Mechanical, Electrical, and Plumbing Systems
What to Master
Know basic HVAC types (forced air, hydronic, split systems, VRF), the refrigeration cycle, and the role of ventilation and exhaust. Understand electrical fundamentals: service, panel, branch circuits, grounding, and GFCI/AFCI protection. For plumbing, know supply versus drain-waste-vent, trap seals, venting to prevent siphonage, and water-heater safety (T&P relief, expansion control).
Traps to Watch
Questions often test that drain lines need slope and venting, and that a trap protects against sewer gas but can siphon without a vent. In electrical, watch for confusion between grounding (safety path) and bonding (joining metal parts). In HVAC, distinguish sensible from latent load and know that oversized equipment short-cycles and dehumidifies poorly. Recall that combustion appliances need makeup air and proper venting.
Worked Example
A bathroom sink gurgles and smells. Rule of thumb: gurgling signals a venting or trap-seal problem, not a supply issue. The fix is verifying the trap has a proper vent and adequate developed length; adding a bigger drain line does not solve siphonage. Similarly, a water heater's T&P valve must discharge to a safe location, never capped.
Key Points
- Drain-waste-vent systems need slope and venting to protect trap seals.
- Grounding provides a fault path; bonding joins metal parts.
- Oversized HVAC equipment short-cycles and dehumidifies poorly.
- Combustion appliances require makeup air and proper venting.
- T&P relief discharge must never be capped or restricted.