Herz pelletfire 20/20, Operating Instructions Manual, Page: 17 / 100

Operating conditions 7
17
7.2 Boiler operation with pellet
Heating off
During this phase the boiler is switched off, i.e. the
burner is blocked.
Ready
The boiler- respectively the buffer temperature is
sufficiently high to provide the required heat load,
or the boiler temperature has reached the switch
off temperature.
Ignition preparation
During this phase the grate gets cleaned and the
lambda probe gets pre-heated.
Pre-aeration
During the pre-aeration phase the burning
chamber and the chimney get purged with fresh
air.
Cold start
If the boiler room temperature is lower than the
identified boiler room ignition temperature (150
°C), the boiler performs a cold start and fuel is fed
to the burning chamber. Materials are pushed in
at intervals. At the same time the fuel gets ignited
by the ignition fan. An ignition monitoring is
conducted during this phase. Successful ignition
is detected when there is a steady increase in the
combustion chamber or exhaust gas temperature
or at the latest when the combustion chamber
ignition temperature is reached.
Thereafter, the system changes over to the scorch
phase, where at the same time the final ignition
fan phase is carried out. During the final ignition
fan phase the ventilator of the ignition fans runs
for a minute longer in order to cool down the
heating element.
If ignition wasn´t possible prior the maximum
ignition period, the boiler will switch off and the
fault “IGNITION” will appear in the fault list.
Scorch phase
During the scorch phase the boiler control tries to
achieve an even fire bed. The length of the scorch
phase can be set in the fuel value settings (only
available in the service area). Pay attention to the
higher oxygen content at the combustion. This
serves to achieve the desired even fire bed more
quickly. This phase should not be set for longer
than 5 minutes.
Start up phase
During the start up phase the boiler operates at
nominal heat output. If the boiler set temperature
is reached, the boiler will switch to the regulation
phase.
Regulation phase
During the control phase the boiler modulates
between nominal load and part load. When the
partial load stage generates too much energy, i.e.
the target boiler temperature + regulation
hysteresis are exceeded and are then changed to
the ready condition.
Burn out phase
If the boiler will be switched off the remaining
quantity of residual fuel will burn independently.
Pay attention to the burn out phase time setup, if
chosen too short, fuel will not be burned
accordingly.
Burner cleaning
During the burner cleaning phase ash gets
removed off the grate. The boiler switches to the
burn out phase and remaining fuel gets burned
out.
Afterwards the grate gets cleaned and the boiler s
witches to normal operation. Afterwards the grate
gets cleaned and the boiler switches to normal
operation. The burner cleaning interval is
calculated by the feeding screw operating time.
The cleaning interval and duration is set up in the
service area with the parameter “heat exchanger
cleaning interval“ respectively „heat exchanger
cleaning duration“. This can be set via the
“Cleaning interval” parameter in the service area,
i.e. in order to achieve more frequent cleaning of
the combustion chamber the parameter simply
has to be shortened.
Heat exchanger cleaning
Heat exchanger cleaning serves to increase the
degree of efficiency. The Heat exchanger gets
cleaned automatically and the fly ash falls into the
fly ash chamber. The cleaning interval and
duration is set up in the service area with the
parameter “heat exchanger cleaning interval“
respectively „heat exchanger cleaning duration“.
Boiler output control
The output control is controlled within the boiler
target temperature and the control end phase.
The control end phase is the boiler target
temperature + control hysteresis. If the regulation
end is reached, the boiler will switch to the burn
out phase.
Flue gas temperature control
If the maximum flue gas temperature is exceeded,
the boiler output will be reduced. If the actual flue
gas temperature is lower than the maximum flue