Furnace short cycling in Herndon, VA

Furnace short cycling in Herndon, VA — the system turning on, running briefly, then shutting off before the house actually warms up — is almost always a safety shutoff doing its job, not the furnace randomly malfunctioning.

Why it's cutting itself off

• Dirty flame sensor — a common one; the sensor can't confirm the flame is lit so the system shuts down as a safety precaution
• Clogged filter causing the furnace to overheat and trip its high-limit switch
• A furnace oversized for the home — common after a retrofit or partial renovation — heats the space too fast and shuts off before a full cycle
• Thermostat mounted near a heat source (sunny window, floor register) giving a false "satisfied" reading
• A cracked heat exchanger, which is a safety issue worth having checked promptly rather than living with

Herndon homes with ductwork or a thermostat added or moved during a renovation sometimes end up with a mismatch between furnace size and the space it's heating — if short cycling started right after any work was done on the house, mention that when you call.

Herndon HVAC contractors who diagnose short cycling

How this works

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