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.
Quick Answer. Gas boilers are tanks that sit on top of a burner that is heated by burning natural gas to spread heat into the tank. The tank heats water for hot water and sends it through the pipes to faucets or, depending on the boiler's function, heats water to create steam that is pumped distributed through the house via pipes or radiators. Keep Learning.