Bypass Valve Control

The bypass valves will be switched depending on the buffer load level input “BufLoadLevel“, the buffer charging by the controlled heat generators and the input “ExtLoading”.

For charging control the application engineering has to take care, to switch the input “ExtLoading” to the correct value if a combination of controlled and un-controlled charging is used.


The states of the bypass valves depending on the switching conditions are shown in the next table:

Table 5.   Changeover valve switching conditions

Bypass valve

Switching Conditions of the Bypass Valves

Overheat protection or Stop Buffer Loading at High Outdoor Temperatures

no

yes

Charging Control and
Buffer Charging

(Charging Control and no Buffer
Charging) or Discharging Control





don’t care

ExtLoading

does not care

1

0

BufLoadLevel

1

2

3

4

does not care

BypassValve1

charge

charge

charge

charge

charge

bypass

bypass

BypassValve2

bypass

charge

charge

charge

charge

bypass

bypass

BypassValve3

bypass

bypass

charge

charge

charge

bypass

bypass

BypassValve4

bypass

bypass

bypass

charge

charge

bypass

bypass


When the input “ExtLoading” = 1 and the buffer is not charged by the controlled heat generators, all the bypass valves will be opened to charge the buffer as much as possible. In this case the bypass valves will switch to bypass only in case of overheat.


When the buffer is charged by the own heat generators (the heat demand output <> 0) regardless of the input “ExtLoading”, the bypass valve’s states are defined in the next table.


All the bypass valves will switch to the position bypass:

We recommend to connect digital outputs datapoints with the engineering units “charge“ and “bypass“.