FAQS

Answers to more specific furnace questions:

• Q: My furnace blower is running constantly, but it’s not heating, just blowing cold air. What could be wrong with it?

  A: On many newer furnaces, the blower comes after a few minutes of the thermostat sending a signal to the furnace to come on. Even if the furnace burners do not come on, that blower may operate as long as the thermostat is sending a call for heat to the furnace. In that case, the blower may run continuously. You would need a technician to diagnose why the burners are not coming on. You can try the following before calling a technician:

  • Turn the power to the furnace off and leave it off for at least 30 seconds before turning it back on. The main power switch is generally mounted to the side of the furnace and looks like a typical light switch.

  • Check your air filter. A dirty filter or a filter that is too restrictive will reduce the airflow of the furnace and can cause a furnace to overheat. Some 1” pleated filters (MERV 13 or higher) can be too restrictive for some systems, so even a brand new filter can cause a furnace to overheat. If you’ve recently changed the type of filter you’ve traditionally used, this may be the problem. A dirty or restrictive air filter can cause the furnace to overheat and in most furnaces, the blower will be turned on to cool the furnace off and to alert you that there is a problem.

  • Make sure all the heat runs are open and the return air grilles are not blocked. Turn the furnace back on.

  • If it fires up and runs like normal, resetting the furnace and changing the filter may have solved the problem. If it still isn’t working, you’ll need to call for service.

• Q: I notice that my burner only comes on for a few seconds, then turns off, so I don’t have any heat. What could be wrong?

  A: This is commonly a dirty or failed flame sensor. The flame sensor can get dirty over time and needs to be cleaned periodically. This is one of the things we clean when we do a furnace tune-up. Some homeowners who are handy may choose to clean the sensor themselves; if you decide to do this, we recommend using a scotch-brite pad (no chemicals) or steel wool.

• Q: My furnace isn’t working, but I can hear something trying to work inside the furnace.

  A: If resetting the power doesn’t solve the problem, most modern furnaces have multiple safety devices that protect your safety and the furnace from damage. There are just too many things that can be going wrong here, you’ll need to call for service.

• Q: Why does my thermostat say there is “no power” or the display is blank?

  A: If you’ve already replaced the batteries and that didn’t solve the problem, many modern thermostats, especially those with a color screen do not have replaceable batteries and they rely on an internal rechargeable battery to operate. If the power is interrupted to the system, the display will only stay on for a few hours.

  • Check to make sure the power to your furnace is turned “on” and the door of the furnace is securely in place

  • Check the circuit breaker that feeds power to your furnace. Homes built since the 1970s will have a separate circuit breaker to the furnace. If the breaker is in a “tripped” state, the breaker position will be between “on” and “off”. If that’s the case, reset the breaker by turning it “off” then back “on”. If it trips again immediately, there is an electrical problem in your system; it may be a shorted wire, motor or circuit board, or possibly water has leaked into the system and caused a short. All of these are serious issues and you should call for a professional to repair the system.

• Q: How often do I need to change my air filter?

  A: First off, a furnace or air conditioner should never be run without a filter. How often the filter needs to be changed is affected by the type and size of the filter, the size of your home and environmental factors. If you live in a dusty area or if you have pets that shed dander, you will have to change your filters more often.

  Airflow is more critical for air conditioning than for most gas furnaces, so you may need to change the filter more often in the summer than in the winter.

  As a general rule for filter changes:

  • 1” fiberglass filters (very low efficiency) will last 2-4 months in most homes, but they don’t really stop any dust, just lint and hair

  • 1” pleated mid-efficiency filters should be changes every 2-3 months in most homes

  • 1” pleated high efficiency filters (above MERV 10) may need to be replaced more often since they catch more particles, and although they have more surface area, in many cases, they get dirty to the point they restrict the airflow too much. So, in some homes, they may last 2-3 months, others, may have to change them every month

  • 4” pleated air filters, MERV 8-10, in most cases you can use them for about 6 months. If you have pets that create a lot of dander, you may have to replace them every 3 months

  • 4” pleated, MERV 13-16 have more pleats and more surface area, but also catch more dust, so they have a similar life expectancy of about 6 months. In some homes (no pets, smaller and very clean), they can last up to 1 year

• Q: My furnace is making a “squealing or grinding noise”.

  A: Most furnaces have 2 motors, an inducer motor that removes the dangerous flue gases and pushes it outdoors. The second motor is the main blower motor that circulates air throughout the building. Both are considered major repairs and once the bearings start to make noise, they are usually failing and you have very little time before the motor actually fails. You should call for service immediately!

• Cooling: General Recommendations for when your air conditioner isn’t working:

  General recommendations:

  • Check your air filter. Anything that reduces airflow substantially can cause the system to freeze and create ice in the indoor air conditioning coil (usually sits on top of your furnace). If the a/c unit is running, but no or very little air is coming out of the vents, there is a high likelihood that your coil is frozen and the dirty air filter is often the cause. It needs to thaw before restoring power to the unit. Try switching the cooling off at the thermostat, turn the fan to “on” and run it for 3-4 hours. Keep a close eye around the indoor unit (furnace or fan coil unit) because as that ice thaws, it can overwhelm the drain system and cause some minor flooding around the furnace and sometimes that water can seep under walls and cause damage to adjacent rooms. If that is occurring, turn the system off completely and let it thaw slowly (it can takes up to 12 hours). When you turn it back the blower back on, if the airflow returns to normal flow rates, you’ve probably thawed the coil and you can turn the cooling back on.

  • If there is any sign of frost or ice on the piping by the indoor or outdoor unit, the system is definitely frozen. If there is visible ice outside of the unit, the coil inside the duct is probably a block of ice. That will need to thaw before turning the unit back on. Depending on how thick the ice is, it may take up to 12 hours to thaw completely. Shut the system down, let it sit for several hours and turn it back on. If after changing the

  • Try resetting power on both the indoor and outdoor units. Many newer high efficiency units “monitor” the incoming electrical voltage and may shut down the power to the unit at the circuit board to prevent potential damage to the unit. In that situation, resetting the circuit board may solve the problem.

  • On the indoor unit, there should be a switch next to the unit (usually a gas furnace), turn power off for about 30 seconds, then turn it back on.

  • On the outdoor unit, there is a disconnect switch (a breaker or a fuse block), usually mounted on the wall next to the outdoor unit. If it’s a breaker, try turning it off for 30 seconds and then back on. If it is a fused disconnect, there is generally a plug that you pull straight out. Pull the plug out and after 30 seconds, plug it back in. On most installations, we use a fused disconnect, so there are often fuses on the back of that plug. Some plugs have an LED light that indicates if a fuse is blown. If that LED light is on, the fuse needs to be replaced. A tripped breaker or blown fuse can sometimes be a “nuisance” trip or failure caused by some electrical disruption from the power company. In most cases however, the tripped breaker or blown fuse indicate a failed component or an electrical short.