Expert guides, diagnostic tools, and industry insights for HVAC professionals. Interactive calculators included.
Superheat is the single most-tested number on the HVAC license exam and the single most-misread number in the field. The fix is not memorizing one normal range — it is understanding what high or low SH actually proves about the system, paired with the other three numbers on your manifold. This is the conceptual + diagnostic entry point: what superheat is, where to read it, the 8-12 degree window, and the two gauge signatures every service tech should know cold.
A grounded compressor is your single biggest red flag that there's acid in the refrigerant lines. Skip the acid test and the suction-line drier follow-up, and you're putting your warranty (and your reputation) on the customer's next 90-degree day. This is the full cleanup protocol — including the 24-72 hour return visit most techs leave off the invoice.
Part 3 of the HVAC Air Distribution Field Series. Now we put it together: the five residential duct layouts and where each is appropriate, how to size the airflow each room actually needs in cooling vs heating, and the energy-conservation triad — insulation, vapor barriers, and air-tight sealing — that turns a working duct system into an efficient one. NCCER-aligned, references ACCA Manual D/J and the IECC.
Part 2 of the HVAC Air Distribution Field Series. Covers every piece of hardware between the blower wheel and the register face: direct-drive vs belt-drive motors, centrifugal blowers, propeller and duct fans, the fan laws that govern what happens when you change speed, the three main duct materials, how diffusers / registers / grilles differ, and the dampers (balancing, fire, smoke) that control where the air goes. Field-tested, NCCER-aligned, in plain English.
Part 1 of a 3-part field series on HVAC air distribution. Covers what airflow and pressure actually are inside residential ductwork, how a residential distribution system is laid out from blower to return grille, and every instrument a tech reaches for when something does not feel right at the registers. Built to match the NCCER curriculum scope so it is useful whether you are studying for a credential or troubleshooting a job.
Dry-bulb, wet-bulb, and relative humidity are the three readings that drive every accurate charge on a fixed-orifice system. This guide explains what each one really is, how to measure them in the field, and exactly how indoor wet-bulb plus outdoor dry-bulb give you a target superheat number you can charge to with confidence.
🧮 Interactive CalculatorMaster the two most critical measurements in HVAC diagnostics. This guide breaks down the math, the meaning, and what the numbers tell you about system health — with a free interactive calculator.
🧮 Interactive CalculatorThe best HVAC system in the world can't overcome bad ductwork. This guide covers the fundamentals of duct sizing — how much air you need, how to know if you're getting it, and what happens when you're not.
A failing capacitor is one of the most common HVAC service calls — and one of the most preventable. Learn the signs of degradation, how to test properly, and why catching it early saves compressors.
🧮 Interactive CalculatorDelta T is the temperature difference between your supply and return air — the simplest indicator of whether your HVAC system is actually doing its job. Here's what your numbers mean and what to do when they're wrong.