This is Carol Fey's second book. Her plain-English explanations of hydronic controls are EXACTLY what the heating industry has needed for years. A look at the some of the chapter headings will give you a good sense of what's in store for you when you get this book: Power Supply, Switch, and Load - Just Count to Three, The Circuit - Thinking in Circles, Hydronic Controls That Are Switches, Hydronic Controls That Are Loads To the Boiler Room and Relays. There's also this great wrap-up chapter that takes the fear out of controls, once and for all.