PT Chart: Superheat Calculator

PT chart, superheat calculator and subcooling calculator for HVAC/R technicians. Look up refrigerant pressure and temperature in one tap, and get superheat and subcooling from your gauge and clamp readings. No account needed, and it works fully offline on the roof, in the attic or in the basement.

WHAT IT DOES
• PT chart: enter a pressure, get the saturation temperature, or enter a temperature, get the pressure. Drag the slider to scan the chart.
• Superheat calculator: suction pressure + suction line temperature = superheat, using the dew point for blends.
• Subcooling calculator: liquid pressure + liquid line temperature = subcooling, using the bubble point for blends.
• Blends done right: dew and bubble shown side by side with the glide, so R-454B, R-407C and R-448A read correctly.
• Altitude setting: enter your elevation once and gauge readings are corrected for local air pressure.

21 REFRIGERANTS
R-410A, R-32, R-454B, R-452B, R-22, R-134a, R-404A, R-407C, R-507A, R-448A, R-449A, R-452A, R-422D, R-427A, R-513A, R-1234yf, R-1234ze(E), R-290, R-600a, R-744 (CO2) and R-717 (ammonia). Each one shows its ASHRAE safety class (A1, A2L, A3, B2L).

BUILT FOR THE FIELD
• Big numbers and big buttons you can hit with gloves on.
• Dark mode for attics and a high-contrast mode for full sun.
• psig, psia, bar, kPa, inHg vacuum, °F and °C. Decimal comma supported.
• Opens on your last refrigerant. Favorites and recents at the top.
• 0.1 resolution, no coarse steps.
• No ads on the PT chart or the superheat and subcooling screens: nothing gets between your reading and the result.

CHECKED ACCURACY
Saturation data is generated with the CoolProp equation-of-state library and checked against published pressure-temperature charts. The Accuracy screen shows the checked deviation for every refrigerant, so you know exactly how far you can trust each number.

PRO (ONE-TIME PURCHASE, NO SUBSCRIPTION)
• Job log: save readings with a job name and notes.
• Share a clean PDF or CSV report with the customer or office.
• Target superheat for fixed-orifice (piston) systems from indoor wet bulb and outdoor dry bulb.
• Target subcooling check against the nameplate value.
• Home-screen widget for your favorite refrigerant.
• No ads anywhere in the app.

Free to use. A one-time in-app purchase unlocks Pro.
The free version shows ads on secondary screens (settings, accuracy and jobs); Pro removes all ads.
Refunds: request through Google Play order history, or e-mail adham@veloxapp.co.uk. We refund if Pro does not work as described.

PT chart, superheat calculator, subcooling calculator and refrigerant pressure temperature chart in one small app.

For trained technicians. Always follow the equipment nameplate and the manufacturer's installation instructions. Values are for reference. Refrigerant handling may require certification in your country (for example EPA Section 608 in the US). Not affiliated with any refrigerant or equipment manufacturer.

Recent changes:
First release: PT chart, superheat and subcooling for 21 refrigerants. Works offline, no login.