Mechanical rooms have very important equipment that needs to be protected. Often mechanical rooms are not conditioned and subject to outside temperatures and freezing conditions that can freeze piping inside the mechanical. For that reason mechanical rooms often have unit heaters located there to protect piping and other things that cannot be frozen or subject to freezing conditions. The components and sequence of operation are fairly simple. The main components in a hot water unit heater include a fan, a valve, and of course the piping and coils along with the cabinet.
Hot Water Unit Heater Sequence of Operation
Each Hot Water Unit Heater shall be controlled by a unit mounted thermostat. Sometimes this will refer to as a wall mounted thermostat. Upon a drop in space temperature below the heating set point of 55° F the fan shall start and the hot water valve shall open. When the temperature rises above the set point, the fan shall stop and the valve shall close.
The location of the thermostat is dependent upon the design engineers specifications. Typically it is located on the wall next to the door of the mechanical room especially if the door has access to the outdoors.
The valve is usually located on the piping near the unit heater and is controlled by thermostat and monitored by the building automation system. Sometimes the unit heater is controlled and monitored by the building automation system so any alarms from the unit heater by the BAS especially in freezing conditions should not be ignored.