# HVAC Psychrometrics Calculator

> HVAC Psychrometrics Calculator is a paid API for AI agents from x402-agent-api.onrender.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-10).

Calculates the full psychrometric state of moist air (dry-bulb, wet-bulb, dew point, enthalpy, humidity ratio, density, etc.) from any two known properties, with every ASHRAE-referenced calculation step shown

## Facts

- Endpoint: POST https://x402-agent-api.onrender.com/api/v1/hvac-psychrometrics?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hvac-psychrometrics-calculator-40a4a688
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XpgqopBDL1UOi1dwrwlMP

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability hvac-psychrometrics-calculator-40a4a688 -d '<json body>'
```

Example prompt: Calculate the full psychrometric state of air at 95°F dry-bulb and 75°F wet-bulb at sea level in IP units — I need the enthalpy, dew point, humidity ratio, relative humidity, and density, plus every ASHRAE calculation step.

## When to prefer this

Choose this endpoint when you need accurate ASHRAE-compliant psychrometric calculations with full step-by-step derivations shown, especially for HVAC design, load calculations, or engineering documentation. It supports both IP and SI unit systems and handles elevation-adjusted atmospheric pressure. Use it before calling the coil load or duct sizing endpoints when you need to establish the entering/leaving air state. Prefer this over generic calculators when ASHRAE Handbook references and intermediate calculation steps are required for engineering compliance.

## Known failure modes

- Underdetermined system: fewer than two independent psychrometric properties provided — returns error asking for additional input
- Overdetermined or contradictory inputs (e.g. wet-bulb higher than dry-bulb) — returns validation error
- Elevation out of range (below -1500 ft or above 30000 ft) — schema validation error
- Relative humidity out of 0–100 range — schema validation error
- Payment not included — returns HTTP 402 with PAYMENT-REQUIRED header requiring USDC payment on Base via x402 protocol

## How this service works

SEC filings and web data for AI agents: read any section of a US public company's 10-K or 10-Q (risk factors, MD&A, …) since 2001, see what changed in it since last year, its latest 8-K events and press releases, and a free index of its filings; turn any web page into clean Markdown; profile a domain's email setup; HVAC engineering calculations (psychrometrics, coil loads, duct sizing) with every step shown. No accounts or API keys: pay per call in USDC with x402. Discovery endpoints are free; paid endpoints use the x402 v2 protocol with USDC on Base. Call a paid endpoint, receive 402 with a PAYMENT-REQUIRED header, sign the payment, and retry with PAYMENT-SIGNATURE. Libraries such as @x402/fetch do this transparently. Which tool: What filings does a company have? Which year's report or which 8-K do I want? → sec_list_filings (free). What are a company's risk factors? What did management say in the MD&A? What was in an earlier year's report? → sec_filing_section ($0.01). What changed in a company's risk factors (or MD&A, business, legal proceedings) since last year? Which new risks were added? → sec_section_changes ($0.04). I need several sections of the same report (e.g. risk factors and MD&A). → sec_filing_sections ($0.015). What are a company's revenue, profit, EPS, cash, debt and free cash flow over the last years or quarters? → sec_financials ($0.005). Are a company's insiders (CEO, CFO, directors) buying or selling its stock? → sec_insider_trades ($0.005). What happened at a company lately: earnings, CEO/CFO changes, acquisitions, cybersecurity incidents? → sec_recent_events ($0.01). Which companies' SEC filings mention a phrase ("material weakness", "tariff", a product or a person)? → sec_full_text_search ($0.01). Who is this company (from a domain, name or ticker): what it does, HQ, founders, CEO, employees, ticker? → company_profile ($0.01). Is this person, company or crypto wallet on a US sanctions (OFAC) list? → sanctions_screen ($0.005). Where are US interest rates, inflation and unemployment right now? → economic_indicators ($0.003). What does this web page, article, PDF, feed or documentation say? → scrape_markdown ($0.002). Read several pages at once, or find a site's pages (pricing, docs, blog) first? → site_map ($0.002). Is this email address real and safe to send to? → email_verify ($0.002). Who hosts a company's email, is SPF/DMARC set up, which SaaS does it use? → domain_enrich ($0.004). HVAC: what are the dew point, enthalpy, RH and humidity ratio of air (from any two properties, at any elevation)? → hvac_psychrometrics ($0.002). HVAC: what is the cooling or heating coil load (sensible, latent, tons), or the mixed air with outdoor air? → hvac_coil_load ($0.002). HVAC: what size duct for this airflow (equal friction or velocity), or what friction and velocity in this duct? → hvac_duct_size ($0.002). Inputs are forgiving: name a company by ticker, CIK or name; sections as "Risk Factors", "MD&A" or "Item 1A"; 8-K events as codes (5.02) or words (earnings, executive changes); unknown fields are ignored. Invalid input returns a valid example, and failed calls are never charged. Every paid result ends with `next_calls`: the natural follow-up questions as ready-to-send calls with their price. Live reliability (answers, failures and latency per tool) is published at /status.

## Output

Returns the complete psychrometric state of moist air including dry-bulb, wet-bulb, dew-point, relative humidity, enthalpy, humidity ratio, grains per pound, specific volume, vapor pressure, and density — along with atmospheric pressure for the given elevation, step-by-step ASHRAE-referenced calculations, unit labels, and suggested next API calls (e.g. coil load calculation).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "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."
  },
  "grains": {
   "type": "number",
   "minimum": 0,
   "description": "Moisture in grains per lb dry air (gr/lb), in either unit system (7,000 gr = 1 lb)."
  },
  "dry_bulb": {
   "type": "number",
   "description": "Dry-bulb temperature, °F (IP) or °C (SI)."
  },
  "enthalpy": {
   "type": "number",
   "description": "Enthalpy: BTU per lb dry air (IP) or kJ/kg dry air (SI)."
  },
  "wet_bulb": {
   "type": "number",
   "description": "Wet-bulb temperature, °F or °C."
  },
  "dew_point": {
   "type": "number",
   "description": "Dew-point temperature, °F or °C."
  },
  "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)."
  },
  "humidity_ratio": {
   "type": "number",
   "minimum": 0,
   "description": "Humidity ratio: lb water per lb dry air (IP, e.g. 0.0100) or g/kg (SI, e.g. 10.0)."
  },
  "relative_humidity": {
   "type": "number",
   "maximum": 100,
   "minimum": 0,
   "description": "Relative humidity, % (0-100)."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "notes": [],
  "state": {
   "grains": 98.46,
   "density": 0.07092,
   "dry_bulb": 95,
   "enthalpy": 38.316,
   "wet_bulb": 75,
   "dew_point": 66.76,
   "humidity_ratio": 0.014065,
   "vapor_pressure": 0.325,
   "specific_volume": 14.2995,
   "relative_humidity": 39.82
  },
  "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": "Humidity ratio",
    "reference": "ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics",
    "calculation": "pws(75.00 °F wet bulb) = 0.43007 psia (ASHRAE Ch. 1 Eq. 6)"
   },
   {
    "step": "Humidity ratio",
    "reference": "ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics",
    "calculation": "Ws* = 0.621945 × pws / (p − pws) = 0.018750 lb/lb (saturated at the wet bulb)"
   }
  ],
  "units": "IP",
  "pressure": 14.696,
  "elevation": 0,
  "next_calls": [
   {
    "why": "What load does a coil carry cooling this air to 55/54 °F at 1000 CFM?",
    "tool": "hvac_coil_load",
    "price": "$0.002",
    "arguments": {
     "units": "IP",
     "airflow": 1000,
     "leaving": {
      "dry_bulb": 55,
      "wet_bulb": 54
     },
     "entering": {
      "dry_bulb": 95,
      "wet_bulb": 75
     }
    }
   }
  ],
  "references": [
   "ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics"
  ],
  "inputs_used": {
   "dry_bulb": 95,
   "wet_bulb": 75
  },
  "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."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hvac-psychrometrics-calculator-40a4a688/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-agent-api.onrender.com](https://www.zero.xyz/host/x402-agent-api.onrender.com/llms.txt)