HVAC Heat Load Calculation: Manual Method Mastery

A: Option A lines up with typical office benchmarks used in early-stage checks. People, lighting, and equipment drive sensible load more than the envelope at this scale, so 80–100 W/m² lands you in the right decade. B feels tempting if you're used to low-occupancy spaces, but it ignores plug and occupant density. C is what happens when multiple safety factors get stacked without noticing; it's defensible for poorly defined projects but pushes you out of order-of-magnitude territory. D borrows residential heuristics, and those understate commercial internal gains even if the math looks tidy.

A: A tracks straight to psychrometrics: people add moisture, so the latent fraction rises fast as occupancy climbs. B and C both add sensible heat only, so the sensible ratio moves the other way. D does introduce latent, which is why it looks plausible, but in conference rooms the moisture from people usually dwarfs short-term infiltration unless the envelope is very leaky.

A: A fits when hand calcs assume everything on at once. The VRF runs flat out, yet individual zones cycle because their real load is lower and non-coincident. B and C are real VRF issues, but they'd show up regardless of occupancy pattern. D affects airflow and capacity, but it wouldn't selectively track with usage diversity the way this symptom does.

A: A mirrors how ventilation really behaves on the psych chart: temperature and moisture both matter. B is a shortcut seen on fast projects, but it hides humidity risk. C assumes the system magically absorbs moisture without capacity limits. D confuses seasonal dominance with load existence; summer ventilation latent is often the controlling case.