Project Numero Uno: Wood Boiler

| by | construction, sustainability, wood boiler | 4 comments:

So we decided that our first project would be to install a wood boiler. This way we’ll be able to heat the house, hot water, and greenhouse with wood instead of burning oil or gas. Unlike oil or gas , wood is a renewable and cheap/free resource. We got plenty of it, and haven’t had to chop down a live tree yet, only standing dead ones.  The boiler burns wood slowly and very efficiently using a natural draft system, and it doesn’t release large amounts of carbon dioxide into the environment like most heating systems do.

For a while, Dave was planning to build our boiler himself, he’s a welder, and there are plenty of plans online. However, after a lot of consideration, we decided it would be the best use of money and Dave’s time to just purchase a high efficiency factory made wood boiler. There are many great wood boilers out there. We ended up going with a Central Boiler. We chose it mainly because it was the simplest of all the boilers we looked at. It had the least amount of moving parts that could break and the simplest maintenance and upkeep. It also has a steel firebox and water jacket so Dave will be able to easily weld it for repairs if it ever needed it.  Other boilers had lots of bells and whistles, but that’s just not our style. We did the math and compared to the cost of using the house’s existing heating oil system and the wood boiler will pay for itself in 4 to 5 years. Save a big bucket of money, AND a reduction of our carbon footprint? It’s a win-win. So the installation process begins…

After we decided on the perfect place for the boiler, the first step was to pour the pad. So one weekend, we invited our good friends Greg from the Cassilly Crew and Tucker’s step-dad Denny Babor from Babor Properties LLC out to the farm to help.

First we leveled the ground as best we could and tamped it down solid. We also dug a small trench around where the pad would be that will get filled with gravel later. This will let rain water break around the pad so it drains nicely. Then we set the forms to the size Central Boiler specified making sure to leave a proper sized notch cut out so we could easily run all the hot water thermo-pex and electric into the boiler. We also added an extra 4ft by 4ft place to stand on the front of the pad so we wouldn’t have to stand in the mud everyday while we’re filling the boiler with wood.  Then we wire tied all the rebar and propped it up on rocks about 2in. We figured we only needed to make the pad 4in thick instead of the usual 6in slab since it just has to hold the boiler and is never going to see any traffic. Now we’re ready to pour some concrete.

Setting the form for the wood boiler pad
Dave and Greg setting the form for the wood boiler pad

Dave and Greg used an old barrel mixer from the farm and about 30 bags of QuickCrete for the pad. They didn’t worry about a slick finish and just used a sidewalk brush for traction.

Dave and Greg pouring the pad using the concrete mixer from the farm.
Dave and Greg pouring the pad using the concrete mixer from the farm.
I tried to help.
Autumn helped… she did.

Now that the pad was poured, it was time for the truly fun part of this project. Digging a big, long, stupid trench across the whole front yard and punching a hole through the foundation. This would become yet another noodle in the underground plate of spaghetti that is our front yard… seriously, we’ve buried a lot of shit. Anyway, Missouri’s free utility location service, Dig Rite (call before you dig!) would only find some of our buried utilities. So we weren’t exactly sure where the power and water lines running to and from the well were exactly at or how deep they were. Instead of springing for a private location service, and renting a trencher which are both pretty pricey, Dave decided to just dig it by hand. “It’s only 100 feet.”  This was a really bad idea. Our only saving grace was that the thermo-pex is so well insulated it didn’t need to be buried 3 ft deep below the frost line. Only 18 inches.

A day and a half (and a lot of cursing, sweating, shoveling, picking, and money saving) later, the trench was dug, and the boiler was delivered and placed on the pad. Now we just have to lay the thermo-pex in the trench, hammer drill through the foundation of the house, shove one end of the thermo-pex through the hole into the basement and connect the other to the supply and return on the boiler. Almost there!

Stupid trench.
Stupid hand dug trench.

The next step was pretty cut and dry, Dave hammer-drilled a hole through the foundation of the house and into the basement. This is easy to do, and easy to fuck up. The best way to go about it is with a horizontal core drill. But if you don’t have the money to rent one, a good alternative is to mark out your hole with spray paint so it can’t rub off, drill a center hole first and stick another drill bit in the hole to use as a guide. Then, use that guide to aim all your other holes as you drill around the edge of the circle. Lastly, use a chisel bit to bust out everything between your holes. This way you won’t intend on drilling an 8in hole and wind up with a 1ft lopsided cone on the other side and look like an ass in front of all your friends.

Hammer drilling a hole for the thermo-pex through the foundation.
Hammer drilling a hole for the thermo-pex through the foundation.

Now we had to shove the thermo-pex through the hole in the foundation and run it in the trench that we dug. This was not hard to do but was also not easy to do. Thermo-pex is extremely insulated and really efficient but it is not very bendy.

See? Not bendy.
See? Not bendy.

Now that the thermo-pex was ran into the house, we sealed the hole around it in the foundation with hydraulic cement so that our foundation would not leak. After that, it was plumbing time.

thermo-pex coming through the foundation into the house with the hole all sealed up with hydraulic cement
thermo-pex coming through the foundation into the house with the hole all sealed up with hydraulic cement

Next is the last and most important step! Properly plumbing the supply and return from the boiler to your hot water heater and home heating system can be kind of complicated. Luckily for us, Central Boiler had really great directions and our dealer, Larry Baumen, from Baumen Wood Heating gives really great advice. I’m not going to try to explain all the complex plumbing and if you do not have much experience soddering copper pipe or assembling complex plumbing systems, I would hire a professional for this part. Fortunately for us, Nemo has a lot of plumbing experience, Dave has a little, and they were able to sort it all out.

Pex going into the house
The Pex lines going up behind the wall from the thermo-pex into the mixing valve with spigots to drain just in case.
Here's the heat exchanger mounted in the plenum above the blower fan. The old oil heater is still hooked up as a backup but we've never had to use it.
Here’s the heat exchanger mounted in the plenum above the blower fan. The old oil heater is still hooked up as a backup but we’ve never had to use it.
Hot water tank in the basement. The black vertical tube is the heat exchanger. We hooked up its electric heater too as a backup but we've never had to use it.
Hot water tank in the basement. The black vertical tube is the heat exchanger. We hooked up its electric heater too as a backup but we’ve never had to use it.

The supply and return hook up on the boiler itself were clearly marked and the Pex lines and pump were easy install. We suggest using either using the Pex clamps that can be tightened down with a wrench or borrowing the right size pex crimper from a friend and using the crimped clamps. Pex crimping tools are ungodly expensive and theres no need to buy one for just one job. However, the wrench-able pex clamps are more expensive than the crimping rings. It’s your call.

Here’s how our wood boiler basically works, the firebox is loaded with wood which burns and heats the water in the water jacket that surrounds it. Our boiler keeps the water around 180 degrees using a natural draft system and a thermostatically controlled solenoid damper on the door. The hot water from the boiler’s water jacket is pumped underground through the thermo-pex and into the house. First the water travels through a mixing valve we hid behind a wall and than across the celling to a regular home hot water tank in the basement.  The tank is outfitted with a special manifold and heat exchanger. Some of the water’s heat is transferred to the water in the hot water heater tank through the heat exchanger, providing the house with hot water. The water then makes its way through another heat exchanger that is mounted in the plenum just above the blower in our existing HVAC system. The blower blows across the hot copper heat exchanger, blowing hot air into the house through the existing ductwork. We also put a bypass on the hot water tank so we can still have hot water in the summer but not heat the house. Finally, the now much colder water heads back out to the boiler to be heated again and BAM! Burning wood now heats the house and the hot water. Our math shows our system will pay for itself in 4-5 years. Suck it, electric company! Get bent, heating oil company! Get out of our pockets!

Aaaaawwwww shit! Wood boiler!!! What what what?!?!?
Aaaaawwwww shit! Wood boiler!!! What what what?!?!?

4 Responses

  1. December 27, 2012

    This is so badass. You guys are hardcore!

  2. February 1, 2013

    […] the manifold. The manifold controls the hot water that comes into the greenhouse from the wood boiler. From the manifold, hot water (heat) goes into the floor, and later (whenever we set it up) under […]

  3. March 7, 2013

    […] greenhouse is radiantly heated from the floor via hot water provided by our wood boiler which is fantastic except for the fact that our “automatic” window ventilation system does not […]

  4. June 27, 2013

    […] ain’t our first rodeo. We’ve had to pour a lot of concrete out here. The pad for the wood boiler, the pad for the greenhouse, replacing drain pipes in the basement floor (that sucked), putting a […]

Leave a Reply