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174 Colonnade Rd #27

Ottawa, ON K2E 7J5


8 Common Furnace Problems And How To Deal With Them

Furnace problems can be a huge inconvenience for homeowner’s in Ottawa and the Ottawa Valley. Having your heater working at its best is critical in our frigid climate! This article deals with 8 common furnace issues and how to best deal with them. Each category will be broken down into items you can immediately investigate and when to call a professional HVAC company to diagnose your heater.

Furnace Not Working At All

When your furnace is not working at all, it can be a very troublesome time, especially if this falls in the middle of the winter! There are many causes of a furnace not turning on at all and many of the common problems are listed below:

  1. Furnace Kill Switch Has Been Flipped: All furnaces in Ottawa Canada are equipped with a kill switch. This disconnect is generally a light switch that is located in a few possible locations. This lightswitch should be labelled furnace but is not always properly identified. Popular locations include, on the stair well down to the basement, just outside of the mechanical room, just inside the mechanical room or just prior to the furnace. Please note these switches are generally installed either high on the wall or mounted on the ceiling. This is a common reason that the furnace is not running as it can be accidentally turned off.
  2. Breaker Has Tripped Or Is Defective: Less commonly, the breaker in your panel (labelled furnace) may have tripped, been switched off or be defective. After confirming that the kill switch is in the on position, it is important to confirm the breaker in the panel is in the on position. Please note that when touching an electrical panel, extreme safety is required and that a professional may be needed in replacement or diagnosis if you are not comfortable with electrical safety.
  3. Furnace Intake Is Blocked: A very common issue, especially in high snow areas like Ottawa and the Ottawa Valley, is blocked intake pipes. Most high efficiency furnaces have pipes that run from the furnace to the exterior of your home. One of these pipes is the flue which expels by products of combustion outside, while the other pipe is a fresh air intake that pulls outdoor air into your furnace to create combustion. When snow levels get high or temperatures get frigid, this intake pipe can become blocked and not allow fresh air into the furnace. Furthermore, items left leaning against these pipes can also block the intake. We commonly see tarps that are covering items such as bbqs, bikes or canoes getting pulled into the intake.
  4. Thermostat Malfunction: The majority of furnaces are controlled by thermostats. These control units can malfunction in numerous ways. The most common issue we see is in battery powered thermostats. Ensure the batteries are operating and the screen is not blank on the thermostat.  If the thermostat has fresh batteries or is powered through the furnace. Ensure thermostat is in heating mode and that the proper set temperature is input into the device.
  5. Filter: In extreme cases, a clogged furnace filter can cause a furnace to completely shut down. Neglecting to change the filter can, over time, can cause parts such as pressure switches, heat exchangers and fans to be overworked to the point of failure.
  6. Other: Numerous other part malfunctions can cause the furnace to shut off. In these cases if all of the above items are addressed it may be time to call a professional HVAC technician. Lack of maintenance or simply mechanical failure may be the culprit and require a diagnostic.

Loud Furnace

We hear complaints about loud furnaces all the time. Below is a list of common reasons:

  1. Filter Related Airflow Issues: Many times a loud furnace can be described as whistling or simply loud air noise. Many times, a dirty filter is once again the cause of this. The furnace needs air to be pulled in from the return side in order to deliver air to the rest of the home. Simply pulling out a dirty filter may reduce this noise dramatically.
  2. Ductwork Problems: Undersized or poorly designed ductwork is a very common issue we see in old and new homes alike in Ottawa. Think of your furnace as the heart of your HVAC system with the ductwork being the veins and arteries. When the heart cannot pump blood through the veins the system does not work. In our case, this can result in a multitude of frustrating noises. Whether is be whistling, intense air noise or loud bangs, this can be a result of poor distribution systems.  Many times ductwork
  3. Loud Motors: Your high efficiency furnace has multiple motors inside the cabinet including a fan motor and an inducer motor. Both of these can create noises that can be described as squealing, grinding or rattling. Sometimes a motor replacement may be in order but many times simply tightening a loose bolt can remedy this nuisance sound.

Furnace Leaking Water

  1. Plugged Drain: High efficiency furnaces create run off water known as condensate.  This water runs through a trap and tube in the furnace known as a collector box.  It can plug up with debris over time causing water to leak onto the floor. Furthermore, the collector box itself may crack, causing water to leak onto the floor. It is generally advisable to have a technician evaluate this and recommend a repair. As with most repairs, this can be avoided by having annual maintenance done on the furnace which includes flushing of the drain system.
  2. Malfunctioning Condensate Pump: If your furnace does not have a dedicated drain located in it’s vicinity it is likely that you have a condensate pump. This small pump is utilized transport the condensate to a different location that has a dedicated drain. This pump may be burnt out or a tube may have been disconnected from the pump. Ensure all drainage tubes/pipes are tied into the pump. If they seem to be tied in, it may be time to bring in a technician.

Furnace Blowing Cold Air

  1. Thermostat Issue: Again the thermostat is a common reason that the furnace is malfunctioning. Many times, especially with quiet, high efficiency furnaces, people do not know if the furnace is running or not. Most thermostats allow you to run your fan only when furnace is heating or constantly. When the furnace hits the desired set temperature, but the fan is in run always mode, you may feel that the vents are blowing cold air. Furthermore, ensure the set temperature is appropriate along with ensuring it is set in heat mode.
  2. Gas Valve Issue: You may have a furnace that is having a gas valve issue. This will require a technician to diagnose and repair. If the furnace is calling for heat but is blowing cold air this is a likely reason.
  3. Pilot Out: Older mid efficient furnaces generally had standing pilot lights. Much like a fireplace these pilot lights can blow out causing the furnace to continue to run without providing heat.

Furnace turning on and off

  1. Oversized: Unfortunately this is an extremely common issue that we see on a nearly daily basis. Many homes have furnaces that are much too large for them. This means that the house heats up very quickly, the thermostat is satisfied and the furnace turns off. This is often called short cycling and happens over and over throughout the day. If you believe this may be your scenario, call Airzone to have a professional home comfort advisor evaluate your system and complete a heat load calculation on the home. This will verify whether your furnace is oversized or not.
  2. Thermostat Location: We have seen some strange locations for thermostats. This can include locations much too close to a supply vent, nestled beside a refrigerator, behind a TV or directly in constant sunlight. All of the scenarios listed may impact the temperature reading on your thermostat causing the furnace to run for short periods of time or not nearly enough! A thermostat should ideally be, out of the sunlight, in a central location on an interior wall and also close to a return air grill.
  3. Distribution Issues: Your ductwork plays a massive part in the temperature distribution of your home. We have seen unbalanced ductwork lead to short cycling many times. This can happen when the ductwork is very restrictive, causing the furnace to overheat, tripping a limit switch and turning it off. This unfortunate cycle will repeat over and over. Furthermore, some homes have vents that blow much harder than others. If this is the case and that specific vent it located close to the thermostat it may cause the thermostat to prematurely satisfy and click off.

Furnace Barely Blowing Air

  1. Filter Problem: This is an incredibly common issue when it comes to poor airflow. If you do not change your furnace filter with frequency you will cause the furnace to be choked of proper air flow.  This results in poor distribution throughout the entire home.
  2. Ductwork issue: Restrictive and undersized ductwork will cause the furnace to feel as though it is barely blowing air. Long and convoluted routing can also cause massive loss of velocity. Furthermore, leaky and unsealed ductwork can cause large amounts of the air to not be delivered to the location of the vent. We have also seen return ductwork systems that are caked with dirt, debris and hair causing air flow issues. Unbalanced ductwork can wreak havoc on distribution causing some areas to receive way too much air and some nearly nothings. Having a certified, Airzone HVAC advisor investigate your ductwork is a great way to determine why you are struggling with airflow.
  3. Fan Setting:  In rare cases, your furnace was never tested nor set up properly at the time of installation. Most modern furnaces allow you to change fan settings to create more or less airflow. A certified technician can determine if there is a way to deliver more airflow where you need it.

Furnace Never Turns Off

  1. Furnace Undersized: Less common than an oversized furnace, undersized furnaces can run for extended periods of time without satisfying the thermostat.  It is important to note that many modern furnaces are multi stage. This means that they can operate at different outputs. There is a very big difference between a furnace that runs constantly and cannot hit a desired set temperature vs one that is running but maintaining a nice warm home climate.
  2. Thermostat Malfunction: A faulty thermostat or one that is programmed wrong may cause a furnace to run constantly. Things like over shooting the desired set temperature or improper readings often times lead to a faulty thermostat diagnosis.
  3. Clogged Filter/Coil: Once again a clogged filter can cause home heating issues. Not allowing enough air flow through the furnace can cause overheating, heat exchanger malfunctions and poor air flow. All of these factors can cause the furnace to seemingly run longer than needed.

Furnace Smells

  1. Dirty Filter: A filter catches dust, debris, pollen and hair that is in your air stream. In many cases it can also catch odours and slowly release them through the home. If you believe you are getting an unpleasant smell through your HVAC system, always check the filter first.
  2. Dirty Ductwork: Much like with the filter, dirty ductwork can also catch smells and odours. Having a duct cleaning and sanitization done can vastly improve the quality of air and also the freshness of air delivered throughout the home.
  3. Burning Component: The most troublesome source of smell comes from a part malfunction. Burnt wires, burnt out bearing and rubbing can all cause a burning smell throughout the house. If you smell burning, call an HVAC professional right away.

**Note, natural gas has a rotten egg smell. If you smell this at anytime you can call your gas provider, an HVAC professional or even the fire department.

Still Having Furnace Problems?

If you are still having issues with your furnace and need a professional’s opinion on a repair or a replacement we are here to help! Check out our new high efficiency furnaces or request a furnace repair quote today from our friendly team. Thank you for checking out our article on furnace problems in Ottawa and have an awesome day!

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