I have recently have talked to several professional equipment installers about chimneys and what effect the newly manufactured equipment will have on the existing masonry types, and I heard many opinions. Although I would not classify myself as an expert in this area, while working in the trade I also experienced some of the same chimney issues that are still in existence today.
Regarding chimneys, let’s take a moment and step back into the past for a moment, after all chimneys have been around since the wood, coal, and the kerosene days.
As oil heating equipment entered the market many years ago, chimneys were seldom mentioned until it came time to perform an annual cleaning, or as it is referred today, a system tune up. At this time the technician would make sure no rodents or obstructions were blocking its passage. Also, at the time of the tune up, a check for proper draft and flue gas temperature would be measured.
Often a flu gas temperature of between 850 to 900 degrees or higher could be escaping up the chimney. Was this a good or bad situation? Well, on the good side, the chimney never really had issues because the chimney stayed warm from the bottom of the lower part to the top, which prevented a condensation freeze-up. Oil was also probably 17cents a gallon at that time, so no one paid to much attention to the oil bill.
Having heat and hot water was all that mattered. Just think—as of this article, oil is retailing at $3.89 and higher in some areas; $3.89 per gal. x 150 gals = $583.50. Did we ever think customers would pay $583.50 for 150 gallons of heating oil? I have!
For the last several years the heating equipment manufacturers have been working diligently to produce units that will produce higher efficiencies in the 85 – 90 + percent range, this in turn will naturally reduce fuel consumption for the homeowner.
However, all these improvements come with new and different chimney issues. Stack temperatures are considerably lower, which in turn makes the flue gas cooler and condensate can be created at the top of an average chimney. Thirty-two degree and lower temperatures could lead to condensation freeze within the clay lining or brick, thus causing serious deterioration.
Keep in mind that condensate conditions occur during every on and off heat cycle of the heating unit. Also, keep in mind that we have to deal with a byproduct of fuel called sulfur, and when mixed, condensation - an acid - is formed. This in turn can lead to destroying flue tiles, bricks, and in some cases, metal.
The best approach before installing a new high efficiency low stack temperature unit is to consult a certified and licensed chimney inspector to review the existing chimney before the start of the installation and follow his recommendation. Remember that if you don’t follow the suggestion, you could find yourself liable for a very expensive repair bill.
There are some states now requiring a metal flex silver type liner to be installed with all new installations and many companies who have resorted to direct vent applications to avoid the liner expense and still be in compliance with codes.
In closing this article, I would suggest getting the LATEST NFPA #31 and review appendix E. Here you will find sizing tables that will help determine the proper silver lining size.
****NEW E-MAIL: ChasBursey@aol.com