Master Management; Slave Management; Pi Control (Proportional And Integral) - Carel ACC User Manual

Anti-sweat controller

Table of Contents

6.3

Master management

In Master configuration, all three probes are required (B1, B2 and B3). The dewpoint is calculated according to the values measured by probes B1 and

B2. The output is controlled according to the value read by probe B3. In the event of alarms on probes B1 or B2, the dewpoint value is forced to 99.9.

If the serial connection is configured as LAN, the Master also becomes the network master and sends the value of the dewpoint calculated to any Slaves

connected.

The value is set at regular intervals in broadcasting mode, thus without needing to define how many Slaves are connected and their addresses. The

dewpoint value sent, when suitably configured by dipswitch, can be increased by the value of an offset set by trimmer, thus allowing simultaneous

control of all the Slaves connected.

If the serial connection is configured as Supervisor, the Master becomes a network slave and responds to the queries from the Supervisor.

Dipswitch

Dip1

Select Master/Slave mode

Dip2

Select serial connection mode, Supervisor/LAN

Dip3

Select Trimmer mode

(Master only)

6.4

Slave management

In Slave configuration, the value of the dewpoint is received via network (from a controller configured as the LAN master or from the supervisor, which

in turn reads the value from a controller configured as the Supervisor master), and consequently probes B1 and B2 do not need to be connected. The

output is controlled according to value read by probe B3.

If the dewpoint value is not received via the network or the value received is 99.9, an alarm is activated.

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If the serial connection is configured as LAN, the Slave does not respond when broadcasting mode is used. The timeout for no data reception

is 10 s.

If the serial connection is configured as Supervisor, the Slave responds even when broadcasting mode is used, however generating a conflict

with any other Slaves connected to the LAN. The timeout for no data reception is 20 minutes. For Slaves controlled by Master, Dip2 must be

in the ON position.

6.5

PI control (proportional and integral)

In addition to the normal contribution of proportional control, the output is also controlled using the integral time on the error (deviation between the

value measured and set point). This is used to reduce the error to zero.

out = Kp*err + Ki*Integral(err)

where err=error, Kp=proportional gain, Ki=integral gain, Ti=integral time, given by:

err = (set point – measurement)

Kp = max. output/diff

Ki = Kp/Ti

By definition the integral time is the time required, when the error if constant, for the integral part to have the same contribution as the proportional

part. The integral time can be set by parameter (default 10 minutes). The contribution of the integral part can be reduced so as to avoid the

phenomenon of "wind-up" (default 50%), however in this case the error will not be removed in steady operation. Special care is required when setting

the Ti, as excessively short times (see the inertia of the system) may lead to instability. For a more detailed explanation of integral control, see the

documents available on control theory.

Associated parameters

name

Carel spv

range

var

INTT

1 to 30

AWUP

0 to 100

EPIR

0/1