Indoor Wood Boiler

Since my waterline splice broke (underground) I've been heating the house with an old wood burner salvaged from the barn. It's done a nice job with the exception of two rooms upstairs and the downstairs bathroom. So, my engineering skills are out in full force again - converting this indoor wood-fired stove into an indoor wood-fired boiler. Words of wizdum: never put a water splice underground if you're using pex tubing. Even if you're in a hurry.

Frankly I'm suprised at the lack of information available on the internet to convert a mid-sized free-standing stove to a boiler that'll heat the entire house as well as domestic hot water. I'm sure it's been done & I've heard of add-on units to oil-fired systems. I read a lot of "hey, you're gonna blow that thing up" when it comes to some boiler ideas and yes, they likely woulda blew those things up.

One thing I'm looking forward to is the minimal amount of wood I'll be going thru compared to the large outdoor one I built in 2003 (Central Boiler inspired design). That thing has been very dependable but seemed to go thru more wood than I was comfortable cutting.

Anyway, I built a reserviour to sit on top of the woodburner - it's 14 x 14 x 27 and will hold a capacity of 23 gallons (most likely will keep it at or around 20). Just sitting on top, the water in it heated to 170 but it seemed like the heating took too long to be effective as a boiler. There wouldn't be enough recovery because the furnace fan removes 30 degrees out of the water that goes thru the water to air heat exchanger on every cycle. That's my outdoor boiler figure but it must be pretty much the same.

That is unless I piped water inside the box (which isn't unheard of and standard on some units that you can buy). So, I made a manifold to sit inside of the burn chamber & this will allow the fire to super-heat the water, thus allowing for a quicker recovery of water temperature.
















Here's what it looks like inside the fire chamber now. I don't think there'll be any problem getting water up to temperature quickly with this arrangement.

So far, it's been a fun project. I've got to plumb in the pump & order the motorized actuator and an aquastat for the automated function. Should be nice. In case you're wondering, it is a non-pressurized system so it's safe, too.

The key is to be sure there is no air or steam in the system. Air expands and steam creates dangerous pressure.

The actuator I'm looking at will take 15 seconds to cycle the draft door once the aquastat sends the signal that the water temp is too low. The draft door will open via the actuator and then when the water is up to temp, the aquastat will break the circuit and the actuator will close the draft door by way of spring return which is another safe feature. It'll spring return in case of power outage or failure. Also in 15 seconds for a smooth and quiet operation.

The pics are sizeable so if you're having difficulty seeing because they're a little fuzzy, right-click & select "open in new window".

More pics & updates to follow.