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.
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.
The TXV is one of the most misdiagnosed components in HVAC. This guide covers the three failure modes — stuck open, stuck closed, and hunting — with the exact pressure readings and symptoms you'll see in the field.
🧮 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.