{"uid":"cap_UgkwliVQcy98arg0XbOgX","slug":"hvac-coil-load-calculator-e4ba3784","name":"HVAC Coil Load Calculator","description":"HVAC coil load calculator: from airflow and entering/leaving air (any two properties each), the sensible, latent and total load, tons, SHR and condensate; or one state plus loads to solve the other. Outdoor/return air mixing and outdoor air % back-calculation. ASHRAE psychrometrics, elevation, IP or SI. Shows every step with the numbers. $0.002 USDC per call.","url":"https://x402-agent-api.onrender.com/api/v1/hvac-coil-load?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"mode":{"enum":["cooling","heating"],"type":"string","description":"When solving a state from loads: cooling (default) removes heat, heating adds it. Detected automatically when both states are given."},"units":{"enum":["IP","SI"],"type":"string","default":"IP","description":"\"IP\" (°F, CFM, in, BTU) or \"SI\" (°C, L/s, mm, kW). Default IP. Applies to inputs and results."},"airflow":{"type":"number","description":"Total airflow through the coil: CFM (IP) or L/s (SI).","exclusiveMinimum":0},"leaving":{"type":"object","properties":{"grains":{"type":"number","minimum":0},"dry_bulb":{"type":"number"},"enthalpy":{"type":"number"},"wet_bulb":{"type":"number"},"dew_point":{"type":"number"},"humidity_ratio":{"type":"number","minimum":0},"relative_humidity":{"type":"number","maximum":100,"minimum":0}},"description":"Air leaving the coil: two properties, like `entering`.","additionalProperties":false},"entering":{"type":"object","properties":{"grains":{"type":"number","minimum":0},"dry_bulb":{"type":"number"},"enthalpy":{"type":"number"},"wet_bulb":{"type":"number"},"dew_point":{"type":"number"},"humidity_ratio":{"type":"number","minimum":0},"relative_humidity":{"type":"number","maximum":100,"minimum":0}},"description":"Air entering the coil: exactly two of dry_bulb, wet_bulb, dew_point, relative_humidity (%), humidity_ratio (lb/lb or g/kg), enthalpy (BTU/lb or kJ/kg), grains (gr/lb), in `units`. With outdoor_air and return_air but no outdoor air amount, it is the mixed air and the outdoor air % is back-calculated.","additionalProperties":false},"elevation":{"type":"number","default":0,"maximum":30000,"minimum":-1500,"description":"Site elevation, ft (IP) or m (SI); sets the atmospheric pressure. Default 0 (sea level)."},"return_air":{"type":"object","properties":{"grains":{"type":"number","minimum":0},"dry_bulb":{"type":"number"},"enthalpy":{"type":"number"},"wet_bulb":{"type":"number"},"dew_point":{"type":"number"},"humidity_ratio":{"type":"number","minimum":0},"relative_humidity":{"type":"number","maximum":100,"minimum":0}},"description":"Return air (two properties, like `entering`).","additionalProperties":false},"latent_load":{"type":"number","minimum":0,"description":"Coil latent load, MBH or kW (default 0 when only sensible_load is given)."},"outdoor_air":{"type":"object","properties":{"grains":{"type":"number","minimum":0},"dry_bulb":{"type":"number"},"enthalpy":{"type":"number"},"wet_bulb":{"type":"number"},"dew_point":{"type":"number"},"humidity_ratio":{"type":"number","minimum":0},"relative_humidity":{"type":"number","maximum":100,"minimum":0}},"description":"Outdoor air (two properties, like `entering`), mixed with return_air ahead of the coil.","additionalProperties":false},"sensible_load":{"type":"number","minimum":0,"description":"Coil sensible load, MBH (IP) or kW (SI): with one state, solves the other."},"outdoor_airflow":{"type":"number","minimum":0,"description":"Outdoor airflow, CFM or L/s (instead of outdoor_air_percent)."},"outdoor_air_percent":{"type":"number","maximum":100,"minimum":0,"description":"Outdoor air share of the total airflow, %."}}},"responseSchema":{"type":"json","example":{"mode":"cooling","loads":{"tons":32.736,"total":392.833,"latent":122.833,"sensible":270,"sensible_heat_ratio":0.687,"total_from_enthalpy":399.538},"notes":[],"steps":[{"step":"Atmospheric pressure","reference":"ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics, Eq. 3","calculation":"p = 14.696 × (1 − 6.8754×10⁻⁶ × Z)^5.2559 = 14.696 × (1 − 6.8754×10⁻⁶ × 0)^5.2559 = 14.6960 psia"},{"step":"Entering air state","reference":"ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics","calculation":"pws(67.00 °F wet bulb) = 0.32772 psia (ASHRAE Ch. 1 Eq. 6)"},{"step":"Entering air state","reference":"ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics","calculation":"Ws* = 0.621945 × pws / (p − pws) = 0.014185 lb/lb (saturated at the wet bulb)"}],"units":"IP","mixing":null,"airflow":10000,"leaving":{"grains":60.42,"density":0.07667,"dry_bulb":55,"enthalpy":22.569,"wet_bulb":54,"dew_point":53.29,"humidity_ratio":0.008631,"vapor_pressure":0.20116,"specific_volume":13.1549,"relative_humidity":93.95},"entering":{"grains":78.18,"density":0.07301,"dry_bulb":80,"enthalpy":31.447,"wet_bulb":67,"dew_point":60.32,"humidity_ratio":0.011169,"vapor_pressure":0.25926,"specific_volume":13.8494,"relative_humidity":51.1},"pressure":14.696,"elevation":0,"condensate":13.69,"next_calls":[{"why":"What duct size carries 10000 CFM at 0.08 in. w.g. / 100 ft?","tool":"hvac_duct_size","price":"$0.002","arguments":{"units":"IP","airflow":10000,"friction_rate":0.08}}],"references":["ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics","Standard-air load equations: Qs = 1.08·CFM·ΔT, Ql = 4840·CFM·ΔW, Qt = 4.5·CFM·Δh"],"solved_for":"loads","unit_labels":{"area":"ft²","load":"MBH (1,000 BTU/h)","grains":"gr / lb dry air","length":"in","airflow":"CFM","density":"lb / ft³","enthalpy":"BTU / lb dry air","pressure":"psia","velocity":"FPM","elevation":"ft","condensate":"gal / h","temperature":"°F","friction_rate":"in. w.g. / 100 ft","humidity_ratio":"lb water / lb dry air","specific_volume":"ft³ / lb dry air","relative_humidity":"%","velocity_pressure":"in. w.g."}}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.002","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.002/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_Eoau4N9posQqhwr5Um85f","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.002","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates sensible, latent, and total HVAC coil loads (BTU/MBH/tons), SHR, and condensate from airflow and entering/leaving air states, with full ASHRAE psychrometric step-by-step workings.","exampleAgentPrompt":"Calculate the cooling coil loads for an air handler moving 10,000 CFM at sea level — the air enters at 80°F dry bulb and 67°F wet bulb, and leaves at 55°F dry bulb and 54°F wet bulb. Give me the sensible, latent, and total load in MBH, the tons of cooling, the SHR, and how much condensate it produces, showing all the ASHRAE psychrometric steps.","exampleUseCases":[{"title":"Cooling coil sizing for new AHU","prompt":"I'm sizing a cooling coil for a 15,000 CFM air handler at 5,000 ft elevation in IP units. Entering air is 78°F dry bulb and 65°F wet bulb; leaving air should be 55°F dry bulb and 52°F wet bulb. What are the sensible, latent, and total loads in MBH and tons, the SHR, and the condensate rate?"},{"title":"Back-calculate outdoor air percentage","prompt":"I know my mixed air entering the coil is 74°F dry bulb at 50% RH. My return air is 75°F dry bulb at 45% RH, and outdoor air is 95°F dry bulb at 78°F wet bulb — all at sea level IP units with 12,000 CFM. Can you back-calculate the outdoor air percentage?"},{"title":"Solve leaving air state from known loads","prompt":"I have a heating coil with 8,000 CFM in SI units at 200 m elevation. Entering air is 12°C dry bulb and 8°C wet bulb. The sensible load is 45 kW and latent is 5 kW in heating mode. What are the leaving air conditions — dry bulb, wet bulb, RH, and humidity ratio?"}],"resultDescription":"Returns a JSON object with the resolved entering and leaving air psychrometric states (dry bulb, wet bulb, dew point, RH, humidity ratio, enthalpy, grains, density, specific volume, vapor pressure), coil loads object (sensible, latent, total in MBH or kW, tons, SHR, total from enthalpy), condensate rate, atmospheric pressure, elevation, mode, units, unit labels, step-by-step ASHRAE calculation array with references, any notes, and suggested next tool calls.","failureModes":["Fewer than two psychrometric properties provided for entering or leaving state — returns validation error","Physically impossible air state (e.g. wet bulb above dry bulb) — returns error","Airflow of zero or negative — rejected by schema","Missing both leaving state and loads when trying to solve — ambiguous input error","Elevation out of range (-1500 to 30000 ft) — validation error","Conflicting or overdetermined inputs — may return note or error","Network timeout from Render cold start — retry after a few seconds"],"whenToPreferThis":"Choose this endpoint when you need rigorous ASHRAE-compliant psychrometric coil load calculations with full step-by-step workings, support for both IP and SI units, elevation correction, condensate calculation, outdoor/return air mixing, or reverse-solving (finding leaving conditions from known loads). Prefer over manual calculations or generic psychrometric tools when you need tons, SHR, condensate, and a complete audit trail of every equation used. Use sibling psychrometric endpoint for single-state property lookups without coil load context.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-10T06:42:16.450Z","isFirstParty":false,"canonicalSlug":"hvac-coil-load-calculator-e4ba3784"}