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

A pictorial diagram shows all connections plus the approximate physical location of devices in the unit (and often wire colors), while a ladder diagram shows the order of component operation as horizontal rungs (individual circuits with loads and controls) between two vertical power lines, with devices near the top energized first.

K-value is heat passing through one square foot of material one inch thick per hour per 1°F difference (Btu·in/hr·ft²·°F), while C-value is based on the material's actual measured thickness rather than a standardized 1-inch thickness.

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

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

Galvanized pipe is treated with zinc anticorrosion material and used primarily in water systems to prevent rust, while black pipe is usually less expensive and used for gas lines and applications that do not carry water.

Three-phase supply is already phase-split (phases peak at different times, so power is constant and never all zero), so no start windings or capacitors are needed, whereas single-phase motors require start components for phase splitting.

The subcooling method is used on systems with thermostatic expansion valves (low subcooling suggests undercharge, high suggests overcharge), while the superheat method is used on fixed-orifice systems such as capillary tubes.

An SSR switches electronically using transistors, SCRs, or triacs with no physical movement of mechanical parts (typically to start single-phase motors), whereas electromagnetic relays switch with mechanical contacts.

Turning the range screw clockwise raises both cut-in and cut-out pressures equally (differential unchanged), while the differential adjustment turned clockwise raises only the cut-out pressure and does not affect cut-in.

In a hot-surface ignition system the glow coil only ignites and cannot sense flame; a separate flame rod proves flame by rectification (a dirty/oxidized rod causes shutdown a few seconds after the gas valve opens), and thermocouples are used in standing-pilot systems, not HSI.

Per the IECC, maximum leakage is 3 cfm per 100 ft² of conditioned space when tested before the air handler is installed, versus 4 cfm per 100 ft² when tested with the air handler installed.

Connecting at the liquid line recovers refrigerant already in subcooled liquid form (faster recovery), while the discharge service valve delivers superheated high-pressure vapor, making recovery slower and less efficient.

IFGC Section 305.5 requires a minimum 6 ft clearance above the floor in private garages versus 8 ft in public garages, with an exception where the appliance is protected from motor vehicle impact and installed per Section 305.3.

A radial system runs individual branch ducts directly from the central plenum to each outlet with no trunk duct, while a perimeter loop system is used with downflow furnaces in slab homes without basements, with branches feeding a perimeter duct embedded in the slab.