WattMaster WCC II - Manual (Page 44)

Section 3: Screen Descriptions
WCC II Operator’s Guide
Operator Interfaces 3-12
On Message #:
Off Message #:
Specifi es a pair of message numbers, the fi rst for the ON state and
the second for the OFF state of the comparator. These numbers
are used by the system to reference a message on the ON/OFF
Units Message Screen. For example, the comparator might be set
up to come on when the outside air temperature is below 55 °F for
economizer operation. Set up the On/Off Message Screen so that
message #3 is “ECON” and message #4 is “REFRIG.” The “On
Message” number would be “3” (ECON), and the “OFF Message”
number would be “4” (REFRIG).
CONTROL OUTPUT SCREENS
The Control Output Screens are used to “tell” the satellite controller
when to open or close the binary output contacts. A binary output
contact may be “programmed” using one of the following
screens:
1) EA Driver
2) Dual Limit
3) Timeclock
EA Driver Screen
The EA Driver Screen is generally used to control the electric
actuators on a Tempmaster variable air volume (VAV) box;
however, it can be used for other applications. The Tempmaster
“EA Actuators” have two 24 VAC motors—one motor drives
the damper closed, and the other motor drives the damper open.
The EA Driver Screen uses two binary outputs on the satellite
controller—the “COM to H” contact closes on a call for heating,
and the “COM to C” contact closes on a call for cooling. The
generic term for the method of control provided by the EA Driver
Screen is “3 point fl oating control.” When the analog input signal is
within the deadband, both contacts open and the actuator does not
move. When the analog input signal falls below the setpoint into
the pulse band, the “COM to H” output contact pulses at a preset
rate to slowly move the actuator toward the required position. If
the analog input signal falls below the pulse band, the “COM to H”
contact closes and the actuator drives full speed. When the analog
input signal rises above the setpoint, the same sequence occurs
with the “COM to C” contact.
Dual Limit Screen
The Dual Limit Screen is used to “program” one binary output on
the satellite controller to open and close based on how the value
of an analog input compares to the setpoints. It is called dual limit
because you have the option of entering two setpoints if required.
For example, if you are using the SAT II to control a heat pump
compressor, the binary output should close if the space temperature
is below 72 °F for heating, close if the space temperature is above
76 °F for cooling, and be open when the space temperature is
between 72 °F and 76 °F.
Timeclock Screen
The Timeclock Screen is used to open and close a binary output
based on time only. For example, if you want the SAT II to run
a pump from 8:00 am to 6:00 pm, Monday through Friday, a
Timeclock Screen would be used to “program” the binary output
for the pump.