UL 378

These requirements apply to the design and construct ion of draft equipment intended to assist in maintaining the desired combustion chamber draft in heating appliances. Draft equipment classifications include draft regulators , automatic damper controls, and draft fans for inducing draft.

Draft regulators are intended for installation in the breeching or flue pipe of heating appliances where a constant draft is desired, but function to regulate draft only when the draft in the chimney is greater than the draft for which the automatic damper is adjusted.

Draft regulators intended for use with liquid, combination gas-liquid, or solid fuel-burning equipment, which provide means for the relief of positive pressures in the flue pipe into the adjoining space, provide arrangements for the installer to interlock the assembly with automatic fuel-burning equipment in a manner which will prevent the continued operation of the fuel-burning equipment for more than a brief period of time under conditions of sustained positive draft.

Draft regulators which provi de means for the relief of positive pressures in the flue pipe into the adjoining space and which do not provide means for interlock as described above are intended for use only with commercial-industrial gas-burning equipment not ordinarily equipped with a draft hood.

Automatic damper controls are designed to automatically regulate the position of dampers installed in the flue pipe or combustion air intake of heating appliances to regulate available draft or combustion air supply to desired values.

Draft fans are intended for installation in the flue pipe or breeching adjacent to heating appliances or to chimneys to induce or create a d raft to supplement the natural draft created by the chimney. Fan units may include automatic dampers or automatic damper control