Date: Sun, 16 Nov 2008
From: Alex Chernov <alex_stovemaster(at)>
To: Dave Misiuk <dave(at)>, Senf Norbert <mheat(at)>,
  Кузнецов Игорь <igor(at)> 

Hi guys.
By Igor's request, below is a translation of Igor's comments in regards to the fireplace retrofit information posted at the MHA news. Since Igor hasn't seen my version yet, his comments only concern Norbert's version.

 Igor's comments in regards to the fireplace retrofit contest.

I'll be glad if my comments will help you to understand basics of the system of free gas movement.

Heater designed by Norbert has two separate paths for gas flow. These paths are of unequal length.  Gas flow must be balanced. Unbalanced gas flow results in uneven heating pattern of the heater. Typically, this problem is solved by creating a separate updraft channel for each bell (path). These updraft channels come to a single volume of a second bell or a smoke chamber. A damper that allows regulating heat pattern of the heater is installed on the shorter path.

Drawings of Norbert's heater show openings in the sidewalls of the firebox. Such openings in the lower part of the vertical walls of firebox can be found in heater inventions that first appeared in the former USSR in 1928.  Many of Russian old-style heaters, similarly to contraflow heaters, have one considerable disadvantage: upper part of the heater is heated much better than the lower part. This happens because lower part of such heaters receives gases that were already cooled in the upper portion of the heater, which receives the hottest gases coming right out of the firebox. This disadvantage is fixed to a little extent by creating openings in the firebox walls on 10-11th row (Russian row is about 7cm high – Alex). The attached picture shows Grum-Grzhimailo's stove that has an opening in the firebox, leading into the downdraft channel. Part of the gases escapes firebox through such opening helping to improve heat-up of the lower part of the heater. Besides, such openings facilitate so-called automated damper effect. This means that such heater will not cool down considerably when the shut-off damper is not closed in time due to the fact that hot gases inside the bell will not let the cold gases up, pushing them out along the bottom part of the firebox into the chimney. 

Besides this advantage, however, these openings bring some disadvantages as well. This will be explained further.

Overheating of the upper portion of the heater is easily solved by building heaters within the double-bell system. Automated damper effect is achieved when the firebox is joined with the bell with a 2-3sm continuous slot.

Product of combustion is a simple mix of several gases, including ballast gases. Molecules of these gases are independent, not connected to each other. Each particle of the gas flow has its own condition: mass, temperature, energy, and takes its own place inside the bell, determined by its condition, during its free movement through the entire bell. Particles of the ballast gases (steam, nitrogen, and excess air), being cold particles, cannot move up inside the bell and come through the lower part. Only slot or dry-joint facilitates condition of the bell (free movement of the particles according to their energy). Openings in the lower part of the firebox only don't facilitate such condition. Any interference with free movement, created by changes in construction of the firebox, leads to alteration of the FGM system. Openings in the firebox walls cannot facilitate free movement of the particles according to their condition. Free movement will happen inside the limits of such opening, but there will be no free movement higher or lower, where movement will only be facilitated by chimney draft and all particles of the gas flow, including ballast cold ones, come together, cooling the whole flow.

I think that seismic integrity of a heater can only be achieved by using a rigid steel harness built from steel angles and flat bars. Such harness should be connected to the structural part of the building by flexible connector of some sort, such as steel rod, that would allow uneven movement of the building and the heater.

Igor Kuznetsov

Date: Mon, 17 Nov 2008
To: alex_stovemaster(at), Dave Misiuk <dave(at)>, Кузнецов Игорь <igor(at)>
From: Norbert Senf <>

Thanks for translating Igor's comments, Alex. And thanks for the comments, Igor.

The comments have been added to the Lopez Labs page on this project: , as well as a note in the MHA News link.

I believe that CCHRC is planning to do some testing on this heater as soon as it is completed.
It will be interesting to get a temperature profile of the outside surface, over time.
Perhaps Dave has access to an infrared camera.

In the Austrian/German channelled systems, the drop in gas temperature from the firebox
to the chimney entry is modulated by varying the wall thickness, so it will be instructive to see how it works in this case, with the thicker midsection.

If one of the "bell" sides were to run hotter than the other, it should be tuneable by reducing the opening from the firebox with a dry set firebrick. We use this technique quite often for tuning heated benches.

The openings at the bottom of the firebox can be blocked with firebrick plugs. If resources permit, it would also be interesting to see if there are any measurable differences between the two configurations. In particular, I am quite interested in seeing whether the "automatic damper" concept can be demonstrated.

Best ....... Norbert