Johnson Controls Penn System 450 Series Technical Bulletin page 19

• the LNO relay contact is open
• the LNC relay contact is closed
• the corresponding Output Status screen in the UI displays OFF
System 450 control and expansion modules are available with one or two relay
outputs. See Table 11 on page 62 and Technical Specifications on page 67 for more
information about the System 450 Series module models used to build standard
control systems.
A relay output's control action is determined by the values that you select in the
ON and OFF relay output setup screens:
• Relay ON values (ON) are the values at which the relay turns On.
• Relay Off values (OFF) are the values at which the relay turns Off.
Table 3 illustrates direct and reverse relay actions. When you select On/Off
condition values where OFF is less than On, the output relay is a direct acting
relay. When you select condition values where On is less than Off, the output relay
is a reverse acting relay.
Table 3: System 450 Output Relay Control Actions and the Relationship
Between ON and OFF Values
Control Action
Direct Acting Relay
Relay State
Relay On
Relay Off
OFF
Condition
Value
Sensed Condition
Reverse Acting Relay
Relay State
Relay On
Relay Off
ON
Condition
Value
Sensed Condition
In temperature applications, direct acting relays are often used to control cooling
equipment, while reverse acting relays are often used to control heating equipment.
System 450™ Series Modular Control Systems with Standard Control Modules Technical Bulletin
Set the Relay Output ON/OFF Value
Relationships for the Desired Control
Action
OFF < ON
OFF < ON
ON
Condition
Value
ON < OFF
ON < OFF
OFF
Condition
Value
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