Processor Module(s) (PSIO)
INPUTS Ð Each input channel has 3 terminals; 2 are used.
OUTPUTSÐ Output of the PSIO module is 24 vdc or 4 to 20 mA dc. There are 3 terminals; 2 are used.
REPLACING DEFECTIVE PSIO MODULES Ð The re- placement part number is printed on a label on the front of the PSIO module. The replacement module order is con®g- ured as a generic replacement module, which will require con®guration in the ®eld.
Before any service work is started, be sure that all elec- trical disconnects are open and tagged.
Installation
1.Verify the existing PSIO module is defective by using the procedure described in the Control Modules section on this page.
2.Refer to the
list does not exist, make a new checklist by ®lling out
the 
and 
con®gurations on paper. Tailor the various options and con®gurations as needed for this particular installation.
3.Check that all power to the unit is off. Switch off all circuit breakers. Carefully disconnect all wires from the defective module by unplugging the 6 connectors. It is not necessary to remove any of the individual wires from the connectors. Remove the green ground wire.
4.Remove the PSIO module mounting screws and remove the module from the control box. Save the screws.
5.With a small screwdriver, set the address switches S1 and S2 on the new PSIO module to match those on the defective module.
6.Mount the new module in the control box using the screws saved in Step 4.
7.Reinstall all 6 wire connectors and the green ground wire.
8.Check all wire connections before restoring power to the unit.
9.Verify that the unit ON/OFF switch is in the ON position.
10.Restore power to the unit and close the control circuit breaker (CCB). Verify that the red and green LEDs re- spond as described in the Control Modules section on this page. The HSIO keypad should begin its rotating display.
11.Using the HSIO keypad and display module, press 
to verify that the software version matches the version number shown on the PSIO label.
12. Press to verify that the factory con®guration
codes agree with the values listed in Table 24 on page 37.
13.Set other applicable inputs required in 
and 
to match the options and accessories installed on the equipment.
14.Enable data reset function to store all data. The HSIO keypad display will blank out after pressing the ENTER key while displaying data reset (DTRS). The rotating dis- play returns when the data reset has been completed.
15.Press 
and verify each item is now con®gured as needed for this particular installation. Verify the fac- tory default settings for both a speci®ed unit and generic control unit.
16.Press 
to check the remainder of the user con- ®guration values.
17.After completing the con®guration steps outlined above, close all remaining circuit breakers and perform a unit test.
18.Complete this procedure and restore the unit to normal operation by returning the STANDBY/RUN mode to
STBY NO.
High-Voltage Relay Modules (DSIO1 and DSIO2)
INPUTS Ð Inputs on terminal strip J3 are discrete inputs (on/off). When 24 vac is applied across the 2 terminals in a channel, it reads as an on signal. Zero v is read as an off signal.
OUTPUTS Ð Terminal strips J4 and J5 are internal relays whose coils are energized by a signal from the microproces- sor. The relays switch the circuit to which they are con- nected. No power is supplied to these connections by the DSIO module.
DSIO REPLACEMENT Ð Before any service work is started, be sure that all electrical disconnects are opened and tagged.
Installation
1.Verify the existing DSIO module is defective by using the procedure described in the Control Modules section on page 53.
2.Check that all power to the unit is off. Switch off all circuit breakers. Carefully disconnect all wires from the defective module by unplugging the connectors. It is not necessary to remove any of the individual wires from the connectors. Remove the green ground wire.
3.Remove the DSIO module mounting screws and re- move the module from the control box. Save the screws.
4.With a small screwdriver, set the address switches S1 and S2 on the new DSIO module to match those on the defective module.
5.Mount the new module in the control box using the screws saved in Step 3.
6.Reinstall all of the wire connectors and the green ground wire.
7.Carefully check all wire connections before restoring power to the unit.
8.Verify that the unit ON/OFF switch is in the ON position.
9.Restore power to the unit and close the control circuit breaker (CCB). Verify that the red and green LEDs respond as described in the Control Modules section on page 53. The LID (keypad) should begin its rotating display.
10.After completing the con®guration steps outlined above, close all remaining circuit breakers and perform a unit test.
11.Complete this procedure and restore the unit to normal operation by returning the STANDBY/RUN mode to
STBY NO.
Refrigerant Feed Components Ð Each refrigerant circuit (2 per unit) has all the necessary refrigerant controls.
Thermostatic Expansion Valve (TXV) Ð On 48/ 50MP units, each circuit has 2 TXVs on which superheat may be adjusted if absolutely necessary.
The TXV is set to maintain 10 to 13 F superheat leaving the evaporator coil. It controls the ¯ow of refrigerant to the evaporator coils.
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