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ICM January-February 2017

Figure 4. Testing a 30 mV circuit Chart 1 scorched or burned and also the cold junction on the thermocouple being burned. Figure 4 exemplifies a problem with the power unit (magnet assembly), which is charted out above the shaded area on the high side. This indicates that the resistance of the magnet is too high and too many millivolts are being dropped through the magnet; the valve will have to be replaced. It is important to note that if this was an ECO type system, a plot of 30 and 20 would fall into the shaded area and would be a good reading. This emphasizes how important it is to use the correct chart when diagnosing problems. These readings apply to some of the rules concerning millivolt readings and what they mean. It illustrates what the minimum and maximum readings are about. The reason for replacing the valve is that the drop out reading is above six, which is the maximum allowed. There is also a lack of a spread of 10 millivolts between the closed circuit and drop out. In this case, the open circuit reading is below the minimum allowed which is 17–18 millivolts. Clean pilot or replace the It would mean thermocouple either replacing the OC - 16 thermocouple, cleaning CC - 10 the pilot or both. If you have to go to the trouble CC (LOAD) - 10 of pulling a pilot for DO - 1 either one you may as well clean the pilot and replace the thermocouple. ICM Replace valve OC - 27 CC -12 CC (LOAD) -12 DO - 7 24 ICM/January/February 2017


ICM January-February 2017
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