Tweaking my boiler for best efficiency

Tweaking my boiler for best efficiency

PostBy: Bobs86GN On: Wed Oct 29, 2008 8:36 pm

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.... :lol:
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.
Last edited by Bobs86GN on Wed Oct 29, 2008 8:56 pm, edited 1 time in total.
Bobs86GN
 
Stove/Furnace Make: Hydra Fire
Stove/Furnace Model: Hitzer 50-93

Re: Tweaking my boiler for best efficiency

PostBy: coalkirk On: Wed Oct 29, 2008 8:39 pm

Bobs86GN wrote:BTW co2 alarm with digital readout has always read 0 and is located 5 ft from the boiler.

Man, you better check your pulse to see if you are alive. If you are there should be a CO2 reading. That's what we exhale. Now CO is antoher matter. That stuff will kill you. :lol:
coalkirk
 
Stoker Coal Boiler: Harman VF3000
Coal Size/Type: antrhcite/rice coal

Re: Tweaking my boiler for best efficiency

PostBy: Bobs86GN On: Wed Oct 29, 2008 8:59 pm

Gee, I have no idea what your talking about. :lol:
Thanks to the ability to edit one's post. :D
Ok, you got me. :oops:
Bobs86GN
 
Stove/Furnace Make: Hydra Fire
Stove/Furnace Model: Hitzer 50-93

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Re: Tweaking my boiler for best efficiency

PostBy: LsFarm On: Thu Oct 30, 2008 12:56 am

I don''t think 40-50# per day is excessive for your house.. I'd be careful about reducing the draft any more,, most hand fired stoves need around .04-.05"wc to fire correctly.. any less and you will either lose the fire, or have CO in the house..

Greg L
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Tweaking my boiler for best efficiency

PostBy: Bobs86GN On: Thu Oct 30, 2008 10:54 pm

Thanks for the suggestions. I have the baro reading ..035 now at times when the fire is at it's coolest temperature. Set the aquastat at 160. When the temp drops to 160 the damper opens. When it rises to 165 it closes. I now understand this aquastat function a little better. I used to now that 25 yrs ago when I set it up for wood but never thought about the details until I switched to coal. So it has a 5 degree differential between open and closed. I found that if no zones call for heat for extended periods the heat will build up now to as high as 200 but usually was more like 180. This is better than where I had it set earlier where it was closer to 220 and sometimes dumping the excess heat into one of the zones through the high limit aquastat. I loaded 40 lbs into the boiler at 3:30 on Tues afternoon (there was probably another40 lbs already burning below that). I shook the ash this morning at around 6:30 (15 hrs after the fill up). I did not add anything at that time. At 3:30 pm this afternoon (24 hrs after the last 40 lb refill) I reloaded with another 40 lb bag. The fire was still burning and the water temp was about 170 but much of the coal had gone dark. I poked some of the dead areas and added small amounts of coal and opened the ash door and watched the stack temp. It looked like I was going to loose the fire so I had to throw in some newspaper and kindling on top of the coal along with some cardboard strips and that got the whole bed glowing again-but it took a while. Once it was lively again I finished loading the rest of the 40 lb bag. That 40 lbs got the level of coal back pretty close to the depth that I had loaded it 24 hours earlier. Maybe another 10 lbs would have brought it up to the mounded pile that I originally had. So I am pretty confident that it used 45-50 lbs over exactly 24 hours. I left all my thermostats set to 71-72 settings just like the previous 2 or 3 days. Similar outside temps (actually colder at night) but somewhat less wind. I'm guessing that this is about as little coal consumption as I can get to for these kinds of conditions. I am getting a fair amount of calls for heat in 2 zones and am getting ample DHW. Would most people agree that this is close to the best I can do?? Are people getting much better results from any hand fired boilers? Are the stokers more efficient in this regard? I guess the only way I could reduce consumption for this weather requirement would be to reduce the firebox size. Any other tricks I might try. It does seem like the Hitzer in my living room is going to use about 1/2 the coal that the boiler would use and produce warmer room temps (74-76) in living room and 70-71 elsewhere in the house. So I end up using 1 lb/hour for room heat only or 2 lb/hr. for slightly less room heat and all domestic hot water. I wonder if I should let the water be heated by the oil burner instead. I have to figure out how to compare 1 lb/hr coal to how much oil would be burned when averaged hourly. I can check the GPH rating of the oil burner nozzle but it isn't running all the time like coal is always burning. Any way to figure this out without sitting and timing the boiler on time for 24 hours? I do actually have a life> :lol: This experimentation is fun though. Oh, I ordered an IR thermometer which sould be here Friday for more fun stuff.
Bobs86GN
 
Stove/Furnace Make: Hydra Fire
Stove/Furnace Model: Hitzer 50-93

Re: Tweaking my boiler for best efficiency

PostBy: Bobs86GN On: Thu Oct 30, 2008 11:03 pm

I may reset the baro up just a hair to .04 and see if that reduces the dead spots after a long slow burn. I alternately could open up another small air inlet hole on the ash door. Its a balncing act between long burns and minimum consumption and a dead fire-and yes co in the house I guess. No readings on the CO meter yet (no matter how Hard I try).
Bobs86GN
 
Stove/Furnace Make: Hydra Fire
Stove/Furnace Model: Hitzer 50-93

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