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3 Operation
3 Operation
3.1 Digital Inputs
Digital inputs VMS
For the VMS to work in accordance with the requirements of the combustion plant, the status
signal of the plant must be reported to the VMS.
These are:
– Burner start-up
– Control release
– Pre-purge signal
– Recirculation release
– Flame signal
– Fuel specification
For application of burner control, the VMS produces 3 messages via relay:
– Fault
– Ignition position
– All channels on highest value (high settings)
3.2 Operating Description
(For example chart, see Appendix)
WARNING!
The operating sequence described relates to a usual configuration of the unit. Depending on
how the parameter of the device is configurated, this can result in a somewhat different (see
appendix) sequence.
A signal is first sent to terminal 2 (burner ON), indicating when the burner has to start. The
display mode changes from "AU"(off) to "BE"(ready). The flue gas damper goes to "OPEN"
mode. This is followed by the pre-purge signal (terminal 3). Continuous ouput runs on the
highest programmed point. Three-step-point outputs receive a continuous "OPEN" signal and
run to the limit switches.
The mode display changes to "VO" (pre-purge). The recirculation channels go to open only
when a signal is applied to terminal 6 and the assigned channel, generally the air valve, is 75%
open. If there is to be no separate recirculation valve delay, a continuous signal can be applied
to terminal 6. The recirculation valve delay is then automatic. Once all active channels have
reached their uppermost point, the high firing rate relay picks up. The fuel channel is then al-
ready going to the ignition position.
During pre-purge, the VMS checks the "CLOSED" and "OPEN" positions of each actuator. On
completion of the pre-purge period (removal of the signal from terminal 3), the air and recircu-
lation channels will close (air to the ignition point and recirculation fully closed). The mode dis-
play changes to "CLOSED". The ignition-position relay then picks up. The flue-gas valve
remains open, or the flue-gas fan remains on top rotational speed.
Following completion of ignition, a signal is applied to terminal 8 (flame signal). The flue-gas
channel goes to the programmed point. The firing rate displayed continues to be the firing rate
at the ignition firing rate point. The mode display changes to "GL" (base firing rate). A signal
to terminal 6 then prompts the recirculation channel to go to the programmed point.
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