Pilz PSS SB FT, Basic license - Manual (Page 108)

6-64 Modular Block System: Burner Management
Standard Function Blocks
Programming guidelines
• ENBL
The negative edge ENBL from SB156 must set a flag to “0” for one PSS-
cycle. This pulse flag must be supplied to the AND-operation before the
global input
ERR or to the AND-operation before the global input CHAI
from SB152 “Burner: Start and operator elements”. The decision to use
ERR or CHAI depends on the user and the respective standards
regarding error reaction.
ERR: If an error occurs a controlled shutdown is carried out,
when
AuSt = 1 with restart
CHAI: If an error occurs a safety shutdown is carried out
A programming example can be found in Chapter 8 under “Managing
enables”.
• Driving the valves VAV1 and VAV3
If tightness is being checked (i.e. monitoring if the valve is seated or not),
the situation could arise where the valves VAV1 and VAV3 can be driven
simultaneously via 2 program sections e.g. the valve VAV1 by SB156
and SB158 and the valve VAV3 by SB156 and SB159.
Solution: Assign different flags to the output parameter VAV1 from
SB156 and on SB158 for VAV1, and to the output parameter VAV3 from
SB156 and SB159 for VAV3. After calling up the SB, perform an OR-
operation on the flags and drive the corresponding periphery output for
the valve using the result of this logic operation.
Example:
SB156
B - SSNR
B - NEXT
X - SyOK
X - V4?
X - P+
X - P-
W - T_V
Z - T
ENBL - X
RDY - B
VAV1 - X - M 90.00 .VAV1 SB156
VAV3 - X - M 90.01 .VAV3 SB156
VAV4 - X
GP+ - X
GP- - X
SB156
TIGHT_C