Full Load Operation; Output Control; Sustain; Cycle For Underfeed Auger Sustain" Too High - Viessmann Vitoflex 300-UF 530 Installation And Operating Instructions Manual

Vitoflex 300-UF Installation & Operating
Operating Modes

Full load operation

As soon as a combustion chamber temperature of
approximately 356°F (180°C) is reached (adjustable value),
the system switches, depending on the boiler temperature,
to operating mode "FULL LOAD" or "SUSTAIN", which is
shown in the upper left of the display.

Output control

The heat output to be produced is adapted to the heat
consumption in a range from 25% to 100% of the boiler's
nominal output. Depending on the deviation of the boiler
temperature from the boiler set-point temperature of
167°F to 203°F (75°C to 95°C), the airflow rate is
set by means of a blower with variable speed. The
combustion chamber and residual oxygen control then
re-supplies the optimum amount of fuel for lowest
emissions.
If, through a corresponding rise in the boiler temperature,
the heat consumption drops below 25% of the rated
output, the system switches to "SUSTAIN", which is
shown in the upper left of the display.

Sustain

In the operating mode "SUSTAIN", the flue gas exhaust
blower only runs at a minimum speed. The supply air
blowers does not run.
Supplying material via the underfeed auger has to be
greater than the speed of back-burn and can be set as a
set-point value by touching Soft touch key 4 "Settings"
in Screen 4 (CYCLE for underfeed auger SUSTAIN). This
depends on the material (light shavings require more
supply of material than wood chips).

"Cycle for underfeed auger sustain" too high

Too much material is pushed into the burner trough so that
the embers are too large for the sustain load operation.
The further consequence of this might cause the
malfunction back burn, excess temperature or overfilling
of the combustion chamber.

"Cycle for underfeed auger sustain" too low

Not enough material is pushed into the burner trough so
that there are too less embers to sustain the load. This
can cause back burn or the fire will go out.

Standby

If too much heat is generated in sustain load operation,
the control system automatically goes into standby
operation. When this threshold value is reached, first the
isolating valve shuts, and the auger module is slowly idled
in the sustain mode.
For the standby mode, all the drive activities (blowers and
auger modules) are stopped. Only then "Standby" appears
in the operating mode display.
When the boiler temperature drops or a minimum standby
period lapses, in the case of a call for heat an automatic
new start is carried out.
(continued)

Transition in output

To obtain a good structure of the fire and thus low
emissions of harmful substances, the switchover from
"SUSTAIN" to "FULL LOAD" is not carried out suddenly
but rather gently.

Switching off

Touching Soft touch key 2 "Boiler OFF" shuts down the
furnace firing process properly. "Burn-out" is indicated
on the display. The firing control system continues to run
until there is no more fuel in the underfeed auger or the
combustion chamber temperature is below the set-point
value and then it switches off.
CAUTION
DO NOT use the main switch to switch off -
DANGER OF BACK BURN!

Emergency operation

The firing optimization function can be switched off in
Screen 7 by touching the "Emergency operation" soft
touch key. If a sensory mechanism is defective, the
switching off takes place automatically. Text shown
on display: "SYSTEM PRESENTLY RUNNING WITHOUT
OPTIMIZATION". The quantities of material and air are
then manually set as set-point values under "Emergency
operation output" and "Emergency operation cycle of
underfeed auger". The negative pressure is no longer
corrected automatically. For this reason the blower
settings must be checked. No positive pressure must
develop in the burner. In case positive pressure should
develop, adjust the mechanical means of throttling on
the supply air blowers.

Measurement operation

It is possible to switch the boiler control system into
"MEASUREMENT OPERATION" in Screen 7 by touching
the soft touch key "Measurement operation" while the
indicator in the upper left of the display is indicating
"FULL LOAD". In "MEASUREMENT OPERATION" the
output control is blocked to guarantee constant full load
operation during the measurement.
IMPORTANT
In measurement operation the system does not switch
to "SUSTAIN". Ensure heat consumption  Danger of
excess temperature!
Operation
63