Monday, 8 April 2013

Minimum Requirements for a Solid Fuel Central Heating System

When replacing an existing central heating system or installing a new one

System circulation of a solid fuel central heating system

  • Do you have a boiler interlock?
    • What is a boiler interlock?
      • A boiler interlock is where the heating system controls are arranged such that the boiler only activates when there is demand for heat. Heating controls include thermostats, programmers and time switches. The way an interlock is usually installed depends on the type of boiler used in the central heating system.
      • If you have a combi boiler then implementing a boiler interlock is as simple as fitting a room thermostat.
      • Central heating systems with regular boilers require special wiring interconnection of the motorised valve, the cylinder thermostat and the room thermostat or an advanced control such as a boiler energy manager. Some people claim that a thermostatic radiator valve will do the job - they're wrong.
    • If you do, then you will need fully pumped circulation in your new central heating system.
      • This means that your central heating system has a pump that moves all of the boilers heat to every part of the system (in comparison to systems that rely wholly or partly on gravity).

  • All instructions listed by the manufacturer of the heat leak radiators used in your new or replacement central heating system must be followed.
    • What is a heat leak radiator?
      • This is a radiator that has been installed in a position such that it will still receive water from the boiler by gravity, even if you're using a fully pumped circulation system. I write even, but you would actually only have this type of radiator in a central heating system that is at least partly pumped.
      • The reason for this is so that heat does not build up and cause a fire. The heat leak radiator is usually installed in the bathroom (often as a heated towel rack).

  • As this post is concerning solid fuel boilers; you must ensure that it is not fitted to a sealed heating system with expansion vessels unless explicitly stated that this is permissible by the manufacturer of the boiler or if you are using a thermal storage interface.
    • What is a thermal storage interface?
      • This usually involves a system where hot water from the boiler does not physically reach the radiators. Instead, a high insulated tank acts as an intermediate between the two.
        • Water pumped from the boiler heats the tank.
        • Water circulates between the radiators and the tank and is heated by the hot water within the tank (the water previously heated by the boiler).