All gas-fired heating systems products elimination system Periodically, conventional are composed of a heat- (exhaust stack, or chimney); gas-fired heating systems need producing source (a in and control mechanisms (such adjustment to keep them running the case of forced air systems as the , gas control in the safest, most efficient and a for hot water systems) valve and safety control devices). and least costly manner. This that contain both a burner and a Understanding how these various publication is designed to help ; a distribution parts operate and work together you understand how gas-fired system (ducts in the case of forced is an important part of any heating systems work (both air systems, pipes in hot water preventive maintenance forced air and hot water systems), systems); a burner by- program. the periodic preventive maintenance the units should have, and what special tasks and problems need the attention of a heating contractor.

This publication covers maintenance of conventional gas-fired heating systems only. Maintenance and repair of the newer condensing gas are not covered. Many of the same procedures and maintenance activities described in this publication are applicable if propane (L.P. gas) is used as the heating fuel. The orifices (the mechanism controlling the amount and direction of the gas flowing to the burners) and the pressure regulator must be changed to convert a natural gas unit to propane. As a unit is converted, a label should be added

Greg Tuttle, Graduate Student, Department of Agricultural Engineering Susan Mireley, Associate Professor and Extension Housing Specialist Department of Human Environment and Design HOW A GAS-FIRED HEATING SYSTEM WORKS

How the Typical How A Typical Gas Burner Works to burn , with additional gas and air fed to the burners by the gas supply Forced Air Distribution When a room thermostat is turned line, the air shutters and furnace/ System Works up or the drops boiler room air. In turn, the When the air temperature in the below the thermostat setting, the combustion gases from the flames heat exchanger reaches a unit signals the furnace or boiler that flow through the flue passages of the predetermined temperature, which is additional heat is needed. As a heat exchanger, heating it, and then controlled by the -and-limit control, result of the signal, the gas control continue to flow up and out the the furnace blower begins pulling cool valve opens, allowing gas to flow exhaust stack (see Fig. 2 for a forced room air through the return air regis- into the mixing tubes (see Fig. 1), air distribution system and Fig. 3 for a ters and ducts (see Figs. 2 and 4). The where it mixes with the incoming hot water distribution system). In the air is passed through an to combustion air. The fuel/air mixture meantime, heat is transferred from remove dust. It then passes through then flows to the burners, where it is the flue gases in the heat exchanger the heat exchanger, as described ignited by either a pilot light or an to the medium (either air or water) above, where it is warmed by hot electronic spark. Ignition occurs that flows through the distribution combustion gases passing through the only during start-up. Once started, system that supplies heat to the heat exchanger on their way out of the the flames continue various parts of the home. house. The furnace blower then forces the warm supply air into a plenum and through the supply ducts, finally distributing it through supply registers located in each room in the home. The two air supplies, the combustion air and the air distributed through the house supply system, should never come in direct contact with each other.

How A Hot Water Distribution System Works When a house thermostat calls for heat from a hot water distribution system, the circulator pump is activated (see Fig. 3) and supplies hot water held in reserve in the boiler throughout the distribution system- through the supply main, the supply branches and finally the baseboard units (i.e., or convectors in some systems) in the various rooms (see Fig. 5). As cool room air passes over the warmed baseboard unit surfaces, the air absorbs heat and dis- tributes it throughout the room. Individuals, furnishings and objects near the baseboard units are also warmed by heat given off by the units. The now cool water completes the cycle, flowing from the baseboard units through the return branches and the return main and back to the boiler. When the water in the boiler drops below a predetermined temperature, the activates the burner (see Fig. 3). The heat given off by the burner warms the heat exchanger and rewarms the water in the boiler, which holds it in reserve until the circulator pump moves it through the distribution system once again. This two-phase process enables the system to maintain an on-demand supply of hot water at all times. The homeowner doesn't have to wait for the water to be reheated and circulated through the system.

MAINTENANCE AND INSPECTION YOU CAN DO

During the heating season, furnaces and can accumulate a buildup of dirt In addition, the various moving parts wear. Dirt and water can lead to a loss of system efficiency, system failures, and health and safety problems. Annual inspections and maintenance are required to keep a gas-fired heating system operating efficiently and safely. You can do a number of maintenance tasks yourself. You may want to ask your heating contractor to show you some of the procedures during his or her next visit, or consult your heating system owner's manual. It should provide an excellent guide to the activities do-it-yourselfers can do. This publication describes some of those activities in a general way, but the owner's people. Novices and heating contractor to clean the manual will give you specifics inexperienced tinkerers should unit and adjust the amount of for your system. be aware of the potential for air entering the system through If the owner's manual is not creating problems. the air shutters. available, write to the 3. Gas is a clean-burning fuel. manufacturer and request that The Furnace/Boiler If during your inspections you one be sent to you. You will 1. Inspect the pilot flame notice greasy dirt or soot built find the manufacturer's name height and color (see Figs. 1 up on the burners, a problem is and probably the address on the and 6). Check your unit's present. Call your heating nameplate affixed to your unit owner's manual for the contractor to locate and repair somewhere..If the procedure and the correct it. manufacturer's address is not height. The flame should be 4. Clean the draft hood (see available, consult your heating blue and fairly sharp. If it isn't, Fig. 1), the mechanism that contractor or search the yellow or if it seems too high or too controls the rate at which pages to find the name of a low, have a heating contractor combustion gases are pulled up heating contractor that sells the adjust it. Some gas burners may and out of the flue or chimney. brand you own. In your letter, have a spark ignition unit in Dust buildup can interfere with give the model and serial place of a standing pilot light. the hood's efficient operation. number of your unit so the This is an energy-saving Vacuum any loose dust. Note: correct owner's manual can be feature that helps cut gas on some gas burners, the draft sent to you. Both numbers can consumption and so saves on hood is incorporated into the be found on the unit's heating bills. body of the unit and may not be nameplate. 2. Inspect the flame color of directly visible. Your owner's If you are a novice do-it- the burners and the pilot light manual will explain the location yourselfer, follow the (see Fig. 1). A natural gas and any care it needs. manufacturer's flame should be primarily bluish 5. Inspect the exhaust stack recommendations carefully and and it should be fairly sharply for bad connections and do only those tasks the manual defined. (It you are burning damaged or corroded pipes explains clearly. All others propane, the tips of the flame (see Figs. 1, 2 and 3). Have a should be done by a heating should be yellow.) If theflame heating contractor replace any contractor. Gas is a clean, is lazy or yellow, the burners damaged parts. efficient and safe fuel if the should be cleaned or the gas-to- 6. Inspect the furnace's/ equipment burning it is well air ratio in the mixing tubes boiler's electrical system maintained by knowledgeable needs to be adjusted. Contact a (master switch and electrical cable, for example). Electrical problems affect the performance of a unit and also present a safety hazard. Bad connections, bare wires, blown fuses or tripped circuit breakers indicate that an electrical problem is present. Contact your heating and cooling contractor to correct it. (Warning: electricity is potentially dangerous for people not familiar with its operation. Use care in trying to correct any problems yourself.) If you ever notice damaged wires in front of the burners, contact your heating contractor. 7. Clean the furnace room bearings are sealed.) Warning: house air supply, or unusual periodically. Dirt and lint from shut off electricity to the unit cycling of the burner or fan or areas surrounding the unit can before starting these both-should be reported to your be pulled into the burners along procedures. heating contractor. with combustion air. Eventually 2. Inspect the blower fan belt 7. Periodically throughout the they will slow the movement of for wear and correct tension heating season, make a combustion air to the unit, (see Fig. 2). It is fairly common conscious effort to listen to causing it to burn inefficiently for the belt to be too tight, your unit as it goes through a and give off soot. which can lead to failure of the heating cycle. The normal 8. Clean the room motor or fan bearings. On the procedure is: the room thermostat(s). Dust buildup other hand, a loose belt can slip, thermostat calls for heat, the interferes with efficient causing faster belt wear and burner goes on, the fan then thermostat operation. Remove premature belt failure. Replace starts. Both should remain on the cover and wipe away dust the belt when slippage can no until the thermostat temperature with a soft brush, such as a longer be corrected or belt is satisfied. Once it is satisfied, watercolor paint brush. Work failure seems likely. Adjust the the burner stops first, followed carefully- are belt tension according to your by the fan. If the burner or the fragile. furnace's owner's manual. fan or both cycle on and off 9. Inspect any visible sections Warning: shut off electricity to frequently before the of the chimney and the the unit before starting belt thermostat is satisfied, a chimney top. If they are worn adjustment. (Note: many newer problem exists. Consult your or damaged, consult your gas furnaces do not have a fan heating contractor. Likewise, if heating contractor. belt-a motor drives the fan the burner ever goes on but the 10. Safety note: gas-fired- directly.) fan does not follow, call a furnaces and boilers require an 3. Replace the air filter heating contractor. adequate supply of air to periodically to ensure that air is ensure proper and safe burning circulating freely and cleanly Hot Water of the fuel. In addition, (see Fig. 2). Dirty air filters Distribution System adequate clearances are slow air movement, make other 1. Clean the circulator motor necessary between furnace components work and lubricate the motor and combustibles such as walls, harder (which shortens their circulator pump (see Fig. 3). doors and framing members useful life) and waste energy. Dust and dirt buildup inhibits and the furnace/boiler, the vent Inspect them monthly to efficient operation. Consult stack and the chimney. Never determine how often they your owner's manual for enclose a unit unless you check should be changed. Follow instructions and lubrication with a heating contractor about directions provided in the needs. the unit's combustion air needs. furnace owner's manual. 2. Clean and bleed baseboard Never store combustible 4. Inspect work for air units (convectors or radiators in materials near the unit. leaks that result in heat loss and some systems; see Figs. 5 and wasted money (see Fig. 4). 7). Both dust and dirt buildup on Forced Air Locate them by running your the baseboard unit's fins and air Distribution System hand over areas where you in the pipes decrease the heat 1. Clean the blower fan and suspect leaks. Seal leaks with transfer efficiency of the the blower housing and clean duct tape. baseboard unit. A vacuum and and lubricate the blower fan 5. Clean and clear room a softbristle brush work well shaft and the blower motor supply and return air registers together for cleaning the fins. If (see Fig. 2). Dust, dirt and of any dust or obstructions (see air is present in the pipes, you'll debris buildup affects the Fig. 4). They reduce air hear a sound similar to water efficient operation and useful circulation and waste energy trickling. Bleed the unit by life of these components. dollars. A vacuum will do a opening the air valve until Remove it with a vacuum or good job. water runs freely from the unit. soft cloth and lubricate 6. Any warning signs noted Then close the valve. (Note: according to your owner's during the heating season such many modern hot water manual. (Note: some newer as unusual odors from the systems contain automatic units may not require registers, discoloration over bleeders and do not require this lubrication because the registers, excessive dirt in the step. Consult and follow your owner's manual for the correct system every two to three years Cleaning improves heat procedures.) and perhaps annually if the transfer between the heat 3. Inspect baseboard units to system is old. The cost will be exchanger and the household ensure that adequate clearance approximately $50 per visit. air or water supply. exists between them and the 8. Check for gas leaks, which floor, particularly carpeted The Furnace/Boiler are extremely dangerous. floors. Clearance is necessary 1. Inspect and clean the Serious health hazards are to allow air to flow freely burners (see Fig. 1). They can possible if sufficient quantities around the unit. If your hand easily become plugged by dust of gas are released into the cannot slip easily into this area, or soot. Cleaning requires home. Gas has a peculiar odor. consult a heating contractor special equipment. If you ever suspect a leak, about raising the unit. 2. Adjust the air shutters (see immediately leave the home Fig. 1 ). The air shutters control and contact your gas company MAINTENANCE AND and regulate the air/fuel mixture or service person from a INSPECTION released for ignition and nearby phone. A SERVICE PERSON combustion. Their correct 9. Check for combustion SHOULD DO adjustment improves overall leaks. Combustion leaks allow furnace efficiency and thus dangerous gases to escape into Though you can do the helps reduce energy costs. the furnace room and duct maintenance and repair tasks 3. Adjust the gas pressure to work. described in your owner's the burner. The pressure manual, other jobs require the affects the volume of gas Forced Air knowledge of a heating delivered to the burner and, Distribution System contractor. Inexperienced thus, the air/fuel mixture. 1. Align the blower pulley and homeowners attempting these 4. Inspect the gas control the blower motor pulley (see tasks may make mistakes that valve (see Fig. 1). This valve Fig. 2). Improper alignment expose them and their families controls the amount of gas can cause abnormal belt wear to unnecessary hazards and flowing into the system. The and slippage. (Note: most possibly damage the heating contractor will newer gas equipment. We mention these determine if it is operating tasks because a heating correctly and inspect for leaks Continued on page 11. contractor should do them in the valve. during a regular maintenance 5. Inspect the thermocouple, a visit. When selecting a safety device designed to sense contractor, ask about the and shut down the gas supply to standard service procedures the pilot flame if the pilot light followed and see if they are goes out (see Figs. 1 and 6). If similar to those described here. it is worn, the heating We suggest that a heating contractor will replace it. contractor service your 6. Inspect and adjust safety devices incorporated into the unit, such as the fan-and-limit switch or aquastat, burner safety devices and any power flue devices, if the unit contains a power draft. 7. Clean the heat exchanger surfaces (see Figs. 2 and 3).

Continued from page 6. furnaces do not have pulleys-a To save energy, you may want to high pressure should occur because motor drives the fan directly.) ask your heating contractor to of overheating, and the limit 2. Adjust the blower fan speed lower these two temperature thermostat, which would turn the (see Fig. 2). Overly high fan speed settings to a level closer to the unit off if the boiler should will cause duct noise and waste house thermostat setting. As a overheat. electricity. If the fan is set result, the furnace will supply 3. Check and adjust air and unnecessarily low, an excessive more heat to the house but the air water levels in the , amount of heat will be lost through will feel cooler. You may which provides a reservoir for the the supply ducts before it reaches experience some draftiness and safe collection of water as it the registers to provide room heat. discomfort after the changes until expands during the heating cycle 3. Adjust and test the fan-and- you become accustomed to the (see Fig. 3). Note: many new limit control, which measures the new settings. expansion tanks contain bladder or temperature of the air surrounding diaphragm devices that control the heat exchanger. It Hot Water water and air levels automatically. automatically turns the furnace Distribution System blower on and off during each 1. Check the circulator pump burning cycle and shuts the burner coupler for wear and broken Sources: down if the heat exchanger coupler springs (see Fig. 3). becomes overly hot. The control Normally, if the coupler springs Brotherson, Donald. ''Heating the monitors three temperatures: a are broken, a loud racket occurs; Home,'' G3.1. Small Homes fan-on temperature, a fan-off they have been known to be Council-Building Research Council, temperature and a temperature broken, however, with little noise. University of Illinois, 1976. limit, which is the safety device 2. Check the operation of all designed to shut the burners off if safety controls (see Fig. 3), such the heat exchanger becomes too as the safety relief valve, which Energy, Mines and Resources hot. It is never adjusted or would relieve the system if overly Canada. "The Billpayer's Guide to changed-the other two can be, Heating Systems.'' Minister of however. For example, the fan-on temperature is usually about 135 degrees F. When the air around the heat exchanger reaches this temperature, the blower fan comes on and moves the heated air throughout the home. The fan-off temperature is usually set at approximately 100 degrees F. When the air surrounding the heat exchanger reaches this temperature, the fan blower stops so it doesn't circulate cooler air through the home and cause uncomfortable drafts.

Supply and Services, Canada, 1983. Knight, Paul A. Mechanical Systems Retrofit Manual.- A Guide for Residential Design. New York: VanNostrand Reinhold Company, 1987. Mireley, Susan and Don D. Jones. "The Indiana Do It Yourself Home Maintenance Checklists: Space Conditioning Systems," HE- 63. Indiana Cooperative Extension Service, Purdue University, July 1986.