
©
Viessmann
5443203
|
10
SCU224
∆
T control for the heat exchange between 2 tanks
DT3O
:
Switch-on temperature diff.
Adjustment range: 2.0 ... 40.0°Ra
[1.0 ... 20.0 K]
in steps of 1 °Ra [0.5 K]
Factory setting: 12.0°Ra
[6.0 K]
DT3F
:
Switch-off temperature diff.
Adjustment range: 1.0 ... 39.0°Ra
[0.5 ... 19.5 K]
in steps of 1 °Ra [0.5 K]
Factory setting: 8.0°Ra
[4.0 K]
Reference sensors for this function are S3 and S4.
In system layout 2 the controller is equipped with an addi-
tional differential control for heat exchange between two
tanks. The basic differential function is adjusted using the
switch-on (
DT3O
) and switch-off (
DT3F
) temperature
differences.
When the temperature difference exceeds the switch-on
temperature difference, relay 2 switches on. If the tempe-
rature difference then falls below the adjusted switch-off
temperature difference, relay 2 switches off.
Note:
The switch-on temperature difference must be
at least 1 °Ra [0.5 K] higher than the switch-off
tempe rature difference.
DT3S
:
Nominal temperature difference
Adjustment range: 3.0 ... 60.0 °Ra
[1.5 ... 30.0 K]
in steps of 1 °Ra [0.5 K]
Factory setting: 20.0 °Ra
[10.0 K]
RIS3
:
Rise
Adjustment range:
2 ... 40 °Ra
[1 ... 20 K]
in steps of 2 °Ra [1 K]
Factory setting: 4 °Ra [2 K]
Pump speed control
A relative minimum pump speed can be allocated to the
output R2 via the adjustment channel
n2MN.
n2MN:
Pump speed control
Adjustment range:
30 ... 100
in steps of 5 %
Factory setting: 30
Note:
When loads which are not speed-controlled (e.g.
valves) are used, the value must be set to 100 % in
order to deactivate pump speed control.
Minimum pump speed
When the switch-on temperature difference is reached, the
pump is activated at full speed for 10 seconds. Then, the speed
is reduced to the minimum pump speed value (
n2MN
).
If the temperature difference reaches the adjusted nominal
temperature difference (
DT3S
), the pump speed increases by
one step (10 %). If the difference increases by the adjustable rise
value, the pump speed increases by 10 % respectively until the
maximum pump speed of 100 % is reached. The response of
the controller can be adapted via the parameter
RIS3
.
Note:
The nominal temperature difference must be
at least 1 °Ra [0.5 K] higher than the switch-on
tempe rature difference.
Note:
For pump speed control of the heat exchange
pump, the operation mode of relay 2 (
MAN2
)
must be set to Auto.
System-specific functions
The following adjustments are used for the specific function
in system layout 2.