D Definitions

Definition Categories


The damper is a piece of ferrous metal that seals the firebox or chimney from the outdoors. The damper is usually located in the fi replace throat, but it may be located anywhere between the throat and the top of the chimney.

Dead front (dead front cover)

A dead front means that a person cannot come in contact with energized components protected by a dead front cover. The term dead front cover usually describes part of an electrical cabinet that when removed allows access to energized parts.

Developed length

Developed length is the length of a pipe measured along the center line of the pipe including fittings. Developed length may be increased to account for losses caused by fittings. Examples of increasing developed length to account for fittings include water supply pipe sizing, gas supply pipe sizing, and calculating the length of clothes dryer exhaust duct.

Direct vent appliance

A direct vent appliance obtains all combustion air directly from the outside and vents all combustion gasses directly outside.  Combustion air intake and venting usually occurs through a short length of concentric pipes run through a rear or side wall near the appliance.

Draft inducer

A draft inducer is a device that pulls combustion products by suction through a vent or through an appliance. A vent draft inducer will usually be located near the vent termination. An appliance draft inducer will usually be located near the final exhaust point of the appliance combustion chamber. Most modern medium efficiency gas furnaces are induced draft appliances.

Drain pipe

Drain pipe usually refers to the pipes inside the building that take soil and waste to the building sewer pipe.