Conventional heating system
First let’s review the situation where you have a central heating system with a modulating boiler, a single room thermostat and thermostatic valves on the radiators. When there is a large difference between the measured room temperature and the demand temperature (e.g., in the living room where the thermostat is located), the modulating boiler will heat the circulating water to a high temperature (e.g., 60 °C). To avoid temperature overshoots, the boiler gradually reduces the water temperature (e.g., 40 °C) as the difference between the room temperature and the demand temperature decreases. When the room temperature reaches the demand temperature, the boiler again reduces the water temperature to somewhere between 30 and 35 °C. This is usually enough to maintain a constant temperature in the room.
If all the thermostatic radiator valves are fully open, every room is adequately heated in the initial phase by the high boiler water temperature. However, as the room with the thermostat (in our example the living room) becomes warmer, the radiator temperature in the other rooms drops to just 30 to 35 °C once the living room is warm enough. Unfortunately, this low temperature is not sufficient to keep some of the rooms at a comfortable temperature. Imagine, for example, a bathroom, an office or a bedroom that is also used for studying or playing.
Fireplace and sunlight
A lit fireplace in the living room can also cut off heating in the other rooms because the thermostat in the living room senses that it is warm enough. The same thing can happen when bright sunlight streams into the living room. In that situation the north-facing rooms cool down faster, resulting in insufficient heating.
With an IHS there is an electronic temperature sensor in each room or group of rooms (for example, all bedrooms as a group). Moreover, each room is also provided with a few buttons to switch to a day or night setting, or to raise or lower the temperature in steps of half a degree Celsius. That eliminates the need for a conventional thermostat and thermostatic radiator valves. Each room has its own heating circuit, controlled by a solenoid valve. The IHS also has a contact for each controlled room. These contacts are connected to the thermostat or boiler contact of the heating system. When a contact is closed, the boiler knows that there is a heat demand and it starts heating the water and running the circulation pump.
To avoid overshoots in the room temperature, the IHS uses Pulse Width Modulation (PWM) to control the temperature of each room individually. When there is a large difference between the room temperature and the demand temperature, the solenoid valve will be open for the entire pulse period. However, when the difference decreases, the valve is only open during part of the pulse period.
Every user can set the temperature in the room where they are, without having any effect on the temperatures in the other rooms. This means that the occupants only need to heat the rooms they actually use. A person who works at home may want to heat their office during the day, but they do not have to heat the living room all day long.
The optimal temperature for a particular room can be set using a screen in the living room or an app on a smartphone or tablet, either at home or remotely via the internet. Thus general commands can be sent to put the entire home in the comfort setting or the night setting. When the occupants leave home, they can press the “All Off” button to put the entire heating system in low-energy mode without having to walk through the entire house.