Cleaning & Maintaining a Vented Gas Heater Posted on November 10, 2015 Vented gas heaters are a popular heating option for both residential and commercial spaces, thanks to easy installation and even, consistent heat. But as with any major appliance, vented gas heaters require routine cleaning and maintenance to ensure safety and function during the cold season. Since the process is fairly involved and requires detailed knowledge, we’ve assembled this comprehensive step-by-step guide for cleaning and maintaining both direct-vent and b-vent gas heaters. A Note on Safety When handling any major appliance, safety is the number-one priority. Always keep the area around the furnace free of any combustible materials, including gasoline or other flammable liquids and vapors, and to not place obstructive furniture too close to the unit while it is in use. As a general rule, furniture and other items should be placed no closer than four feet from the front of the cabinet and two feet from either side, lest the combustion and ventilation air supply becomes blocked. Nothing should ever be placed in or on the furnace cabinet, as doing so poses a dangerous fire hazard. Always check your product manual for specific clearances and warnings. Preparing for Routine Inspection and Cleaning Safety precautions should be taken when preparing to clean the unit, as well. Components inside your unit’s furnace cabinet may belive, and so it is extremely important to switch off your electric power supply at the disconnect switch, fuse box, or service panel before removing any access doors. Although these units are gas-powered and electricity is only required for optional blowers, the inside of your furnace still contains electrical wiring and failing to switch it off can result in serious bodily harm or death. Cleaning & Maintaining Vented Gas Heaters 1. Exterior Because dust and dirt on the exterior of the heater often finds its way inside the unit, cleaning the exterior is just as important as servicing the interior parts. To clean the outside of the furnace: Wipe down the surface with a damp rag, being careful not to get any moisture inside the vents. Furnaces are typically finished in a heat-resistant powder paint, so never use any abrasive cleaners or try to repaint your unit with wall paint. Furnace dusting/cleaning can, of course, be done by the homeowner, and should take place as often as you would dust or clean any other surface in your home. 2. Interior Cleaning After the electrical power supply has been properly shut off, carefully remove any access panels or doors to expose internal components such as the burner, blowers, and heat exchanger. The inside of each furnace will look slightly different, depending on whether it is a direct-vent furnace, which pulls and vents air directly through an outside wall, or a B-vent furnace, which vents air through the ceiling. But all furnaces have the same main components, including a fan (if using the optional blower), a burner, and exposed air passages, and these are the parts that need inspection and cleaning. Vacuum dust and debris using a soft-bristle attachment or small brush: Burners and burner compartment Blower wheel and housing (brush gently and use vacuum; avoid disturbing wiring or the wheel balance). Heat exchanger If the unit has the optional blower attached, clean the fan blades and fan motor of any lint, dust, or dirt. This can be easily done with a brush. 3. Cleaning the Venting System The unit’s venting system is most likely the dirtiest part of the furnace, as air pulled in from outside the unit contains debris that can get stuck all along the inside of the vent pipe. Locate the vent pipe and, wearing a dust mask and rubber gloves, open it with a screwdriver. Use a brush and a damp rag to clean out any debris. A vacuum cleaner can also be used to clean out any excess material. Use an undone wire hanger or metal stake to prod around inside the pipe to check for blockages, and inspect the pipe for any rust or holes. Check for chemical vapor corrosion, especially near solvents or household chemicals, which can damage flue metals over time. If the vent pipe is rusted or damaged, it will have to be replaced. Re-seal the vent pipe when you are done. Ensure vent connections are secure to prevent flue gas leakage, which can be very dangerous. Next is the burner compartment. This is another place where lint, dust, and dirt build-up is common. Disconnect the gas line inside the combustion chamber Use a vacuum to work in and around the burner. Inspect the burner box gasket for damage, and replace if needed. Vented gas furnace maintenance can help avoid common furnace issues. 4. Filters, Thermostat & Airflow Many units like this do not have filters, but if your unit does: Replace or clean air filters regularly to ensure good airflow and maintain efficiency. Test and calibrate the thermostat. Ensure it reflects accurate temperatures and functions properly. Inspect ducts and vents for dust or obstruction; vacuum thoroughly from the furthest vent inward. Testing the Furnace Testing the Flame 1. To test the furnace for proper function, reconnect the gas line and light the pilot according to the directions in the unit’s manual (pilot ignition can differ from model to model). 2. Examine the size of the flame, which should surround the generator tip(check your manual for specifics or use these general rules): 3/8″ – 1/4″ for B-vent furnaces 5/8″ – 1/2″ for direct-vent furnaces 3. Also take note the shape and color of the flame, which should be a soft, clear blue cone with a blueish-red or blueish-violet outer mantle. 4. If you see a yellow flame, this indicates abnormal function. The build-up of foreign material (dust, lint, etc.) in the burner’s primary air opening can interfere with proper air gas mixture, which causes the flame to appear yellow. This can produce carbon monoxide and soot, which is incredibly dangerous and potentially deadly. 5. Cleaning around the burner can also accidentally mis-adjust the pilot. If flame quality is off, adjust the pilot following the manufacturer’s instructions. Readjusting the Burner Re-adjust the pilot until the flame is the correct size, shape, and color. Again, this should be done according to the directions in the particular furnace’s manual, as pilot operation can differ between models. When all inspections and cleanings are done, replace or close all access doors and panels and switch electricity back on. Checklist Summary TaskNotesTurn off power & gasAlways first safety stepClean exterior & panelsUse damp cloth, no abrasivesVacuum burners & blowerBrush floats and vacuum carefullyClean heat exchanger & ventsUse soft brush, inspect for corrosionInspect vents & flueClear blockages, ensure secure fitObserve flame & adjust pilotAim for clean blue cone flameReplace filter & test thermostatEnsures efficiency & accurate heating Periodic Maintenance Schedule Semi-annual Visual check of venting systems for blockages and corrosion Professional inspection recommended for full safety compliance Before heating season Clean blower, burners, filters, vents, inspect thermostat. Check for soot, yellow flame, or reduced performance Annual maintenance Should be performed by a licensed technician. A clean, well-maintained vented gas heater runs safer, lasts longer, and delivers better performance. Feel free to share any brand or model–specific questions you have in the comments below, so we can help you get the most out of your vented gas heater! Also check out our related entries: Gas Heater Safety Tips for Home Ventless Gas Fireplaces: Everything You Need to Know Kristen Turner Featured blogger for Total Home Supply.
