A major part of the Coal Gun's appeal is it's simplicity. The only moving parts on the Coal Gun™ are the induction fan and the grates. Coal flows entirely by gravity from the hopper. This movement of unburnt coal into the combustion area occurs with grate motion, when as ash is removed, coal flows in to replace it. The grate plates on the S130 and S260 come with a lifetime warranty!
Coal Gun simplicity extends to the controls. Where many stokers utilize timer based systems that require periodic tweaking, the Coal Gun uses a temperature based controller to maintain the position of the fire. This greatly simplifies operation for users inexperienced with burning coal. Add coal. Take out ash. Repeat every two to seven days, depending on demand (S130). Burning coal doesn't get any simpler than this.
Often, only end of season maintenance will be required, as the boiler is taken out of service for the summer. In applications that involve year round operation, twice a year service maintenance is suggested.
The Coal Gun heat exchanger consists of an arrangement of fire tubes. For the S130 and S260, there are two concentric tubes. For the larger Coal Guns, there is an array of inner firetubes inside a large outside tube. In all cases, the large outside tube features a swirl chamber. The swirl chamber funnels exhaust, and causes it to swirl around the tube. This swirling motion is accompanied by an increase in velocity while increasing contact time with the heat exchange surfaces. Higher velocity contributes to a self-cleaning effect, a key feature of the design. The fly ash contained in the exhaust stream serves as a scouring agent. All boilers will have some fall off in efficiency between cleaning operations. This fall off is much less for Coal Guns than for other solid fuel boilers.
This heat exchanger design leads to the high efficiency that the Coal Gun is famous for. This efficiency shows up directly in low stack temperatures. The Alternate Heating Systems Coal Gun™ Stoker Boiler operates with one of the coolest stack temperatures of any coal boiler on the market (if not the coolest). The stack temperature of a Coal Gun™ runs at approximately 350 degrees Fahrenheit. The low stack temperatures of our boilers are almost unheard of on the market.
The Coal Gun is over engineered for a lifetime of service. Many units are into their fourth decade of operation. While good maintenance is key, when the principles of good maintenance are followed, Coal Gun boilers will reward owners with very long boiler life.
Burning coal produces ash. Typically, ash will weigh in between 10% and 20% of the weight of the original unburnt coal. On other stokers, a forced draft fan constantly blows air toward the slanted grate that contains the burning coal. With positive air pressure throughout the system, just opening the ash door to remove ash is likely to result in fly ash coming out into the boiler room.
Conversely, the Coal Gun uses induced draft, and ashing takes place inside the grate base where there is negative air pressure (partial vacuum). This means that fly ash is not likely to be scattered throughout the boiler room, unless you spill them by accident!