Sherlock Holmes has always been one of my favorite fictional characters. I envied how he would notice each detail and use every one of his senses to solve the crime.
Figure 1 shows a hydronic system that's intended to supply four panel radiators, each with its own thermostatic radiator valve, and an indirect water heater from a gas-fired sectional cast-iron boiler.
An installer is asked to connect an old (but still working) propane-fueled cast-iron boiler, which was salvaged from another project, to a slab-on-grade floor heating system in a new workshop.
As a designer/installer of any hydronic radiant system (especially one that incorporates hydro-air, old preexisting standing cast iron radiators and an indirect water heater), you have dozens of steps involved that are not unlike setting up a winding row of dominoes.