Penn System 450 Series User Manual

System 450™ Series Modular Control Systems with Standard Control Modules Technical Bulletin
14
Table 3: System 450 Output Relay Control Actions and the Relationship Between ON and OFF Values
In temperature applications, direct-acting relays are often used to control cooling equipment, while reverse-acting
relays are often used to control heating equipment.
In pressure applications, direct-acting relays are often used for condenser fan cycling control or pump-down
control, while reverse-acting relays may be used for high pressure cut-out.
In humidity applications, direct-acting relays often control dehumidification equipment, and reverse-acting relays
often control humidification equipment.
Binary Input Control for Relay Outputs
You can connect a binary input or a set of dry contacts to any of the three control module inputs (Sn-1, Sn-2, or
Sn-3 and C) and control the output relays in your control system based on the binary input’s state (open or closed).
A sensor (Sn-1, Sn-2, or Sn-3) set up as a binary input can only be referenced by a relay output. Sensors set up as
binary inputs are not available for selection when you set up an analog output.
When a relay output references a sensor (Sn-1, Sn-2, or Sn-3) that is set up as a binary input, the ON and OFF
parameter screens are not available as you set up the output. The relay output’s On/Off state is controlled by the
binary input’s state and any of the timer parameters (ONT, OFFT, ONd, or OFFd) that you set up for the relay
output. When the binary input is closed, the relay is On. When the binary input is open, the relay is Off. If no timer
parameters are used, the relay output state directly follows the binary input state. Figure 5 and Figure 6 show
examples of the binary input state and the resulting output states with and without the timer parameters applied to
the output.
See Relay On and Off Duration Control
for more information on binary input control, relay output behavior, and the
resulting On/Off behaviors when applying the On/Off Delay Time and the Minimum On/Off Time parameters.
Control Action Set the Relay Output ON/OFF Value Relationships for the
Desired Control Action
OFF < ON
ON < OFF
Relay State
Relay On
Relay Off
Sensed Condition
OFF
Condition
Value
Direct-Acting Relay
OFF < ON
ON
Condition
Value
Relay State
Relay On
Relay Off
Sensed Condition
ON
Condition
Value
OFF
Condition
Value
Reverse-Acting Relay
ON < OFF

Penn System 450 Series Specifications

General

Brand	Penn
Model	System 450 Series
Category	Control Unit
Language	English