heating large shop in alaska

[Alaska1]

From the title you can see I will need heat in the shop ALL winter. Plans are to keep in running until spring (Mid May) then shut down for the summer.

Specs:
Interior Alaska ( can reach -30 to -40 but average is probably 0)
45 x 50 x 14 Shop
300K Sequoyah outdoor wood/coal boiler with 1 1/4 Thermopex for the supply
60-80K wood/coal stove ( only used when I am in the shop)
3x 70K hydronic heaters w/ fans -- two horizontal and one cabinet style
R 40 in walls
R 60 in ceilings
R20 in back wall (connects to unheated space in the barn... this is actually a 50x88)
Heat loss shows 120K -150K needed depending on which calculator
Very Remote so little to no help from plumber/HVAC without considerable expense

Plans are to

1)Heat the shop this year for a place to retreat during the winter and actually be able to do things outside.
2)Put a well in the shop for running water both hot and cold
3) Plumb shop on one zone so when calls for heat all heaters work
4) use 1 1/4 throughout the barn to keep the head down and the btu availability up
5) Minimize pipes as much as possible
6) Also heat hot water as a well is in the future
7) minimize the height of rise to 6 feet to keep the water from boiler one it reaches the negative pressure area. ( expect water line to be 4 feet so a 10 foot rise is a difference of 6 feet approx -2.6 this should give me fluff for a 190 degree water temp boiling based on psi.
8) mount the bottom of the heaters at about the 8 foot mark

Question:
1) Best way to plumb this-- zone valves through manifold or just push water through the heaters and thermostat the fans-- electricity is expensive here so want to balance initial cost with operating cost for a warm shop
2) are the placement of heaters correct

Just need some help on this one. I can do the work but design of plumbing not my strong suit

Thanks -- attached a diagram to help visualize

 

[PassionForFire&Water]

Most of these outdoor wood boilers are not very efficient.
If it says 300,000 BTU/hr, you probably will get around 50% of this; 150,000 BTU/hr

Your calculations tell you that you need around 150,000 BTU/hr
So, you are more or less covered

BUT, the hydronic heaters typically need a high water temperature input to give their rated value
I don't think the outdoor wood boiler will be able to give you 180F water

So, it all comes down to what temperature you want the space heated; 70F or all the way down to 45F
45F will not be a problem, if you can feed the wood boiler on a regular base, probably like 2 or 3 times per day

For the piping:
I would pipe the pex from the outdoor wood boiler into a 2" manifold inside your shop.
From the manifold you run to each of the hydronic heaters with a good size pump; 10 to 15 GPM
These hydronic heaters need a large flow because of the small detla-T to the water

 

[maple1]

That looks like a good situation for in-floor heat. But that doesn't likely help much at this point.

 

[Alaska1]

I think I have decided that the best way to do this is to pipe the boiler which is an open loop not pressurized to a heat exchanger. Then from there go with a closed loop system.

How do you figure the head loss .... some of the ones I have found have the specs some do not and google does not always render the results. I see there is quite a range on the head loss.

Also since I figure the boiler is a 300K i figure 50% efficiency just to be safe. if it is more then so be it. I would like to transfer as much of the heat to the inside as possible so I have it available if needed. To do so I will need to pump through 1 1/4 pex.... say at 10 gpm to get 150K. the close loop system has 3 heaters that will run at about 4 GPM max and a baseboard unit from 1 to 4.

Since the close loop and open are separated the flows can be different correct???? I understand that If i exceed drastically then the temps will suffer but at least the circulators will not cavitate.

Hence 10 GPM to Xchanger and three 4 gpm hanging heaters and a small loop of baseboard heaters at 1-4 gals.


If all of this is correct then the HEAD LOSS is the only thing I am having trouble with to ensure I have the right pumps to accommodate. I can figure the rest of the head loss but not all xchangers give you the loss or the psi operating .... any rules of thumb or ways to calculate

really want to get this up and running as it is getting cold here.

thanks

 

[jebatty]

I'm having difficulty understanding the numbers and why you are having so much difficulty heating your shop. Something is missing. What were the parameters you used to measure your heat loss?

My shop is 32 x 48 x 14, not too much smaller than yours; my calculated heat loss at -35F was about 35,000 btuH at interior temperature of 60F (very comfortable for a shop), but the greatest actual measured heat loss was just under 20,000 btuH, and average heat loss is around 12,000 btuh. Perhaps you are much, much colder than my location in northern MN.

What kind of wood do your burn? Is it seasoned to around 20% MC before burning? Do you burn green wood? How much wood (full cords or weight) do you burn? Seasoned wood has about 6050 btu/lb. Assuming 80% delivered heat efficiency to your shop, that would be about 4850 btu/lb. At 150,000 btuH for 24 hours, that would be about 740 lbs wood per hour, or about one cord every 3 days (aspen, birch, pine). Is that what you are burning?

Another example which give me confusion is that I am very familiar with a school facility near me that can heat 56,000 sq ft with one 500,000 btuH output wood gasification boiler down to temperatures of -10F, and can add a second 500,000 btuH output wood boiler when temperatures get below that. The school has fan coil units (water to air heat exchangers) for space heating. At these burn rates, each boiler with seasoned wood only consumes 100/lb of wood per hour, a small fraction of what you use.

I'm not disagreeing with the info you provide, I just find it hard to believe that you require so much wood to heat your shop, and somethings seem to be missing to get to your experience.

 

[Alaska1]

JEBATTY.... thanks for your reply .. I used the US Boiler website to calculate the heat loss as well as hydronic application that calculated the heat loss. This shop has not yet been heated so I really do not know how it will perform. I see you are in MN so you know cold as well. US boiler you just input your shop sizes windows doors ext and then the factors based on you insulation factors... pretty easy. I used the worst air infiltration to be safe but think i will perform somewhat better based on the fact that I took great care trying to air seal but 2x 12 x12 and 1x 10x10 old wood doors are drafty... I will blanket them and seal as well but just wanted to be safe.

I am not burning wood but rather coal... but that really does not matter as coal is more BTU than wood pound for pound but have the option to burn wood if needed.

You say only 35K BTU load on your barn. Those are actual measurements? I hope so because that gives me hope.

Also at the bottom of the US boiler website it gives you the heat loss based on your temp difference ... -30 was used as my worst although it can get worse here but HOPEFULLY will not last for months. but -20 is common. so if you keep it 50 that is a 70 degree difference to overcome.

 

[jebatty]

Yes, actual measurements. I did this by measuring the temperature drop in my 1000 gal storage tank in my shop as it delivered its heat to the shop. For example, 1000 gal at 190F fully mixed holds 1,584,600 btus. if after 24 hours the tank is at 140F fully mixed, it still holds 1,167,600 btus, but the difference of 417,000 btus translates into heat transferred into the building, and over a 24 hour period that comes to 17,375 btuH. This is a simple example but fairly accurate.

I have no experience with coal, and I see depending on the variety btu content is about 12,000/lb. I understand some coal still contains a fair amount of moisture, and I haven't seen an analysis of available btus for coal, which would vary depending on moisture content and flue temperature. The info I provided on wood was at assumed 20% MC and 400F flue temperature.

Our winters also are much warmer than they used to be. Brief periods into the -40'sF were not uncommon, and periods of 1-3 weeks in the -30's range were quite usual. Now, dropping to the low -20's usually is only for a brief period, and -10F is fairly common, but not for an extended period of time. There has been a huge increase in winter temperatures over the last 50 years. Some people think this is great, but it also is accompanied by some pretty drastic environmental and ecological changes, many of which are of great concern as to what the longer future bodes.

 

[Alaska1]

JE: I ran a US boiler heat calculator on your building. with the basic description you gave. I also assumed only 1x 8x8 garage door and no windows and no man door with the best of the best rating on everything... 6" wall about R20 insulation, 10" about R 30 ceiling insulation, Double insulated garage door, 9" overhang on your slab and a minimal air infiltration of .81 (tight) and the results are below. -35 calculation to 60 degree in the room and that is at the 90 degree mark and they calculated 51.2. SO this gives me hope as you are doing MUCH better than the calculations that their calculator is very conservative.

Question ... do you remember the outside temp for that 24 hour period of time and what the inside temp was... basically the heat calculation below no matter what type of building you have would assume 0 degrees outside... I doubt very many shop owners in the southern regions keep there shop at the 80 to 90 degree mark since 60 degree overcome is the lowest heat calculation they do. Ha.... knowing the info of the 24 hour period of time would give even more credit to how this is an over estimation and although you may have a VERY well built and tight shop I would bet that you do not have the 9 inch overhang slab and you probably have at least a man door ... these would be even a further down grade as well as windows and air infiltration. .81 would most likely be 5 star rated.

I figured mine based on actual known data I have with a very LOOSE air infiltration for safety since I have no idea what the air infiltration on mine would be.

R40 walls...
R 60 ceilings
but 2x large 12 x12 doors not insulated.. and another 10 x 10 not insulated. No windows in my shop unfortunately... and 2x man doors front and back. But i tightened it up a great deal when i remodeled.


Your heat calculation below.

Based on:

(broken link removed to http://www.usboiler.net/resources/contractor-toobox-calculators.html#disclaimer)

Area (ft2) H.M.(BTU/Hr.) Heat Loss
1. Windows & Doors 64.00 x 30.00 = 1,920.00
2. Net Walls 2,176.00 x 4.00 = 8,704.00
3. Ceiling 1,536.00 x 2.00 = 3,072.00
4. Floor 1,536.00 x 2.00 = 3,072.00
5. Infiltration 21,504.00 x 0.81 = 17,418.24

Total Heat Loss for 60o F Temp. Diff. = 34,186.24
Total Heat Loss for 70o F Temp. Diff. = 40,339.76
Total Heat Loss for 80o F Temp. Diff. = 45,809.56
Total Heat Loss for 90o F Temp. Diff. = 51,279.36
Total Heat Loss for 100o F Temp. Diff. = 56,749.16

 

[jebatty]

Based on memory as to window size, my shop has 2" foam under the entire slab, 2" foam around the perimeter of the slab extending 4' down, 6" fiberglass wall insulation, 1" solid wood paneling interior on bottom 8' of walls and sheetrock on top 4' of walls, 12+" blown in fiberglass in ceiling, metal interior ceiling and exterior walls, 1 - 12 x 12 overhead insulated door, 1 standard height man door 3' wide, one standard height man door 4' wide, 2 - 2' x 3' slider insulated windows. The shop has in-floor hot water heat, 5" concrete floor. The boiler and storage are located in the shop. Average seasonal heating wood use is about 4 cords of mostly pine with some aspen and a small amount of other mixed hardwoods. The winter of 2010-11 was the first heating season for the shop.

Correction: windows are 3' x 4'; sheetrock extends up about 5-1/2 feet to the ceiling from the top of the bottom 8' wood paneling

Here are several threads you may find interesting.
https://www.hearth.com/talk/threads/62762/
https://www.hearth.com/talk/threads/67685/
https://www.hearth.com/talk/threads/67685/
https://www.hearth.com/talk/threads/87414/