When you light up your fireplace, you're typically looking forward to a relaxing evening spent in front of the warm, large flames. When those flames die down in a traditional wood burning fireplace, you can stoke the wood to create a larger fire, but in a gas fireplace, the gas valve sets the limit for the size of the flame. If you love a big, roaring fire in the fireplace, tiny gas-powered flames can cause frustration. The first place to start is by checking the gas pressure reading at the fireplace switch, as this directly affects the size of the flame and is straightforward to fix. If the pressure reads within a normal range, it's a good idea to call a gas technician to make other adjustments or to identify faulty parts that need replacement.
Understand Natural Gas Safety Before You Begin
Natural gas can be a hazardous fuel to work with if you fail to take basic precautions. If natural gas is left on for too long or leaks, it can cause a significant fire hazard as well as potential carbon monoxide poisoning.
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Natural gas is inherently odorless, but gas suppliers add mercaptan to the gas in order to give it a distinctive smell. Smelling sulfur or rotten eggs in your home is a sign of a gas leak, and you should take care to not light anything and immediately blow out lit candles, open windows, evacuate your home and call 911 from a safe location to report it. One spark could ignite the cloud of natural gas seeping throughout your home.
Barring a gas leak, the best thing you can do to prevent a natural gas disaster is to not leave the gas valve in the on position when it's not in use.
Checking Gas Pressure
Now that you know what to do to keep yourself safe, you can gather the tools you need to check the gas pressure: a gas pressure manometer and a flat head screwdriver.
First, make sure the gas switch for the fireplace is off. Look for two taps with screws marked "in" and "out" near the gas valve or the on/off knob (if applicable).
Loosen the screw for the inlet tap, but don't remove it. Place the end of the tube from the gas pressure manometer firmly over the inlet tap screw. Turn on the gas and take a pressure reading. For natural gas, look for an ideal pressure of 8 inches at the inlet tap or the pressure rating indicated in the manual. Turn off the gas and remove the tube from the tap. Tighten the screw in the inlet tap again.
Now for the outlet tap: Loosen the screw without removing it. Firmly place the end of the manometer's tube over the outlet tap screw. Then, turn the gas on and light the pilot. Turn the burner on and set the flame height to high. Take a reading. This time, you want to see an ideal reading of 3.5 inches or the pressure rating indicated in the manual. Don't forget to turn off the burner and the gas and then tighten the screw again.
Adjusting Gas Pressure
If the pressure readings aren't ideal, you need to turn the regulator by 90 degree turns using your flat head screwdriver. Turn it clockwise to increase pressure and counterclockwise to decrease pressure. Retest the pressure taps after each rotation until it matches the ideal pressure readings as stated in the owner's manual.
Now, turn on your gas fireplace and note whether the flames seem higher now that the pressure has been adjusted. If not, a more invasive procedure may be required. For safety purposes, call a gas technician for assistance if you can't easily identify the problem or achieve a solution.