chimley wrote:I'm under the impression that the coal-trol will regualte the feed. As soon as I can confirm that, i will share.
I can't see how it can accomplish that, but I await your feedback after you talk to the Coal-Trol guys.
chimley wrote:I'm also thinking about a house I may sell in the next couple of years, where an "automated" system may not be as intimidating to a potential buyer.
Unless you have made the boiler mostly "hands-off" with a huge coal bin and an ash removal system, I don't think a fancy control is going to make or break the deal.
chimley wrote:I'm actually surprised someone hasn't tried something similar already and posted results on this topic.
I have done plenty of experiments, but I have been lax posting the results (I figured most people don't care). From what I have observed, I can tell you that the biggest variable in daily coal consumption (assuming you held everything else constant) is the boiler's operating temperature. Recently I did an experiment with the feed rate...basically I monitored the outside temperature and DHW usage for 24 hours, then I doubled the feed rate and monitored everything for another 24 hours. I got lucky with the weather...the average outside temperature was within 1 degree between the two days, there was little/no wind, and each day had two showers and two loads of laundry. The results were too close to call. The stoker had exactly half as much run time on day 2, so the amount of coal burned was the basically the same for each day. With the higher feed rate the boiler rapidly reached the high limit and skipped timer cycles as a result. I concluded that any efficiency lost by operating at the higher feed rate was cancelled out by the reduced number of timer cycles.
If you want to try and save some coal with fancy controls, look up a Hydrostat 3250 aquastat...this control will change the boiler's operating temperature based on observed heat demand...very useful for systems with multiple zones; especially if some are small, a bathroom for example. You can also set the control pre-purge the boiler down to 135 degrees before the stoker is allowed to start. This wouldn't work with a tankless coil, but in the right application it would help avoid short cycling from small heat calls and provide longer circulation times.