Open field tools

14 field tools for the next service call.

Practical tools for technicians, estimators, and owners. No account required. Use them in the field, then come back when you need the operating system behind the work.

Built for real decisions: fast estimates, transparent assumptions, and results you can explain to a customer or a teammate.

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Refrigeration

Pressure–Temperature Chart

Convert refrigerant pressure and saturation temperature with bubble/dew support.

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Refrigeration

Superheat & Subcooling

Measured superheat/subcooling from gauge readings, plus fixed-orifice target superheat.

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Airflow

Ductulator

Size round and rectangular duct from airflow and target friction rate.

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Air properties

Psychrometric Chart

Solve moist-air state points from any two independent properties.

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Air properties

Mollier h-x Diagram

Inspect air processes on an enthalpy–humidity-ratio diagram.

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Hydronics

Hydronics Calculator

Calculate flow, load, pipe velocity, and head loss for water or glycol loops.

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Electrical

Wire Sizing

Check ampacity and voltage drop for copper and aluminum conductors.

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Loads

Heat Load Calculator

Create a fast field estimate for heating and cooling load.

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Rigging

Crane & Lifting

Estimate sling-leg tension and compare the lift against rated capacity.

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Airflow

Airflow & Delivered Capacity

CFM from velocity/area or traverse, plus sensible, latent, total, and delivered tons.

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Airflow

Duct System Designer

Available static pressure, target friction rate, and fan external-static comparison.

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Electrical

Electrical Service

Three-phase voltage imbalance (NEMA), single/three-phase power, and measured-vs-FLA check.

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General

Unit Converter

Convert common HVAC, mechanical, electrical, and pressure units.

01 / Sizing

Heat load

Heat Load Calculator

Simplified Manual J–style heating & cooling load estimate.

Floor area (ft²)Ceiling height (ft)Window area (ft²)OccupantsInsulationWindowsAir tightnessSun exposure

Cooling design

Indoor °FOutdoor °F

Heating design

Indoor °FOutdoor °F

Estimated load

25,885

Btu/h cooling

2.2 tons

26,567

Btu/h heating

26.6 MBH

Sensible: 20,679 Btu/hLatent: 5,206 Btu/h

Cooling load breakdown

Walls2,092 Btu/h

Roof / ceiling3,312 Btu/h

Windows (conduction)2,156 Btu/h

Windows (solar)6,600 Btu/h

Infiltration3,499 Btu/h

People & appliances3,020 Btu/h

Latent (moisture)5,206 Btu/h

Quick estimate for sizing discussions only. A full room-by-room ACCA Manual J load calculation is required for permit and equipment selection.

02 / Flow

Hydronics

Flow, heat load & pipe sizing for water and glycol loops.

Heat load (Btu/h)ΔT (°F)Fluid

Water · cp 4.19 kJ/kg·K · ρ 992 kg/m³

Result

GPM flow

60,000

Btu/h load

Pipe sizing

2.4fps

Velocity

9.1ft/100ft

Head loss

Ideal range

Estimates use the standard q = ṁ·cp·ΔT relationship and Hazen-Williams (C=140) for pressure drop. Verify against manufacturer data and confirm glycol properties at your operating temperature.

04 / Refrigeration

Pressure–Temperature Chart

PT Chart

Refrigerant pressure ↔ saturation temperature reference.

Refrigerant

Temp unit

Pressure unit

Saturation temperature (°F)

Result

Liquid pressure (bubble)118.3 psig

Use for subcooling on the liquid line

Vapor pressure (dew)118.3 psig

Use for superheat on the suction line

Field-reference approximations at sea level. Always verify against the manufacturer's official PT chart for critical work.

05 / Refrigeration

Superheat & subcooling

Gauge readings

Refrigerant

Metering device

Suction pressure (psig)Suction line temp (°F)Liquid pressure (psig)Liquid line temp (°F)

Target superheat (fixed orifice)

Outdoor dry bulb (°F)Indoor return WB (°F)

Measured

12.1 °F

Superheat

Sat 39.9°F (dew)

14.8 °F

Subcooling

Sat 104.8°F (bubble)

Target superheatN/A

Target-superheat charging applies only to fixed-orifice systems. Charge TXV/EEV systems to subcooling per the dataplate.

Superheat uses the dew curve; subcooling uses the bubble curve. Always confirm charge against the equipment charging chart before adding or recovering refrigerant.

06 / Airflow

Ductulator

Equal-friction duct sizing. Results update live as you adjust the dials.

Air flow rate400 CFM

Friction rate0.08 in wg/100 ft

Residential supply is typically 0.08–0.10 in wg/100 ft.

Round duct

10.3"

Exact diameter

12"

Nearest standard

Velocity (12" duct)509 FPM

Low — supply branch OK

Rectangular equivalents

Size (W × H)	Velocity
16" × 6"	600 FPM
11" × 8"	655 FPM

07 / Air properties

Psychrometric chart

Psychrometric Chart

Pick any two known properties and solve the complete air state.

Known property 1

°F

Known property 2

Altitude (ft)

Barometric pressure 101.33 kPa (29.92 inHg)

Air properties

Dry bulb: 75.0 °F
Wet bulb: 62.6 °F
Dew point: 55.2 °F
Rel. humidity: 50.0 %
Humidity ratio: 64.6 gr/lb
Enthalpy: 28.1 BTU/lb
Specific vol.: 13.68 ft³/lb
Vapor press.: 1.48 kPa

Tip: click anywhere on the chart to drop a state point.

08 / Air properties

Mollier h-x diagram

Mollier h-x Diagram

The European/UK enthalpy–humidity chart. Pick any two known properties to solve the complete air state.

Known property 1

°C

Known property 2

Altitude (m)

Barometric pressure 101.33 kPa (1013.3 mbar)

Air properties

Dry bulb: 22.0 °C
Wet bulb: 15.4 °C
Dew point: 11.1 °C
Rel. humidity: 50.0 %
Humidity ratio: 8.2 g/kg
Enthalpy: 43.0 kJ/kg
Specific vol.: 0.85 m³/kg
Vapor press.: 1.32 kPa

Tip: click anywhere on the chart to drop a state point.

09 / Electrical

Wire sizing

Wire Sizing

NEC conductor sizing by ampacity and voltage drop for copper and aluminum.

Load (amps)Voltage (V)ConductorPhaseInsulation tempOne-way length (ft)Max voltage drop (%)

Voltage drop uses 2× R·I·L. Length is one-way circuit distance.

Recommended size

AWG / kcmil

A ampacity

6.1V

Voltage drop

2.55%

Drop at load

Carries 40 A within 3% voltage drop over 100 ft.

Ampacity reference (Copper, 75°C)

Size	Ampacity	Ω/1000ft
14	20 A	3.07
12	25 A	1.93
10	35 A	1.21
8	50 A	0.764
6	65 A	0.491
4	85 A	0.308
3	100 A	0.245
2	115 A	0.194
1	130 A	0.154
1/0	150 A	0.122
2/0	175 A	0.0967
3/0	200 A	0.0766
4/0	230 A	0.0608
250	255 A	0.0515
300	285 A	0.0429
350	310 A	0.0367
400	335 A	0.0321
500	380 A	0.0258

Based on NEC Table 310.16 ampacities and Chapter 9 resistance values. Does not apply ambient or conduit-fill derating. Always verify against the current NEC and your AHJ.

10 / Airflow

Airflow & delivered capacity

Measured airflow

Average velocityFPM

WidthinHeightinSite altitudeft

Coil entering / leaving air

Entering DB°FEntering WB°FLeaving DB°FLeaving WB°F

Airflow

900 FPM

Avg velocity

1.11 ft²

Free area

1000 CFM

Airflow

Delivered capacity

23,760 Btu/h

Sensible

9,928 Btu/h

Latent

34,479 Btu/h

Total

2.87 tons

Delivered

Sensible heat ratio69%

Delivered capacity reflects measured air only. Confirm against equipment rated capacity and superheat/subcooling before drawing conclusions.

11 / Airflow

Duct system designer

Blower & measured static

Rated ESPMeasured TESP

Static pressures in inches of water column (in. wg).

Component pressure drops

Cooling coil (wet)Filter (1")Supply registersReturn grille

Effective length

Supply TEL (ft)Return TEL (ft)

Design targets

0.04"

Available static

0.020

Target friction /100 ft

Total effective length200 ft

Friction rate is low — ducts will be large. Acceptable for quiet, low-static systems.

Blower check

Measured vs. rated ESPOver rated ESP

Trunk preview

Sample trunk airflow

Round trunk at target friction20.5" → 22"

12 / Electrical

Electrical service

Line-to-line voltage

L1–L2 (V)L2–L3 (V)L1–L3 (V)

Power

Voltage (V)Current (A)PF (0–1)

Motor FLA check

Measured amps (A)Nameplate FLA (A)

Results

Voltage imbalance

1.27%Investigate (>1%)

Avg 472 V · max deviation 6 V

Power

19.12 kVA

Apparent

16.44 kW

Real

Motor FLA

86%Within range

of nameplate FLA

NEMA MG-1: derate above 1% voltage imbalance and do not operate above ~5%. De-energize and follow lockout/tagout before servicing.

13 / General

Unit converter

Unit Converter

HVAC/R field measurement conversions.

Value

FromTo

1 Fahrenheit (°F)

-17.2222

Celsius (°C)

Temperature chart

1 Fahrenheit (°F) equals:

Fahrenheit (°F)	1
Celsius (°C)	-17.2222
Kelvin (K)	255.9278
Rankine (°R)	460.67

Conversions use standard reference factors. US (short) tons and US gallons are used for weight and liquid flow. Verify critical values against manufacturer documentation.

14 / Rigging

Crane & lifting

Crane Lifting

Sling leg tension and crane capacity check for equipment lifts.

Load weight (lb)Rigging weight (lb)Sling legsCrane capacity (lb)

Sling angle from horizontal: 60°

Equalized rigging (all 4 legs share load)

Lower sling angles dramatically increase leg tension. 30° is the typical minimum allowed. A 4-leg sling on a rigid load is rated as 3 legs unless equalized.

Lift analysis

Within capacity

70% of rated capacity (8,400 lb gross)

3,233

lb tension / leg

1.155

Angle load factor

3 effective legs

2,800lb

Vertical / leg

1,617lb

Inward side load

3,600 lb of capacity remaining.

Field-reference only. Verify against sling capacity tags, the crane load chart at the actual working radius, and a qualified rigging plan. Capacity must account for boom length, radius, and outrigger setup.

03 / Refrigeration

Diagnostic tools

When the work gets bigger

Move from one useful calculator to a connected operating system.

See Service Install