Burkert Type 8620 - Manual (Page 95)

mxCONTROL Type 8620
Page 95
14.3.1 On-/Off-Control (COND_CONTROL)
This module allows a simple On-/Off Control of the conductivity with the optional interface to the
"Biocide-Dosing" module.
These modules are
explained below.
Figure 35:
COND_CONTROL
Pre-bleeding and "Biocide Dosing" Module
For optimizing the biocide dosing the bleed valve is held shut during the biocide dosing by means of
output override so that the contact time of the dosed biocides is maximized. But there is the risk of
hardness salts precipitating due to over concentration, since the dosed biocides increase the
conductivity.
So the biocide dosing usually starts with a pre-bleed phase, in which the conductivity is reduced to
a parameterized pre-bleed limit before the dosing of the biocide starts.
Therefore the "Biocide Dosing" module overrides the conductivity set point with the pre-bleed limit
during the pre-bleed phase in automatic mode.
If the conductivity process value is equal or smaller than the pre-bleed limit or if the operational mode
is switched to manual mode, the pre-bleed phase will be finished.
For more detailed information on the time-controlled biocide dosing process or "Biocide Dosing"
module, please refer to the chapter 14.9.
For the use of the pre-bleed function the following things have to be provided:
• the pre-bleed functionality has to be enabled (in the configuration file)
• The link between conductivity module and "Biocide Dosing" module has to be
configured correctly (in the configuration file),
the pre-bleed limit is smaller or equal than the current set point of the conductivity control
Only one of the Conductivity modules can be connected with the “Biocide Dosing” module!