Sightglass

Superheat, subcooling and PT charts for HVAC/R techs. iPhone.

Sightglass tells you whether a system needs refrigerant, needs some taken out, or is right where it should be. Type the gauge readings and line temperatures, and it gives you the number, the target and a plain call: add, recover or leave it. Everything runs on the phone, so it works in a basement, a crawlspace or on a roof with no signal.

What it does

Superheat for fixed-orifice (piston) systems, with the target from indoor wet-bulb and outdoor dry-bulb, or a target you type in.
Subcooling for TXV and EEV systems, using the bubble point.
Airflow by temperature split across the indoor coil.
PT chart for 29 refrigerants, with liquid (bubble) and vapor (dew) columns for blends with glide, R-454B and R-32 included.
Wet-bulb from dry-bulb and relative humidity.
°F or °C, psig, kPa or bar, and your elevation for the gauge correction.

Where the numbers come from

Saturation tables are computed with CoolProp (MIT licence) and checked against published manufacturer PT charts. Superheat targets follow the standard fixed-orifice charging chart, and the temperature-split targets follow the Proctor Engineering table. Sightglass is a calculator for trained technicians: always follow the equipment manufacturer's charging instructions where they differ.

Subscription

Sightglass needs a subscription, weekly or yearly, bought in the app through the App Store. Manage or cancel it in Settings > Apple Account > Subscriptions, or from Settings inside Sightglass. Terms of Use (EULA).

Support

Questions, a refrigerant you need, or a number that looks wrong: info@callmemcp.com.