About psychart.kr

What psychart.kr is

psychart.kr is a free set of web tools for HVAC and building-services engineers and for students preparing for engineering exams. You can draw and read a psychrometric chart in the browser and run common HVAC calculations (duct, pipe, load, dew point and more) in one place.

No sign-up or installation is needed, and most calculations run inside your own browser. Pages are available in 20 languages, including Korean and English.

Tools on the site

• Psychrometric chart calculator: enter two values such as dry-bulb temperature and relative humidity to get enthalpy, wet-bulb, dew point and humidity ratio, then draw mixing, heating, cooling and humidifying processes on the chart to get coil load (kW), condensate and sensible heat factor. A calculation can be shared as a link.
• HVAC calculators: duct sizing, pipe sizing, cooling load, dew point / condensation / insulation thickness, pump head, fan static pressure, coil capacity, economizer decision, enthalpy, and unit converters (refrigeration tons to kW, CMH to CFM, mmAq to Pa and more).
• Blank psychrometric chart PDF: sharp A4 / A3 charts for printing (standard colour, light, black and white).
• How to read a psychrometric chart and practice problems: reading the lines, the cooling drawing sequence, and original problems modelled on engineering-exam types, with answer checking.
• FAQ and community board: answers about the calculations, feature requests and discussion.

How the results are calculated

• Moist-air properties (saturation vapour pressure, humidity ratio, enthalpy, specific volume, and the wet-bulb / dew-point inversions) use the equations in ASHRAE Handbook Fundamentals 2017 (SI), Chapter 1. Saturation pressure uses the Hyland-Wexler equations. The same equation family as the open-source library psychrolib is used, and the results are checked against psychrolib output and ASHRAE table values in automated tests.
• Friction loss for ducts, pipes, fans and pumps is based on the Darcy-Weisbach equation with the Colebrook friction factor (Hazen-Williams is also selectable for pipes); fittings such as elbows, tees and valves are added as equivalent lengths or loss coefficients.
• The cooling and heating load calculators are rough estimates from floor area and use type. They do not replace a proper design-load calculation.
• The economizer decision follows the ASHRAE 90.1 differential-enthalpy, differential-dry-bulb and fixed-dry-bulb limit methods.
• The older view (/classic) uses a simplified Magnus-Tetens-type approximation for saturation vapour pressure. Its values can differ slightly from the current calculator, so use the current calculator for reference work.
• The steps and equations used are shown on each tool page.

Limits and disclaimer

Results on this site are for reference, learning and preliminary checks. Before using them for design, construction, test reports or anything safety-related, verify them against the applicable codes and standards, manufacturer data and recognised software.

We work to keep the calculations accurate but do not guarantee they are error-free, and we are not liable for losses resulting from their use. Inputs outside the supported range, or states that cannot exist (for example a wet-bulb temperature above the dry-bulb temperature), are reported instead of being calculated.

Operation and advertising

psychart.kr is run by an individual and is free to use. To cover the cost of the servers and tools, it may show Google AdSense ads. Ads do not affect the results or explanations, and the information that may be collected in connection with them is described in the Privacy Policy.

Feedback and error reports

• Leave a post on the community board. No sign-up is needed.
• You can also use the "Feedback" button at the top of the page.
• When reporting a calculation error, include the inputs, the value you expected (with its source) and the value you got, so it can be checked quickly. Please do not put email addresses or phone numbers in board posts.
• Email: contact@psychart.kr (private questions, partnerships, bug reports)