Before we get into anything else, it is important to find out what type of gas fireplace you have. Most gas fireplaces in the same category function the same way. Also, many gas fireplaces use the exact same components, but just have a different brand name on the front.
Gas Fireplaces fall into 3 main categories
DIRECT VENT (DV)
NATURAL VENT (NV or B-Vent)
If you still have the owners manual, it should tell you if it is either a direct or natural vented appliance. But if you are like 99% of fireplace owners, you most likely do not.
Because of this, that are some rules of thumb we can follow. In general, if your fireplace has a sealed single-pane of glass on the front of it (where it requires clamps or screws to be removed to access the area where the flame usually is), you have a DIRECT VENT fireplace:
Conversely, if you have Bi-Fold type doors, or the fire is open to the room, you have a Natural, B-Vented, or vent free unit. These types of fireplaces rely on natural draft, a process that involves creating an updraft in the chimney by heating it up. These will use air from inside your home to fuel the fire.
There is another way to determine this as well. Most fireplaces have a rating plate that looks something like this:
It will tell you the brand and model number, which you usually do a quick Google search and find out what type of fireplace it is. The make and model of the fireplace is essential to know if you ever need to order replacement parts. The rating plate can be located in many places:
1.) Most commonly, underneath the lower louver of the appliance (in most direct vent fireplaces):
2.) On the upper baffle of the fireplace (in natural drafted fireplaces):
3.) Bolted to the back side of a freestanding fireplace or stove:
4.) Behind an access panel
Feel free to view the video below to help assist you in finding the make and model of your fireplace:
Sometimes, your fireplace may have been a woodburning fireplace that has been converted to gas by adding a gas log insert to it. In this case you may not have a rating plate, or the rating plate will tell you that it is a wood burning fireplace. All gas log inserts are considered Natural Vented appliances. This type of fireplace will fall into two categories:
For repair purposes, we will categorize vent free fireplaces in a separate category. Vent free units are open-door style units that do not have a chimney. If you look inside a vent free unit (there should not be a single pane of glass on the front) you should not see an exit at the top to the chimney.
Once you have at least determined what type of fireplace you have, please keep both your fireplace type, make, and model handy. This will be important for the rest of the troubleshooting process.