You basically have two choices with your Heating Systems and they are:-

1.Conventional open vented tank fed un-pressurized type:- we call them 'Y' plan or 'S' plan systems.  They involve installation a convential boiler coupled to a separate pump and 3 port valve or zone valves which divert heat from the heating system or hot water system on demand.

2.The more modern pressurized system incorporates a combi-boiler which by name is a combination unit which has all the diverting valves and pump fitted in one compact unit.

(please view the layout diagrams below for more information)

These new pressurised systems make installation simple - all that is required is hanging the boiler on the wall and running the heating loop to your individual radiators without the complex problems of the conventional system.

It is a known fact the more modern pressurized systems stay free from debris and sludge for longer due to the fact that being sealed they are not open to outside air which can cause rust to the inside of your radiator panels.