Draft Control Installation Options
Recommended Locations for Field Draft Controls
For gas-fired equipment, the preferred location of the control is on the bull head tee. This location provides maximum relief of downdrafts with minimum positive pressure. (See Figure 1, Diagram A-C)
With oil or solid fuels, the bull head tee is not recommended, so locate the control as shown. (See Figure 1, Diagram D-J) These locations are acceptable for gas units as well. Except on forced draft systems, locate the control as close as possible to the furnace or boiler, at least 12" beyond a stack switch on oil-fired units, and at least 18" from a combustible ceiling or wall.
Multiple Appliance Location Recommendations
Commercial and industrial furnaces and boilers are frequently installed in multiples. (See Figure 2) Use a draft control for each boiler located on the uptake between the smoke outlet and the breach (location A). When this uptake is too short to permit the installation of a control, locate a separate control for each boiler on the main breach (location B). If neither of these locations is possible, use a single large control in the breaching between the chimney and the nearest boiler (location C). Where several units are vented into a common breaching, the most draft-critical should vent highest in, or be placed closest to the chimney. Incinerators should generally be placed farthest from, or vented lowest in the chimney.