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The Importance of Proper Gas Pressure in a Furnace


There are numerous parts of a gas furnace that must be carefully synchronized and optimized in order for your heating to proceed efficiently. One of the most important considerations is the pressure of the incoming gas. If you would like to learn more about how gas pressure affects the overall performance of a furnace, read on as article will discuss the importance of proper gas pressure.

Gas Flow to Your Furnace

If gas were to simply flow into your furnace’s combustion chamber at the pressure it was entering your home through the gas company supply line, chances are your furnace wouldn’t operate very efficiently. One of the many functions performed by your furnace’s gas valve is to help regulate the pressure of the incoming gas, closely tailoring it to the needs and abilities of your furnace. Over time, however, it is necessary to test your gas pressure to ensure that it still falls within the optimum range, otherwise unwanted problems may ensue.

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How to Test the Gas Valve on Your Furnace

There are a few checks you should go through before you zero in on the gas valve. First, check to make sure that gas is actually flowing to your home by seeing if:

  • Your home still has hot water
  • The burners will ignite on your stove
  • Your water heater's pilot light is on
  • Any other gas-fueled appliances will turn on

If everything looks alright here, then you should go on to check your furnace. If it stopped running mid-cycle, then it should still be warm – if this is the case, then odds are the issue isn't with your gas valve but with your thermocouple. This part is designed to keep the valve open and will shut the valve at any point if it develops a fault. If your furnace didn't shut down mid-cycle and is cold to the touch, the next thing you can do is to check the electrical side of your heater by using a multimeter:

  • Shut down the furnace at the wall control.
  • Access the service panel on the side of the unit and locate the gas valve. You should see two wires connected to the side or on top of the valve.
  • Remove the wires, but make sure to note where each one was connected so you can reattach them after the check.
  • Set the multimeter to test for millivolts (mV), and hold the tester wands to one of the gas valve terminals. It should read between 145 and 195 mV – anything outside of this range means that you're dealing with a defect and need to replace your gas valve.

If all of your tests come back with normal results, then your gas valve is likely the problem and needs to be replaced.

Problems with Gas Pressure to Your Furnace

If the gas pressure is too low, your furnace’s efficiency will go down. Not only that, but it will lead to a greater amount of condensation of burned gases. That is because the proportion of air in the air-fuel mixture will be too great. This condensation tends to accumulate inside of the heat exchanger, where it will eventually lead to the formation of corrosion, thus necessitating the replacement of this vital component.

High gas pressure can be just as bad for your furnace. That’s because it greatly increases the risk of furnace overheating. When this happens, all manner of internal components may become damaged by the excessive heat. Thus it is important to have your gas pressure tested and, if necessary, adjusted, on a fairly regular basis.

Contact Mid-Florida Heating and Air today with any questions or service needs you may have.


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