A combustion assembly housing contains primary and secondary combustion chambers and an ash receptacle. The primary combustion chamber has primary and exhaust grates. Fuel pellets fall in downward onto the primary grate; intake air flows in upward through the primary grate; exhaust gas flows out rearward through the exhaust grate. The primary grate supports unburned fuel pellets and permits partially burned pellets to fall through. Multiple vertical passages through the primary grate are each deeper than they are wide. The secondary combustion chamber has a secondary grate. Partially burned pellets fall in downward onto the secondary grate; intake air flows in rearward, through the secondary grate, and out upward into the primary combustion chamber. The secondary grate supports partially burned pellets and permits ash to fall through downward into the ash receptacle. Intake air flows rearward into the ash receptacle and upward into the secondary combustion chamber.

A combustion assembly housing contains primary and secondary combustion chambers and an ash receptacle. The primary combustion chamber has primary and exhaust grates. Fuel pellets fall in downward onto the primary grate; intake air flows in upward through the primary grate; exhaust gas flows out rearward through the exhaust grate. The primary grate supports unburned fuel pellets and permits partially burned pellets to fall through. Multiple vertical passages through the primary grate are each deeper than they are wide. The secondary combustion chamber has a secondary grate. Partially burned pellets fall in downward onto the secondary grate; intake air flows in rearward, through the secondary grate, and out upward into the primary combustion chamber. The secondary grate supports partially burned pellets and permits ash to fall through downward into the ash receptacle. Intake air flows rearward into the ash receptacle and upward into the secondary combustion chamber.

A combi stove (1) is arranged for combusting both logs and granular material. The combi stove (1) has a common combustion chamber (2) arranged so that both the logs and the granular material may be combusted in the common combustion chamber (2). The combi stove (1) further has an ash collector (3) arranged under the combustion chamber (2) and a front aperture (4) through which logs may be placed in the combustion chamber (2). Also the combi stove (1) includes a granular material combustion area (5) arranged in the combustion chamber (2), wherein the granular material combustion area (5) has a bottom combustion surface (6) including bottom airflow apertures (7) arranged to enable an airflow to the granular material during a combustion of the granular material in the granular material combustion area (5). The granular material combustion area (5) is at least partly surrounded by a granular material area sidewall (8) having sidewall airflow apertures (9) arranged to enable an airflow to flue gasses generated during a combustion of the granular material in the granular material combustion area (5). At least a part of the granular material area sidewall (8) is releasable from the granular material combustion area (5). Furthermore, a use of a combi stove (1).

Various implementations include a hot water heating system having a spine and two or more water heating units. The spine includes a top surface defining one or more top openings, two or more coupling areas, and cold water, hot water, and fuel manifolds. One or more top openings provide access to a cold water manifold inlet, a hot water manifold outlet, and a fuel manifold inlet. At least one of the coupling areas is located above another coupling area when the spine is oriented with the top surface facing upwardly. The water heating units are coupled to coupling areas such that a cold water inlet of the unit is fluidically coupled to the cold water manifold outlet, a hot water outlet of the unit is fluidically coupled to the hot water manifold inlet, and a fuel inlet of the unit is fluidically coupled to the fuel manifold outlet.

Disclosed is a combi stove (1) arranged for combusting both logs and granular material. The combi stove (1) comprises a common combustion chamber (2) arranged so that both the logs and the granular material may be combusted in the common combustion chamber (2). The combi stove (1) further comprises ash collecting means (3) arranged under the combustion chamber (2) and a front aperture (4) through which logs may be placed in the combustion chamber (2). Also the combi stove (1) includes a granular material combustion area (5) arranged in the combustion chamber (2), wherein the granular material combustion area (5) comprises a bottom combustion surface (6) including bottom airflow apertures (7) arranged to enable an airflow to the granular material during a combustion of the granular material in the granular material combustion area (5), wherein the granular material combustion area (5) is at least partly surrounded by a granular material area sidewall (8) comprising sidewall airflow apertures (9) arranged to enable an airflow to flue gasses generated during a combustion of the granular material in the granular material combustion area (5), and wherein at least a part of the granular material area sidewall (8) is releasable from the granular material combustion area (5). Furthermore, a use of a combi stove (1) is disclosed.