The CE mark, or formerly EC mark, is a mandatory conformity marking for certain products sold within the European Economic Area (EEA) since 1985. The CE marking is also found on products sold outside the EEA that are manufactured in, or designed to be sold in, the EEA.
Condensing boilers are water heaters fueled by gas or oil. They achieve high efficiency (typically greater than 90% on the higher heating value) by condensing water vapour in the exhaust gases and so recovering its latent heat of vaporisation, which would otherwise have been wasted.
1 a gas combi boiler system contains almost all components within the boiler itself, which makes the boiler system more compact and neater looking. 2  there's no need for a cold water or feed and expansion tank in the loft, and you can immediately get hot water heated on demand. a combi gas boiler system is better suited to a home with a smaller number of people, as you'll only be able to use hot water from a combi boiler system for one task at a time. 2  For example, one person wouldn't be able to have a shower while someone else does the washing up using hot running water.