February 2014: The months tale of the "coal burning" tape

Re: February 2014: The months tale of the "coal burning" tape

PostBy: hcarlow On: Thu Mar 06, 2014 2:07 pm

For Feb. I used 1440 lbs. of coal and had 1322 HDD for Feb. or 1.09 lbs. per HD

For Jan. I used 1880 lbs. of coal and had 1410 HDD for Jan. or 1.33 lbs. per HD

The reason for the increase in Jan. was I had a pallet of coal with lots of fines in it .

I am heating about 1200 sq. ft. and dhw for 2
hcarlow
 
Stoker Coal Boiler: Leisure Line WL 110

Re: February 2014: The months tale of the "coal burning" tape

PostBy: kstills On: Thu Mar 06, 2014 3:20 pm

HDD for Feb here was 1075, and I was literally shoveling the coal into the boiler. I don't think there was a day that went by that I didn't refill the hopper.

January here was 1275 hdd, and I just did a calc on the predicted HDD for March:

876.......

Last year March was 492.

This is the winter that will not end.......
kstills
 
Stoker Coal Boiler: WL 110
Stove/Furnace Make: Leisure Line

Re: February 2014: The months tale of the "coal burning" tape

PostBy: mikeandgerry On: Thu Mar 06, 2014 3:44 pm

Isayre:

Just curious...how did you estimate the DHW component of your coal usage?

Just to shed some light on a good estimate of what an s-130 might use from an actual statistical standpoint, reference the Bureau of Mines Report on the Axeman Anderson Anthratube 130-M here on this site. Bureau of Mines Report 4936 Axeman-Andersen Antratube Boiler

They have accurate (I assume) numbers of coal consumption for June and August for a family of 4 which would likely be just DHW and no heating load. it was about 450 and 550lbs per month respectively to "idle" the unit AND produce DHW.

I am not sure how to extract the idling component which would also be a factor in your calculations. I would think the "hold fire" idling mode would burn the unit 24 minutes for the timer cycles and for boiler heat loss the unit might run another 30 minutes. Let's say an hour per day. The feed rate of the coal maxs out at 130kbtu/h or 130kbtu. I would assume the grate would cycle at each run considering that the ash should be cool with such infrequent use thus the feed rate should be a good estimate of use even though it might not burn completely. Coal contains 12000 btu/lb. 130000/12000=10.83 pounds per day to idle or 325lbs per month for the pleasure of on demand heat from coal.

Thus, DHW consumed an additional 200 pounds of coal per month for a family of 4 approximately. The Bureau of Mines report estimated 100lbs per month but makes no mention of measuring "idling" consumption. They calculated idling consumption mathematically and deducted it from total coal usage then estimated a split between DHW and heating. Personally, I don't know how accurate their math could be in determining the area of radiation on such an irregular surface and their piping estimate is partial for convective loss.

I would love to try to measure it myself on my AA130 but it's in my shop and the heat is too much punishment in the summer!
mikeandgerry
 
Stoker Coal Boiler: Axeman-Anderson Anthratube 130-M


Re: February 2014: The months tale of the "coal burning" tape

PostBy: Rob R. On: Thu Mar 06, 2014 4:32 pm

It is a tough thing to get your head around...the more water you use, the less it idles. ;)
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Other Heating: Dad's 1953 EFM Highboy

Re: February 2014: The months tale of the "coal burning" tape

PostBy: lsayre On: Thu Mar 06, 2014 5:03 pm

mikeandgerry wrote:Isayre:

Just curious...how did you estimate the DHW component of your coal usage?

Just to shed some light on a good estimate of what an s-130 might use from an actual statistical standpoint, reference the Bureau of Mines Report on the Axeman Anderson Anthratube 130-M here on this site. Bureau of Mines Report 4936 Axeman-Andersen Antratube Boiler

They have accurate (I assume) numbers of coal consumption for June and August for a family of 4 which would likely be just DHW and no heating load. it was about 450 and 550lbs per month respectively to "idle" the unit AND produce DHW.

I am not sure how to extract the idling component which would also be a factor in your calculations. I would think the "hold fire" idling mode would burn the unit 24 minutes for the timer cycles and for boiler heat loss the unit might run another 30 minutes. Let's say an hour per day. The feed rate of the coal maxs out at 130kbtu/h or 130kbtu. I would assume the grate would cycle at each run considering that the ash should be cool with such infrequent use thus the feed rate should be a good estimate of use even though it might not burn completely. Coal contains 12000 btu/lb. 130000/12000=10.83 pounds per day to idle or 325lbs per month for the pleasure of on demand heat from coal.

Thus, DHW consumed an additional 200 pounds of coal per month for a family of 4 approximately. The Bureau of Mines report estimated 100lbs per month but makes no mention of measuring "idling" consumption. They calculated idling consumption mathematically and deducted it from total coal usage then estimated a split between DHW and heating. Personally, I don't know how accurate their math could be in determining the area of radiation on such an irregular surface and their piping estimate is partial for convective loss.

I would love to try to measure it myself on my AA130 but it's in my shop and the heat is too much punishment in the summer!


Lots to consider here. First though, the Coal gun has no idle fire (hold fire) timer and it does not fire periodically merely to sustain the fire. It does that without the assistance of a timer and if no DHW is being used it fires merely by heat loss to the air over time if need be. Hard (impossible?) for the AA guys to get their heads around perhaps, but having a timer firing it intermittently to keep it burning is an unnecessary waste of coal, electricity, equipment, etc...

Lots of available statistics show that DHW takes 17% of the total energy used by the average residential home. On average when we were all electric we used 27,000 KWH per year. 17% of that is 4,590 KWH for DHW. Divide by 12 and you get 382.5 KWH per month. That comes to 12.58 KWH per day.

12.58 KWH x 3,412 BTU/KWH = 42,993 BTU's per day for DHW via electricity at 100% efficiency

42,993 / 0.822 efficiency factor for coal = 52,303 Gross BTU's of input for DHW from coal

52,303 Gross BTU's per day divided by 13,100 Gross BTU's/lb. for anthracite = 4 lbs. of anthracite per day for DHW

Thus my 4 lbs. per day ballpark guesstimate of coal consumed to provide DHW.
Last edited by lsayre on Thu Mar 06, 2014 6:23 pm, edited 2 times in total.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13 KW)

Re: February 2014: The months tale of the "coal burning" tape

PostBy: lsayre On: Thu Mar 06, 2014 6:02 pm

Ah, I see where you are confusing July and August with November through April. Two different animals.

In the summer I go through about 15 lbs. of coal per day, but that does not change the fact that it only takes 4 lbs. per day to heat DHW. It only means that roughly 11 lbs. per day are required to idle away the time doing nothing for 24 hours other than maintain a fire.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13 KW)

Re: February 2014: The months tale of the "coal burning" tape

PostBy: mikeandgerry On: Fri Mar 07, 2014 3:04 am

Exactly. That's what I am saying. There are two components of fuel usage to create the DHW. I understand your calculations and think they are correct. The difference is that electricity, oil and gas are "on demand" fuels requiring no consumption between DHW calls for heat. You must burn some coal for the "privilege" of readiness to a call for heat with coal or wood. I actually think my 200 pounds for DHW is a high estimate. I think your 120 pounds is a little low. But maybe you just don't use as much as we do. I just dont' know! You and I and the Bureau of Mines are all estimates. Maybe I will get out my feed barrel for my auger, carefully measure out coal and put up with the excess heat this July, finally getting a good idea of the true usage!

As for the timer, most members have stated that it is totally unnecessary to have the timer on an AA except during the summer if you are using the unit for DHW. My timer motor kicked the bucket last year. I didn't replace it that season and never missed it.

I did discover the real drawback to a timer last season when that timer motor burned out. As it happened, the timer motor gave up the ghost as it was tripping the circuit (closing it to run the hold fire cycle). So there is was, stopped right on the switch, running the fan indefinitely. Axeman Anderson recommends a hi-limit aquastat setting of 220degF. Being the good doobie that I am, I dutifully set it as recommended. Little did I know, since the hold fire circuit was stuck closed, therefore running all the time, which overrides the triple aquastat, the hi-limit aquastat became my new primary thermostatic control device! My boiler fan ran until the boiler hit 220degF! Despite having a thermostatic mixing valve, so much heat transferred through the copper pipes and our DHW was seriously hot. I kept ignoring the wife until a few days later I burned the crap out of my hand forgetting to wait for the cold to mix in. The timer was bypassed and all was well again. It probably needs a switch for summer use only.
mikeandgerry
 
Stoker Coal Boiler: Axeman-Anderson Anthratube 130-M

Re: February 2014: The months tale of the "coal burning" tape

PostBy: lsayre On: Sat Mar 08, 2014 8:02 am

Another perspective on our DHW usage, still assuming the above requirement for 42,993 daily hot water input BTU's.

1 BTU = the amount of energy required to raise 1 pound of water one degree Fahrenheit
The average shower is taken at ~110 degrees F.
Our well water comes in at a constant 50 degrees F.
110 - 50 = 60 degrees of rise for our DHW
1 gallon of water = 8.34 lbs.
60 degrees of rise for 1 gallon of water takes 60 x 8.34 = 500.4 BTU's
42,993 BTU's per day / 500.4BTU's/Gal. = 86 gallons of hot water used per average day for my wife and myself.

For the two of us this comes to 43 gallons of DHW used per person per day. Does that sound about right for per person hot water usage?

We have low flow shower heads installed that are supposed to be in the range of 2.4 GPM of flow. Since each of us takes a roughly 5 minute shower each day that accounts for roughly 24 gallons of our hot water usage out of 86 gallons, leaving 62 gallons per day for dishes, laundry, etc...

There are only the two of us. Perhaps a general assumption of 2 lbs. of coal per person per day for DHW is in the ballpark.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13 KW)