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Heat exchanger (HX)
A copper tube running through the steam boiler — brew water flows through it on demand and is heated by surrounding boiler water.
Category: Boilers & Heating
An espresso machine architecture with a single steam boiler and a brew-water tube ("heat exchanger") running through it. Cold water in the tube heats up as it passes through the hot boiler.
Why it matters — HX machines deliver near-commercial steam performance in a smaller footprint than dual boilers. Trade-off is that idle water in the HX tube overheats, so cooling flushes are required before the first shot.
Good to know
- E61 group + HX boiler is the classic Italian prosumer combination — used by Rocket, ECM, Bezzera, Profitec, and many more.
- For most users, HX is a good middle ground between single boiler (simpler, but no simultaneous brew/steam) and dual boiler (more stable, more expensive).