HVAC Basics

Learn how target superheat is derived from equipment and operating conditions, how actual superheat is measured, and why no universal target applies.

Learn how restricted airflow, temperature rise, blower setup, filters, coils, and ducts can trip a furnace high-limit switch—and why bypassing it is unsafe.

Learn what low-side saturation temperature reveals about evaporator conditions, airflow and load—and why it is not the temperature of every coil surface.

Heat-pump defrost duration and frequency are model- and weather-specific. Learn what to observe, why cycles end, and which patterns indicate a fault.

A pressure-switch open code does not automatically mean a bad switch. Learn how the inducer, vent, condensate, tubing, and controls affect the fault.

Blower airflow changes coil temperature and the sensible-latent capacity split. Learn why lower airflow is not a universal humidity fix and requires testing.

A crankcase heater keeps the compressor warmer during off cycles so refrigerant is less likely to condense into and dilute the oil.

Heat-pump sizing must reconcile heating and cooling loads, certified performance, humidity, ducts and backup—not simply choose the larger load.

High subcooling may reflect overcharge, liquid backing, condenser conditions, a restriction or measurement error. Learn how technicians choose the next check.

Heat strip staging divides electric backup capacity into controlled increments. Correct operation depends on thermostat demand, equipment logic, airflow and electrical design.