Your Central Heating System Design is going to be critical to the safe use and efficient running cost long term.

Without going in depth here, there are three main types of boiler..

• Combination Boiler
• System boiler
• Conventional boiler

The type of heating system that will be connected to these boilers will vary from boiler to boiler, for example, a combination boiler is the simplest to fit and pipe up, basically only two pipes for your radiators, one for your hot water, a mains feed to it and a fuel supply... there is obviously a little more to it but its main selling point is it's simple installation and the lack of need for tanks.

The other two require more work to install due to the need for external hot water cylinders. Either pressurised in the case of system boilers, or conventional type cylinders fed by tanks normally in the loft space.

Due to the need for more efficient use of energy, there really are now only a few designs that can meet these requirements, most commonly these will be either a 'Y' Plan system or 'S' Plan or variants thereof, especially if there is a need to control different zones.

But a typical Domestic System, it should be controlled by the use of

(1) Thermostats on radiators (but not necessarily all)

(2) Room thermostat

(3) Cylinder thermostat

(4) Boiler thermostat

Room & Cylinder thermostats will control the flow of hot water via a motorised valve, and will shut the system down once the desired temperatures are reached, provided the boiler thermostat is set sufficiently enough to enable them to reach temperature.

Problems will occur if they have been incorrectly installed by incompetent plumbers, especially in open vented systems.

This then would result in system failure and premature corrosion, by the system not venting properly. Causing at best, constant need for the bleeding of air from the radiators, to a total sludged up non functioning system.

Inhibitors are added at final stage of installation.

The above comment's are not meant to be an instruction on how to pipe up your heating system, just to help in understanding what goes on when having a central heating system installed.

Typical Y plan layout on a open vented system

A more commercial 'Y' plan system with specially made cylinders

Before, old coal fire..

After, new efficient combi (inset)