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A Better Barrel Stove | Fire and Water Part 1
Fire and Water Part 2
Building A Barrel Stove Hot Water Heater
By Robert Saunders
Nwwpa@newnorth.netTest Report #1
Test Results.As is the case with any new design and as experience is gained, improvements become necessary or desirable. This is part of the design process. In this case, after three weeks of operation, it became evident that the buildup of creosote in the stack and around the coils was unacceptable. The water temperature from the coil was not as high as it was when the heat exchanger was first installed, when no creosote was present. As the creosote built up it insulated the coils from the direct heat of the gases in the stack, greatly reducing the overall efficiency of the system. The buildup was confirmed by removing the section of the stack above the heat exchanger. Inspection showed a thick layer of creosote inside the stack and around the coils. The consistency was like a thick coating of varnish.
The explanation is obvious but the solution is more elusive. As indicated in an informative article by David Baker:
www.cdc.gov/nasd/docs/d000001-d000100/d000046/d000046.htmlThe stack temperature should always exceed 250 degrees F to reduce condensation of the gasses in the stack.. At the same time, the temperature of the coil cannot exceed 212 degrees F or steam will build up in the tubing. The problem is obvious.
The first step is to clean out the existing creosote from the coils and the stack. Using a catalyst will help to crystallize the residue and change the buildup from a varnish consistency to a crystallized buildup, which can be removed with a chimney brush. With no other design changes, the system can be operated safely provided the creosote buildup is removed weekly.
A more permanent solution will be implemented by removing the coil from the direct flow of gasses. This will be done by essentially wrapping the coil around the outside of the stack and insulating it from direct contact with the hot gasses and from the outside ambient temperature. Test results of this modification will be published with the next Test Report.
Copyright © 2003 by Robert Saunders