Siemens Building Technologies
CM2N3204E / 05.2001
Landis & Staefa Division
5/20
For ventilating and air conditioning plants using hot water heating coils:
All values for frost protection (response temperatures, setpoints, P-bands, and integral
action times) are preset and can be changed. The temperature is acquired either in the
water circuit or at the air outlet of the hot water heating coil.
The protective actions are the following:
•
Continuous opening of the heating valve, activation of the hot water circulator
•
Deactivation of the fan or closing of the air dampers
•
Maintaining the temperature when the fans are deactivated (only on the water side,
setpoint "Standby controller")
•
Fault status signal when there is risk of frost
Use of the following sensors is a prerequisite:
QAE21.9 or QAD22 for frost protection on the water side.
QAF63.2, QAF63.6 for frost protection on the air side.
T
Temperature in the hot water heating coil’s circuit, or air temperature just after the
heating coil
Q
Load
Y
Manipulated variable
Y10
Control command "Heating valve"
Q13 / Q14
Relay output "Hot water circulator or electric air heater battery"
Q33 / Q34
Relay output "Fan speed I"
Q33 / Q44
Relay output "Fan speed II"
X
pd
P-band "Frost protection controller" (data point 18)
X
pn
P-band "Standby controller" (data point 19)
w
w
Frost alarm value (data point 16)
w
wn
Setpoint "Standby controller" (data point 17)
t
Pmin
Min. running time of hot water circulator (data point 48)
This function enhances comfort and optimises energy consumption in rooms with
varying occupancy levels. An integral CO
2
/ VOC controller reduces the CO
2
or
CO
2
/ VOC concentration in the room. The P-band, the switching values for the fan
speeds, and the design value at full occupancy are adjustable; the switching differential
is 160 ppm. Using the sensors connected to signal inputs Z, B1 and B2, the controller
acquires the actual temperature and CO
2
values. If CO
2
or CO
2
/ VOC concentrations in
the room exceed the switching value of fan speed I + ½SD, the temperature controller is
activated and the fan runs at speed I. The temperature controller maintains the prese-
lected setpoint (Comfort or Economy). If CO
2
or CO
2
/ VOC concentrations increase
further, fan speed II is activated. Between this function and the step output of the
scheduler program, maximum value selection takes place, with both functions having
the same priority. In the case of systems with recirculated air dampers, damper control
is activated also. Here, Y30 minimum limitation, recirculated air start-up mode, and the
frost protection controller with a higher priority act on the Y30 control signal.
Frost protection
(on the water or air side)
Function diagrams
100
100
Y
[ % ]
0
0
T
Q
Q33/Q34
Q33/Q44
Q13/Q14
Y10(P)
Y10(PI)
Q13/Q14
100
0
T
Y10(P)
Q13/Q14
Y
[ % ]
Y
[ % ]
2 K
X
Pn
t
Pmin
t
Pmin
t
Pmin
X
Pd
½ X
Pd
2 K
w
wn
w
w
w
w
On the air
and the water side
Plant ON
Plant OFF
On the air
and the water side
On the air side
3
204
D
0
5E
(DtPnt 16)
(DtPnt 48)
(DtPnt 48)
(DtPnt 17)
(DtPnt 48)
(DtPnt 18)
(DtPnt 16)
Legend
Demand-controlled
ventilation
