iWorx® MPU2
505-009, Effective: June 30, 2015
15
© 2015 Taco Electronic Solutions, Inc.
APPLICATION DESCRIPTION
The MPU2 is a multiplexed package unit controller that permits a single zone package unit to operate multiple zones.
Figure
6 illustrate typical MPU2 applications. The MPU2 operates in conjunction with up to 32 multiplexed
zone controllers. The control is achieved by multiplexing the primary supply air between cooling and heating based on
the various demands from the Zone Controllers. In addition to multiplexing, the MPU2 controls an economizer and
bypass damper.
Figure 5: Multiplexed Package Unit - Staged Heating & Cooling, Modulated Economizer
The starting and stopping of the supply air fan is controlled by the MPU2. The fan is energized when the there is a call
for heating or cooling from the Zone Controllers. During the occupied periods, the fan can be configured to run continu-
ously.
The enthalpies of the outside and inside air are calculated periodically. A comparison is performed to determine if “free
cooling” is available. If “free cooling” is available, the economizer is enabled. Optionally, free cooling can be determined
by a dry bulb comparison of the outside air temperature and average zone temperature.
The economizer can be configured as two-position (digital) or modulated (analog). If enabled, the two position econo-
mizer output is energized when there is a call for cooling. It is used as the first stage of cooling to take advantage of the
energy savings. The two-position economizer output is off when the economizer is disabled.
