Cleaning Up Your Ventilation System
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Cleaning Up Your Ventilation System

When I moved into my first place, I couldn't believe how dirty everything was all the time. I found myself dusting and mopping continuously, only to deal with a fresh layer of grime later. After awhile, I realized that the problem was blowing straight out of my air ducts. My ventilation lines were so dirty that it was spreading grime through my house every single time the air clicked on. Fortunately, I called an HVAC contractor who was able to clean my vents to a gleaming shine. I know how big of a difference cleaning up your ventilation system can make, which is why I want to spread the word.

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Cleaning Up Your Ventilation System

How To Check Your Oil Furnace For Soot Accumulation And Understand What The Readings Mean

Rick Wells

A problem that affects oil furnaces on a regular basis is soot accumulation in the heat exchanger and chimney. Accumulations of soot can cause problems with the furnace operation including a puffback, a localized explosion inside the combustion chamber. A puffback can be destructive to equipment and even be the source of a house fire. That's why measuring the level of soot accumulation is so important for preventing puffbacks in oil furnaces. Below is more information on how to measure soot accumulation and interpret the results:

Some early warning signs of soot accumulation

Ideally, oil burns inside furnaces without leaving any visible residue. The only byproducts from a perfectly-clean burning oil furnace are carbon dioxide, carbon monoxide and water vapor. However, due to any one of several possible problems, the combustion process can be altered, and unburned fuel (soot) accumulates inside the furnace heat exchanger and stack.

Soot accumulation doesn't occur overnight; instead, it happens over a period of time as a result of imperfections in the combustion process. There are several warning signs that it may be occurring in your furnace:

  • Odor of burned or scorched oil

  • Visible black smoke from your furnace exhaust stack

  • Noisy furnace startup, operation and shutdown

  • Increase in oil use

The importance of checking oil furnace draft pressure

Should any of these signs begin to appear, it is important for you to check the draft pressure of your furnace; this process will help you identify the location of soot build-up as well as provide you with an idea of how severe the problem may be.

To check the draft pressure, you will need to use a device known as a manometer. A manometer provides information on the specific local air pressure within a space. This air pressure reading is provided in a unit known as a inches of water column, and positive readings indicate the pressure is higher in the confined space than the external environment. Likewise, negative readings indicate the pressure is lower inside the confined area.

Inside the furnace heat exchanger and stack, the desirable reading will be negative as this coincides with a draft that moves up and through the furnace out the stack. Positive readings or less-than-sufficiently negative readings are indicative of soot accumulations.

How to check oil furnace draft pressure

Fortunately, testing the draft pressure of most oil furnaces is simple and quick. Oil furnaces are constructed with sampling holes in both the heat exchanger and stack, and inserting the manometer probe will provide the readings you need. However, be sure to read the operating documentation that comes with your manometer before use, so you can avoid false or misleading readings. Below is how to interpret your findings:

  • Heat exchanger sampling - to check the heat exchanger, insert the measurement probe into the lower sampling hole on your furnace. The reading seen in a soot-free heat exchanger should be minus 0.02" and minus 0.03", which equates to between negative two-hundredths of an inch and negative three-hundredths of an inch of water column. A reading that is anything closer to zero or is in the positive range is indicative of soot buildup.

  • Exhaust stack sampling - for checking the stack, insert the probe into the upper sampling hole on the furnace. A normal reading will be between minus 0.04" and minus 0.06", or negative four-hundredths to negative six-hundredths of an inch of water column. As with the exchanger, if the reading increases toward zero or encroaches into positive territory, there is a high likelihood of soot accumulation.

The bottom line

It is important not to ignore abnormal draft pressure measurements since soot accumulation can cause a fire or even an explosion. Contact a qualified heating professional to assist you in diagnosing and correcting the problem that is causing your oil furnace to burn inefficiently. Go to website for more information. 


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