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Siemens Building Technologies
HVAC Products
22.3.3 Mode of operation without outside sensor
Frost protection for the plant operates in 2 stages:
1.
If the flow temperature (sensor B1) falls below 10 °C, the heating circuit pump will
be activated for 10 minutes at 6-hour intervals.
2.
If the flow temperature falls below 5 °C, the heating circuit pump will be activated
and runs continually.
When active, the respective frost protection stage will be switched off when the flow
temperature has exceeded the limit value by 1 K.
22.3.4 Frost protection for the heating circuit flow
In addition to frost protection for the plant through activation of the heating circuit pump,
frost protection acts separately on both heating circuits. This frost protection is single
stage and will be activated when the heating circuit flow drops below 5 °C. The switch-
ing differential is 2 K; switching off takes place at >7 °C. Frost protection for the heating
circuit flow generates a demand for heat (flow temperature setpoint) of 10 °C and, after
reaching the switch-off criterion, will be active for a minimum of 5 minutes.
22.4
Flow alarm
22.4.1 Heating circuit and d.h.w. circuit with storage tanks
The purpose of this function is to detect bottlenecks in the heat supply of the district
heat network.
The flow alarm triggers a fault status signal when the flow temperature in
• one or both heating circuits
• the common flow
• the d.h.w. circuit
does not reach the setpoint band (setpoint ± switching differential of 3 °C) within a de-
fined period of time when there is demand for heat. This period of time can be set on
operating line 143.
The flow alarm becomes inactive as soon as the setpoint band is reached.
The flow alarm appears on the display as ERROR and, on operating line 50, with an
error code.
The correlation between sensor, plant type and error code in the heating circuit control
systems is the following:
Heating circuit
control
1–x
Common flow
Heating circuit 1: B1/Y1
Heating circuit 2: B12/Y7
The following table applies to d.h.w. heating:
Plant type
1–8, 1–9, 2–2, 4–8, 4–9
2–6
Plant type 1–3 has no flow alarm since there is no flow sensor in the d.h.w. circuit.
Basic documentation RVD240
22 Function block Device functions
Sensor / controlling element per plant type
2–x
B1/Y1
2–0, 2–1, 2–6:
B12/Y1
2–2:
B12/Y7
Sensor / controlling element
B3 / Y5
B3 / no mixing valve
Error
number
3–x
4–x
B1/Y1
B1/Y1
120
B12/Y5
121
B3/Y7
B12/Y7
122
Error code
123
123
CE1P2384en
27.05.2004
81/126
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