Wood pellet systems FAQ
Subject: Suitability for other primary energy sources
Question/problem:
Are the emissions in partial load operation also measured by the chimney sweep?
Subject: Wood pellet storage room
Question/problem:
From which rated heat output do pellet boilers have to be measured, and how often must the chimney be swept?
Subject: Compulsory measurements
Question/problem:
Ab welcher Nennwärmleistung müssen Pelletskessel gemessen werden und wie oft muss der Schornstein gekehrt werden?
Subject: Planning
Question/problem:
Why is the thermometer connection at the rear of the underside?
Subject: Automatic smoke piping cleaning
Question/problem:
Even in summer, the pellet boiler cleans the smoke piping automatically every day. If an effective solar energy system heats the domestic water, the boiler seldom runs, if at all. How can this cleaning be deactivated?
Subject: Full outside air operation
Question/problem:
Is there a permit for full outside air operation, and how long can a combustion air pipe be, or how many direction changes are permitted?
Subject: Flue gas temperature too low
Question/problem:
How can the flue gas temperature be increased?
Subject: Soot characteristics
Question/problem:
Do the soot characteristics of pellet boilers have to be determined, and what are the soot characteristics?
Subject: Suction system
Question/problem:
The storage container is automatically refilled in Pellettis with a suction system. What happens when there are no more pellets in the storage room (empty)?
Subject: Flue gas dust content
Question/problem:
How can the dust content in the flue gas be measured?
Answers for wood pellet systems
Question/problem:
Is a condensate drain required for stainless steel chimneys? Could ice form at the opening if the boiler is inactive for extended periods??
Answer: A condensate drain is always required, as condensate can form due to the relatively low flue gas temperatures (e.g. during partial load operation). In our experience, ice has never formed at the head of the chimney in pellet boilers.
Move up  Question/problem:
Are the emissions in partial load operation also measured by the chimney sweep?
Answer: No, the flue gas losses, the CO content, and (where necessary) the dust measurement (for boilers with rated outputs of over 15 kW) are measured at full load by the chimney sweep.
Move up Question/problem:
What wall thickness and structure are recommended for a pellet storage room (bunker storage), or are there regulations for this?
Answer: To date, there are no specific requirements for the structure and implementation of wall thicknesses. However, the German Energy Pellet Association (Deutsche Energie-Pellet-Verband e.V.) has developed a recommendation in which the structure of pellet storage systems is explained based on examples. You can download this brochure free of charge on the website of the DEPV: www.depv.de
Move up Question/problem:
From which rated heat output do pellet boilers have to be measured, and how often must the chimney be swept?
Answer: In accordance with the currently applicable German Federal Emissions Control Act (1. BimSchV) mechanically charged firing systems (such as pellet boilers) with a rated heat output of over 15 kW must be inspected annually by the chimney sweep to ensure that they comply with CO and dust limits.
Move up Question/problem:
Why is the thermometer connection at the rear of the underside?
Answer: The return temperature at the integrated return temperature increase can optionally be displayed on the boiler controller.
Move up Question/problem:
Even in summer, the pellet boiler cleans the smoke piping automatically every day. If an effective solar energy system heats the domestic water, the boiler seldom runs, if at all. How can this cleaning be deactivated?
Answer: nfortunately, the daily cleaning process cannot be deactivated on the pellet boiler. It is a programmed sequence which cannot be changed easily. In pellet boilers in which the controller (VE module and controller) are located outside the boiler, the power supply to the boiler can be switched off to prevent it from running.
However, as the VE module and the controller are generally integrated in the boiler, the only solution is to pull the connection plug of the cleaning motor. To do so, pull plug X5 (RM) on the right side of the circuit board of the automatic pellet firing device, which interrupts the power supply to the cleaning motor. Don’t forget to plug it in again when the solar yield decreases.
Move up Question/problem:
Is there a permit for full outside air operation, and how long can a combustion air pipe be, or how many direction changes are permitted?
Answer: Our Pelletti units are approved by the building authorities (German Institute for Construction Engineering [Deutsche Institut für Bautechnik, DIBt]). The approval number is Z-43.1-178. No general specifications for piping lengths, number of direction changes and cross section can be supplied. The type, length, cross section, direction changes etc. of the combustion air pipe must be taken into account when sizing the flue gas system in accordance with DIN EN 13384, to ensure correct functioning.
The flue gas inspection and cleaning of the flue gas piping are regulated in the Sweeping and Inspection Regulations of the individual federal states - taking the German Federal Emissions Control Act (BImSchV) and state building regulations etc. into consideration. For solid fuels, chimneys must almost always be swept four times a year for systems used all year round, or three times for systems used in the heating period only. Systems which are used in addition to a central heating system must be swept twice a year. Systems which are used infrequently must only be swept once a year (twice and once a year thus only applies to individual furnaces such as tiled stoves and fireplace inserts). The local master chimney sweeping are responsible for determining whether the frequency of sweeping can be reduced. This is standard practice for modern pellet boilers, particularly when combined with solar energy systems.
Move up Question/problem:
How can the flue gas temperature be increased?
Answer: There are three (size 10) screws on the interior lid of the boiler. Tightening the screws raises the interior lid, so that part of the heating gas is routed directly to the flue gas connection. For optimal chimney functioning during the entire year, we recommend setting the flue gas temperature at full load operation to approx. 150 to 170°C.
Move up  Question/problem:
Do the soot characteristics of pellet boilers have to be determined, and what are the soot characteristics?
Answer: A measurement of the soot characteristics of solid fuel boilers is not required for small automatic firing devices in accordance with the German Federal Emissions Control Act (1. BimSchV) and is not common. They can be measured on a voluntary basis only, but this is not essential when solid fuels are used. Some practical tests have shown that, with clean combustion, there is a resulting soot factor of 1 to 2 (according to Bacharach). The following measurements must be implemented in accordance with the German Federal Emissions Control Act (1. BimSchV): wood fuel • CO classification measurement • Dust measurement*
Boilers with outputs lower than 15 kW do not have to undergo recurring measurement (annual) measurement.
*Dust must be measured gravimetrically, i.e. a filter is weighed before and after measurement. Only the measurement principle is prescribed for this measurement, as there are no devices for determining dust emissions which have been tested for suitability. In practice, the regional master chimney sweep sends the filter to a suitable test centre for evaluation. Further information: your competent regional master chimney sweep.
Move up Question/problem:
The storage container is automatically refilled in Pellettis with a suction system. What happens when there are no more pellets in the storage room (empty)?
Answer: The suction turbine is activated for max. 10 minutes. If the fill level sensor on the storage container does not send a “full” signal within these 10 minutes, a second filling attempt is made after a 30 minute pause. Max. three filling attempts are made. If the storage container has not been filled after the third attempt, an fault message is displayed by the boiler control unit. However, the boiler continues to operate normally until the available fuel has been used up..
Move up Question/problem:
How can the dust content in the flue gas be measured?
Antwort: Dust can occur in the flue gas if the boiler has not been cleaned for a very long time (recommendation: carry out maintenance once a year). The amount of dust in the flue gas can only be measured by a chimney sweep. A special measuring device fitted with a special filter is required for this. The chimney sweep sends this filter to a laboratory for evaluation.
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