Heating System Questions

Causes include: thermostat set incorrectly, pilot light out, flame sensor dirty, gas supply issues, overheating from dirty filter, or ductwork problems. Check thermostat settings and filter first. If the pilot light is out or you smell gas, call a professional immediately.

A properly functioning furnace typically cycles 3-8 times per hour, running 10-15 minutes per cycle. Frequent short cycles (under 5 minutes) indicate problems like oversizing, dirty filters, or thermostat issues. Cycles longer than 20 minutes may indicate undersizing or heat loss.

A heat pump transfers heat rather than generating it, working like a reversible air conditioner. In winter, it extracts heat from outdoor air and moves it inside. In summer, it reverses to cool. Heat pumps are highly efficient, especially in mild climates like the Bay Area.

AFUE (Annual Fuel Utilization Efficiency) measures furnace efficiency. An 80% AFUE furnace converts 80% of fuel to heat; 20% is lost. High-efficiency furnaces achieve 90-98% AFUE. A 95% AFUE furnace uses about 16% less fuel than an 80% model, significantly lowering heating bills.

Consider replacement if your furnace is over 15-20 years old, repairs exceed 50% of replacement cost, it has a cracked heat exchanger, or energy bills are climbing despite maintenance. New high-efficiency furnaces can reduce heating costs by 15-30%.

A burning smell when you first turn on heat is often just dust burning off after months of disuse—it should clear within an hour. Persistent burning smells may indicate electrical problems, overheating, or debris near the heat exchanger. Turn off the system and call for service if smells persist.