78 EB 5573-1 EN
Functions of the heating circuit
6.5 Buffer tank systems Anl 16.x
The systems Anl 16.x are tted with a butter tank. The buffer tank can be charged by the dis-
trict heating system according to an adjustable characteristic or to an adjustable xed set
point. The storage tank charging pump SLP is controlled to the storage tank set point (e.g.
45.3°C), which is based on the outdoor temperature. Storage tank charging starts when
temperature falls below the outdoor-temperature-based set point at SF1. The charging tem-
perature results from the outdoor-temperature-based set point plus 6°C (e.g. 51.3°C). The
storage tank charging is nished when the temperature at SF2 exceeds the outdoor-tempera-
ture-based set point by 3°C (e.g. 48.3°C).
With CO1>F21-1, Y1 for speed control of the storage tank charging pump is available.
All storage tank charging actions start with the minimum pump speed (function block param-
eter: 'Min. speed signal'). As soon as the charging temperature at VF1 is nearly reached, the
speed of the storage tank charging pump is increased and the valve controls the ow rate. If
the temperature at SF2 reaches the value entered in Start speed reduction, the signal level at
Y1 is reduced within the range between the limits entered in Start speed reduction and Stop
speed reduction. Y1 is set to 0V when the storage tank charging pump is switched off.
For systems without a downstream control circuit, a transmitted external demand causes the
feeder pump UP1 to be activated and can override the current buffer tank set point, if neces-
sary. For systems with a downstream control circuit, either a transmitted external demand or
the demand of the downstream control circuit causes the feeder pump UP1 to be activated,
regardless of the CO5 > F14 setting. Regardless of the CO5 > F14 setting, the external de-
mand and the demand of the downstream control circuit can override the current buffer tank
set point.
The pump UP2 of the solid-fuel boiler circuit starts to run when the temperature reaches 'Start
temperature for boiler pump' at VF2. The boiler pumps is switched off again when the tem-
perature at VF2 falls below the temperature T = 'Start temperature for boiler pump' – 'Boiler
pump hysteresis'.
In systems Anl 16.3, 16.4 and 16.6, a solar circuit is integrated, which uses sensor SF2 for
control. The collector circuit pump CP is activated when the temperature at the collector sen-
sor RüF2 is higher than that at storage tank sensor SF2 by the value entered in 'Solar circuit
pump ON'. It is deactivated when the temperature difference falls below the valve entered in
'Solar circuit pump OFF' or when the temperature at the storage tank sensor SF2 reaches
'Max. storage tank temperature'.
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