Potential problems and pitfalls
Oversized boilers
Wood pellet boilers have a typical turndown ratio
(the ratio between their maximum and minimum
outputs) of 4:1 or 25% of rated output. For wood chip
boilers the value is 3:1 or 33%. Biomass boilers are
not normally sized to meet the peak heat load but
rather to provide a large percentage of the annual
heat requirement for reasons of capital cost and
overall system efficiency.
For example, a boiler sized on 50% of the peak
load will normally provide between 85% and 90%
of the annual heat energy required, and at this size
it is usually able to meet the typical minimum heat
requirement when operating at its minimum output
in summer.