heating-2016
  • Natural Gas Meters may have a regulator to provide the right gas pressure for the home. These discharge gas into the atmosphere through a relief vent. Regulators should vent to the outside, at least three feet from sources of ignition, windows, doors and appliance intakes or exhausts, and at least ten feet from mechanical air intakes.
  • Gas piping should not be used to ground the electrical system; however, metal gas piping is typically bonded to supply piping (usually at the water heater) or something else that is connected to ground. The bonding prevents the gas piping from becoming a dangerous electrical conductor if a live wire touches the piping.
  • Propane Tank location is determined in part by the size of the tank. Most tanks are at least 10 feet from buildings, property lines and sources of ignition. Tanks should not be covered by roofs, awnings or overhangs, since relief valves discharge propane straight up.
  • Carbon monoxide detectors help warn people of poisonous carbon monoxide due to incomplete combustion and back drafting.  They should be placed on every floor of a home and in every room with a wood burning appliance.
  • The vent connector carries the hot exhaust gases from the furnace or boiler to the chimney. It is typically a single-wall galvanized steel pipe, four inches to ten inches in diameter.
  • Vent connectors for gas systems typically require a six-inch clearance from combustibles, and vent connectors for oil systems need nine inches or more.
  • An undersized vent connector may restrict the flow of exhaust gases. An oversized vent connector may allow exhaust gases to linger and not move up and out the chimney.
  • High efficiency systems and some mid-efficiency gas systems with relatively cool exhaust have plastic vent pipes rather than a chimney.  There have been recalls on High Temperature Plastic Vents (HTPVs) for mid efficiency gas furnaces.
  • Brick chimneys can be lined or unlined. An unlined chimney has brick or concrete block on the interior. While this is suitable for many oil furnaces, it is not suitable in most areas for gas furnaces or boilers, because condensing exhaust gases can damage the chimney. The liner can be metal, clay tile, or asbestos cement pipe. Where more than one appliance vents into a chimney, the smaller appliance should connect above the larger one.
  • Two appliances sharing a single flue is not usually a good situation because exhaust from one appliance may come into the home through the vent for the other. A furnace and a fireplace, for example, should not share a flu. There are some circumstances where flues can be shared safely.
  • Type B and Type L vents require a one-inch clearance, and the special heavy metal chimneys used for wood-burning fireplaces typically require a two-inch clearance. Inadequate clearances may lead to overheating and fire.
  • Many modern thermostats are programmable and allow the temperature to be lowered when the occupants are away or sleeping. The maximum set-back should be less than twelve degrees Celsius, since cooler temperatures create higher relative humidity levels, which can result in condensation problems.
  • Heat exchangers in conventional furnaces have an average life expectancy of 18 to 25 years. The life expectancy of heat exchangers in high efficiency furnaces is somewhat less.
  • Many furnaces have a humidifier to add moisture to the house air through evaporation, combating the dry winter air in homes.
  • A humidifier duct damper should be provided if there is an air conditioner connected to the furnace. This damper should be kept closed during the cooling season to prevent air conditioner coil ice-up due to short-circuiting of the airflow.
  • Furnace Supply registers in basements are often located in the ceiling, which is not ideal. Many people install supplementary electric baseboard heaters rather than relocate the registers.
  • Furnace Supply air registers or return air grilles should not be provided in garages, since automobile fumes may be drawn into the house air.
  • Common problems with Furnace supply ducts and registers are disconnected or obstructed ducts, dirty ducts, ducts sized adequately for heating but inadequate for air conditioning, ducts sized for conventional furnaces, but inadequately sized for high efficiency systems, and unbalanced ductwork (too much air coming through one register and not enough air coming through another).
  • Until the mid-1970s, all furnace systems were of similar (conventional) design and efficiency. Almost all had an operating (steady state) efficiency of approximately 80%. When the system was operating, 80% of the heat produced from burning the fuel went into the house. The other 20% went up the chimney. The systems are not 80% efficient over the entire heating season.
  • When a conventional furnace is not operating, warm house air is escaping up the chimney. Even when the system is operating, a good deal of warm air is lost up the chimney, just maintaining adequate draft for the exhaust gases.  On gas-fired systems, some fuel is wasted keeping the pilot on. Also, when a boiler or furnace is starting up or cooling down, it is not operating at full efficiency. If you combine the off-cycle losses with the startup and cool-down losses, and add in the 20% losses during normal operation, the average seasonal efficiency of a conventional boiler or furnace is about 55% to 65%. That means 35% to 45% of the heat from the fuel is lost. With the advent of more efficient furnaces and boilers, this system became known as a conventional system. Conventional systems were phased out in the early 1990s.
  • Most mid-efficiency furnaces are conventional units (although some have a secondary heat exchanger) with modifications to reduce off-cycle losses. The enhancement is often an induced draft fan in the exhaust, which only operates when the burner is on. Alternatively, a motorized vent damper may be used in the exhaust to prevent heat from escaping up the chimney when the system is shut down. Both of these strategies prevent heat loss to the outdoors when the system is idle. Continuous pilots on gas systems are replaced with intermittent pilots. This avoids wasting fuel when the systems are not working. These improvements combine to almost eliminate the 20% off-cycle losses.
  • High efficiency systems also limit the off-cycle losses, just like mid-efficiency systems. They have a seasonal efficiency in the 90% range, with some over 95%.
  • Since there are more components in a high efficiency system, there is more to go wrong and repair and maintenance costs are typically higher than a conventional furnace.  At the very least, annual servicing is required. Many believe their life expectancy is also shorter.
  • Typical Furnace Life Expectancy: Conventional and mid-efficiency furnaces – 18 to 25 years High efficiency furnaces – 15 to 20 years Combination heating systems – 5 to 10 years
  • On modern hot water boiler systems, water is automatically added to the system through a pressure reducing valve as needed. The valve connects the boiler to the house plumbing system. It is typically set at 15 psi (pounds per square inch). If the pressure in the heating system drops below 15 psi, the pressure reducing valve allows water in from the plumbing system. When the plumbing system is drained, there is a risk of unhealthy water from the heating system draining back into the plumbing system.  Modern systems include a backflow preventer to keep this from happening.
  •  If the boiler is cold, the pressure gauge on the boiler should indicate roughly the same pressure as the pressure reducing valve (12-15 psi). If the two numbers are not the same, the pressure reducing valve may be out of adjustment or the pressure gauge may be wrong. There may    also be a closed valve between the pressure reducing valve and gauge.
  • Sometimes with hot water boilers the top floor of the home is cool, and radiators are not hot. If no water discharges after opening a radiator bleed valve on the top floor, the system is probably not full of water. There may not be enough pressure to push water up to the top of the home to fill the upper radiators. The pressure reducing valve may have to be adjusted or replaced. Bleeding the radiators is part of annual maintenance.
  • All water heating boilers should be provided with pressure relief valves. The valves are typically set at about 30 psi. If the pressure in the boiler gets too high, this valve will allow the pressure to escape safely by releasing water. This device should be tested by a qualified contractor during regular servicing since it is not tested during a home inspection.
  • The use of polybutylene (PB) piping for hot water heating in a baseboard convector configuration is not considered good practice. The connections are prone to leakage due to the cycling of pressure and water temperature. The piping is rated for 180°F, and the water temperature can exceed that.
  • When non-oxygen barrier polybutylene (PB) tubing is used in a hot water heating system, oxygen may pass through the tubing into the boiler water. This can cause the boiler to rust and fail prematurely. The condition of the boiler interior cannot be determined by a visual inspection. It is recommended that a heating specialist evaluate the system to determine whether improvements are needed. These could include adding a chemical to the system to discourage corrosion or adding a second heat exchanger system to separate the boiler water from the water circulating through the system. The heat exchanger option is costly but needs less maintenance.
  • Conventional boilers are roughly 60% seasonally efficient. More modern mid-efficiency boilers are roughly 80% seasonally efficient. There are very few high-efficiency boilers with efficiencies of up to 90%.
  • Typical Boiler Life Expectancy: Conventional and mid-efficiency cast-iron boilers – 25 to 50 years Conventional and mid-efficiency steel boilers – 20 to 35 years Conventional and mid-efficiency copper boilers – 15 to 25 years
  • An Electric baseboard heaters clearance from combustible materials should be followed. Draperies, for example, should typically be kept eight inches above the heaters.    Alternatively, the drapes can be three inches in front of the heaters as long as they are at least one inch above the floor.
  • Electrical receptacles should not be installed on the wall above an electric heater because appliance cords may touch the heater and overheat.
  • Heaters designed to operate at 240 volts can be incorrectly wired at 120 volts. They will not work as efficiently as they should. This will not normally be picked up on a home inspection.
  • For most furnaces and boilers, catastrophic failure is usually a crack or a hole in the heat exchanger. Since most of the heat exchanger is not visible, the heat exchanger cannot be fully inspected during a home inspection. Because a home inspection is not technically exhaustive, the likelihood of failure is based on probability rather than testing or equipment tear-down.
  • Most high efficiency furnaces require more air flow across the heat exchangers than conventional furnaces. Replacing a conventional furnace with a high efficiency furnace can be tricky. Older, smaller ductwork and/or an air conditioning coil can restrict air flow, increasing the temperature rise within the furnace. This can result in premature failure of the heat exchangers and void the warranty. This condition may not be identified in a home inspection.
  • Steam boilers are typically old and most are considered near the end of their life. Steam boilers have a heat exchanger, like hot water boilers and when this fails, the system is typically replaced.
  • Electric furnaces and boilers contain electric heating elements and controls for the elements. Every single component can be replaced. With age, however, electric systems get to a stage where replacement of the entire unit makes sense due to lost reliability and a lack of available replacement parts. Electric boilers have a water jacket that will eventually rust. Although there are not great statistics on these units, a life expectancy of 20 to 25 years may be reasonable. With individual electric heaters, failure probability is not meaningful, since replacing individual heaters is not a significant expense. Electric heating elements are like light bulbs. Their life expectancy is not well defined, and their failure can’t be predicted.
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