Siemens Synco RMK770, Basic Documentation, Page: 144 / 232

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Building Technologies Boiler Sequence Controller RMK770 CE1P3132en
HVAC Products 9 Precontrol 23.04.2009
9.8 Limit and protective functions
9.8.1 Frost protection
Here, the setting is made whether or not function “Frost protection for the plant” shall
act on the pump for precontrol.
For more detailed information about frost protection for the plant, refer to section 5.4
“Pump overrun and mixing valve overrun”.
Function “Frost protection for the plant“ is only available if an outside sensor is installed
(locally or connected via KNX bus). The function can be deactivated.
The minimum flow temperature is monitored. If the flow temperature falls below 5 °C, a
heat demand signal is sent to the heat source and the mixing valve opens. The function
will be ended as soon as the flow temperature has risen to 7 °C. The function will be
active for a minimum of 5 minutes.
9.8.2 Limitations
This setting provides maximum limitation of the flow temperature setpoint.
This setting provides minimum limitation of the flow temperature setpoint. Minimum
limitation is only active when there is demand for heat.
Using setting --- (none), the function can be deactivated.
This function is only available with primary controller type 1. The rate of increase of the
flow temperature setpoint can be limited to a maximum (heating up brake). In that case,
the maximum rate of increase of the flow temperature setpoint is the selected tempera-
ture per unit of time (K per hour).
Purpose of heating up brake:
•
Preventing cracking noises in the pipework
•
Preventing excessive loads on heat generating equipment
Setting --- deactivates the function.
t
t
252
2D
07
T
Vw
T
Vw
Maximum rise: = Δ T
Vw
/ Δ t
t Time
Δ
t Unit of time
TVw Flow temperature setpoint
Δ TVw Rate of setpoint boost per unit of time
Refer to subsection 9.8.3 “Limitation of the return temperature”.
With setting “System pump locking signal“, it can be parameterized whether or not the
system pump shall respond to critical locking signals.
Setting “System pump locking signal“ Effect on locking signal
Off System pump is switched off
On System pump remains switched on
Frost protection
for the plant
Frost protection
for the flow
Maximum limitation of
the flow temperature
Minimum limitation of
the flow temperature
Limitation of the rate
of flow temperature
increase
Return temperature
limitations
System pump and
locking signals