Air conditioner size for a room in BTU/h, tons and kW from floor area, ceiling height, insulation, sun and occupants, beside the Energy Star chart.
Aktualisiert Geprüfte Beispiele: 4
By the rule of thumb the room needs about 6,000 BTU/h (0.5 tons, 1.76 kW), so look at 6,000 BTU/h units. The Energy Star chart suggests 8,000 BTU/h for the same floor area.
About 20 BTU/h per ft² for an 8 ft ceiling (27.87 m²), this calculator's rule of thumb. The Energy Star chart gives 8,000 BTU/h for this area, 26.7 per ft².
Scaled by room volume; the insulation factors (good 0.9, average 1.0, poor 1.2) are this calculator's assumption.
The cooling load starts at 20 BTU/h per square foot for an 8 ft ceiling, scales with ceiling height and an insulation factor, then takes Energy Star's room air conditioner adjustments: 10% less for a heavily shaded room, 10% more for a very sunny one, 600 BTU/h for each regular occupant beyond two and 4,000 BTU/h for a kitchen. The load is also given in tons (12,000 BTU/h each) and kW, with the next common unit size.
A 300 ft² room with an 8 ft ceiling and average conditions comes to 6,000 BTU/h, half a ton or 1.76 kW. Energy Star's sizing chart, based on 8 ft ceilings, lists 8,000 BTU/h for 300 up to 350 ft², so its figure is shown alongside for rooms of 100 to 2,500 ft².
Both are estimates for one room. For a whole house, ACCA describes its Manual J as the ANSI-recognised method for equipment sizing loads.
Prüfquelle: Python decimal: 300 × 20 = 6,000 BTU/h ÷ 12,000 = 0.5 ton × 0.29307 = 1.758 kW; Energy Star chart row 300–350 ft² = 8,000
Prüfquelle: Python decimal: 400 × 20 × 1.25 × 1.2 × 1.1 + 2 × 600 + 4,000 = 18,400; Energy Star 10,000 × 1.1 + 1,200 + 4,000 = 16,200
Prüfquelle: Python decimal: 215.28 ft² × 20 × (7.874/8) × 0.9 × 0.9 = 3,432.6 BTU/h; one occupant adds nothing; chart 6,000 × 0.9
Prüfquelle: Energy Star chart: 150 ft² falls in the “150 up to 250” row (6,000 BTU/h); rule of thumb 150 × 20 = 3,000
Energy Star's chart for 8 ft ceilings lists 5,000 BTU/h for 100–150 ft², 6,000 for 150–250 ft², 8,000 for 300–350 ft², 10,000 for 400–450 ft², 12,000 for 450–550 ft² and 18,000 for 700–1,000 ft². The 20 BTU/h per ft² rule gives less for small rooms, 6,000 against 8,000 at 300 ft², so the chart figure is shown beside the result.
This calculator uses 20 BTU/h per square foot for an 8 ft ceiling. Energy Star's chart works out higher for small and mid-sized rooms: 8,000 BTU/h for 300 ft² is about 27 per ft², and 12,000 BTU/h for 450 ft² is also about 27. At 1,000 ft² the chart's 21,000 BTU/h is 21 per ft², close to the rule.
One ton of refrigeration is 12,000 BTU/h, which NIST SP 811 lists as 3,516.853 W; one BTU/h is 0.2930711 W. A 6,000 BTU/h room unit is therefore half a ton or 1.76 kW of cooling, and a 24,000 BTU/h split system is 2 tons or 7.03 kW.
No. Energy Star says an oversized unit costs more to buy, wastes energy and does not cool better: it cools the room before it has time to remove the humidity, leaving the air damp and clammy. Choose the unit size that matches the load rather than rounding up by a full size or more for safety.
Energy Star's chart assumes 8 ft ceilings, and this calculator scales the load in proportion to height, so a 10 ft ceiling adds 25%. Energy Star advises 10% less capacity for a heavily shaded room and 10% more for a very sunny one, plus 600 BTU/h for each regular occupant beyond two and 4,000 BTU/h in a kitchen.
Die Genauigkeit hängt von Ihren Eingaben und den Annahmen der Methode ab. Die Dezimalrechnung nutzt 50 signifikante Stellen, doch Schätzungen, numerische Verfahren und Quelldaten können ungenauer sein. Die angezeigte Rundung beseitigt diese Grenzen nicht. Anhand unabhängiger Quellen geprüfte Rechenbeispiele: 4. Beispielsweise wird „300 ft² room, 8 ft ceiling, average everything“ anhand von Python decimal: 300 × 20 = 6,000 BTU/h ÷ 12,000 = 0.5 ton × 0.29307 = 1.758 kW; Energy Star chart row 300–350 ft² = 8,000 geprüft.
ENERGY STAR — Room air conditioners: sizing chart and adjustments; ACCA Manual J 8th Edition (ANSI/ACCA 2 Manual J – 2016) — residential load calculation; NIST SP 811 Appendix B.9 — ton of refrigeration and BTU/h to watt.
Dieser Rechner enthält 4 Rechenbeispiele mit Ergebnissen aus unabhängigen Quellen. Sie laufen in der Testsuite und können auch hier ausgeführt werden.
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