Physical Address

304 North Cardinal St.
Dorchester Center, MA 02124

What Causes Delayed Ignition On Gas Furnace

Does your furnace start up with a boom or bang? There’s a good chance that the unit is having delayed ignition problem. The good news is that there are some simple steps you can take to try to fix the ignition problem.

When the burners are getting gas, but the gas doesn’t light right away, this is called delayed ignition. So, that gas has time to build up, and when it finally starts to burn, it makes a small explosion.

What is delayed ignition on gas furnace?

When your thermostat tells the furnace to heat up, a gas valve opens and gas flows to the burners, which then light the gas. With delayed ignition, the gas isn’t set on fire right away, so it builds up in the furnace. The gas keeps building up until it reaches a flame and explodes in your furnace.

Imagine being in a room full of gas and someone lighting a match, or you turning on the burners on your gas grill but waiting a moment before pushing the “ignite” button. Yes, that’s how delayed ignition on gas furnace is.

What’s causing the delayed ignition?

There are many problems that could happen, and all of them need to be fixed by a trained technician. But if you want to talk the talk, you should know that delayed ignition can be caused by:

  • There’s too much fresh air. Before the gas is lit, it is mixed with air, which is called primary air. Too much primary air makes it hard to light the gas-air mix, which makes gas build up. This is easy for the tech to fix.
  • The burners don’t have enough gas. If there isn’t enough gas, like when there’s too much air, it’s hard for the mixture of gas and air to light. This can happen when the gas pressure isn’t high enough. The tech will need to figure out what’s going on.
  • The pilot light is dirty, too small, or too weak. If your furnace is old, this could be the problem. Because of these problems with the pilot light, the main burners won’t light.

Is there a danger in delayed ignition?

Not only does a delayed ignition sound like an explosion, it is an explosion. If you don’t pay attention to these small gas fires, it could get very dangerous.

A delayed start is bad for more than one reason. For one thing, every time gas explodes, it puts stress on the parts of your furnace and can cause them to break. A delay in starting the car is also dangerous. Because the problem lets your furnace fill up with extra (flammable) gas, you could get burned by a flash fire if you try to manually relight the pilot light.

If nothing is done to stop them, the ignition problem will probably get bigger over time. The more shaking there is, the more likely it is that the stack pipe will come loose and soot will get all over your house.

The extra flames that come from delayed ignition can also crack the heat exchanger, which is one of the most expensive parts of your furnace. When this happens, most people choose to replace the furnace instead of the heat exchanger because replacing the heat exchanger is too expensive and may cause carbon monoxide leaks during installation.

How can I stop a delayed ignition on gas furnace?

The problem of a slow-starting furnace is easy to avoid. All you have to do each fall is make sure your furnace is cleaned well before you turn it on. A professional heating technician will clean the burners and ports and remove any dust, lint, rust, or sulfur buildup that could block the ignition and cause a delay.

How will a professional clean your gas furnace?

  1. Cleaning the surfaces: After wiping down the outside of your furnace with a damp cloth, they will vacuum the base and burners and clean other parts that are dirty or grimy.
  2. Cleaning the blower: Your technician will carefully clean the boiler of your furnace with a small brush and a vacuum, taking care not to move the counterweights on the fan blades or the wiring.
  3. Cleaning the pilot or igniter: Since a dirty pilot light or surface igniter can cause problems with your furnace, your technician will carefully blow off any dust from these parts without breaking them.
  4. Cleaning the flame sensors: They will also use a soft cloth to lightly clean the flame sensor to make sure it works well.
  5. Lubricating parts: When your HVAC technicians clean your furnace, they will put a little bit of lubricating oil on the blower motor and shaft bearings.
  6. Changing the filter: You should change the air filter in your furnace every three months. If you don’t want to deal with this yourself, your HVAC technician will do it for you.

If your furnace sounds like it’s booming or banging when it turns on, you should call a professional right away. It might seem like a small problem right now, but if it keeps getting worse, it could become a much bigger one. On the other hand, a precise tune-up and professional cleaning of your furnace can find a problem with delayed ignition on gas furnace that is causing the dangerous problem.