Network & Power
Rack heat load
Equipment watts → BTU/hr and the cooling airflow the rack room needs.
Every watt an amplifier, switch, or processor draws ends up as heat in the closet. Add the gear (or a total wattage), get BTU/hr, tons of cooling, and the CFM of airflow required for a target temperature rise. Amplifiers get a duty-cycle factor because they rarely run at rated output.
gear in the rack
Enter load as
heat 60 W
heat 44 W · 125 W out × (1/0.90 − 1) + 30 W idle
heat 157 W · 120 W + 10% of 370 W PoE; the rest leaves on the cables
Heat load
890BTU/hr
261 W of heat · 0.07 tons of cooling
W × 3.412 = BTU/hr · ÷ 12,000 = tons · amps at 1/8 duty, 90% efficient
Airflow for 15 °F rise
55CFM
93 m³/h
BTU/hr ÷ (1.08 × 15) — free-air rating; fan trays deliver 40–60% of nameplate once filters and rack impedance are counted
- ▸ Size rack fans at roughly 2× the CFM above to cover filter loading and back-pressure. Pull hot air out at the top; let cool air in low at the front. Blank unused rack units so air goes through gear, not around it.
- ▸ PoE power leaves the rack with the cable and becomes heat at the camera or AP. Only the switch's own draw plus ~10% PSE conversion loss stays in the closet.
- ▸ Amplifier heat is input minus acoustic output. A 4 × 250 W class-D amp at music duty is closer to 45 W of heat than 1000 W — size the room, not the nameplate.
- ▸ If the closet has no mechanical cooling, this heat raises the room temperature until the walls and door shed it. Above ~1000 BTU/hr in a small closet you need a duct or a split unit, not a fan.
heat by device
Each slice is one row's contribution to the total heat staying in the rack. The arrow scales with the airflow needed to carry it away.