Flame Distortion also known as Flame Rollout
Often times, inspectors will call out “flame distortion” on inspection reports. Flame distortion can have a few meanings, either improper color of flames or the size and shape of the flames. However, arguably the most important flame distortion is flame rollout. Flame rollout is where the flames of the furnace push outside of the combustion chambers. Much like a chimney, flames should remain inside of the combustion chamber and draft upwards into the flue.
Evidence of Flame Rollout
Looking at the exterior of the furnace, there are some visual keys that can point to flame distortion. The first being a white, chalky residue that builds up around where metal flues connect to the furnace. This is typically evidence of poor combustion within the combustion chamber. However, not all furnaces have metal flues. If you have a high efficiency furnace, it will instead have PVC flues. Having a high efficiency means that furnaces produce condensation rather than typical smoke, allowing for the use of PVC flues. In this case, look to see if there is a condensation leak around the furnace and the PVC flues. High efficiency furnaces have two heat exchangers, and if there is a crack in the second heat exchanger, there is likely a condensation leak as well.
The most reliable way of determining flame rollout is to open the furnace cover and observe the ignition of the flames. While watching the flames, look for symmetrical blue cones of flame. Flame distortion can take on a few distinctive signs. The first being an orange color. When observing, if the flames are mostly orange, you will want to call out and HVAC technician and potentially budget for replacement. If you notice there are some puffs of orange, it may be an easier fix economically. The next distortion to watch for is the size and shape of the flames. A smooth cone is what we are looking for, if the flame appears to be shaped like a Christmas tree, you should call a technician. Then, we have what appears to be a pooling of the flame. If the flame pools around the front exterior of the ignition chamber, or is pushing out back away from the ignition chamber, then the system has flame rollout.
The Potential Dangers
Flame distortion and rollout can cause damage to your furnace. The internal mechanisms outside of the combustion chamber are only rated for so much heat. With fire pooling outside of the appropriate area, this can damage the electrical components, and overheat the circuitry. This can be quite an expensive replacement, or worse. If the system gets too hot, it can potentially cause a house fire.
Cracked Heat Exchanger
A cracked heat exchanger is not something that can be determined via a visual inspection. Finding out, however, should be of the utmost importance. A cracked heat exchanger typically means danger. Either it causing fire damage to your furnace, and potentially your house, or a carbon monoxide leak. Leaking carbon monoxide is an immediate threat you you and your family, and should be taken seriously. If there is flame distortion or flame rollout, getting a technician out to assess the situation further is the best call.
Whether it is some flame discoloration or flame rollout, the simplest and best solution is to call a licensed HVAC technician. From there, its mostly a contrast in how much it will cost. Having an improper fuel to air ratio is a quicker and cheaper fix, whereas a cracked heat exchanger is normally far more expensive.
Maintenance can be key in preventing a crack in the heat exchanger. We recommend you replace the filter of the system according to the type of filter in the venting. Annual maintenance of the HVAC system is the best preventative measure. This will not only help prevent a crack in the heat exchanger, but often times will help prevent many other defects from forming.