Trouble with the Clear Skies CS-200 catalytic combustor.
I purchased 2 of what should be the CS-200 catalytic combustors made by or for Clear Skies Unlimited Inc., 11208 Cochiti SE, Albuquerque, New Mexico 87123 ((broken link removed to http://www.clearskiesunlimited.com/woodburningstoves.html)) which have failed to perform. This sounds like the ones referred to in the previous post as found at (broken link removed) but that link returns a server not found so I can’t check. Actually I purchased them through the linked web site (broken link removed) and received order confirmation saying that it was from
[email protected] identifying the purchase only as “6 inch round canned”. The package I received shows a return address of stovecombustors.com, 11208 Cochitti SE, Albuquerque, New Mexico 87123 and included “ Manufacturers instructions for the operation, care and maintenance of the CS-200 series wood stove catalytic combustor”. (broken link removed to http://www.clearskiesunlimited.com/woodburningstoves.html) says that they are “more efficient than the ‘old’ honeycomb combustors…Higher performance at a lower price…Guaranteed!”
On 1 Dec 2009 I started using one of the catalysts in the wood burning stove I bought used and have used for many years. When I first used the stove the original catalytic combustor was in good condition and last year it was not, so I have seen normal performance with the 6” diameter 3”thick ceramic with 4 partitions/inch and no gasket that came with it. Normally when the combustor is in good condition the viewport immediately above it stays clean. This was still true after I noticed substantially less heat being produced in the combustor. When the combustor is ineffective or absent the viewport becomes covered with soot. Before installing the CS-200 I cleaned the flue and viewport. I fired the stove and monitored the temperature directly above and almost touching the center of the catalyst and in the center of the flue as close as I could get to the stove using type K thermocouples. I tried cleaning the viewport and firing the stove twice, the second time with binder free fiberglass packing around it to prevent flue gas bypass. In 92 minutes during which the temperature was never below 235°C and not below 322°C for over 6 minutes the viewport became black. At the end of the burn, the catalyst was ash colored on the bottom and the thermocouple was clean. I then added the second CS-200 in series with the first. Over three hours when the temperature never fell below 325°C the viewport gradually blackened. About the only indication of catalytic combustion I have seen was as the fire burned down with the air inlet 1/8 open. As the temperature above the catalyst fell below 292°C , I started opening the air inlet and the temperature quickly fell to 200°C and could not be brought back. This suggests that the catalyst was working at 292 °C but quit as more air cooled it a bit, but not enough to fall below the operating temperature of 193°C specified by Clear Skies. As I remember the original, I could see that the central area was hotter than the top (probably due to radiative cooling). These are a more open foamed alumina fiber with much less surface area, which would result in less heat trapping, less catalyst and lower price (I paid $135 for the two) but they don’t work well enough for me to even know if they quit working. (I don’t have a thermocouple directly below the catalyst, with that addition I could detect an absolutely dead catalyst but it would be hard for me to tell much more.)
I did not get any response from the order confirmation folks or Clear Skies and am continuing to use two in series till I get a replacement in the form of the original. This turns out to be a difficult task. (broken link removed) says “In order for the catalytic combustor to engage the stove must reach an internal temperature of around 1100 degrees” (at that temperature you don’t need a catalyst!) so there must be a variety of catalysts. (Clear Skys says theirs starts at 380°F) If I have to worry about the type and amount of catalyst after I find the correct substrate form, this may be a hopeless proposition. I have seen one advertised as being a catalyst deposited on steel ((broken link removed to http://www.woodstovecombustors.com/steel_advantages.html)) but without specifying the type of steel it’s durability, or its effectiveness (other than saying it complies with EPA requirements, same as Clear Skies). I hope others with experiences with something that works over the long term will post.
To address the size question in the previous post, the canned (have a metal ring around them) combustor from Clear Skies is 6”+- very little. This is one of a few common sizes. The hole it needs to go in is 6.15” dia and
www.woodstovecombustors.com has expanding non reusable high temperature gasket material to fill the gap.
