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External static pressure, CFM, duct leakage, charging, balancing, and commissioning notes.
Run the numbers
HVAC field calculators for sizing, quantities, and loads.
ACH to CFM calculatorFind the airflow for a target air change rate: CFM = room volume x ACH / 60, from floor area and ceiling height.Ventilation rate calculatorFind the breathing-zone outdoor air a space needs: Vbz = Rp x Pz + Ra x Az.Tons to BTU calculatorConvert a cooling load to tons of refrigeration: tons = BTU per hour divided by 12,000.Dew point calculatorFind the dew point from air temperature and relative humidity, and the surface temperature condensation forms at.Duct equivalent diameterConvert a rectangular duct to its equal-friction round diameter: De = 1.30 x (a x b)^0.625 / (a + b)^0.250.Affinity laws calculatorScale fan or pump flow, pressure, and power for a speed change using the affinity laws: flow with speed, pressure with the square, power with the cube.
All HVAC calculators Check you're ready
Readiness checks before you start the work.
Cold storage readinessA 2 minute check on whether your refrigerated warehouse handles the floor heave, vapor drive, and ammonia risk a walk-in never faces, before the slab cracks or a leak shuts you down.Succession & exit readinessA 2 minute check on whether your business is built to transfer for real value, before the day you want out arrives and you find out it is worth less than you hoped.EPA 608 practice testTen questions across the Core section and all four certification types, the way the real EPA 608 exam splits the work.HVAC Cx readinessA 2 minute check on whether an HVAC system will actually pass commissioning and run as designed, before the Cx agent and the owner find the problems.
All HVAC readiness checks Choose between options
Side-by-side decision guides with a decision table.
Air-side vs water-side economizerAir-side economizer vs Water-side economizerCentrifugal vs ScrewCentrifugal chiller vs Screw chillerChilled water vs DXChilled water vs DX (direct expansion)Ducted vs mini-splitDucted system vs Ductless mini-split
All HVAC comparisons Learn the work
Start with the HVAC pillars, then go deep.
Cold storage and refrigerated warehouse designScaling a walk-in to a warehouse: heat the sub-floor or the freezer heaves, keep the inward vapor barrier continuous or ice fills the panels, manage the ammonia with PSM, and pull the building down slowly.Thermostat types and wiring field guideWhat a thermostat does, why it has to match the equipment, the type ladder from mechanical to communicating, the terminal letters and the C-wire, heat pump and staging setup, and how to install and troubleshoot one.Steam heating fundamentals field guideHow a steam system actually moves heat: the boiler makes steam, the steam rides its own pressure to the terminals and condenses, and the condensate finds its way home.Refrigeration cycle field guideCooling moves heat, it does not make cold. Read the four-part loop, the phase change that carries the load, the high and low side, and the saturation numbers that tell you what the system is doing.Refrigerant types and A2LWhy refrigerants keep changing, what A2L means under ASHRAE 34, which low-GWP refrigerants replace R-410A, and how to handle a mildly flammable charge safely in the field.Radiant floor heating designPick the install method, size the tubing and loops, hold the loops equal, drop the water to a low supply temperature, insulate under the heat, and start it without trapping air.
All HVAC field guides Prove it and get paid
Capture the HVAC job in the field, build the proof, and send a clean record.