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Service Figure 3 those gasses moving because if they slow down and begin to cool, they will condense more quickly. Many still don't believe in properly sized liners. That's a shame because today's equipment can do a lot of damage to a house with smoke and soot damage if not properly vented, and that doesn't include the damage done to the chimney, Figure 4. In addition, installation of a new oil or gas fired appliance into an unlined chimney or one that has not been inspected to the requirements of NFPA may in fact void insurance and warranties. Figure 4 is a picture of the top of my chimney after repairs and addition of a stainless liner with caps for both the fire- 28 place and boiler. It had, for 25 years, an oil-fired boiler operating at about 350ºF gross stack temperature, 280ºF Net. The problem was that on a 10°F day the net chimney temperature was only 93°F and so the result was damage to 29 bricks on the outside chimney facing through a process called "slicing." Slicing is caused by dew point condensation and freezing. If the fluegas is too cool as it leaves the chimney, the water will go into the brick and when the brick freezes it will throw off pieces from expansion of the ice. In addition, those lower temperatures also did some damage to the inside clay liner mortar and the best and easiest way to fix that is the stainless liner, Figure 5. JUNE 2013 | FUEL OIL NEWS | www.fueloilnews.com As I said, I agree with many of the OEM requirements for new boilers, but I no longer agree with at or under 350ºF stack temperatures, it's just plain stupid and a lawsuit looking to happen. I think a well operating oil burner or gas conversion burner should be run at no less than 400°F, but it's just my opinion, my legal expert one, by the way, and I have lots of proof about it now. There was also a lot of damage to the chimney crown and so the top three courses, or rows, were removed and replaced with a banked concrete apron cap. That cap is pitched a way from the tile liner and chimney in the hopes more slicing will not occur. You may remember I've been warning about the dangers of too low stack temperatures venting into chimneys for about 15 years now, and for the record, I'm hearing about more chimney collapses from my associates in the fire service, chimney sweeps and insurance adjusters. High efficiency equipment, gas or oil, is great, but it takes a little extra work to make installations long lasting. Let's go back to Figure 3. I keep hearing of problems with oil and gas burner venting and draft issues except when the equipment is running during cold weather periods. Problems increase during the fall and shoulder periods and are worse in the summer. It's simple, if you are depending on natural (thermal) draft and you have no temperature differences, you have no draft. So, the problem is not from your burner, it's from your chimney or vent. Figure 4