Doc: 70-00-0792B V1.3, 20220830 © Vector Controls GmbH, Switzerland Page 20-34
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5.6.4 Manual vs. auto heat/cool change
Manual heating or cooling allows the user interface (via Controlling Mode button ) and Modbus master to change
between heating and cooling. No input (RT1/2) can use the function “Heat/cool changeover” (P400/P402 = 2).
To allow only Modbus master control the heat/cool state parameter, P107(Enable manual control of heat/cool/fan only)
must be set to 0 = OFF. Modbus master can control the Controlling mode (heat/cool/fan only) with controller runtime data
D1101.
Auto heat/cool changeover allows one of the inputs (RT1/2, where RT1 has higher priority) to act as a control input for
heat/cool changeover. See chapter 5.9 Temperature and digital inputs, page 27. User interface and Modbus master
control of heat/cool change are disabled in auto heat/cool application (P200 = 3 or 5). Via user interface the user can only
change to fan only.
5.6.5 3-position valve control
Output DO4 the OPEN command, output DO5 provides the CLOSE command to the 3-position valve.
The default setting for the valve running time is 150 seconds. It can be adjusted via parameter P204.
Valve synchronization:
• After power up the CLOSE command (DO5) is on for two times the valve running time (P204).
• When the control output is <5%, the CLOSE command (DO5) is on for an additional valve running time.
• When the control output is >95%, the OPEN command (DO4) is on for an additional valve running time.
5.6.6 Fan extension time for electric heater
When the electric heater is switched off, the fan keeps running for the time specified with P202 to avoid over-heating of
the electric heater.