Furnace turns on and off too frequently (short cycling)
Common Causes
- Clogged air filter causing heat exchanger overheating (most common)
- Oversized furnace — common after replacement with incorrectly sized unit
- Cracked heat exchanger (serious — produces CO, requires replacement)
- Flame sensor needs cleaning (causes burner to fire and shut off within seconds)
- Faulty high-limit switch
- Blocked condensate drain (high-efficiency furnaces)
When to Call a Pro
- Furnace is cycling on and off more than 6-8 times per hour
- Furnace is short cycling even with a clean filter installed
- Home is not reaching the thermostat set point
- You notice a burning smell when the furnace runs
Alberta Gas Fitting Regulations
All gas line and appliance work in Alberta must be performed by a holder of a valid Gas Fitting Certificate issued under the Safety Codes Act. Unlicensed gas work is illegal and voids home insurance.
As ticketed journeyperson plumbers, we hold gas fitting certification — one call covers both trades. We serve Innisfail, Red Deer County, and all of Central Alberta.
Alberta Context
Many Central Alberta homeowners upgrade from a 60-70% AFUE furnace to a 96% AFUE unit and notice short cycling. This can occur if the new furnace was not right-sized using Manual J calculation — a smaller, more efficient furnace produces less heat per cycle and the previous oversized unit "masked" the short-cycling with sheer output. Always request a load calculation when replacing a furnace.