Mechanical, Electrical, and Plumbing Systems
Mechanical
Understand HVAC system types (split, packaged, VAV, chilled water), load calculation, duct sizing, and airflow principles. Know sensible versus latent heat and the role of economizers. Traps: confusing CFM with FPM, and forgetting that duct friction and fittings reduce available static pressure.
Electrical
Study service entrance, panelboards, feeders, branch circuits, and voltage drop. Know the difference between amps, volts, watts, and VA, and how three-phase versus single-phase calculations differ. Understand conduit fill, box fill, and grounding requirements. Traps: applying single-phase formulas to three-phase loads and ignoring power factor.
Plumbing
Know water supply versus DWV systems, fixture units, slope requirements (typically 1/4 in per foot for small drains), venting, and backflow prevention. Understand water hammer, trap primers, and the purpose of cleanouts.
Coordination
Study clash detection, sleeves and penetrations, and firestopping at rated assemblies. MEP rough-in must precede close-in, and coordination drawings prevent rework.
Worked example
A 120 V circuit drawing 15 A uses 1,800 W (P = V x I). For a three-phase load, P = 1.732 x V x I x power factor. A 208 V, 30 A three-phase load at 0.9 PF draws about 9,730 W.
Rule of thumb
Drain lines slope at 1/4 in per foot for pipes 2 in and smaller; larger lines may use 1/8 in per foot.