FieldTech AI — Field Tech Assistant

Application & Category

Application Equipment category Brand

Model & Condition

Model / series Unit age Last PM service

Operating mode

Outdoor ambient

Select all symptoms observed

Superheat & Subcooling calculator

Refrigerant Suction pressure (PSIG) Suction line temp (°F)

Discharge / liquid pressure (PSIG) Liquid line temp (°F) Indoor wet bulb (°F) — for TXV target SH

Enter pressures and temperatures above.

Airflow & Static Pressure Estimator

System tonnage Measured TESP (in. w.c.) Filter type

Supply registers (count) Duct type Blower speed

Enter values above.

Tonnage / Capacity Verification

Return air dry bulb (°F) Return air wet bulb (°F) Supply air dry bulb (°F)

Airflow CFM Nominal system tonnage

Enter values above.

Refrigerant Charge Estimator

Refrigerant type System tonnage Liquid line length (ft)

Liquid line OD System type

Enter values above.

Refrigerant saturation pressure / temperature reference

Refrigerant	40°F sat (PSIG)	105°F sat (PSIG)	SH target	SC target	GWP	Class	Notes
R-22	68.5	226	10–15°F	10–15°F	1810	A1 legacy	Phased out — recover, never vent
R-410A	118.2	393	10–15°F	10–15°F	2088	A1	High-pressure gauges required
R-32	117	380	8–12°F	8–12°F	675	A2L	Mildly flammable — A2L protocols
R-454B	114	368	8–12°F	8–12°F	466	A2L	Puron Advance / EcoFlex (2025+)
R-407C	55	196	10–15°F	10–15°F	1774	A1	R-22 drop-in (approximate)
R-134a	35.1	171	10–20°F	10–15°F	1430	A1	Coolers, chillers, automotive
R-404A	87.2	295	8–12°F	6–10°F	3922	A1 HGW	Phasedown underway — high GWP
R-448A	89	301	8–12°F	6–10°F	1387	A1	R-404A replacement (Solstice N40)
R-449A	85	290	8–12°F	6–10°F	1282	A1	R-404A / R-22 retrofit option
R-290	70.2	240	10–15°F	8–12°F	3	A3 HC	Max 150g — no ignition sources
R-600a	17.5	70	10–15°F	8–12°F	3	A3 HC	Household fridges — combustible detector
R-744 (CO2)	499	1466	varies	varies	1	A1	Transcritical — 1500+ PSIG possible

Field targets by system type

Parameter	Residential A/C	Heat pump	Light commercial	Walk-in / display
Superheat (TXV)	8–12°F	8–12°F	8–12°F	8–12°F
Superheat (fixed orifice)	10–18°F	10–18°F	10–18°F	N/A
Subcooling	10–15°F	10–15°F	10–15°F	6–10°F
Supply air ΔT (cooling)	17–22°F	17–22°F	17–22°F	—
Supply air temp (HP heat)	90–110°F	90–110°F	90–110°F	—
Airflow per ton	350–400 CFM	350–400 CFM	350–450 CFM	—
Max TESP residential	0.5 in. w.c.	0.5 in. w.c.	0.8–1.0 in. w.c.	—
Evap coil temp (A/C)	35–45°F	35–45°F	35–45°F	10–25°F med-temp
Condenser split	Amb +25–30°F	Amb +25–30°F	Amb +25–30°F	Amb +20–30°F
Cooler case target	—	—	—	34–38°F
Freezer case target	—	—	—	-10 to 0°F
Flame sensor hold-in µA	—	—	0.5–4.0 µA DC	—
Gas valve voltage	—	—	24V AC ±10%	—
Glycol chiller setpoint	—	—	26–28°F	26–28°F
CO2 pressure (dispenser)	—	—	90–100 PSI	—
Syrup / BIB pressure	—	—	70–80 PSI	—

Error codes — residential & light commercial

Brand	Code	Meaning	First check
Carrier / Bryant	E1	Low pressure lockout	Refrigerant charge, TXV, filter-drier
Carrier / Bryant	E2	High pressure lockout	Condenser fan, coil fouling, overcharge
Carrier / Bryant	E3	Freeze protection trip	Airflow, low charge, coil temp sensor
Carrier / Bryant	E6	Communication fault	Thermostat wiring, C wire, control board
Trane / Am. Standard	126	High pressure trip	Condenser fan, refrigerant overcharge
Trane / Am. Standard	179	Low pressure trip	Refrigerant leak, TXV stuck closed
Lennox	E077	High pressure lockout	Condenser coil, airflow restriction
Lennox	E080	Low pressure lockout	Refrigerant charge, TXV
Lennox	E221	Freeze protection	Coil temp sensor, airflow
York / Johnson	4 blink	High pressure cutout	Condenser fan, fouled coil
York / Johnson	6 blink	Low pressure cutout	Low charge, TXV stuck
Goodman / Amana	3 flash	Pressure switch open	Filter, inducer motor, flue blockage
Goodman / Amana	4 flash	Open high-limit	Airflow, blower motor, filter
Goodman / Amana	6 flash	Rollout switch open	Heat exchanger crack, flue obstruction
Rheem / Ruud	5 flash	Flame sensor fault	Flame sensor dirty, gas valve
Rheem / Ruud	6 flash	Ignition lockout	Gas supply, igniter, flame sensor
Daikin	E7	Outdoor fan fault	Fan motor, capacitor, control board
Daikin	U4	Communication error	Indoor/outdoor wiring, PCB
Mitsubishi	E6	Communication error	Signal wire polarity, PCB
Mitsubishi	P8	Outdoor unit fault	Refrigerant charge, outdoor PCB
LG Mini-split	CH01	Indoor temp sensor	Sensor resistance vs temp chart
LG Mini-split	CH10	Communication error	Signal wiring, control boards
Fujitsu	E:EE	EEPROM fault	Replace indoor PCB
Samsung	C4-00	Communication fault	Signal wiring, indoor/outdoor boards

Thermostat wiring — standard color codes

Terminal	Color	Function	Notes
R / Rh / Rc	Red	24V power (hot)	Rh = heat transformer · Rc = cool transformer
C	Black or Blue	Common (24V return)	Required for smart / wifi thermostats
Y / Y1	Yellow	Compressor / cooling stage 1	Energizes contactor coil
Y2	Yellow/dark	Compressor stage 2	Two-stage compressor only
G	Green	Indoor fan (blower)	Fan-only / circulation mode
W / W1	White	Heat stage 1	Gas valve or aux heat strip
W2 / Aux	White/stripe	Heat stage 2 / aux	Electric backup or 2nd-stage gas
O	Orange	Reversing valve (energize = cool)	Carrier, Trane, most brands
B	Blue	Reversing valve (energize = heat)	Some older Rheem / York heat pumps
E / Em	Gray	Emergency / aux heat	Bypasses compressor lockout

Mini-split line set sizing & flare torque

Capacity	Liquid line OD	Suction line OD	Torque (liquid)	Torque (suction)	Max run
Up to 9k BTU (0.75T)	1/4"	3/8"	10–13 ft-lb	14–18 ft-lb	25 ft
12k–18k BTU (1–1.5T)	1/4"	1/2"	10–13 ft-lb	25–33 ft-lb	50 ft
24k BTU (2T)	3/8"	5/8"	14–18 ft-lb	33–40 ft-lb	65 ft
36k BTU (3T)	3/8"	5/8"	14–18 ft-lb	33–40 ft-lb	98 ft
48k+ BTU (4T+)	1/2"	3/4"	25–33 ft-lb	40–50 ft-lb	Per mfr

Dispenser Selection

Brand / platform Chilling method Number of valves

Install Parameters

CO2 line distance to source (ft) BIB rack distance (ft) Equipment age

Select all symptoms observed

Account & Equipment

Brand / account Category Model

Site Conditions

Unit age in service Last PM service Ambient temp

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System Configuration

Fountain type Number of outlets / nozzles Pump flow rate (GPH) Tube material

Routing Parameters

Vertical rise (inches) Longest horizontal run (inches) Routing priority Bundle method

Equipment age

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Freestyle Unit Selection

Freestyle series Unit age Last PM / cartridge service

Site Conditions

Chilling method CO2 supply type Connectivity Ambient temp at site

Select all symptoms observed

Equipment Type

Setting Category Brand

Model & Condition

Model / series Unit age Last PM service

Power type

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Machine Type & Brand

Vending machine type Brand / manufacturer Model / series

Unit Condition

Unit age Last PM service Location / ambient Payment system

Select all symptoms observed

FIELDTECH AI

Select a context above then ask me anything — diagnostics, refrigerant specs, wiring, error codes, parts, repair procedures, or field calculations. I give practical job-site answers.