The HVAC field reference built by Taddy Digest — components, diagnostics, PT charts, calculators, training guides, and an AI troubleshooter.
41 components with test procedures
9-refrigerant PT chart & 8 calculators
6 training & sizing guides (mini-split, geothermal, gas, wire, combustion)
AI troubleshooter for field problems
Works offline once installed
$20/month
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Taddy's AC Tool
AC + Heat Pump Ref
Sat. Temp °F→ PSIG
Typical suction / evap range (30–50°F)
Typical condensing range (90–120°F)
Blends (R-407C, R-454B): Bubble / Dew shown
⚠ Reference values only (PSIG). Verify with gauge set software for critical decisions.
Quick field calculators — type values and results update live. Reference only; verify against equipment specs.
💨 Airflow CFM Return Grille Traverse
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Length in
Width in
Free Area
—Avg FPM
—Grille 1 CFM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Length in
Width in
Free Area
—Avg FPM
—Grille 2 CFM
System Tons
—Total CFM
—CFM / Ton
CFM = Avg FPM × Free Area × (L × W ÷ 144). Hold the anemometer ~1" off the face, take up to 16 readings across the grille, hit Enter to jump to the next. Blanks are ignored. Got two returns on one system (e.g. a 4-ton on two 20×20s)? Tap Add second grille and both add into Total CFM — leave it closed and nothing changes. Tonnage is entered once for the whole system. Return grilles should average ≤500 FPM with the filter in. Target 350–450 CFM/ton — low means raise blower speed, high means drop it, then confirm with Delta-T below.
🔥 Heating BTU Capacity
CFM
Supply Air °F
Return Air °F
—TD (SA − RA)
—Heating BTUH
BTUH = CFM × 1.1 × TD (TD = supply − return air temp). Leave CFM blank to pull the Total CFM from the grille traverse above. First-stage heat — let it run ~10–15 min, then read SA and RA in the duct.
❄️ Cooling BTU Capacity
CFM
Return Enthalpy RAE
Supply Enthalpy SAE
—H (RAE − SAE)
—Cooling BTUH
BTUH = H × CFM × 4.5 (H = return enthalpy − supply enthalpy, Btu/lb). Read return & supply wet-bulb temps, look up enthalpy on a psych chart, enter both above. Leave CFM blank to use the Total CFM above. This is total capacity (sensible + latent).
🌡️ Target Superheat Fixed Orifice
Indoor Wet Bulb °F
Outdoor Dry Bulb °F
—Target Superheat
(3 × indoor WB − 80 − outdoor DB) ÷ 2. Fixed-orifice / piston systems only. For a TXV or EEV, follow the manufacturer target (often 8–12°F).
❄️ Superheat Actual
Refrigerant
Suction PSIG
Suction Line °F
—Superheat
Suction saturation temp: —. Blends use the dew point. Target ~8–15°F on fixed orifice; per spec on TXV/EEV.
💧 Subcooling Actual
Refrigerant
Liquid PSIG
Liquid Line °F
—Subcooling
Liquid saturation temp: —. Blends use the bubble point. Target often ~10–15°F (TXV) — verify nameplate.
🌤️ Delta-T Air Temp Split
Return Air °F
Supply Air °F
—Temp Split
Typical cooling split is 16–22°F. Low split = low charge or high airflow; high split = low airflow (dirty filter/coil, weak blower).
⚡ Voltage Imbalance 3-Phase
Leg 1 V
Leg 2 V
Leg 3 V
—Imbalance
Keep under 2%. Over 2% overheats 3-phase motors and shortens life (NEMA). Over 5% can cause failure — find the cause.
🔋 Capacitor µF Amps & Volts
Amps thru Cap
Volts across Cap
—Capacitance
(Amps × 2652) ÷ Volts at 60Hz. Measure amps on the cap lead and volts across it while running. Good caps read within ±6% of the rating.
🔥 Temperature Rise Furnace
Supply Air °F
Return Air °F
—Temp Rise
Must fall within the furnace data-plate rise range (often 35–65°F). Too high = low airflow (stresses the heat exchanger); too low = overfiring or oversized.
🧮 Ohm's Law Volts & Amps
Volts
Amps
—Resistance
—Power (Watts)
Enter measured volts and amps to get resistance (V ÷ A) and power (V × A).
⚠ Calculators are field references. Always confirm against manufacturer specifications and safety procedures.
Taddy's Guides
Field training & sizing references — straight from the van.
Taddy's AC Tool
About
Taddy's AC Tool is a field reference for HVAC technicians covering air conditioner and heat pump components — what each part does, how it works, the tools to test it, target readings, and common failure symptoms — plus a refrigerant PT chart and a set of field calculators.
Parts — browse or search components, tap any for full diagnostics. PT — enter a temp to get saturation pressure for 9 refrigerants, or reverse it. Calc — superheat, subcooling, delta-T, voltage imbalance, capacitor µF, temp rise & Ohm's law. AI — describe symptoms, get likely causes first. Works fully offline once installed (except AI).
Account
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Built for the trade
"I'll keep you cool if you let me."
Taddy's AC Tool v1.0 · For reference only · Always follow manufacturer specs & safety procedures.
🤖
Describe what you're seeing on the unit and I'll tell you what to check — most likely cause first.
⚠ AI guidance — a second opinion. Verify readings & follow safety procedures.