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NORA Oilheat Technicians Manual

Figure 9-6: One of several transformer testers available Several types of transformer testers are available, Figure 9-6. These testers are dependable and usually come in their own carrying case with all the instructions. The one shown will also act as a backup transformer and can be left on the job as a temporary solution and this can be especially helpful with older obsolete burners. When using any one of these testers, read the instructions for that particular tester because competitive units will operate differently. Resistance testing Another test for iron-core transformers is to check the quality of the windings using an ohmmeter. The following procedure is used: 1. Turn the power to the unit off. Disconnect the primary leads from the circuit. 2. Test the resistance across the primary winding. Attach the test leads from your ohmmeter to the primary leads of the transformer. You should get a reading of 3 ohms, plus or minus 10% (2.7 through 3.3 ohms). If your reading is higher or lower, you should replace the transformer. 3. Test the secondary side of the transformer. Touch one of your ohmmeter leads to a secondary terminal and the other to a mounting screw or ground. You should get a reading of 12,000 ohms plus or minus 10% (10,800 through 13,200). Then perform the same test from the other secondary terminal to a mounting screw or ground; you should read approximately the same. If you get a higher or lower reading that varies widely, you should replace the transformer. The following table is used with this procedure for specific brands: Trade Brand Primary Leads Secondary Posts Allanson 2.4 ohms 9,200 ohms Dongan 3 ohms 12,000 ohms France 3 ohms 12,000 ohms Solid state oilburner ignition systems, electronic ignitors Chapter 9 Ignition Systems (each post to ground) Manufacturers are now mostly using solid-state electronic ignitors. These units are known for their small size, light weight, and starting power. They may be for dedicated use on a particular type of burner and are also available in generic Chapter 9—Ignition Systems 9-9


NORA Oilheat Technicians Manual
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