A System boiler operates in a similar fashion as to that of a regular boiler. Within the system it still operates using the idea of a stored hot water cylinder, but even though they have this same attributes to a System and Regular boiler differ in some crucial aspects. A System boiler directly heats your homes central heating system and also produces hot water that is stored in your hot water storage tank. In a majority of installations an immersion heater is still used in the storage tank to maintain the water temperature or to give it a boost. Because of the direct feed of hot water from the boiler a cold water storage cistern and expansion cistern aren’t needed in this system. This type of system is extremely beneficial as it offers you a better response time when demanding hot water and central heating.
A TRV senses the air temperature in the room and can be set higher in the rooms you use most and lower in rooms used less often such as bedrooms. They usually have a large valve at one end, typically marked from 0 to 6. Turning the dial up when the radiator is already on will not increase the room temperature! They can be used to turn an individual radiator on or off. At least one radiator should be left without a TRV and left permanently switched on, this radiator may be a bathroom towel rail (where the heat is always likely to be useful), or in the same room as the room thermostat where a TRV is not needed.