Outdoor Wood Boiler
Heating oil is expensive, the price is unpredictable, and the price just goes up. Two years ago, when the price of oil spiked, the cost of heating oil went from $2.25 to $4.50 per gallon. Even with a prebuy contract it's not cheap.
I've been thinking of taking steps to decouple myself from the price of oil, and finally jumped in: We bought an outdoor wood boiler (OWB). Though I could tout this as a "green" thing because OWB's are carbon neutral, the overwhelming motivation is financial.
An OWB is simply an outhouse-sized contraption that creates very hot water by burning logs. That hot water is then pumped to the house and used for heating. It's really very similar to our current system, except that instead of burning oil we burn wood.
Two things finally motivated me to do it: (1) A very well-informed friend installed one last year and raves about it, and (2) there's a $1500 federal tax credit that expires at the end of 2010.
The system isn't cheap - it's about $10,000 all in - but if it saves $3,000 a year in oil (a conservative estimate) it will pay for itself in 3 years.
Following my friend's example, we bought a (Central Boiler e-Classic 1400).
Additionally, I'll be building a 12' x 24' woodshed to to feed the beast. It's important to keep the wood dry, so the woodshed will have a simple roof and canvas side coverings.
Note: Click on any picture to see a larger version of it
Here's where the OWB and woodshed will be located:
Clearing the land
December 5, 2010 - I cut down a bunch of trees behind the house to begin clearing the area where the boiler will live.
Then in the Spring:
The boiler arrives
December 9, 2010 - The boiler arrives!
I bought it from the same dealer as my friend, Rick & Donna Young, aka
Farmer-4-Hire. Very nice, helpful folks.
They have a very cool custom trailer built specifically for delivering OWBs:
Click here to see a youtube video of the boiler being unloaded. It weighs aboout 2,000 pounds.
The OWB connects to the house via PEX tubing.
The tubing is in a custom package called ThermoPEX - two 1" PEX tubes inside a 5" flexible pipe that is filled with insulating foam. One tube brings heated water from the OWB, the other tube returns cool water to the OWB to be reheated.
Here's a cross-section of the ThermoPEX:
Our OWB will be about 85 feet away from the house, so I got 90' of ThermoPEX:
At $11/foot, you want to estimate your actual length as closely as possible - that roll cost $1000!
The ThermoPEX will enter the house thru the foundation, so I drilled a pair of holes thru the bottom of the foundation wall:
Of the two holes, the larger 5" one is for he ThermoPEX and the smaller 1.5" hole is for an electrical conduit. The OWB requires a small amount of power for it's controls and circulating pump.
Drilling the holes was incredibly hard work - it took me 3 hours to drill both holes.
You can actually see two 5" holes, one above the other, with the smaller power hole to the right. The bottom 5" hole was my 1st attempt; after an hour of drilling I hit a piece of rebar and had to start over!. I filled the unused hole with cement.
Installation - Spring 2011
The snow has melted and the rain has gone away, so it's time to start installing everything.
I hired a local contractor to so the heavy digging. Here he's digging the trench from the house to the boiler site:
I then laid the ThermoPEX and electrical conduit in the trench:
The ThermoPEX is incredibly difficult to work with - it's very stiff and does not want to unroll.
Here's where the pipes enter the foundation:
The pipes on the inside of the foundation:
(with the ThermoPEX stripped, the electric connected, and the concrete patched)
The pipes reach all the way to the boiler site (of course):
Here's the trench all the way from the boiler site back up to the house:
Next, we planted all the woodshed posts:
I prebuilt a base for the boiler:
This will be filled with rock, then I'll place concrete paving stones over the gravel as a solid base for the boiler.
We used the excavator to move the boiler to the site and lower it onto the pad:
I connected the electric to the boiler (lower left):
I also stripped the ThermoPEX insulation - a messy job.
The PEX is just loose at the moment - I'll trim it after I get the metal piping installed.
The boiler on the pad with the back doors closed:
The entire site with the boiler and posts in place, and the ground cleaned up:
Time for some plumbing!:
Here's the heat exchanger with my fittings that will allow it to mount on the wall:
This thing is big and heavy - all stainless and copper. It must weigh 60 lbs.
The heat exchanger mounted on the boiler room wall:
I attached unions to all four ports just in case I need to remove it some day.
I plan to encase it in insulation in order to keep the heat in the pipes instead of heating the boiler room's air.
Update - June 19, 2011
The chimney is attached and ready to go!
The boiler is all hooked up to the PEX. The pump (green thing on the right) will push the boiler-heated water up to the house.
The other end of the PEX, all plumbed.
The black thing is a thermostat mixer that does some useless thing but you gotta have it for the warranty.
The smaller pipe at bottom fill s the boiler system with water from the house.
Another view of the PEX/copper connections; here you can see the green-handled isolation valves.
The water supply connections, circled in yellow.
Many people fill their boilers with a garden hose, but a friennd hooked his up directly to the house plumbing and that made a lot of sense to me.
Rebuilding the yard from digging the trench, starting with the back path stairs.
The base frame of the woodshed is complete. Next step is to fill it with gravel.
The current backyard scene, looking a bit more put together.
Completed plumbing - July 5, 2011
Yesterday (the 4th of July!) we lost hot water. I went to the boiler room and found that the boiler was cold, and it
would not restart. This had nothing to do with my activities... something just randomly failed. I was planning on doing
the final bit of plumbing (which requires cutting into the exising boiler pipes) later in the summer because I'd need to
turn the boiler off for 24 hours because I'm not interested in working with scalding hot pipes.
I called the boiler maintenance folks 1st thing in the AM and they said they'd be out in a few hours, at which point
I realized that the boiler failure is a blessing in disguise - it gave me the opportunity I've been waiting for!
The first step was to partially drain the boiler because you can't solder pipes that contain water. I just ran a garden house to dump the water outside on the ground:
I then cut the return pipe - no going back now!
I had prebuilt the the recirculating pump assembly so it was just a matter of sticking it in the gap & soldering it up.
I then cut the supply side of the loop:
And soldered in the prebuilt valve/filter assembly:
It took a couple tries to get it all working. Once everything is connected, I have to reopen the water supply line and
wait 10 minutes for the system to refill and repressurize. The first two times I found minor leaks, each of which
required shutting everything down, re-draining the boiler, clearing the pipes of water, and re-soldering the leaky
joint. This is the tedious part of every plumbing job that everyone hates.
The third time was the charm - everything is now at full pressure with no leaks.
And the boiler repair guy arrived just after I had finished (it was minor, just a dirty oil nozzle), so in on fell
swoop I've completed the plumbing AND we have hot water! It was a good day in wood boiler land.
Woodshed - July 23, 2011
Now that the plumbing is done, it's time to finish the woodshed.
The floor of the woodshed will be gravel.
I had 12 yards (55,000 lb!) of 3/4" gravel delivered as far up the woods road as the big dump truck could go:
I then borrowed a friend's tractor to move the gravel the final 200 feet:
It took about an hour and 10 scoops to move it all ... a HUGE time and labor savings over wheelbarrow & shovel!
I dumped it in the woodshed as best as I could; the tractor is actually a bit too big for the job, but hard to complain about the free loan of a tractor:
All the gravel is now dumped in and near the woodshed:
We (mostly Jenny!) then used rakes and shovels to spread the gravel evenly within the woodshed floor:
And started framing:
Splitting wood - August & September 2011
Firing it up - October 2011
It took a few tries to get the boiler water running. I had a couple leaky pipe connections in the boiler room, and I had empty the water (just from the inside pipes), resolder, refill & repressurize a few times.
One joint simply would not stop leaking, so I did what I should have done at the outset: I cut out the fancy copper pipe and clamped a flexible radiator hose in place:
The boiler keeps the water between 170° and 190° F:
When the water falls below 170° the boiler pumps up the fire.
It gets very hot in the firebox... here it's 653° on its way to over 900°.
The hotter the fire burns the more efficient and clean it runs, so the boiler keeps the firebox very hot.
When the boiler brings up the fire, it pumps lots of air thru the coals to start the fire and we get a decent amount of smoke for about a minute:
Then once the firebox gets hot the smoke diminishes greatly:
And once the water is up to temperature the boiler closes the flue and there's no smoke at all.
Here's the inside of the firebox with the logs burning:
Same picture with camera flash, showing how charred the logs get:
The logs burn slowly and completely, and there's very little ash once it's done.
Finally, after everything is running correctly, I packed the boiler's pipe closet with fiberglass insulation to reduce heat loss:
Compare that with the uninsulated closet
With the wood boiler heating things, the lack of oil boiler noise makes the house seem very quiet.
So quiet in fact that at night I hear the faint mechanical sound of the circulation pumps and wonder if it's just the pumps or if the oil burner has fired up (which would indicate the wood boiler's fire has died).
Last night I was lying in bed at 10pm, listening to the house, and wondering if the sound was the pumps or the oil boiler.
I realized that I'd never fall asleep while wondering, so I finally went to the basement and checked the oil boiler (it hadn't run), then got dressed and went out to the wood boiler (it was running perfectly).
This morning I decided that unplugging the oil burner would be the only way I could fall asleep at night without worring about the system.
So now we're on wood ONLY and any sounds I hear CANNOT be the oil burner!