off the grid coal boiler

I live "off the grid" in Alaska and am getting ready to build a new house that I would like to heat using a hand stoked coal boiler. I have access to all the free bituminous coal I need. My situation is trying to design a setup that is compatible with living off the grid meaning trying to avoid as many high demand electrical components as possible. I am shying away from a traditional closed loop system in which I would be relying on a pump to safely disperse heat through my heating zones, PRV and cold make up water etc. Although I plan to use a pump to move water from the boiler and a PRV etc I don't want to take the risk of leaving the house and having the battery bank run down and have the circ pump and make up water pump fail and have a catestrophic meltdown. My current thought is to use an open loop system that uses a hand stoked boiler with a large (~50 gal capacity) tank that is vented to atmosphere (?). My idea is that in a worst case scenario I stoke the boiler for a 12 -18 burn and leave only to have the electrical system fail. Excess heat and pressure is relieved as the tank vents to atmosphere and my boiler fluid level slowly drops (boils off). I'm thinking the 12-18 hour burn time wouldn't consume the entire 50 gals and spare me the meltdown scenario. I would also still include PRV's in the event that condensation freezing in the open to atmosphere vent clogs the vent.

As for specifics the house is one level below grade/ with a daylighted garage and a single story above (approx 1100 sq ft per floor including garage). It gets wicked cold here (-50 is not unheard of) but I am a carpenter that is much better versed in building efficient warm houses than I am in burning coal.

If anyone else out there has ever worked with an off the grid system or has any other advice on this matter I'd greatly appreciate it.

I'd be looking at using hot air instead if you want to use it off the grid. These were actually quite common around here even as large furnaces to heat whole homes many, many years ago. The basic principal is to use a cold air return. My house is about 100 years old and I redid the basement if you want to call it that a few years back and one thing I ripped out was the old cold air returns. These were very primitive in that they simply used the gap between two studs and extended into the top floor. Wooden ducts went from the sill to where the air inlet for the furnace would be.

Do a search for "cold air return" as many people are doing this now becuse the hot air stokers are quite popular.

Hummmm..... off grid, I'd use hot air heating and set up DHW coil to thermosiphon to storage tank. No power needed.

off-grid if i had the money i'd use one pipe steam with aquastat draft control on the underfire air; bituminous coal can be shut almost completely off from combustion air if there's a deep bed and firebrick surrounding it and it will produce little heat, but will awaken quickly if called for. i've fired an old single pipe steam (oil) system with wood during power outages many times and it worked flawlessly (obviously me periodically adjusting the shutter on the oil burner was the only draft control but with an aquastat underfire draft control i wouldn't have had to)

I'd say go with a hot air system too, but, no harm in researching a boiler. The one huge question that looms overhead is: How are you producing electricity and how much can you, will you, produce. If you have unlimited funds and this is all a big science experiment, I'm sure it can be done, but, if you're doing this because you have limited funds and want to live "close to the Earth" so to speak, then I truly think a boiler is out of the question. So... tell us how many kilowatts a day you are confident you will have and we'll go from there.

one pipe steam for a low/no grid power installation is a great idea with a back up from a gravity pressure make up water tank,

or - maybe consider reviving the art of gravity flow hot water distribution - big pipe to haul into an off grid installation but lots to haul in anyway, right.

I would venture it will depend on the structure configuration - can you design and build a low point ( basement boiler room ) or will you use an outhouse to hold the production equipment?

scorched air is still the simplest but not the most comfortable

During the heating season, build a gravity feed...snow collector,make-up water/melter feed system and use the heat from the steam system to keep it flowing?

I just firmed up plans to ride shotgun on a household goods move to Fairbanks in March 2010

Thanks everyone for the responses. I've been away from the computer for a few days but grilling the other local coal boilers. I think I'm back to leaning towards the boiler. Berlin's comment re: the air damper...duh...I kind of forgot about that aspect, being able to really clamp down on the fire by controlling the O2.

Living off the grid is a necessity not a luxury for me. I've done it for 12 years in my last home. Its amazing how well you can live without using a lot of electricity. You do a lot of conservation and using alternative systems like propane refrigerators, on demand hot water, etc and the simple things like compact florescents. My last system had four 6-volt batteries wired in a 12 volt system with an inverter/charger. I primarily relied on a 3000 watt honda generator (still running after over 10yrs) for my power to charge the system. On average I ran it 9hrs per week to provide all my electrical needs. It equated to an electrical bill of about 10-15 gals of gas a month...pretty good these days.

Back to burning coal...I believe I've figured out how to arrange a system with 120v zone control valves (avoid the transformer drain) and wire them in conjunction with the circ pump so that it only comes on when a zone control valve opens or when I need to dump excess heat to the garage slab. I keep it as a simple open loop system by installing a make up reservoir above the highest point in the system and letting it vent through it. I will also likely route the drain from the PRV into the firebox, others around here have had success with it...a good way to cool down a overheated fire. All this combined with a thermal air supply damper an I think I've got a good thing going.

In the end the only real electrical draw is the circ pump and only when called for. I may splurge and spring for an autostart function on the next generator...they automatically start when the battey voltage drops below a given set point. After reading other "off grid" pubs I think the general consensus is that it is always more efficient to move fluid rather than air.

I'll be sure to keep the forum posted on my progress. Thanks again for the input and feel free to send more.

Alaska_Range wrote:the general consensus is that it is always more efficient to move fluid rather than air.

Well, yes & no. Gravity is the least energy hog. Most times it's easy to make air flow by gravity. It takes careful planning and proper size pipes to gravity water.

You didn't mention infloor tubing the first post. You will not gravity water through infloor tubing. The fact is that infloor likes to have water moving almost constantly. It'll cost you around 60 KWH per month to keep that pump running.

Are others in your area running a similar system? I know living in Alaska is different than anyplace else. The best knowledge comes from experience....someone else's experience!

Alaska_Range wrote:Thanks everyone for the responses. I've been away from the computer for a few days but grilling the other local coal boilers. I think I'm back to leaning towards the boiler. Berlin's comment re: the air damper...duh...I kind of forgot about that aspect, being able to really clamp down on the fire by controlling the O2.

Living off the grid is a necessity not a luxury for me. I've done it for 12 years in my last home. Its amazing how well you can live without using a lot of electricity. You do a lot of conservation and using alternative systems like propane refrigerators, on demand hot water, etc and the simple things like compact florescents. My last system had four 6-volt batteries wired in a 12 volt system with an inverter/charger. I primarily relied on a 3000 watt honda generator (still running after over 10yrs) for my power to charge the system. On average I ran it 9hrs per week to provide all my electrical needs. It equated to an electrical bill of about 10-15 gals of gas a month...pretty good these days.

Back to burning coal...I believe I've figured out how to arrange a system with 120v zone control valves (avoid the transformer drain) and wire them in conjunction with the circ pump so that it only comes on when a zone control valve opens or when I need to dump excess heat to the garage slab. I keep it as a simple open loop system by installing a make up reservoir above the highest point in the system and letting it vent through it. I will also likely route the drain from the PRV into the firebox, others around here have had success with it...a good way to cool down a overheated fire. All this combined with a thermal air supply damper an I think I've got a good thing going.

In the end the only real electrical draw is the circ pump and only when called for. I may splurge and spring for an autostart function on the next generator...they automatically start when the battey voltage drops below a given set point. After reading other "off grid" pubs I think the general consensus is that it is always more efficient to move fluid rather than air.

I'll be sure to keep the forum posted on my progress. Thanks again for the input and feel free to send more.

Here is some info for you EFM has a dealer up in Alaska they make Hot air furnace Hot water boiler and steam they use Anthracite coal . They also are making a Bituminous Stoker boiler . They have a WCB-24 boiler aswell Coal & wood hand fed . check there link out below . You can also contact Blaschak coal company they my have a dealer up there not sure
I know they have dealers in 37 states not sure abot Alaska .
http://www.efmheating.com/dealers.html#ak

http://www.blaschakcoal.com/html/home.htm

coal berner:

I checked out the EFM site but I didn't see anything on the WCB-24...any suggestions?

Alaska_Range wrote:coal berner:

I checked out the EFM site but I didn't see anything on the WCB-24...any suggestions?

Yea they need to update there site Try here and PM stoker -man he will send you out info

The Re-introduction of the efm WCB-24

http://nepacrossroads.com/member/stoker-man/

i have a off grid house i'm heating with a hs tarm boiler via wood (i can use coal)

i run a 600 gallon pressurised system.

look into el sid pumps @ 12v they draw less than 1a.

i fire the boiler anywhere from once a day to once a week depending on the outside temp

if it's around 20ºf i can go three days between fires.

a fire is usually 8-12hrs

i use flow check valves and el sid pumps on each zone instead of zone valves.

in the future i may convert a stoker boiler to run on 12v dc.

Sting wrote:maybe consider reviving the art of gravity flow hot water distribution

My house had gravity-fed radiators for years. Boiler got hot, radiators got hot, very simple and it worked flawlessly. The radiators heated more evenly and almost as fast as with the modern circulator-pump system that replaced it. The new one may be more efficient, but that's due to boiler/oil-burner efficiency, not the circulation system. I think a gravity system requires greater water volume within the boiler than with forced circulation, but I could be wrong on that.