Why isn?t your furnace running??? Do you know? Do you want to know? If you do want to know then I suggest you keep reading. Even if you do know, I suggest you keep reading either to see if I?m right or maybe even I teach you something you didn?t know.

HAHA!

Anyways, furnaces can be a huge pain in the ass! Lots of moving parts, lots of hot parts. It can seem a tad intimidating. However, once you know how a furnace works, and its sequence of operations, you may be a little less intimidated.

To start it?s as easy as flipping the switch. In most homes, if you are near the furnace and you look up, you?ll see a switch that says furnace off/on. Turn that baby on and listen to her purr. Then head upstairs and turn that thermostat to the desired temperature. If you have an older mid-efficient furnace you?ll her some clicks, these are the thermostat and the controller letting each other know we want heat. This sends a message to turn on the gas valve. Either the pilot flame or the spark igniter will light the gas. Your furnace is now producing flames. You?re wondering why the blower hasn?t fired up yet. There are flames, why isn?t the fan on? Well there is a thermally controlled switch, that once hot enough, closes and sends power to the blower motor. Now as the heat is blown throughout your home, its heating up the two metals that are inside your thermostat. If you have seen an old thermostat with a metal coil in it. That is 2 dissimilar metals that expand and contract at different rates. As it heats and cools it tells your furnace to turn on or off. As this happens it stops the call for heat, thus shutting down the furnace. They?re easy and usually pretty reliable. If you do have one of these older furnaces, please make sure you have it tested for CO (Carbon Monoxide) at least once a year. Preferably before the heating season. As always make sure you have working CO detectors in your home and near your bedrooms.

Now The newer furnaces have some more complicated parts and may more checks to keep you safe.

When you flip the switch on a newer high efficient furnace you will hear a couple clicks, again relays saying there is a call for heat. This is followed by a whirring sound. That?s the inducer motor. It?s the black cylinder in the upper portion of the furnace. It moves the air through the heat exchanger and out through the vent. The furnace ensures this is happening by using pressure switches. These are either metal or plastic disc-shaped items with rubber hoses and 2 wires coming out of it. They will either turn off or on based on the amount of air pressure being moved by the inducer motor.

This will then send a signal to the control board saying to turn on the igniter. Now depending on the ignitor in your furnace, you may either hear a clicking sound or you will see a bright orange glow. This is telling the furnace it?s ready to go. The gas valve will now open and the igniter (either version) ignites the flames. Now the control board wants to know that those flames are actually there. This is done with a flame sensor. It?s a small metal rod with a ceramic base. Its held in place with 1 screw and you?ll find it in front of the burners. (If you notice that your flame goes out right away. This can be cleaned with a green scrub pad. This removes the carbon buildup allowing it to send the correct voltage back to the board. DO NOT USE SANDPAPER)

So once it proves that the flame is there, that same switch from the old-style furnace. Remember what that does? Closes the thermally controlled switch, sending power to the blower motor. Then, same deal. The fan heats the house. Turns off the t-stat and thus the furnace. There are other sensors and switches on a furnace that is there to keep you safe. They should be left to the professionals though. If they are causing your furnace to fault out, there are bigger problems.

So After reading this, you can follow the sequence and hopefully diagnose the issue. DO NOT ATTEMPT TO REPAIR ANYTHING ON A FURNACE UNLESS YOU ARE A LICENSED GAS FITTER!!!

From this point, call us at 780-818-3021 and let us know what your diagnosis is and we can get you fixed up from there. Boisvert & Croft Plumbing & Heating has been keeping Alberta wet and warm since 1953. Trust us to solve any of your plumbing or gas fitting needs.