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Siemens A6V10631832_en--_f

Smart Infrastructure 2021-10-20

Engineering and commissioning

Engineering

Engineering mainly consists of implementing the data model into a VAV application, espe-

cially sending the setpoint from the supervisory controller to the VAV compact controller and

receiving the actual values (cf. Modbus register list) for control and monitoring. System limi-

tations of Modbus RTU apply, especially number of devices per segment and cable lengths

depending on the baud rate.

Commissioning

Two basic workflows are supported:

• Full or partial configuration (bus configuration and optionally VAV parameters configura-

tion) by a tool (AST20 or ACS941),

• Full or partial configuration over bus, usually using addressing by push-button, with subse-

quent configuration over bus.

Commissioning workflow 1: Full or partial configuration by tool

When using the AST20 handheld tool or the ACS931 / ACS941 PC tool, all bus and VAV pa-

rameters can be set.

• Connect AST20 or ACS931 / ACS941 (for PC tools, use AST22 interface converter) to the

VAV compact controller and navigate to the bus configuration menu

• Set bus parameters as desired

• Optionally make changes on VAV parameters.

Note

With AST20, all parameters can be set using the mass configuration function. The bus parameters are included in the

mass configuration function. It can be selected that the address is automatically incremented with each programmed

VAV compact controller. ACS931 / ACS941 supports saving and loading of parameter sets.

Commissioning workflow 2: Configuration over bus (full or partially)

The devices can be configured over bus if the pre-commissioning settings allow for a con-

nection between the Modbus master / programming tool and peripheral devices (i.e. non-

conflicting addresses and matching baudrate / transmission format).

• Full configuration over bus: If the address is unique per segment when powered up, the

device can be accessed by the Modbus master (or programming tool) and the address

and other parameters can then be set to the definitive values.

• Partial configuration over bus: If the address is not unique per segment when powered up,

each device must get a non-conflicting address before connecting it to the bus (e.g. using

the push-button addressing method). After addressing all devices, the remaining configu-

ration can be done over the bus using the default settings for baudrate (auto-baud) and

transmission mode for the Modbus master.

• Overwriting the bus configuration over bus uses a timeout. If “1 = Load” is not written into

Reg 768 within 30 seconds, all values are discarded.

Example: Table shows bus configuration registers before and after changing them over bus.

Reg.

Name

Pre-commissioning

New value (ex.)

764

Address

246

765

Baudrate

0 = auto

1 = 9600

766

Transmission Mode

0 = 1-8-E-1

3 = 1-8-N-2

767

Termination

0 = Off

768

BusConfigCmd

0 = Ready

1 = Load