saia-pcd.com
100
PCD
7L
Dedicated room controller
Project planning information
Maximum number of room controllers
The maximum number of room controllers which can be managed by a PCS/PCD system depends on the maximum electrical load
of the serial S-Net, the bus system cycle time and the resources used by the functional objects.
Types of use and modes of operation
The function of the room controller is based on various types of use or modes of operation.
Each of the selectable modes of operation can be assigned different control parameters.
Bus terminating resistor and bus cable for serial S-Net
(S-Bus/RS-485)
S-Bus cables must be installed as a line. Stub lines are not per-
mitted and both ends of the cable must be terminated with
a resistor (approx. 120 Ω) between the D and /D cables. The
best signal quality is achieved using an active bus connection
with a resistor to +5V and ground.
Use/Comfort
The room is used and should be brought to the comfort temperature.
This state can be reached by pressing the presence button, reacting to
an external presence detector or a parameter on the network side.
Window contact
open
Presence
recognition
Time program
Room use
Comfort
Standby
Reduced
Frost protection
0 h
2 h
4 h
6 h
8 h
10 h
12 h
14 h
16 h
18 h
20 h
22 h
24 h
Example: Operating mode switchover
Schematic illustration of an S-Bus/RS-485 bus
Safety mode/Frost protection
No heating or cooling energy is fed into the room. This state is desirable
if a window is open. The room controller keeps the room temperature
above the preset frost line of 8° C.
Non-use/reduced
Reduced operation mode which is used when the the room is not oc-
cupied for a long period. In this operation mode, the specified setpoint
value offset is not active.
Standby
The room is prepared for use but no presence has yet been registered in
the room. As long as the room is not classified as occupied by the pres-
ence function, the room controller keeps the room temperature within
the specified limits at the standby temperature.
With S-Bus controllers, the 111 configuration register can be used to activate the integrated active bus termination resistor or
an external PCD7.T161/2 termination box can be used.
Bus cable: a 2-strand twisted and shielded bus cable with cable strands of at least 0.5 mm
2
must be used. For additional
information please refer to the S-Bus manual 26/739 (available on
).
Recommendation: max. 4 S-Bus interfaces with up to 25 room controllers per interface so that in the majority of cases the
resources are sufficient and the communication cycle time remains at < 2 seconds.
At a communication speed of 38’400 baud, the communication time for a controller is approx. 15 ms, or 80 ms. If the PCD program
requires longer than 15 ms or 80 ms per PCD cycle, this value must be used as the basis of the calculation used to estimate the commu-
nication cycle. For additional information please refer to chapter 1.1.
Communication cycle = «15 ms or 80 ms per controller» × «Number of controllers».
PCD7.L79xN
Resources:
max. 600 program lines per FBox, max. 40 registers per FBox, max. 16 flags per FBox. 1 DB
Bus cycle timer per controller:
approx. 15 ms
PCD7.L60x-1 (with all FBoxes maximum removable)
Resources:
max. 95 registers, max. 36 flags
Bus cycle timer per controller:
approx. 80 ms
Start station
End station
Intermediate
stations
Pull down
Pull down
Termination
resistor
Termination
resistor
Pull up
Pull up
RS-485
S-Bus
+5V
+5V
/D D
/D D /D D
/D D
