Heat Required as Outside Temp Falls

 
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Post by 2001Sierra » Sun. Dec. 21, 2014 4:54 pm

Wow Hambden Bob, well said. With my hand fed I really was a weather watcher. With my stoker I just monitor everything and cannot help but tweak because I can. You really have a way with words, and I can only assume you type really well :shock:

 
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Post by windyhill4.2 » Sun. Dec. 21, 2014 4:58 pm

Where is the cold blast ? :eek2: :notsure: HB,you had better give the rest of us a heads up when its coming this way so we can stay ahead of it. :)

 
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Post by Lightning » Sun. Dec. 21, 2014 5:01 pm

lsayre wrote:When it hit minus 17 degrees here last year my coal consumption was virtually dead on with the predicted consumption derived from the linear HDD's formula. That shows me that at minus 17 degrees there is no change due to the really cold temp. But then my coal gun could probably heat two of my houses, so I was not taxing it much at minus 17 degrees. Perhaps some of the extra coal consumption (if in fact there really is any vs. HDD's) comes from really taxing the limits of the stove or boiler or furnace?
That is amazing, really it is.. and I think it speaks volumes about your home having very controlled cold air infiltration and the sizing of the appliance that you've chosen.

 
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Post by whistlenut » Sun. Dec. 21, 2014 5:03 pm

Larry has this down to a science, HOWEVER you forgot to mention wind mph as it affects the heat loss. Lets face it, keeping a house or shop at 70 is no big deal at virtually any outside temp, but simply add a 30 mph west wind and we are all POed at HB for not warning us. The hand fed situation requires much more anticipation due to slower reaction to temp difference ; a stoker simply needs to have fuel to operate, and it could care less.

Having a dinky boiler or furnace will shoot you in the foot......don't bring a knife to a gunfight! :idea:
Last edited by whistlenut on Sun. Dec. 21, 2014 5:04 pm, edited 1 time in total.

 
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Post by Lightning » Sun. Dec. 21, 2014 5:04 pm

windyhill4.2 wrote:Where is the cold blast ? :eek2: :notsure: HB,you had better give the rest of us a heads up when its coming this way so we can stay ahead of it. :)
Oh you just wait another month, Mid to late January? Oh yeah... You'll be lettin that stoker in the truck box stretch her legs a bit.. 8-)


 
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Post by windyhill4.2 » Sun. Dec. 21, 2014 5:12 pm

Well, Lightning , We did get a trial run back in Nov. with the 10* we had that 1 morning. That cold morning gave me a bit of assurance that all should be well with the 520 when Jan drops the cold bomb on us.

 
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Post by Lightning » Sun. Dec. 21, 2014 10:20 pm

scalabro wrote:In Laymen's terms....

The greater the difference between OAT & IAT, the greater the rate of transfer through the wall, ceiling etc.
Julie250 wrote:I'm no expert, but I believe the loss can be attributed to thermodynamics and heat conduction, in which heat is lost through transference through the wall of the stove, the walls of the house, and the floor and/or ceiling. Combine those losses with a drop in temperature and the losses increase significantly due to the increased difference. Heat energy always travels from warm to cold areas, even to those cold areas we don't want to heat.

Found this website with formulas that may help you calculate it if you want to.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo ... ss.html#c1
I just reread this thread and caught these two posts.. I just wanted to add that this is what I expect would cause the linear increase of coal usage. IE, Triple the difference between OAT and IAT should result in triple the coal usage. But if air infiltration volume is tripled due to household stack effect, it should skew the usage as not to follow a linear outcome of coal usage. So it seems that what can be taken from all of this is that extra cold air infiltration in a relatively tight house doesn't measurably occur when its extremely cold out.

This could be a very good indicator that if a member comes to the board with an excessive coal per HDD usage when it gets really cold out, he may want to look at tightening the house instead of wondering why his appliance isn't keeping him comfortable.. :)

 
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Post by Rob R. » Mon. Dec. 22, 2014 5:02 am

whistlenut wrote:Larry has this down to a science, HOWEVER you forgot to mention wind mph as it affects the heat loss. Lets face it, keeping a house or shop at 70 is no big deal at virtually any outside temp, but simply add a 30 mph west wind and we are all POed at HB for not warning us.
Especially in an older home with hundreds of small drafts throughout the structure. There is some good discussion about it in an older thread:

Anticipated Coal Consumption Vs. Temp. & Degree Days
lsayre wrote: Perhaps some of the extra coal consumption (if in fact there really is any vs. HDD's) comes from really taxing the limits of the stove or boiler or furnace?
I think that is the case for some folks. On more than one occasion I have heard of people adjusting some of the boilers with small inclined-bed stokers to have burning coal right at the edge of the grate to try and get some more BTU's out of it. Hand fired equipment is another example, a lot of guys report that their stove has a "sweet spot" and once you get beyond that there is diminished returns for the extra coal you burn.

The Axeman Anderson and Coal Gun units seem to be happiest when run at rated capacity.

 
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Post by Rob R. » Mon. Dec. 22, 2014 5:05 am

windyhill4.2 wrote:Well, Lightning , We did get a trial run back in Nov. with the 10* we had that 1 morning. That cold morning gave me a bit of assurance that all should be well with the 520 when Jan drops the cold bomb on us.
You will probably hit the limit of what the heat exchangers can do before you max out "the power plant". That is the case in my house.

 
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Post by windyhill4.2 » Mon. Dec. 22, 2014 6:54 am

Rob, we have never maxed out the heat exchangers YET,but we have not had any -35* temps since we live here. That temp would probably create an issue with our shop,i doubt the heat available in 1 pair of pex will be enough for that temp.


 
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Post by lsayre » Mon. Dec. 22, 2014 7:27 am

Assuming 550 BTUH's per foot for fintube baseboards with 180 degree water, I have enough hot water baseboard footage for about 78,000 BTUH's (with about 61,000 of that in the house proper, and the rest in the garage). From what I can figure my homes heat loss on the coldest day(s) of the year is about 45,000 BTUH's. So both my boiler BTUH's and my radiator BTUH capacity are overkills vs. my homes requirements.

 
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Post by blrman07 » Mon. Dec. 22, 2014 8:54 am

This winter I have used the VC 2310 hand fired stove. I have payed attention to the amount of coal in relation to OAT. Momma wants to stay warm and by anticipating the OAT drops I can accomplish this task.

Temps down to around 25 I use a single 5 gallon bucket a day which is around 30-35 lbs. When the temp dropped from 25 to 20 coal usage crossed a magic line somewhere between 25 and 20 degrees and usage went to 1 1/2 buckets a day. That represents a 50% increase in coal usage to maintain 70 in the LR with an OAT drop of 20%. In order to maintain a linear track every 20% drop should increase coal usage by 50% of existing usage before that drop.

This assumes that I continue to use the same coal, same size, same supplier, measured the same way with no changes in tending times or practices. It was already noted that coal usage dropped in one instance by changing one variable. Change one of the variables and you skew the results.

When it drops below 20 I will keep track of the usage to see if I do indeed have a linear track to believe in.

 
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Post by waldo lemieux » Mon. Dec. 22, 2014 10:54 am

Perhaps some of the extra coal consumption (if in fact there really is any vs. HDD's) comes from really taxing the limits of the stove or boiler or furnace?[/quote]

Having a dinky boiler or furnace will shoot you in the foot......don't bring a knife to a gunfight! :idea:[/quote].

:idea: :idea: ding ,ding,ding. We have a winner :D

 
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Post by Lightning » Mon. Dec. 22, 2014 11:15 am

Rev Larry, thank you for contributing to this thread. Your example is what I was wondering existed for some of the other board members.

It's what I kinda see happen too. When OAT descends below a particular threshold, my usage increases more dramatically. It's like above 35 degrees I use 40-45 pounds then below 35 it increases to 55-60 pounds per day..

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