Sep 16

What Should You Know about Your Furnace

It’s getting that time of year that you are going to want to turn up the thermostat and turn on some heat.  As a homeowner what should you know about your forced-air heating system (furnace).  In this article I’ll cover what is a forced-air heating system, maintenance tips, and what we look for during the inspection.  I’ll also answer a question I get a lot from home buyers about the furnace.

Forced-Air Heating

Warm-air heating systems are of two types: forced-air and gravity.  Gravity systems are occasionally still found in older single-family houses, but most gravity systems have been replaced or converted to forced-air (so for this article I will discuss forced-air systems only).

Most forced-air systems use natural gas, propane, or fuel oil as the heat source, but some systems use electric resistance heaters or heat pumps.  The circulation blower and air-distribution ductwork for electric resistance heating systems and heat pumps are identical to those of gas-fired and oil-fired warm-air systems and should be regularly serviced and maintained.

Heat exchanger.  The heat exchanger is located downstream of the burner in gas-fired and oil-fired furnaces and separate the products of combustion from the air to be heated.  It is critical that the heat exchanger be intact and contain no cracks or other openings that could allow combustion products into the warm-air distribution system.  Visual detection of cracks, even by experts, is a difficult (if not impossible) process.

Monitor.  Look for signs of soot at supply registers and smell for oil or gas vapors.  Observe the burner flame as the furnace fan turns on; a disturbance or color change in the flame may indicate air leakage through a crack in the exchanger.  A major cause of premature exchanger failure is water leakage from humidifiers or blocked air-conditioner condensate lines.  Check for signs of water leakage.  The durability of the heat exchanger determines the service life of the furnace.

Circulation blower fan.  If the fan is worn or misaligned, or has excessive dust and dirt on the fins, the fan may rumble or make unusual sounds that may actually shake the ductwork.

Distribution system.  The distribution system is made up of supply and return ducts, filters, dampers, and registers.  Supply and return may be made of sheet metal, fiberglass or other materials.  Check ducts for open joints and air leakage wherever the ducts are exposed.  Air ducts can be cleaned by an HVAC contractor or a professional duct-cleaning  contractor.  Ducts could be cleaned every five years.  Cleaning ducts is part of maintaining a healthy home.  There should be no openings in return ducts in the same room as a combustion furnace.

Check the air filter.  Air filters are usually located on the return-side of the furnace next to the blower, but they may be found anywhere in the distribution system.  Check for their presence and examine their condition.  You should check and replace the air filter every month (or according to the manufacturer’s recommendations).

Humidifiers.  If humidifiers are installed they may be located in the supply air ducts.  (Here in western Colorado I don’t see a lot of humidifiers because people like their dry air).  Ideally, they are not located in the return air ducts because the moist air will pass through the heat exchanger and evaporator coil, rendering the humidification ineffective and corroding the heat exchanger.  Humidifiers require regular maintenance.

Maintenance Tips

Maintaining your furnace really is an issue where “an ounce of prevention equals a pound of cure”.  Replacing a forced-air furnace is a costly process.  Mid-efficiency furnaces cost $2600 to $3300 to replace.  High-efficiency furnaces cost $3600 to $4700 to replace.  Therefore performing regular maintenance is essential for saving money and keeping your family warm in the winter.

Air filter replacement.  Every month replace your air filter on a forced-air furnace.  It’s as easy as locating where the filter is located, going to the hardware store and buying a few air filters of the exact size that need to be replaced.  Non-electronic air filters cost a few dollars (usually less than $5 per filter) and are worth the small price to help keep your furnace running efficiently.  High-efficiency and electronic air filters cost more, but are still worth the price.

Annual maintenance.  Your furnace should be inspected and cleaned annually by a licensed HVAC contractor.  These contractors are trained and licensed to be able to look for problems with your furnace.  They will make sure that the furnace is in proper working order and if anything needs to be repaired.  Call them early in the season before you need to use their furnace, because by late September or early October they are booked up a month or two out and it will be difficult to find one that is available.  I typically call my HVAC guy in late August.  The maintenance and cleaning should cost between $100 and $200.

Also, make sure that the HVAC contractor attaches a label, or gives you a label to attach, somewhere to the furnace that indicates the date of inspection, what was inspected, and who inspected the furnace.  This will give you a record for yourself and the next person that may own your home when the furnace was last inspected and cleaned.  All good HVAC contractors do this without being asked to do it.

Furnace Inspection

According to the Standards of Practice here is what we will inspect for any heating system:

  1.  The inspector shall inspect:
    1. the heating system, using normal operating controls.
  2.  The inspector shall describe:
    1. the location of the thermostat for the heating system;
    2. the energy source; and
    3. the heating method.
  3. The inspector shall report as in need of correction:
    1. any heating system that did not operate; and
    2. the heating system was deemed inaccessible.
  4. The inspector is not required to:
    1. inspect or evaluate the interior of flues or chimneys, fire chambers, heat exchangers, combustion air systems, fresh-air intakes, humidifiers, dehumidifiers, electronic air filters, geothermal systems, or solar heating systems.
    2. inspect fuel tanks or underground or concealed fuel supply systems.
    3. determine the uniformity, temperature, flow, balance, distribution, size, capacity, BTU, or supply adequacy of the heating system.
    4. light or ignite pilot flames.
    5. activate heating, heat pump systems, or other heating systems when ambient temperatures or other circumstances are not conducive to safe operation or may damage the equipment.
    6. override electronic thermostats.
    7. evaluate fuel quality.
    8. verify thermostat calibration, heat anticipation, or automatic setbacks, timers, programs or clocks.

Frequently Asked Questions about the Furnace

“I’m buying this home and the inspection report states that the furnace is past it’s estimated useful life, will I have to replace my furnace? If so, will the seller replace the furnace for me?”

The estimated useful life for most forced-air furnaces averages 15-20 years.  With regular maintenance most gas-fueled furnaces may last much longer.  Replacing a furnace that is working properly is not something needs to be done.  It is also something that the seller is not going to do if the furnace is working properly.  If there is no indication as to when the last HVAC contractor inspected and cleaned the furnace, then that should be done immediately.  HVAC contractors can tell if all is well with your furnace, but even they can’t tell you how long it will last.  If you are still worried about it, buying a home warranty would be good insurance against this possibility.

“The inspection report states that the furnace burner flame was not blue in color, what does that mean and do I have to replace the furnace?”

There are various conditions that can cause the incorrect flames (not blue, noisy, floating above the burner) including incorrect drafting, dirty burner orifices and improper gas pressure.  The seller is not going to replace the furnace because of these issues.  You should get a licensed heating contractor to evaluate and repair the furnace before using it.

Contact me Now to schedule your home inspection.  Proudly serving Montrose, Ouray, Ridgway, Delta, and Grand Junction in Colorado.