First year burning coal in my Hydrafire (combination wood/coal boiler). I posted pics and had some discussion earlier about trying to burn coal in this unit. So far, I have no complaints about starting a new fire, reloading an existing one, and am pleased with how evenly the coal bed burns. I am trying to squeeze as much efficiency out of it as I can and get the burn times extended. The outside temps have been in the mid-high 30's at night and maxing out around 48-50 during the day. I have 5 zones in my 2800 sq ft 2 story colonial. I have only been using 2 zones on the first floor and have them set at 71 at night and 72-73 during the late afternoon until about 11:00 pm. The rooms upstairs stay about 70 due to my open foyer located in the center of the house. So basically I am maintaining at least 70 degrees for the entire 2800 sq ft. so far. The boiler idles (damper is closed)most of the time and the water temp was bumping near 220 degrees. The boiler does not have any forced induction air. Inlet air is controlled by a honeywell aquastat wired to a damper control with a chain attached to a flapper door. I have added about six 3/8" diameter holes to the front ash pan door which I cover or uncover with magnets (no problem with demagnetization). I found that with the baro set to control the max vacume to .06 that all I needed to maintain a fire for extended periods with the flapper shut was to have 1 hole uncovered. Even idling the manometer registered .04-.06. It has been extremely windy for 2 days with gusts as high as 50mph. The amount of coal used for 24 hours was between 40-45 lbs. I thought this was a little high????? So I I did the following:
1. Turned down the low temp aquastat 10 degrees to 130. (At 130 the small circulator pump turns on and circulates water from coal boiler to oil burner jacket in a loop.)
2. turned down high temp aquastat 10 degrees to 170. (At 170 the flapper door closes on a rise. I believe when the temp drops down to about 160 it opens again.)
3. I had the weight on the baro (8") all the way forward to maintain .06 max on the manometer before. At idle it stayed at .045 to .05 So I added the weight of a small magnet onto the baro weight in order to reduce the draft at idle to a lower number. It now idles at a steady .03 and is rock solid at idle. I also have 1 hole on the ash pan door only partially open (almost completely closed). I left 1 of the 2 over fire holes open just to lessen the likelihood of an explosion due to gas buildup and extended idling soon after a reload of fresh coal. They are only 1/4 in diameter on the loading door and are not designed to be adjustable-but with my trusty magnets....
Result: Water temp still wants to idle around 190-200 but will drop VERY slowly when a zone calls for heat. This tends to keep the water at 170 for a long time but doesn't seem to want to drop below that even with the circulator sending water to the radiators. Not sure how long it will take for the temp to dip below 160 and open the flapper door again but there seems to be enough air to keep the fire temp (and the stack temp steady) Digital temp gauge was damaged and is now out of calibration but the temp is very steady within 2 degrees.
The adjustment to the manometer seemed to be the only way to reduce air through the fire and actually get the temp down more in line with the aquastat setting. All gaskets are new and I was not able to find any underfire leaks using a smoke test.
Am i on the right track do you think? What kind of coal consumption might I try to achieve in conditions like this?? I know its only guesswork for the most part .
If I fire up my Hitzer in the living room I can burn about 1 lb/hr or slightly less and maintain pretty much the same inside temps(but warmer in the room with the stove). Main difference is my 1500 sq ft uninsulated cellar is warm and cozy and I have plenty of hot water when the boiler is running. Trying to get the boiler consumption lower to figure out which I should be using????????????
Sorry that was soooooooooooo loooooooooooooong. Man, I'm open to any and all feedback.
BTW co alarm with digital readout has always read 0 and is located 5 ft from the boiler.