The boiler is read as the hidden source of warmth in a home, working unseen. A broken or overheating one is taken as pressure building up below the surface.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.