6.8 Boiler circuit pump
6.8.1 General information
The unit can drive an external boiler circuit via outputs MFA 1, MFA 2 or VA1.
The pump remains activated as long as heat requirement prevails. When no more heat
is needed, the pump runs for the specified run-on time (NLZ) preset in parame-
ter
41
.
Continuous pump operation can be set with parameter
40
, if this is required.
Pump control logic
Type of operation
Standby/ Summer
Control option
with external sensor
without external sensor
Setting P 40
P 40 = 1
P 40 = 0
P 40 = 1
P 40 = 0
Pump operation
NLZ, OFF
NLZ, OFF
Continuous
operation
NLZ, OFF
Type of operation
Winter
Control option
with external sensor
without external sensor
Setting P 40
P 40 = 1
P 40 = 0
P 40 = 1
P 40 = 0
Pump operation
Continuous
operation
NLZ, OFF
(1
Continuous
operation
Continuous
operation
(1
The specified functions for the pump control apply to setback operation. In normal
operation, the pump runs continuously and independently of P 40.
6.8.2 Speed controlled pump
If a speed controlled pump is used, the control is carried out via a PWM control signal.
Without control signal the PWM pump control to 100 %.
▶
Connect control signal at plug (see Ch. 5.6.1).
Standard control
Here, the pump rating is assigned to the required burner load. The pump is operated
at minimum load when the burner is switched off.
▶
Set parameter
43
at
1
.
▶
Set the modulation limits for the pump via parameter
44
and
45
.
Temperature differential control
With this control option, the pump is controlled depending on the differential tem-
perature between the flow and return sensors set in parameter
48
.
▶
Set parameter
43
at
2
.
De-couple control
With this control option, the pump is controlled depending on the differential tem-
perature between the de-couple sensor and the flow sensor. The differential temper-
ature control prevents a return flow temperature increase caused by unbalanced
volume flows in the primary and secondary circuit. The function can be adapted to
the conditions of the system via parameter
47
.
As the control influences the de-couple sensor, DHW loading is not possible ahead
of the hydraulic de-couple.
▶
Set parameter
43
at
2
.
▶
Connect de-couple sensor to input B11.
Installation and operating instruction
Gas condensing boiler WTC-GB 90-A
6 Operation
83266502 • 1/2010-08 • La
46-95
