Anticipated coal consumption vs. Temp. & Degree Days

So does this mean I burn more coal when it`s cold ??

Larry,
I believe Wistlenut was suggesting using windchill factor instead of the degree day figure. He seems to be very interested and supportive in the information you're trying to develop.

The lbs. burned per degree day do indeed go down as the temperature decreases outside. Rob is correct. The warmer it is outside, the more coal is used merely to sustain the fire and to provide for DHW. As it gets really cold outside these two factors become of lesser significance. Also, the greater percentage of the time the boiler fan is running, the higher the overall efficiency. If there was no DHW demand, and the burner could turn on and off completely as T-stat calls are satisfied as for NG, propane, or oil, then perhaps the fuel consumption line would be more likely to linearly track the HDD's more perfectly with respect to units of energy as a ratio to degree days. For me if coal could turn on and off with the T-Stat calls and I was only heating my home (no DHW) then the result would probably be about 1.5 lbs. of coal burned per degree day from one end of the chart to the other end.

NOAA does not see wind chill as affecting inanimate objects the way it impacts living things. http://www.nws.noaa.gov/om/windchill/im ... ochure.pdf

A brief quote from this link: "Wind Chill does not impact inanimate objects like car radiators and exposed water pipes, because these objects cannot cool below the actual air temperature."

But that said, wind chill and wind infiltration are two totally separate entities. Rob's problem seems to be wind infiltration, and not wind chill, so if the wind infiltration is appreciable then Rob's observations are valid. Rob made no mention of wind chill. Neither did whistlenut to my knowledge.

I've seen little correlation to wind infiltration. But then my house probably has a lot less places to let in the wind than many of the older homes. Mine was made in 1964, and we had foam insulation injected into the walls, plus there is a pretty decent layering of pink fiberglas insulation in the attic. Windows and doors could use some upgrading.

mope#2 wrote:So does this mean I burn more coal when it`s cold ??

That is a great way to sum it up.

Wind chill does cool down warm or heated objects, just like our bodies.. but wind chill cannot cool anything below the real temperature..

So, if you have poor insulation, so your outside walls are warmer than ambient, and single pane windows, which are warmer than ambient, then wind chill will cool the building down faster than calm winds with the same ambient temperature.

So if you really want to come up with a mathmatical formula for life burning coal,, include the wind, figure out a coefficient for your windows, outside walls, infitraton rate, and insert them whereever in a formula..
Oh, don't forget internal orgainic heating.. that's the heat generated inside the house when you and the wife have a big fight, or the opposite, you are getting along and generate some extra body heat.

But the bottom line is: buy some estra coal, unless you think the Farmers Almanac is a scientific standard to go by..
And as mentioned above, just shovel it in as needed, and enjoy the heat..

By the way, did I mention that mathmatics gives me a major headache ??

Greg L

lsayre wrote:Rob's problem seems to be wind infiltration, and not wind chill, so if the wind infiltration is appreciable then Rob's observations are valid. Rob made no mention of wind chill. Neither did whistlenut to my knowledge.

Yes, our home suffers from 'excessive infiltration'. Before you imagine the curtains blowing around and snow drifts in the corners, I can tell you that is not the case. I have the old house buttoned up pretty good, but the wind exposure is SEVERE. Some people that live in town/city think it gets windy...I ask them if they have ever had a window blown out from a gust? Siding ripped off? Chimney caps blown 200' away? I have had all of those happen, so let me re-emphasize that it gets pretty extreme here at times. The Northwest wind has over a mile to gain speed, and it really hammers us. I don't know if the house feels "wind chill" the same way I do, but on those days when I feel like my nose is going to freeze off when I go get the mail, the EFM burns a lot of coal.

Here is the view looking West from my mailbox. House is on the left.

Sure is a nice looking location. Would be well worth the extra coal for a spot like that!! You got any shots with the white stuff just to give us a better idea of a "cold" day?

Video from up the road, it was 10 degrees. http://youtu.be/4tIj69dTNnk



Old picture from the wood boiler days.

I love it! Someone as geeky as myself!

I notice that your consumption seems to increase linearly. When I fit a line to my data http://nepacrossroads.com/about25857.html I got a better fit with a non-linear line. I can't remember if it was an exponential or if it was a second or third order polynomial.

On the wind chill, I think the correct factor to use would not be wind chill but rather wind speed. Wind chill is a calculated number to illustrate the effect of wind speed and temeperature on the skin of your face when you're walking at 3.1 miles per hour into the wind.

Don't forget about the solar gain or the ITWCF (Is The Wife Cooking Factor)! I like the ITWCF the best!

One of the things that I'm looking forward to the most is taking a look at my consumption numbers after I insulate the basement. I should be able to put a dollar figure to the fuel savings and then calculate a return on the investment. This year I'm burning Reading rice and I'll be comparing that to last years Blackshak rice.

Mike

My coal consumption all last year was very linear. It tracked heating degree days very well, sans for the slight deviation that DHW introduces. I could predict in advance to within typically +/- 8 lbs. of coal how much was going to be needed in order to fill my hopper. That was for filling it roughly every third day, and every other day for the coldest stretches. I was amazed at how many times my calculation and reality were one and the same.

Rob, you have a very nice home!

lsayre wrote:Rob, you have a very nice home!

It is in a nice location, but the repairs never end. I shudder to even think about how much I've spent on this place in the last three years.

The basic formula I'm using (quite specific and tailored to my home) to calculate our coal consumption is:

Coal required per day = Daily HDD's x 1.5 +3

This formula assumes that 3 pounds of coal per day are required for DHW, thus the added 3 lbs.

Also, our coal consumption never falls below about 14.5 lbs. per day.

This is my chart from last year. I got lazy in the spring and quit updating it, but you can still see how the amount burned tracks the outside temperature. The period from Xmas to 1 New Year's was my biggest week for coal consumption. My notes indicate a few days of roaring wind, and since we have that entire week off...I'm sure the heat was cranked, the doors got opened a lot, and there was a lot of hot water used.

Now that I have those detailed records on the shelf, I have decided to adopt Greg's philosophy.

But the bottom line is: buy some extra coal, unless you think the Farmers Almanac is a scientific standard to go by...And as mentioned above, just shovel it in as needed, and enjoy the heat..

I bought as much coal as I could afford, I set the thermostat where I want, and a shovel coal & ash as needed.

Rob, that looks rather linear overall. If you plotted a best fit line to this you could generate a chart much like mine. Then you can reduce it to a simple formula.