheat the home when it has cooled down. For the latter it depends how many rooms are reheated at a time, and how fast you want them re-heating, and when one has a large home, then it is likely all rooms will not need heating at the same time, so radiator output needs to likely be twice the output to the boiler.
However, looking at my own house, the radiators are only about equal to boiler, so if the boiler can't modulate down to the size of the radiators being used at the time, it is forced to use a mark/space ratio and keep switching on/off.
Now I know my living room although quite large, can be maintained with a 750 watt oil filled radiator. And I have not seen many boilers which can modulate that much.
