The Importance of Solid Fuel System Design
The goal of a good, solid fuel system design is to have a solid fuel-burning system that is safe and performs well for many years. Good system design would have eliminated most situations that cause poor performance. Poor performance can include the following: downdrafts when the appliance is not in use; smoke spillage when the appliance is operating; appliances that do not sustain combustion or overfire; and cold chimneys, which can cause rapid accumulation of combustible deposits.
Solid Fuel System Chimney Design Considerations
Many things need to be taken into account when designing a system. The draft created by the chimney is the engine that drives the stove. The warm air rising up the chimney is what draws air into the firebox; the fire itself does not accomplish this. Primarily, the chimney height, the chimney temperature, and the appliance’s location relative to the exterior determine the strength of the chimney’s updraft. Important factors influencing this are the type of building, the building envelope and the appliance’s location within it. The type of building (bungalow, bi-level, multi-story) will also influence the stove’s burning characteristics by determining the required chimney height. The airtightness of the building envelope, as well as any mechanical systems such as exhaust fans and heating appliances, will affect the air pressure differences within a house. Since wood stoves rely on natural drafting, mechanical systems may create enough negative pressure within a house to cause poor performance. Since chimney draft is related to the temperature of the flue gases, cold flues will have a weaker draft than warm ones. If the chimney is cold or not well insulated, the flue gases may cool enough to condense inside the chimney, leading to soot and creosote formation.