Equivalent round diameter
API · /ductwork-api
HVAC Ductwork API
healthy
3,153 Subscribers
HVAC duct-sizing maths as an API, computed locally and deterministically — the duct dimensions an installer or designer sizes a system with so the air moves quietly and efficiently. The round-duct endpoint gives the round duct for an airflow at a target velocity: area = airflow ÷ velocity (CFM ÷ ft/min = ft²), then diameter = √(4·area/π) — 400 CFM at a 700 fpm trunk velocity wants about a 10.2-inch round, rounded up to the next 12-inch trade size. The velocity endpoint gives the air speed inside a duct from the airflow and its size, round or rectangular — 400 CFM through a 12 × 8 duct runs at 600 fpm, comfortably quiet, while the same air in a 10-inch round moves at 733 fpm. The equivalent endpoint gives the equivalent round diameter of a rectangular duct by the ASHRAE relation De = 1.30 · (a·b)^0.625 ÷ (a+b)^0.25, so a 12 × 8 rectangular carries the same air at the same friction as a 10.7-inch round — letting you size on a round friction chart and convert to fit the space. Everything is computed locally and deterministically, so it is instant and private. Ideal for HVAC-design and installer apps, duct-sizing and takeoff tools, building-services calculators, and trade-school aids. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 compute endpoints. For room air changes use a ventilation API; for the cooling/heating load use an HVAC API.
api.oanor.com/ductwork-api
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 81 ms
- Server probes · 24h
- Subscribers
- 3,153
- active
- Total calls
- 76
- last 7 days
Pricing
Pick a tier — billed monthly, cancel anytime.
Free
Free
- 450 calls / month
- 2 requests / second
- Hard cap (429 above quota, no overage)
- 450 calls/month
- 2 req/sec
- Round duct + velocity + equivalent
- No credit card
Starter
€5.80 /month
- 12,000 calls / month
- 6 requests / second
- Hard cap (429 above quota, no overage)
- 12,000 calls/month
- 6 req/sec
- ASHRAE equivalent diameter
- Email support
Pro
€18.10 /month
- 78,000 calls / month
- 15 requests / second
- Hard cap (429 above quota, no overage)
- 78,000 calls/month
- 15 req/sec
- Design & takeoff pipelines
- Priority support
Mega
€53.40 /month
- 255,000 calls / month
- 36 requests / second
- Hard cap (429 above quota, no overage)
- 255,000 calls/month
- 36 req/sec
- Platform scale
- Dedicated SLA
Built by
Related APIs
Other APIs with overlapping tags.
HVAC Air-Side Load API
HVAC air-side heat maths as an API, computed locally and deterministically with the classic standard-air factors — the sensible, latent and airflow numbers a mechanical engineer or HVAC technician sizes ducts and equipment with. The sensible endpoint gives the sensible heat an airflow carries to change temperature: Qs = 1.08 × CFM × ΔT (dry-bulb difference), where the 1.08 bundles standard-air density and specific heat — 2,000 CFM across a 20 °F difference is 43,200 BTU/hr, 3.6 tons — with the result in BTU/hr, tons and kW. The latent endpoint gives the latent (moisture) heat: Ql = 0.68 × CFM × ΔW, where ΔW is the humidity-ratio difference in grains of water per pound of dry air, the dehumidification part of a cooling load that runs high in humid climates and from people and cooking, and why air conditioners are sized on total, not just temperature. The airflow endpoint inverts the sensible relation: CFM = sensible load ÷ (1.08 × ΔT), the supply air needed at a chosen supply-to-room temperature difference (comfort cooling runs ~18–22 °F below room), the number that sets fan and duct size — sanity-checked against ~400 CFM per ton. Everything is computed locally and deterministically, so it is instant and private. Ideal for HVAC-design and load-calc tools, mechanical-estimating and commissioning utilities, and building-engineering apps. Pure local computation — no key, no third-party service, instant. Standard-air factors — adjust for altitude. 3 compute endpoints. For room rule-of-thumb sizing use an HVAC API; for moist-air properties a psychrometric API; for duct sizing a ductwork API.
api.oanor.com/hvacload-api
Electric Motor FLA API
Electric-motor electrical maths as an API, computed locally and deterministically — the full-load-current, NEC-sizing and starting-current numbers an electrician, panel designer or estimator runs for every motor circuit. The full-load-amps endpoint gives the motor current from its power, voltage and phase: FLA = (output ÷ efficiency) ÷ (√3 × volts × power factor) for three-phase (drop the √3 for single-phase) — a 10 hp, 460 V, three-phase motor at 90 % efficiency and 0.85 power factor draws about 12.2 A — and it also returns the input kW and kVA. The sizing endpoint applies NEC Article 430 from the full-load current: branch-circuit conductors at 125 %, overload protection at 115–125 % by service factor, and branch-circuit short-circuit/ground-fault protection up to 250 % for an inverse-time breaker or 175 % for a time-delay fuse — the larger protection lets the inrush pass while the overload guards the windings. The starting endpoint gives the locked-rotor (inrush) current, about six times full-load for an across-the-line start, the figure that sets the voltage dip and why soft starters and VFDs exist. Everything is computed locally and deterministically, so it is instant and private. Ideal for electrical-design and estimating tools, panel-builder and field utilities, and engineering calculators. Pure local computation — no key, no third-party service, instant. Calculated values — use the NEC FLC tables for code work. 3 compute endpoints. For general three-phase power use a three-phase API; for conduit fill a conduit API.
api.oanor.com/motorfla-api
Heat Pump COP API
Heat-pump and refrigeration performance maths as an API, computed locally and deterministically — the efficiency numbers an HVAC engineer, energy auditor or heat-pump installer actually works with. The cop endpoint gives the coefficient of performance and the US EER rating from the thermal capacity and the electrical power: a unit moving 7 kW of heat on 2 kW of electricity has a COP of 3.5 (an EER of 12), meaning 3.5 units of heating or cooling for every unit of electricity — which is why a heat pump beats resistance heating, where the COP is exactly 1. The carnot endpoint gives the unbeatable ideal limit set only by the absolute temperatures — heating = Th ÷ (Th − Tc), cooling = Tc ÷ (Th − Tc) in kelvin, where heating COP always equals cooling COP plus one — and, given a real COP, the second-law efficiency that says how close the machine runs to that ceiling; the smaller the temperature lift, the higher the limit, which is why ground-source and low-temperature systems beat air-source on a cold day. The capacity endpoint turns electrical power and a COP into the delivered heating or cooling in kilowatts, BTU per hour and tons of refrigeration — the extra energy over the electricity is pulled from the outside air, ground or water. Everything is computed locally and deterministically, so it is instant and private. Ideal for HVAC and refrigeration engineers, energy auditors, heat-pump and building-performance tools, and sustainability dashboards. Pure local computation — no key, no third-party service, instant. Estimates at the stated conditions — real COP falls as the temperature lift rises. 3 compute endpoints. For room sizing use an HVAC BTU API; for moist-air properties use a psychrometric API.
api.oanor.com/heatpump-api
Steam Boiler API
Steam-boiler engineering maths as an API, computed locally and deterministically — the three numbers a boiler operator, plant engineer or steam-system designer actually works with. The boiler-hp endpoint converts a required heat output into boiler horsepower (heat ÷ 33,475 BTU/hr, the standard definition), the equivalent steam output in pounds per hour "from and at" 212 °F (34.5 lb/hr per BHP) and the output in kilowatts — a 1,000,000 BTU/hr load is about 29.9 BHP or 1,031 lb/hr of steam. The factor-of-evaporation endpoint gives the real capacity for your feedwater: the factor = (the total heat of the steam − the feedwater heat) ÷ 970.3, always greater than one because the boiler must add the sensible heat to bring water up to boiling, so a boiler rated "from and at" 212 °F actually makes less with 60 °F feedwater — which is exactly why preheating feedwater with an economiser raises capacity and saves fuel. The blowdown endpoint gives the continuous blowdown rate to hold the boiler water within its dissolved-solids limit: blowdown = steam × feedwater TDS ÷ (boiler limit − feedwater TDS), with the cycles of concentration and the blowdown as a percentage of feedwater — better feedwater means more cycles, less blowdown and less wasted hot water. Everything is computed locally and deterministically, so it is instant and private. Ideal for boiler operators, steam-plant and HVAC engineers, energy auditors, water-treatment specialists and process-engineering tools. Pure local computation — no key, no third-party service, instant. Engineering estimates — verify against the manufacturer data and local code. 3 compute endpoints. For moist-air properties use a psychrometric API; for compressed air use a compressor API.
api.oanor.com/boiler-api
Frequently asked questions
Quick answers about pricing, quotas, and integration.
How do I get an API key for HVAC Ductwork API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call HVAC Ductwork API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for HVAC Ductwork API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does HVAC Ductwork API cost?
HVAC Ductwork API has a free tier with 100 calls / month. Paid plans start at €5.80 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is HVAC Ductwork API GDPR-compliant?
All requests to HVAC Ductwork API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.
Pick an endpoint from the list on the left to see its details and try it.
Code snippets
Sign up to get an API key, then call any path under your slug.
curl https://api.oanor.com/ductwork-api/SOME_PATH \
-H "x-oanor-key: oanor_test_..."const res = await fetch("https://api.oanor.com/ductwork-api/SOME_PATH", {
headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();$ch = curl_init("https://api.oanor.com/ductwork-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);import requests
r = requests.get(
"https://api.oanor.com/ductwork-api/SOME_PATH",
headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())Ratings
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