To make sure your family is safe this winter, have your furnace serviced by a reputable HVAC Technician. Annual servicing can increase the longevity of your furnace. Below are tips for Homeowners so they can recognize hazards with their 80% or less efficient furnaces.
1. Flame Rollout – Having a large crack in the heat exchanger or a blocked flue pipe will cause the burner flames to roll under the burner or out at you during operation. Normal flames on a furnace with a clam shell heat exchanger should be vertical and mostly blue. If your furnace has flame rollout, turn it off, and contact a licensed HVAC Company immediately.
2. Wafting or slanted flame – If the burner flame appears to dance or slants off to the side on a clam shell heat exchanger, there’s a strong chance there’s a crack in the heat exchanger or an opening where the faceplate meets the exchanger. Either way, there’s a strong potential for carbon monoxide and other flue gases to leak into the supply air and be blown throughout the home. Turn it off and call a licensed HVAC Company immediately.
3. Rusting out of the flue pipe – Many older furnaces will have a metal flue pipe with lots of tiny holes rusting through it. If drafting issues exist, holes may develop even faster because the flue gases are highly acidic. When holes develop, this is a potential for flue gases to leak into the home and it needs to be addressed immediately.
4. Inadequate Combustion Air – For 80% (or less) efficient furnaces, they normally draw combustion air from their surrounding area such as the basement. It’s crucial that the furnace can breath properly through louvered doors or wall vents into the utility room or closet and at the top of the stairs. To make sure their is adequate combustion air, the rule of thumb is 1 square inch per 1,000 BTU’s subtract 25% if you have metal vents or 75% if you have wood vents.
5. Opening in the cold air return ductwork within 10′ of the burners – The blower is strong enough to draw flue gases from the burner opening into the supply air and throughout the home. Check to make sure the filter opening is sealed and that there are no vent openings cut into the cold air return near the furnace.
6. No Solid Separation Between Bedrooms and Gas Appliances – When your gas furnace and water heater operate, they draw oxygen from their surroundings for combustion air. If one of your family members is sleeping in a nearby room, you don’t want the gas appliance depleting that room of oxygen. That is why it’s crucial to have a solid door between the two.
7. Backdrafting of Carbon Monoxide – Take a tissue and hold it near the draft diverter box of the furnace or by the draft hood of the water heater. If the tissue is blown away from the pipe during operation, you may have a backdraft situation. This can occur if a bird’s nest is clogging the flue, if a portion of the flue pipe has collapsed, or if a bathroom vent fan is installed in the same roof as the gas appliances and forces the flue gases to go the wrong direction and come back into the home. Turn the furnace off as this needs to be addressed immediately.
8. Inadequate Clearance Around B-Vent Flue Pipe – 80% (or less) efficient gas furnaces will have single-wall or double-wall flue stacks. There needs to be 6″ and 1″ respectively minimum clearance to combustibles.
9. Unlined Chimneys or Breached Flues – Homes typically built in the 1960′s and prior have their gas furnaces and water heaters dumping into a chimney. Of the homes I inspected in 2009, 21.3% had either no liners or the liners were breached. Either instance poses a threat of either catching the house on fire or of carbon monoxide poisoning. The wood that runs up along the outside of the chimney lowers its ignition temperature each time the chimney heats up and cools down.
10. Furnace Cabinet is Too Hot – When the high-limit control switch is faulty, the insides of the heat exchanger can become too hot, the wires inside the control box can begin to melt, and the sides of the furnace can exceed 120 degrees F. When this happens, the metal of the heat exchanger will fatigue, possibly crack, and maybe catch fire.
To learn more about Furnace Defects, explore our videos or check out our website at Omaha-Home-Inspection.com.
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