All solid fuel appliance require a good draft to allow for efficient operation. This usually requires a chimney of some description. We usually makes our from twin wall stainless steel and design the system, have it made and shipped to the customer.
The boiler operates into a flue which will have natural draft that is measured at the time of installation. The underpressure will need to be at least 10 to 15 pascals of draft pressure for proper burner operation that will allow for efficient combustion at high temperature, little ash, little soot, and low maintenance for the customer. The desired flue height is 4 to 5 m off the boiler. A flue fan is installed if the site is found to have general low pressure which is true for about 10% of the installations we have encountered to date.
In the event of power failure a natural draft will be required. All systems have draft stabilizers fitted as standard set at 20 pascals in the event of high winds to maintain efficiency.