Coal Consumption for Dhw Question

With my boiler, I set the aquatsat low setting at 140, high at 190, and the timer at 2 minutes per hour on. If the temp ever goes below 130 the stoker will come on and bring the water up to 160. The 2 minutes per hour keeps the boiler warm enough so this doesn't happen until the kids have a bath or I'm doing laundry. I got a hold of some low, low, low ash 7% red-ash coal so it's been really easy, once a week I dump a couple bags in and take out the ash pan. I don't see a need for using a hot water tank, a properly designed coil will supply all the hw you can ever use. I have no tank and you can take a hot shower as hot as you can stand it for hours and hours and it never gets cold.

I'm using a PLC based control system, not the standard Harman timer, so I can set on/off times down to the second. It also gives me the ability to vary this on/off ratio in proportion to the difference between the boiler water temp and the desired temp. This helps with overall efficiency, not so much though when burning in pilot mode. I also have the ability to run the combustion blower at a slower speed when its not stoking, by adding a variable speed control that is typically used for ceiling fans. The blower runs 24/7, but only kicks in at high speed when stoking.

Sting as far as byproducts of combustion go, remember when you burn oil, gas, wood, etc you are burning a hydrocarbon. The byproducts of hydrocarbon combustion are CO2 and H20 if one has perfect combustion. With anthracite coal, its almost all carbon, so there is very little if any water vapor. Haven't you noticed that you don't see water vapor from a coal fire chimney, even on the coldest days?

Highlander wrote:Sting as far as byproducts of combustion go, remember when you burn oil, gas, wood, etc you are burning a hydrocarbon. The byproducts of hydrocarbon combustion are CO2 and H20 if one has perfect combustion. With anthracite coal, its almost all carbon, so there is very little if any water vapor. Haven't you noticed that you don't see water vapor from a coal fire chimney, even on the coldest days?

Never burned that there Ant Tracks stuff

So with the help of Greg and posts like this -- I'm learning the semi-hard way - posting stupid stuff and watching for correction

But still, I would not run below 145 at any time - other than cold start or occasional load demand lag before boiler protection comes on line.

first off I like to thank everybody for all there help. I filled my coal boiler up with three bags of coal on 4/25/2008 at about 9:00 am and then went out for the night with the wife. nobody was home so no hot water was used and the heat not was on. just got home 4/26/08 at about 2:00pm and it seems the boiler used about 40# of coal in a 15 hour span. that is way too much coal to be burning with no demand for hot water. my timer is set at 1minute of stoke every 10 mimutes/stoker adjustment is set at 12 turns out and I lowered my aquastat to 140-160 stack temp 150 draft .02. can somebody tell me what might be happening on the excessive coal consumption.

thanks chris

If this is the first time it has run,, you had to raise water in the system up to temp... That will take some extra.. keep an eye on the consumption for the next few days...

You said your draft is at .02", do you have a barometric damper installed?? If not, and the wind was blowing strong while you were gone, this could have pulled a lot of heat up the chimney.... just a thought.

Greg L

boiler has been running since january and I do have a baro damper.

[thinking out loud]

If the boilers are in series and they have roughly the same storage capicity, and there is no call for heat, the oil boiler would cool down to room temp.

Now, when the indirect HW heater calls for heat, you have to heat up all the water in the oil boiler and the water in the indirect heater. Before the call for heat is satisfied.

To me this seems like it could waste an aweful lot of coal.

Why this also makes sense to me, is that in the winter there are 4 zones calling for heat. Lets assume one of the zones calls for heat every 1/2 hour. This should keep the water in both boilers pretty hot. Now, in summer use you cold go hours before you get a call for heat. This would allow the oil boiler to temps to drop down to room temp.....

just a thought.... anyone agree or disagree?

Chris, I have no idea why you would have used about 40 lbs of coal in about 15 hours assuming you had the same heat wave that we just had.(it's over for now) I will tell you that 40 lbs in 15 hours would be quite a bit of heat. Can you detect where this heat has gone? If I were to have run that amount of coal in that amount of time through the KA-6 last week my basement would be HOT the boiler gauge would be showing excessive temps and the pressure would be up a bit and probably the house would be hot because the over-temp aquastat would have run the circulator to dump heat. What I'm trying to say is if the excess coal consumption is the only clue you have then what is eating up all those BTUs ? If it were me I would plan a project of some sort that I could be near the boiler for at least half a day. Closely monitor temps, check it every time it runs to see if it is just running on the timer. Verify timer settings with a stop watch. If the stoker runs because of demand what is causing the demand, a "boiler mate", I don't have one but I'm thinking they only cycle a couple or few times a day depending on the amount of hot water you use. Bottom line is something is eating a lot of heat or someone is stealing your coal

1975gt750 wrote:my timer is set at 1minute of stoke every 10 mimutes/

I have not burned coal yet, so maybe I'm out of line here, but from what I've read, a cola boiler "on bank", that is, with no call for heat, the timer might need one or two minutes per hour. It seems that 6 times an hour is a lot.

Freddy wrote:

1975gt750 wrote:my timer is set at 1minute of stoke every 10 mimutes/

I have not burned coal yet, so maybe I'm out of line here, but from what I've read, a cola boiler "on bank", that is, with no call for heat, the timer might need one or two minutes per hour. It seems that 6 times an hour is a lot.

Different stokers have different needs. The old Keystoker timers were a wheel that rotated once every 15 minutes with an adjustable notch in the wheel that operated a switch to run the stoker. The stoker would run 4 times an hour, the only adjustment being run time. The newer Keystokers use a different timer that, if I am correct, permits adjustment of run time and time between runs. I have seen some older EFM timers that could be set to run once or twice an hour. I don't know what everyone else is doing but not all stokers are the same when it comes to timer settings and requirements.

well I think I figured it out I pulled a bunch of pins from my timer. I went from 6 pins every to minutes to 2 pins every 10 minutes. and already noticed a difrence. in 12 hours the coal has barley dropped and my boiler room in a nice cool temp of 67 when before it was about 78-80 degrees. hopefully I got it . if I have enough hot water I might try to turn the stoker back and try to save some more coal.

As you try to 'wean' the boiler,, remember that you need not only enough fire to keep the coal burning,, but to create enough heat to keep the chimney drafting... since it sounds like you have a full time manometer,, this should be fairly easy to do..
if you have thermometer in the flue pipe before the baro damper this will help as well.. you want to keep the temp in the flue warm enough to keep the draft at least .02-.04" this wll ensure all the fumes are pulled up the chimney..

And while you have the fire set really low.. make sure you monitor your CO meter/alarm as well Saving a few pound of coal isn't worth being unsafe and getting CO poisoning..

Greg L

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i am on top of that greg I have my co meter plugged in and a stack thermometer in at all times. I also have my draft meter and I was debating to drill an other hole in the pipe to keep constant watch on it. with my low fire my stack temp is 158.6 degrees

That temp in the flue should be plenty,, how much fire do you see on the bed/grate with the current settings?? As long as you have a fire the full width of the grate/bed, you should be fine... when the fire gets too small or low,, then the ends of the fire tend to shrink away from the sidewalls of the grate.. Leaving some unburnt coal along the sides.

Greg L

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gaw wrote:Using a Keystoker KA-6 I use about 100 lbs. per week for hot water and to maintain fire. Timer is set for 45 seconds run time, 14 minutes and 15 seconds off time. For the "off season" I turn the low setting of the aquastat to 140, all other adjustments remain the same as during heating season.

The KAA-2 being a smaller unit, I would think should use less than the KA-6 unless you are using a lot of hot water.

Gaw, how many turns back is your feed nut going from the boiler side towards you?
Jon