Is the coal-trol just an efficient thermostat or does it increase the efficiency of the stoker in other ways?
Coal-Trol makes no modifications to the stoker mechanism in any way. The efficiency increases are mostly the result of our control being able to dynamically adjust the feed rate.
Do you have the various stokers on site, or some other type of partnership?
We have three stoker stoves on site: one Reading, one Leisure Line, and one Keystoker. We also have access to two alaska stoves through partners and friends of the company who serve as in-home testbeds (they've been running coal-trol in various forms for the last 2-3 years). There is a mix of 2-motor and 1-motor stoker mechanisms.
(From what I understand the stoker manufactures may have tested it on their own, but I haven't seen anything that summarizes their findings). If you're not currently testing and tweaking your product in cooperation with the manufactures can you tell us if that being discussed?
Since we started selling Coal-Trol we've been in frequent contact with stove makers (and dealers and others) and many have evaluated it. If you're interested in their impressions and findings we encourage you to contact them. Also we are currently working on next season's product offerings with input from manufacturers, individual customers, our in-home testers, and our own ideas. For now we aren't discussing details publicly, but in the coming months we will be making a 2006-2007 product line announcement and updating the website.
Have you found the continuous feed or the on/off feed to be more efficient.
We have not carried out comparitive testing like that, and I kind of doubt we ever will. I could explain the testing methodology and math that leads me to say this (feel free to PM if you want to discuss it), but suffice it to say that in the end what the test will end up determining is that the Coal-Trol and it's two modes will not play into the efficiency differences observed. What will be determined is the relative efficiency of one stove to another or one stoker mechanism to another. As a company we want to do business with all stove/stoker makers and will not step on toes by doing such a test or releasing such findings. What we are interested in is the relative fuel use people see between using their old control methods and using the coal-trol (regardless of stove/stoker type) and those are tests we're doing and intend to release results on. Anectodal evidence so far indicates that the fuel savings estimate of 11% is pretty conservative.
Have you found the varying speed of the convection blower to increase efficiency?
Increased air circulation in the space being heated is always good for fuel use efficiency. So to is making sure the thermostat isn't in the radiant heat area of the stove or in a hot air plume, such as in the path of air from the convection blower. That said, our varying the speed is because of the comfort factor you bring up. Blowing on high speed when there is a lower fire means that the air coming out will be relatively cool, so we dial up varying amounts of fan speed for different feed rates in an effort to keep that convection air relatively warm.
Are you testing whether varying the rate of the combustion fan increases efficiency. I think it was implied that the combustion fan on the current model doesn't vary, but that it might on future models. A slower fan on lower feed rates would seem to keep steadier temperatures and avoid the potential to burn out on lower settings.
You're correct we do not currently vary the combustion speed directly, and it is a possiblity it will show up on some future model. However, do not assume it will be on the next model.
We know there are efficiency gains to be had through control of the combustion air, the burn area, and other parts of the stove, but it becomes a question of diminishing returns and prioritizing all the different feature ideas and balancing that against time pressures and product cost. We're a small company just starting out, we need to pace ourselves.