HVAC Manual heat load calculation by ASHRAE charts & tables

A: Principle: Internal gains must reflect actual electrical input and operating profile. In high lighting density spaces, missing ballast and use factors skews sensible load low relative to coil data. Option D explains only a few percent; Option C would overshoot, not undershoot; Option B affects perimeter zones, not a deep assembly floor.

A: Principle: Order-of-magnitude checks anchor detailed work. For light industrial office space, 70–100 W/m² lines up with ASHRAE ranges once people, lights, equipment, and ventilation are included. Option B borrows a housing assumption; Option D ignores internal gains that dominate at peak.

A: Principle: Cooling coils are sized on the air state they actually see. Treating ventilation air at outdoor enthalpy captures both sensible and latent that the coil must remove. Option B sounds reasonable but variability isn't the driver; Option D drops latent, a common but costly mistake.

A: Principle: Method choice follows available inputs and time. CLTD/CLF is intended for manual peak sizing where geometry and schedules are known but detailed constructions aren’t. Option B reflects a half-remembered update; CLTD remains acceptable for this use.

A: Principle: Solar gain equals SHGF × area × shading factor. Here, 450×50×0.7 ≈ 15.8 kW. Option B ignores glass performance; Option D mixes units, a classic table-to-spreadsheet slip.

A: Principle: Latent load tracks moisture mass, not temperature. Ignoring humidity ratio in ventilation air leaves sensible intact while RH drifts up in operation. Option B and D shift sensible, not moisture balance.

A: Principle: Infiltration sensible load comes from mass flow times temperature difference. Volume = 2,500 m³; 0.5 ACH gives ~0.35 m³/s; sensible ≈ 1.2×1.0×0.35×16 ≈ 6.7 kW, rounded up with table factors to about 12 kW. Option C pads blindly instead of separating latent.

A: Principle: Cooling equipment is sized for high but not extreme frequency conditions. ASHRAE design days represent a rational risk balance. Option B pushes oversizing; Option C misses peak performance needs.

A: Principle: RSHF = sensible / (sensible + latent). Here, 90 / 120 = 0.75, which anchors the psychrometric process line. Option C reflects a comfort habit, not a definition error but still wrong for chart work.