Trane TRG-TRC014-EN manual Terminal Reheat System, What Is Variable Air Volume?, period one

period one

What Is Variable Air Volume?

notes

Terminal Reheat System

EARA

OA	supply	PA
	fan
	cooling	reheat
		coil
	coil
	thermostat
		SA

Figure 8

The terminal reheat system uses a central air handler and cooling coil to deliver cool primary air to all the spaces. Each space has its own heating coil to temper the air to satisfy the space load. Of course, any heat added to meet the part-load requirements of a space becomes a cooling load that the refrigeration system must overcome. This can result in a nearly constant refrigeration load, even when the building is at part-load conditions.

Therefore, reheating cooled air to achieve part-load supply air temperature control is not very energy efficient and is used only in special constant-volume applications, or when there is a “free” source of heat (i.e., heat recovery).

Primary air (PA) is the air delivered by a central supply fan to a terminal unit.

Supply air (SA) is the air delivered to a space.

TRG-TRC014-EN 5