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NORA Oilheat Technicians Manual

Chapter 7 Combustion for proper size and horizontal pitch and be sure there is no blockage, restriction, leakage, corrosion, or other deficiencies that could cause an unsafe condition. 2. Shut off the unit and any other fuelgas burning appliance within the same room. 3. Inspect burners for blockage and corrosion. 4. Furnaces: Inspect the heat exchanger for cracks, openings, or excessive corrosion. 5. Boilers: Inspect for evidence of water or combustion product leaks. 6. Insofar as is practical, close all building doors and windows and all doors between the space in which the appliance is located and other spaces of the building. Turn on the clothes dryer. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will operate at maximum speed. Close fireplace dampers. 7. Place the appliance being inspected in operation. 8. Determine that the burner ignition and operation is satisfactory. 9. Turn on all other fuel and gasburning appliances within the same room. 10. Determine that all units are burning properly. 11. Use a monometer to test if the pressure in the room that the unit is in is less than the pressure outdoors. 12. Return doors, windows, exhaust fans, fireplace dampers, and any other fuel-gasburning appliance to their previous conditions of use. Testing for a leaking furnace heat exchanger A combustion analyzer can be used for finding leaking cracks or holes in a furnace 7-28 Combustion heat exchanger. The static pressure created by the system blower can overcome any positive pressure in the heat exchanger causing air to leak into the fire side of the exchanger rather than out. Readings that change when the blower comes on after stabilization has taken place are indicative of a combustion air, venting, or mechanical problem such as a cracked heat exchanger. Furnaces can have cleanout doors leaking that will test positive for leakage. This is not a heat exchanger failure. Inspection door gaskets should be replaced and doors should be properly sealed. Procedure: 1. Follow the manufacturer’s instructions to properly zero the combustion analyzer. Insert the combustion analyzer probe in the flue pipe. 2. Start the furnace and observe the oxygen reading for stability (1-3 minutes). 3. When the blower starts, watch for a change in the O2 reading. If the O2 reading goes up, there is a leak. Corrective action: Attempt to visually find the crack or hole. A. If you can find the defect, show it to the customer. B. On the service invoice, write that your testing indicates a leak in the heat exchanger. (Do this even if you cannot find the leak.) C. Inform the customer, in writing, that the heat exchanger has a defect and that the furnace should be replaced. You should not attempt to repair a heat exchanger. Checking and caring for the instruments 1. Smoke tester A. Clamp a piece of filter paper in the


NORA Oilheat Technicians Manual
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