System 450 Functional Sensors; Relay Outputs - Johnson Controls Penn System 450 Series Technical Bulletin

System 450 Functional Sensors

System 450 control modules also enable several functional sensors based on the
input from one or more of the hard-wired sensors in your control system. Selecting
a functional sensor for an output on a System 450 standard control system enables
the differential or high signal selection control feature on the output.
Beginning with firmware Version 2.00, System 450 standard control modules
provide for three additional functional sensors:
• When Sn-1 and Sn-2 are set up as the same Sensor Type, the High Input Signal
Selection functional sensor (HI-2) and Differential Control functional sensor
(Sn-d) are enabled and available in the Sensor Selection screens for each
output in the control system.
• When Sn-1, Sn-2, and Sn-3 are the same Sensor Type, the High Input Signal
Selection functional sensor (HI-3) is also enabled and available.
See High Input Signal Selection on page 24 and Differential Control on page 25 for
more information about these functional sensors and system control features.

Relay Outputs

Relay outputs provide low and line-voltage on/off control for devices and
equipment in your controlled systems. Each relay output is a Single-Pole,
Double-Throw (SPDT) set of dry contacts. See Figure 15 on page 38.
Note: System 450 output relays are SPDT dry contact relays only and do not
provide any power source for your controlled equipment.
Selecting an ON value that is less than the OFF value (ON < OFF) turns the relay
on when the sensed condition value decreases, which is the typical heating mode in
temperature applications and referred to as reverse acting on/off control.
Selecting an ON value that is greater than the OFF value (ON > OFF) turns the
relay on when the sensed condition value increases, which is the typical cooling
mode in temperature applications and referred to as direct acting on/off control.
You can set up multiple relay outputs to create a variety of equipment staging
control systems. See Wiring System 450 Components on page 37 for information
on wiring output relays. See Technical Specifications on page 67 for the relay
output electrical ratings.
A green LED on the relay control and relay expansion module housings (Figure 2)
indicates the relay output status.
When a relay output is On:
• the corresponding green LED on the module housing is lit
• the LNO (Line Normally Open) relay contact is closed
• the LNC (Line Normally Closed) relay contact is open
• the corresponding Output Status screen in the UI displays On
When a relay output is Off:
• the corresponding green LED on the module housing is not lit
18 System 450™ Series Modular Control Systems with Standard Control Modules Technical Bulletin