Carrier 17EX Processor/Sensor Input/Output Module Psio Fig, Starter Management Module SMM Fig

If all modules indicate a communications failure, check the communications plug on the PSIO module for proper seating. Also check the wiring (CCN bus Ð 1:red, 2:wht, 3:blk; Sensor bus Ð 1:red, 2:blk, 3:clr/wht). If a good connection is assured and the condition persists, replace the PSIO module.

If only one 8-input module, the SMM, or the 4-in/2-out module indicates a communication failure, check the com- munications plug on that module. If a good connection is assured and the condition persists, replace the module.

All system operating intelligence rests in the PSIO mod- ule. Some safety shutdown logic resides in the SMM in case communications are lost between the 2 modules. The PSIO monitors conditions using input ports on the PSIO, the SMM, the 8-input modules, and the 4-in/2-out mod- ules. Outputs are controlled by the PSIO and SMM as well.

3.Power is supplied to the modules within the control panel. The transformers are located within the power panel, with the exception of the SMM, which operates from a 24-vac power source and has its own 24-vac transformer located in the starter.

In the power panel, T1 supplies power 21-vac to the LID, the PSIO, and the 5-vac power supply for the transduc- ers. T3 supplies 24-vac power to the 4-in/2-out module. T4 is another 21-vac transformer, which supplies power to both 8-input modules (if present). T4 is capable of sup- plying power to two modules; if additional modules are added, another power supply will be required.

Power is connected to Terminals 1 and 2 of the power input connection on each module.

PSIO (J8)			SMM (J5)			8-INPUT (J5)			8-INPUT (J5)			4-IN/2-OUT (J3)
	1	+		1	+		1	+		1	+		1	+
	2	GRD		2	GRD		2	GRD		2	GRD		2	-
	3	-		3	-		3	-		3	-		3	GRD

			LEGEND
GRD	Ð	Ground	PSIO Ð Processor/Sensor Input/
J	Ð	Junction	Output Module

SMM Ð Starter Management	Pins
Module

Fig. 51 Ð Sensor Input/Output (SIO) Wiring

Schematic for COMM3 Bus

Processor/Sensor Input/Output Module (PSIO) (Fig. 52)

INPUTS Ð Each input channel has 3 terminals; only 2 of the terminals are used. The chiller application determines which terminals are normally used. Always refer to individual unit wiring diagrams for terminal numbers.

OUTPUTS Ð Output is 20 vdc. There are 3 terminals per output, only 2 of which are used, depending on the appli- cation. Refer to the unit wiring diagram.

NOTE: Address switches on this module can be at any position. Addresses can only be changed through the LID or CCN.

Fig. 52 Ð Processor (PSIO) Module

Starter Management Module (SMM) (Fig. 53)

INPUTS Ð Inputs on strips J2 and J3 are a mix of analog and discrete (on/off) inputs. The chiller application deter- mines which terminals are used. Always refer to the indi- vidual unit wiring diagram for terminal numbers.

OUTPUTS Ð Outputs are 24 vdc and wired to strip J1. There are 2 terminals used per output.

NOTE: SMM address switches should be set as follows: S1 set at 3; S2 set at 2.

Fig. 53 Ð Starter Management Module (SMM)

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