System Operation - Schmid UTSK-180 Operating Instructions Manual

5 Operation
5.1.1

System operation

To guarantee minimum system wear, continuous operation is necessary. With contin-
uous operation, the thermal loads from repeated cooling and heating are prevented,
which has a positive effect on the service life of the entire system.
With regard to the set number of activation/deactivation operations per day and the
minimum combustion time, in Switzerland the regulations of the canton must be taken
into account. A capacity range of 30 – 100% for 24h/d is recommended as a minimum
operating time for optimum and low-wear operation. If the minimal loads are frequently
underrun, it may not be possible in some cases to comply with the emission require-
ments and the filter availability.
Generally running the system with short-term load changes should be avoided.
Optimum combustion can be impeded with fast load changes. Due to the mass of the
refractory lining (slow heat absorption and discharge) as well as the large grate surface
(slow increase and decrease of the covering with fuel) the control behaviour is slow. If
the loads change quickly, emissions and wear can be negatively affected.
Typically it takes around 45 - 70 minutes to increase the wood boiler capacity from 30%
to 100% (when the combustion system is warm), this corresponds to 1...1.5 % / minute.
Running the system down from 100% to 30% takes approximately 30 minutes, which
corresponds to approx. 2 % / minute. This control behaviour must be taken into account
when looking at load peaks and integrating the combustion system by means of an
external capacity signal.
When managing the boiler it must be ensured that the entire boiler capacity of the boiler
is utilised. This can cover load peaks, has a positive effect on the control behaviour and
the minimum operating time of the combustion system as well as the availability of the
filter system.
Contaminants in the fuel as well as changes to the defined fuel quality during operation
influence the emissions as well as the efficiency and can result in higher wear and addi-
tional maintenance work.
Underfeed grate UTSK
1.10 en D-45