How far to place an outdoor wood boiler from the house depends greatly on the manufacturer and the size of the unit. Every manufacturer has specific recommendations for each of their models. Central Boiler, a manufacturer of outdoor wood boilers, states that their boilers can be placed within 30 to 500 feet from a house, business or other structure.
Zoning regulations, if any, dictate the minimum distance from an outdoor wood boiler to the house or other structures. In order to prevent fines and other legal action; outdoor wood boilers must be installed to comply with zoning laws. In some areas outdoor wood boilers are banned due to concerns about air pollution.
Review the manufacturer's recommendations for your particular outdoor wood boiler and compare it to the zoning regulations. Install the boiler so that it complies with local zoning regulations and meets the manufacturer's recommendations.