MECHANICAL ROOM LAYOUT
The Mechanical Room Layout schematic shows the major equipment and their piping connections. The Overall Control Logic for the system is based on this drawing. As well and start-up and shut-down procedures.
This drawing will show the boiler or heat-pump and the circulator (or pump) that circulate the heat source and the circulator or circulators that circulate the hydronic heating system. And if an "Indirect" domestic hot water (dhw) tank is included as part of the boiler package as in the example at right, will show the tie-in and the diverter valve or pump that allows the boiler control logic to prioritize the dhw demand.
A second page might detail the Zone Valves and Thermostats that control the valves. And depending on layout, might show room headers and recommended shutoff valves and high point air vents.
Note: Domestic hot water tanks are very popular with a boiler system as they allow one heat source (the boiler) to supply all of the heating needs at the high efficiency of the boiler. Indirect tanks are generally stainless steel for long life. Indirect tanks are usually cost more than a stand-alone hot water tank but are less expensive to install as do not to be vented or gas lines piped. And given the long life, may be the best value when considered on a life-cycle cost.