User`s guide

Appendix B - Loop Application Examples
Setpoint Programmer Examples
252 UMC800 Control Builder User’s Guide Release E
1/01
Example 6 - Controlled restart after power loss
SCENARIO A
To prevent stress to the work in a furnace on
power up after a power loss, you may use the
Restart feature of the SP programmer. This
feature will use the PV (connected to PV1) as
the initial starting point for the Setpoint and
will use a configurable ramp rate for the
profile. When the temperature gets to the
original Setpoint prior to power down, the
program will continue. You may gate this
Restart input to the programmer to only apply
after a certain time off and/or a certain
segment if desired using Compare function
blocks.
This example uses the System Monitor
block to provide a restart pulse to the
programmer Restart input after power
restore. This will initiate the restart
procedure.
power loss
Initial PV
value on
power
restore
restore ramp
rate
program
continues
SCENARIO B
A System Monitor block output
(RESTART) is on for the first scan
cycle after a power loss plus
TIME_OFF output indicates the time
the power has been off. A Compare
block can be used to evaluate the time
off and cause an output to initiate the
restart if greater than a set amount.
Time OFF is in seconds.
If Time OFF is greater than SET_TOFF, execute restart
NOTE: Execution sequence relative to SPP block