ABB i-bus VC/S 4 1 Series, Product Manual, Page: 180 / 199

ABB i-bus® KNX PLANNING AND APPLICATION
The supply and return flow are normally connected together by a 3-way mixing valve. The water from the
supply flow is mixed with the water from the return flow to achieve the required supply flow tempera-
ture. A circulating pump ensures that the water circulates in the heating/cooling circuit.
12.2.9 Hysteresis
The hysteresis indicates the difference by which a value must change before a control operation is per-
formed. Hysteresis prevents switching in response to minimal changes.
12.2.10 Manual valve override
During manual valve override, the active valve control value is overridden. The active valve control value is
the valve control value calculated by the controller (controller mode) or received via the bus
(ABB i-bus® KNX) (actuator mode).
If manual valve override is enabled (→ parameter Enable manual valve override ), the active valve control
value is overridden with the value of group object Override valve control value X .
If manual valve override is disabled, the active valve control value cannot be overridden.
Possible applications:
• System function test
• Specific override of the active valve control value
12.2.11 Master/slave operation
In master/slave operation, a central master takes over the control of the slaves. In master/slave opera-
tion, there can be several slaves but only one master.
Slaves send requests to the master via a "Request" telegram (e.g. manual temperature adjustments). The
master checks whether the request is within the valid parameterized range, implements the request and
sends the value back to the slave via a "Confirm" telegram.
12.2.12 Refreshed KNX state
If an input or an output is blocked by device-specific functions (e.g. manual operation, alarms, block,
forced operation, switching delay), it will not react to telegrams received via the bus (ABB i-bus® KNX)
while the block is active.
While a block is active, the device processes the telegrams received in the background. Active functions
(e.g. staircase lighting, logic, position, brightness value) are executed in the background, but the results
are not sent. The actual value is sent to the input or output when the block is canceled.
If the input or output has not received any telegrams via the bus (ABB i-bus® KNX) while a block is active,
the input or output will assume the state it was in before the block.
Product manual | EN-US | VC/S 4.x.1 | 2CDC508220D0211 Rev. B 180
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