Louisiana Heat, Air Conditioning, Ventilation, Duct Work and Refrigeration

Pictorial diagrams show approximate physical location of devices and wire colors, while ladder diagrams show order of component operation using horizontal rungs between two vertical power lines.

In a series circuit, the same current flows through all loads and any single open breaks the entire circuit; in a parallel circuit (implied by PTC/run capacitor wiring), current takes multiple paths and one path can open without stopping others.

BRI is a specifically diagnosable illness caused by airborne agents whose symptoms do not disappear when the occupant leaves the building, while SBS has no specific identifiable cause and symptoms disappear when occupants leave.

K-value measures heat transfer through one square foot of material at a standardized one-inch thickness per 1°F difference, while C-value is based on the material's actual measured thickness.

ACR tubing is sized by its actual outside diameter, while copper water tubing nominal size equals the outside diameter minus 1/8 inch.

Galvanized pipe is coated with zinc for corrosion resistance and used primarily in water systems, while black pipe is less expensive and used for gas lines and non-water applications.

HSI systems use a glow coil for ignition and a separate flame rod for flame sensing via rectification, while standing-pilot systems use a thermocouple for flame sensing.

A current-limiting fuse uses a temperature-sensitive resistor that opens and resets upon cooling, while a multipurpose fuse combines fast-acting and time-delay properties, blowing immediately only for overloads exceeding 500% of rated current.

A potential relay actuates based on counter electromotive force (cemf) rising in the start winding as the motor approaches speed, while a current relay actuates based on the decrease in run-winding current draw as the motor accelerates.

When tested before the air handler is installed the maximum allowable leakage is 3 cfm per 100 ft² of conditioned space, while with the air handler installed the maximum is 4 cfm per 100 ft².

A radial system runs individual branch ducts directly from a central plenum to each room with no trunk duct, while a perimeter loop system uses ducts embedded in a concrete slab connected to a perimeter loop, typically used with downflow furnaces in homes without basements.

An SSR switches circuits using electronic components (transistors, SCRs, triacs) with no physical mechanical movement, while an electromagnetic relay uses physical mechanical contacts that open and close.