Recently, I had an expert on heating, ventilating and air conditioning come to my new home to assess what to do about my oil-fired furnace. Though the home has approximately 10 percent more square footage than our previous home, our annual heating costs at the new home have been nearly 75 percent higher. I was at a loss as to what could be causing the lower heating efficiency and asked the HVAC expert to come out to see about putting in a new and more efficient oil-fired furnace.
The first thing the HVAC expert was able to tell me about the oil boiler was that it was old and inefficient. He explained that it was a Peerless boiler that was manufactured in the 1980s and was not efficient compared with the ones today. He stuck a probe into the duct exhaust and confirmed that the oil burner was only operating at 82.5 percent. That level was considered good for this particular vintage of furnace, but it's not good in comparison with today's oil burners. Today's burners operate at 87 to 91 percent efficiency.
The other thing he pointed out about my oil burner was that it was "oversize" for the home. More specifically, it had a 1.5 gallon-per-hour fuel consumption rate if it were to operate nonstop for an hour. For my home, he suggested that I should be using an oil burner with a fuel consumption rate of 0.9 gallon per hour. He indicated that not only would I save on home heating costs because of the lower fuel consumption rate but also my house would have steadier and more consistent heating. Using a burner with a lower burn rate causes the furnace to run longer and thus provide steadier heating. On the surface, that may sound like a bad idea from a cost of operation standpoint. However, he explained to me that by having the furnace run for longer periods and then subsequently shut down for longer periods, less oil would be consumed.
He also pointed out that the exhaust temperature from my oil burner was approximately 475 F, or approximately 175 degrees hotter than it should have been. That extra heat was all wasted energy going up the chimney. The extra heat was caused by the oversize burner and its associated 1.5 gallon-per-hour fuel consumption rate. With a lower consumption rate, the exhaust temperature should only be about 300 F.
Another concern he saw with my boiler was that the burner itself was sucking air directly in from our basement. Note that a burner needs both fuel and oxygen to cause combustion, thus the air intake on the oil burner. He said that by pulling air into the burner from outside the home rather than from the basement, we'd also improve the heating efficiency of our furnace and lower our home heating costs. He explained that by having the oil furnace draw air directly from the basement, a low air pressure was being created in our basement. In turn, it was causing warm air in the home itself to be sucked into the basement to, in effect, feed the oil burner. And subsequently, by creating a lower pressure in the main living area of our house, cold outside air was being drawn into our home through door and window cracks. Thus, the main living area of our home was effectively being cooled off by sucking cold air into it while the furnace attempted to heat it.
And another important fact was that even when the oil furnace was not running, the residual high chimney temperatures produced by the oil burner when it was on were causing warm air from the basement to continue to be pulled up the chimney. Thus, even when our furnace was not operating, its effects were causing heat to be pulled from the home.
The HVAC expert explained that ductwork and a smaller motorized fan assembly should be installed on the oil burner itself. The other end of the ductwork would be fed out the side of the home. This way, outside air would be the source of oxygen for the oil burner.
Lastly, the HVAC expert asked to go up into our attic. This is where one of the two water to air heat exchangers resides, along with all the ductwork to pump air into the second-floor bedrooms. As soon as the HVAC expert walked into the attic, he pointed out a significant problem. He pointed to the R-value numbers on the rigid ductwork associated with the main trunk of the heat exchanger. The R-value was only 4.3. Similarly, the various lengths of flexible ductwork tubes that flowed to the second-floor bedrooms only had a 4.2 R-value. He explained that the attic, with its very low winter temperatures, was sucking out much of the oil furnace's generated heat along the lengths of the poorly insulated ductwork. He recommended that we spray foam insulation around all the ductwork to improve the insulation's R-value to at least 12, preferably higher.
So based on the recommendations of the HVAC expert, I installed a new oil-fired furnace that operates at greater than 87 percent efficiency and has a fuel oil consumption rate of only 0.9 gallon per hour. In addition, ductwork was installed to draw air from outside the home to feed the oil burner. Lastly, I had all of the attic HVAC ductwork insulated. I hope that with these three major changes, we'll improve the heating efficiency of our home and dramatically lower our annual heating costs.
Mark J. Donovan's website is at http://www.homeadditionplus.com.