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Furnace Troubleshooting: 8 Causes of Inconsistent Building Heat

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Last Updated on June 25, 2015


If you’re are building or facility manager, one of the least pleasant parts of your job may be handling all the complaints about the building’s temperature.

How can it be that some complain about working in a meat locker, while others are opening the windows? It may not be just people’s individual comfort levels that are causing the problem. In fact, uncovering the associated furnace problems causing inconsistent heating system performance can sometimes be pretty complex.

But, never fear; basic furnace troubleshooting skills can help you hone in on the issue! Take an inventory of the following common 8 causes of heating inconsistency and take control of your building comfort!

1. Clogged air filter

Proper air flow is your furnace’s best friend, and keeps it operating efficiently and effectively. When your furnace’s air filter gets clogged with dust and debris, the reduced air flow impedes the operation of your furnace, making it more difficult to blow air through the entire ventilation system. This creates cold spots. How long has it been since you changed your furnace’s air filter? For most commercial spaces, air filters need to be changed monthly.

Related Article: Fall Furnace Maintenance – How to Change Your Furnace’s Air Filter

2. Inadequate return air flow

Take a walk around your building, and look for the vents that supply air and return air back to the heating system. Chances are, you’ll find at least a few that are blocked by furniture, cubicle walls, equipment, drapes or other impediments. You may even find some that have been closed or blocked intentionally by employees who don’t want air blowing on them. Remember what we said about proper air flow? Blocking vents prevents the system from operating as designed, and will create hot and cold spots in your building.

3. Worn or loose belts

If you haven’t done your yearly hvac preventative maintenance on your furnace, it could have worn or loose belts that are no longer able to turn the blower fan. Guess what happens next? Reduced air flow through your system, which once again prevents the furnace from getting the warm air to all parts of your building.

Related Article: What Do Flu Shots & HVAC Preventative Maintenance Contracts Have in Common?

4. Compromised ducts

Your ducts are an important part of your HVAC system, since they carry the heated and cooled air to the occupied spaces throughout your building. If they have not been cleaned and inspected in a while, there could be numerous holes and tears in the ducts, which causes all that expensive heated and cooled air to leak out into your building’s crawl spaces, where it’s not doing anyone any good. It’s also driving up your utility bills.

Your ducts could also be blocked with dust, debris, and even insect, bird or rodent nests. These blockages prevent air from getting where it’s supposed to be, and causing hot and cold spots.

5. Dirty evaporator coil

Your furnace probably also has an evaporator coil that’s used for air conditioning. If this coil gets covered with dust and grime, what do you suppose is the result? That’s right, impeded air flow. All that dirt prevents heat from transferring out of the coils, which causes your system to have to work harder to keep the space at the set temperature.

6. Faulty or improperly set thermostats

Your building probably has multiple thermostats controlling the temperature in different areas, some of which may have different heating needs based on occupancy and usage. First of all, today’s programmable thermostats and building automation systems can be more complex than the old dial thermostats. Check to make sure they are being set correctly. It’s also possible that one or more thermostats may need to be re-calibrated.

7. Building renovation or redesign

Has your building been renovated recently? Even if you haven’t broken any walls, but just re-arranged cubicle layouts, you’ve may have changed the occupancy and the air flow in certain areas. Your HVAC system’s ventilation may need to be modified to keep up with changes in usage and building design.

Related Article: 8 Steps to a Successful HVAC System Redesign: An Infographic

8. Wrong size furnace and/or ductwork

Inconsistent heating is a common symptom of a furnace that’s incorrectly sized for your building’s heating needs. This doesn’t always mean it’s too small; in some cases an oversized furnace causes the same problem.

It’s also important that the design and length of your duct work match the capacity of your furnace. The ducts must be able to channel the correct amount of air at the right pressure to each occupied area.

This is a problem that’s more than just an annoyance. Temperature variance causes much more serious issues than just discomfort. Studies show that worker productivity can be significantly reduced when people are too hot or too cold. And if you are running a restaurant, retail store, or health club, uncomfortable temperatures may be driving away customers and costing you money.

Relax, there is also some good news. In the majority of cases, bringing in an HVAC service company to clean and inspect your system will uncover problems that are relatively easy and inexpensive to fix. Want to learn more? Grab a copy of our free guide, Improving an Imperfect World: Mitigating Office Temperature Extremes.
Find out how to win the battle for optimal office temperature