Coming home from work to discover your furnace isn't running can cause nearly anyone to panic, especially in subzero temperatures. Your first instinct may be to make a call for emergency services. But before you pick up the phone, there are some simple things you should check.
Do you have fuel?
If you rely on automatic deliveries, or call for fuel at regular times, you may not have noticed if the fuel has run low. This can happen if the delivery is late or you have experienced a cold snap and used more fuel than you anticipated. If you rely on a gauge to tell you when it's time to reorder fuel, the gauge may have failed causing you to run out of fuel without realizing it. If you have noticed that your tank registered the same level for weeks at a time, your gauge may be stuck or may have stopped working. Even if running out of fuel seems unlikely, checking it to be sure is necessary. Open the tank and look in to see if you have fuel. You can also use a clean stick to measure the level of fuel in your tank.
Does your furnace have power?
Check that the furnace is turned on, that it is plugged in, and that the circuit breaker is on. Check that the emergency switch on the side of the furnace has not accidentally been tripped and that all doors to the furnace are closed securely and the button is pushed in. A loose or open door may disengage the furnace. Check that you have power in your home. An electrical outage will prevent your furnace from running.
Is the thermostat working?
Check that the thermostat is set to the on position and is set for heat. Verify that the temperature setting on the thermostat is set higher than the ambient air in your home and that there are no loose wires to the thermostat. If you have a thermostat with a timer, check the date and times in the settings to be sure they indicate you need heat at this time. If you suspect that your thermostat is not working correctly, test to see whether the signal from the thermostat is reaching the furnace by having one person turn up the thermostat while another stands by the furnace and listens for a tiny click. This indicates the signal from the thermostat is reaching the furnace, explains SF Gate.
Are your filters clogged?
Your furnace has both air and fuel filters. If either of them clogs, your furnace will not function properly. Remove the air filters and replace them with new filters, or vacuum them clean until you can get new filters. Air filters clog easily with dust and pet hair. If you are the do-it-yourself kind, you can also replace the fuel filters. These are typically located in the filter housing (it looks like a cup) close to the fuel tank. These filters may clog with residue from your fuel tank and may also freeze if you have any moisture in your tank. The fuel may also gel inside the filter during extremely cold weather. If you suspect the fuel filter is the culprit, change the filter. If you are uncomfortable with changing the filter, your HVAC dealer will gladly do it for you.
Checking for obvious reasons why your furnace has stopped working will save you the embarrassment and cost of an emergency call when the real problem was as simple as turning on the power. If you are unable to determine why your furnace is not running with these quick checks, call your HVAC dealer or visit a site like http://www.advancedheatingandcooling.com to find an HVAC contractor. He has the experience and expertise to troubleshoot and correct the problem for you.