National Oilheat Research Alliance 43 Figure 1 Figure 1 Spillage and between the breach and the draft regulator for oil. The test hole should not be in an elbow. Draft should be measured under steady-state conditions (after five to 10 minutes of operation.) Acceptable draft is dependent upon the outside temperature and the appliance. A minimum of -2.5 to -5 Pascals (-.01 to -.02" wc) is required to pass the BPI Draft Test. Worst Case Depressurization Test The Worst Case Depressurization Test is a safety test to see if there are combustion air or draft problems. If all the windows are closed and all the exhaust fans are on, will the combustion gases still go up the chimney? The test determines how strong the negative pressure in the CAZ is with respect to outdoors and the rest of the building. Then it determines if the appliance vent will create negative draft under that condition and if so, how strong will the chimney draft be? Figure 2. Fan Wars There are a lot of fans in homes these days: bathrooms, kitchens, blowers for furnaces and air conditioners, and dryers. When they are all turned on, they create a large pressure difference between inside and outside the home. When the air pressure drops inside relative to atmospheric pressure outside the house, the house is said to have “gone negative”. Fans can move significant volumes of air. The volumes of air measured in cubic feet per minute, that some common fans can draw are listed below: • Clothes Dryers—200 cfm (often installed in the CAZ) • Kitchen Range Hood Fans—200 to 1,200 cfm • Bathroom Fans—25 to 90 cfm • Open Fireplace dampers—500 cfm • Fuel Burning Appliances without Sealed-Combustion—35 cfm. • Blower on a warm air funace— 1,200 cfm Central vacuum systems and attic ventilation fans can also cause depressurization problems. Depressurization Test Steps Before doing the test, be sure there is no fire nor hot ashes in the woodstove or fireplace. The test will take the house negative, so air will be pulled down the chimney. This could rekindle the smoldering ashes and pull the sparks and smoke into the house. Close the attached garage door. There may be hazardous chemicals (cleaners, degreasers, insect repellents and poisons) in the garage as well as gases from the cars and other internal combustion engines and possibly even gasoline fumes). Do not suck fumes from any of these sources into the home. Turn off all the combustion appliances, close all exterior doors, windows, and fireplace dampers. With everything off, test the air pressure in the CAZ with reference to the outside pressure to establish a baseline pressure. Insert the probe from your manometer (digital draft gauge) through a slightly open window. A tester hose extension may be needed to reach the nearest window. Then turn on all exhaust fans and the furnace
NORA Advanced Efficiency
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