Frost Protection; Demand-Controlled Ventilation - Siemens RWI65.02 Manual

Frost protection

(on the water or air side)
Function diagrams
Legend
Demand-controlled
ventilation
Siemens Building Technologies
Landis & Staefa Division
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.
Plant ON
On the air
and the water side
Y [ % ]
100
Y10(P)
0
w
X
w
Pd
(DtPnt 16)
(DtPnt 18)
t
Pmin
2 K ½ X
Pd
(DtPnt 48)
Q33/Q34
Q13/Q14
Q33/Q44
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 P-band "Frost protection controller" (data point 18)
pd
X P-band "Standby controller" (data point 19)
pn
w Frost alarm value (data point 16)
w
w Setpoint "Standby controller" (data point 17)
wn
t Min. running time of hot water circulator (data point 48)
Pmin
This function enhances comfort and optimises energy consumption in rooms with
varying occupancy levels. An integral CO
CO / VOC concentration in the room. The P-band, the switching values for the fan
2
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
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
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.
Plant OFF
On the air
and the water side
Y [ % ]
100
Y10(PI)
0
T
w
wn
(DtPnt 17)
/ VOC controller reduces the CO
2
values. If CO
2
or CO
2
On the air side
Y [ % ]
100
0
Q
w
w
(DtPnt 16)
X
t
2 K
Pmin
(DtPnt 48)
Q13/Q14
2
or CO / VOC concentrations in
2 2
/ VOC concentrations increase
2
CM2N3204E / 05.2001
Y10(P)
T
t
Pn
Pmin
(DtPnt 48)
Q13/Q14
or
5/20