User Guide · Gulf Coast Edition
WiseSeer™
HVAC Enthalpy Calculator
Everything you need to understand the enthalpy method, use the calculator confidently on the job site, and interpret what the numbers mean for your system.
Everything you need to understand the enthalpy method, use the calculator confidently on the job site, and interpret what the numbers mean for your system.
Enthalpy is the total heat content of moist air — temperature and humidity combined into a single number. It's what actually gets removed when your system cools a building.
When a technician measures dry-bulb temperature alone, they're only seeing half the picture. A 75°F room at 30% humidity feels and loads completely differently than a 75°F room at 80% humidity — but dry-bulb reads the same. Wet-bulb temperature captures both. It's what a sling psychrometer reads when moisture evaporates off the wick and equilibrium is reached, encoding both the heat and the moisture content of the air in one measurement.
Enthalpy (H) is the number that comes out of that wet-bulb reading — expressed in BTU per pound of dry air. The difference between the return enthalpy and supply enthalpy is the actual energy your coil removed from every pound of air that passed through it.
The classic sensible-only formula ignores latent heat — the energy required to condense moisture out of the air. In a humid Gulf Coast climate, latent load can be 40–60% of total load. Using ΔT alone will significantly underestimate your system's actual work and lead to oversizing errors.
Four inputs, one tap. Here's what each field means and how to get accurate readings in the field.
Cubic feet per minute — the volumetric airflow across your coil. Get this from your air handler specs, an anemometer reading, or a calculated traverse. Accepted range: 100 – 10,000 CFM. For residential split systems, 350–450 CFM per ton is typical.
Your job site elevation above sea level. Gulf Coast technicians can leave this at 0 (sea level). At elevation, air is thinner — the same CFM carries less energy. Leaving it blank also defaults to 0.
Take your sling psychrometer or digital wet-bulb reading at the return air grille — before the coil. This is the warm, humid air entering the system. Range: 45–95°F. For a typical Houston home in summer, expect 67–73°F wet bulb.
Wet-bulb reading at the supply register — after the coil. This must be lower than the return wet bulb (the coil is removing heat). A properly loaded system typically shows a 10–15°F wet-bulb drop across the coil.
WiseSeer looks up enthalpy values from a corrected ASHRAE table, applies your elevation's air density, and returns BTU/hr and tons. The result is saved automatically to your Job Log. Voice output reads the result aloud if enabled.
Take the return reading inside the return plenum if possible — not in the room. Take the supply reading in the supply plenum or at the discharge of a supply trunk, not at a register. Mixing with room air will skew your readings and produce inaccurate BTU results.
The results panel shows six values. Here's what each one means and what a healthy system looks like.
Nameplate tonnage is rated at AHRI standard conditions (95°F outdoor / 80°F DB / 67°F WB indoor). Your measured BTU/hr reflects actual current conditions — it will vary. A system consistently delivering 10–15% below nameplate under design conditions warrants further diagnosis.
Air at altitude is less dense. The same CFM carries less energy — and the same equipment does less work. Elevation correction is the difference between a correct diagnosis and a costly one.
At sea level, a cubic foot of standard air weighs about 0.0750 lb. As elevation increases, atmospheric pressure drops and fewer air molecules occupy that same cubic foot. By 5,000 feet, density has dropped to roughly 0.0624 lb/ft³ — a 17% reduction. That means a system moving 1,500 CFM at Denver is moving 17% less mass of air than the same system in Houston, and therefore delivering 17% fewer BTU/hr — even with identical wet-bulb readings.
WiseSeer's elevation table covers 0–10,000 ft in 100–200 ft steps with linear interpolation, based on ASHRAE Standard 111 correction factors cross-checked against the ICAO Standard Atmosphere model.
Houston sits at roughly 50 ft above sea level. The density difference from sea level is negligible. If you work exclusively in the coastal plain, elevation correction adds almost nothing. It becomes significant above 2,000 ft — relevant if you work in the Texas Hill Country or take calls elsewhere.
When either wet-bulb temperature exceeds 85°F, WiseSeer flags an extreme conditions warning. Here's why that number matters — and what to do about it.
If return or supply wet bulb exceeds 85°F, a prominent orange banner appears: "Extreme conditions — wet bulb above 85°F. Gulf Coast severe heat event." This is not a calculation error — the math still runs. It's a situational awareness alert.
A wet-bulb temperature above 85°F is physiologically significant. Wet-bulb temperature is one of the best single-number measures of heat stress on the human body — it accounts for both heat and humidity simultaneously. Research has established that wet-bulb temperatures above 35°C (95°F) are lethal even to healthy adults regardless of activity level, and conditions above 30–32°C (86–90°F) are dangerous for outdoor work.
On the equipment side, return wet-bulb above 85°F also means your coil is operating far above standard design conditions. Suction pressures, superheat, and subcooling will all read outside normal ranges — not because the system is failing, but because it's handling an unusual load. Compare your measured BTU/hr to the system's rated capacity at these conditions before concluding a problem exists.
What to do when you see the flag: Stay hydrated, limit exposure, and use the app to document your readings for the service record. If the building cannot reach setpoint under these conditions, calculate the load and compare to equipment nameplate — you may have a design-day load that exceeds equipment capacity, not a refrigerant issue.
Heat index (the "feels like" temperature you hear on the news) is a perceived temperature at a fixed shade reference. Wet-bulb temperature is a measured physical property of the air. Both matter for safety, but WiseSeer uses wet-bulb — the more physically precise measurement — for its extreme conditions threshold.
WiseSeer is built for one-hand, one-tool use. Tap the mic, say the number, and move on — no typing, no fumbling.
Each input field has its own microphone button. Tap it and say just the number for that field. The app listens, confirms with readback, and fills the field.
Say "fifteen hundred" or "1500" for CFM. Say "sixty-three point five" for wet bulb. Both word-form and digit-form are recognized.
When Voice Output is on, the app reads back every accepted value and announces the full result after Calculate. Tap the 🔊 header button to toggle it off in noisy environments.
In Settings, the Confidence Threshold slider controls how sure the app must be before accepting a voice value. Raise it in quiet environments; lower it if it's too picky in the field.
Voice recognition runs on-device via the Web Speech API — no internet required once the app is cached. Results are always available offline.
Speak clearly and wait for the mic button to glow orange before starting. In very loud environments, shield the phone mic with your hand. The fallback: the lowest-confidence alternative is still accepted if nothing else passes threshold.
Keyboard shortcuts (desktop / Bluetooth keyboard on tablet):
Common questions from the field, answered plainly.