Outside Wood Boiler-Furnace Installation Tips

As I write this, it is twenty degrees outside, and my family and I are nice and toasty! Best of all it's cheap! Cheap! Cheap!! I am fortunate enough to have an inexpensive supply of wood, but even if I didn't, it would still be less costly compared to buying heating oil, natural gas or propane.

An outside wood boiler, also known as an OWB, or an outdoor wood burner, does not actually "boil" the water. Water temperatures never reach boiling, and wood boilers commonly operate in the 160-185 degree range. The water is heated in the boiler and is circulated by pump through a pair of one inch pipes to your home, where the heat is transferred via a heat exchanger to your existing system. The existing system may be a forced air or hot water/boiler system.

Smoke Pollution is a nuisance for some outside wood boilers depending upon your location, and is also the single biggest point against their use. There is no way to entirely eliminate smoke, however you can signifigantly reduce it by following these suggestions:

*Size the heat exchanger correctly, or turn down the thermostat on the boiler. Overkill is a waste! If you find that your indoor water temp is around 140 degrees, you may be wasting wood, and creating unecessary smoke. You will also be shortening the lifespan of the wood boiler. The less you have to open the door to add wood, the less heat you waste. I run my water around 120 degrees. I am amazed at the diference in wood intake. Maybe on a smaller home it isn't as signifigant, but on my monstrosity of a house, it was very noticable.

*Adding a fan near the bottom of your exhaust stack helps move and disperse the smoke.

*Lengthening the exhaust stack as much as possible will keep the smoke higher, also helping to disperse.

*One of the biggest "stretches" by wood boiler manufacturers is the concept of how often you add wood. I've heard it said, add once every 12 hours, 24 hours up to 96 depending on the efficiency and size of your home, as well as the wood or biomass boiler model. It is true that you can add a bunch of wood and walk away for many hours. However, I've found that you will get a better, less smokey burn, by adding wood more frequently in smaller amounts. Bad burn practices creates angry neighbors, which in turn leads to poor public opinion and perception of outdoor wood boilers. If more first time wood boiler users are aware of this from the start, this tip alone will save tons of headache.

The brazed plate heat exchanger pictured here is used for hot water applications, and a water to air heat exchanger is used in forced air applications. You can save big bucks buying these direct on the net. You will pay a premium if you purchase them with your "installation kit."

The same principle of premium pricing applies for the feed and return lines, as well as the fittings, and pump. In addition to the wood boiler sale, the dealer is making a very sizeable markup on accessories. Watch out for fittings and hoses that are exclusive to the manufacturer! The fittings and tools can be very expensive and you will find yourself calling the dealer to do the final hook-ups. Fittings, hoses and associated tools can be purchased at most major home improvement stores.

Side Arm Heat Exchanger. A sidearm exchanger will heat hot water for home use, saving a ton of money in electricity or gas. It is used with your existing hot water heater, and as with the plate heat exchanger, and the water to air heat exchanger, the water from the outside wood boiler does not mix with the potable hot water. The dealer may offer a sidearm heat exchanger as an accessory, however there are a number of these available on E-bay and through online vendors that are often better priced. Check the e-bay listings I've provided if you like.

Hot water lines to and from the outside wood boiler. The dealer will be happy to sell you this item and the price tag can add up very quickly! Around 5 to 6 dollars a foot for pre-insulated. If you are patient, you can buy and insulate the lines yourself like I did and can use more common fittings and crimping tools from the larger hardware stores. One of the more common brands of water lines is called Pex.

Base for the furnace. After an outside wood boiler is installed and filled up with water it can be extremely heavy. I placed mine on concrete but many dealers offer a pre-fabbed base.

Water to Air Heat Exchangers used with outside wood boilers or furnaces are installed inside the plenum of forced air heating systems. Most manufacturers offer instructions on how to accomplish this. The furnace fan blows through the water to air heat exchanger and heats the air inside the duct work. Installation tip: the nipple that is closest to the fan must be the return to the outdoor wood furnace. The nipple farthest away from the fan must be the hot water feed. Reversing this will decrease the efficiency of the exchanger!

A correctly sized water to air heat exchanger will be one inch smaller then the size of the the plenum. For example: If the plenum measures 20x20 then purchase a 19x19 heat exchanger. The Water to Air Heat exchanger can be placed on a shelf inside the plenum. The shelf is made of 90 degree angle iron or sheet metal attached on three sides. The video below is a great example of a typical Water to Air Heat Exchanger used in an Outside Wood Boiler-Furnace Installation.

It is alot more fun to saw wood, then to saw off digits and appendages or get bit by a flying wood chip. I highly recommend chaps and headgear. It only takes a minute to be safe, but you can carry an injury around permanantly!