A heat exchanger is a device that transfers heat between two fluids without them directly coming into contact or mixing with each other. It can be used to cool or heat air, liquids, or gases without contaminating them.
An “exchanger” is a person, thing, or device that facilitates the exchange of one thing for another. This can encompass various contexts, from financial transactions to heat transfer in engineering.
Usually, a combo boiler will have two heat exchangers – one for central heating and one for hot water.
Primary heat exchanger. The primary heat exchanger is used to heat the radiator water, which travels to the radiator and then back to the boiler. It is consistently warmed as it cycles through the heating system.
Secondary plate heat exchanger. This is heated by the primary heat exchanger. When a hot water tap is turned on, water is diverted from the Primary Heat Exchanger into the secondary heat exchanger until the hot water tap is turned off.