If you live in a modern apartment complex or a development with a communal heating system, you likely have a Caleffi Heat Interface Unit (HIU). Usually tucked away in a utility cupboard, this white or grey box is the "engine room" of your home's heating and hot water.

While Caleffi units are known for being reliable, they can occasionally run into hiccups. If your morning shower is more "lukewarm" than "steaming," here is a quick guide to understanding what’s going on and how to fix it.

Ever wondered how that toasty radiator heat arrives in your apartment or building, especially if you don't have a traditional boiler on-site? The answer lies in a clever piece of technology called a Heat Interface Unit (HIU).