5
CONTROL OPTIONS MODULE — The PSIO2 module
does not contain software. Through input and output channels
on the hardware, it supports the sensors used for:
• suction thermistors
• relative humidity
• outdoor-air cfm
• indoor-air quality (IAQ)
• smoke control
• supply air set point reset via external device
In addition, the PSIO2 supplies the outputs (4 to 20 mA sig-
nal) for humidifier and hydronic heating coil control, a discrete
output for timed clock control (for outdoor building or parking
lot lights), condenser fan staging (088-104 only), and a remote
alert light (088-104 only).
The PSIO2 options module is available as a factory-
installed option or as a field-installed accessory for sizes 034-
074 and is standard on sizes 078-104.
CB
—
Circuit Breaker
CCB
—
Control Circuit Breaker
CH
—
Crankcase Heater
CLO
—
Compressor Lockout
COMP
—
Compressor
CR
—
Control Relay
DPT
—
Duct Pressure Transducer
DSIO
—
Module Relay
DU
—
Dummy Terminal
ECON
—
Economizer
EQUIP
—
Equipment
FU
—
Fuse
GND
—
Ground Connection
HIR
—
Heat Interlock Relay
*Standard on sizes 078-104.
Fig. 2 — Major Control Components in Control Box
HPS
—
High-Pressure Switch
HR
—
Heater Relay
IDC
—
Induced-Draft Contactor
IFC
—
Indoor-Fan Contactor
IFM
—
Indoor-Fan Motor
IGV
—
Inlet Guide Vanes
LPS
—
Low-Pressure Switch
MM
—
Motormaster® Control
MMC
—
Motormaster Contactor
NEC
—
National Electrical Code
OAT
—
Outdoor-Air Thermistor
OFC
—
Outdoor-Fan Contactor
OFM
—
Outdoor-Fan Motor
PEDM
—
Power Exhaust Damper Motor
PL
—
Plug Assembly
PRI
—
Primary
PSIO
—
Processor Module
RAT
—
Return-Air Thermistor
RFM
—
Return Fan Motor
SAT
—
Supply-Air Thermistor
SCT
—
Saturated Condensing Thermistor
SEC
—
Secondary
SGT
—
Suction Gas Thermistor
SPT
—
Suction Pressure Transducer
TB
—
Terminal Block
TRAN
—
Transformer
U
—
Unloader
LEGEND
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