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November 1999 41 COUNTER TOP IMPINGER
THERMOCOUPLE
1. Remove control box cover.
2. Remove six (6) acorn nuts holding motor cover and remove.
3. Remove four (4) acorn nuts holding oven back assembly and remove oven back.
4. Remove thermocouple bulb from wire form in rear of oven cavity.
5. Disconnect and mark wires from temperature control board (red=neg., white=pos.) and remove
thermocouple.
6. Reassemble in reverse order and check operation. NOTE: Be certain to replace insulation seal
each time oven back is removed.
INFORMATION:
When two wires composed of dissimilar metals are joined together and one of the ends is heated,
a continuous current flow is generated. We use an iron constant (Type J) thermocouple. The
iron wire increases the number of dissimilar junctions in the circuit.
It is possible to check a thermocouple with a properly calibrated D.C. millivolt meter. At 32°F, the
millivolt reading should be 0.00. This can be checked by inserting the thermocouple into an ice
bath. The millivolt reading at 72°F should be 1.134.
When using the following chart, the temperature at the terminal connections must be noted. This
temperature is called the Junction Temperature.
The following chart lists the thermocouple millivolt readings from 200°F to 600°F.
O V E N T E M P E R A T U R E
200°F 250°F 300°F 325°F 350°F 400°F 425°F 450°F 500°F 550°F 600°F
90°F 3.26 4.77 6.30 7.06 7.83 9.37 10.14 10.91 12.46 14.00 15.53
88°F 3.32 4.83 6.36 7.12 7.89 9.43 10.20 10.97 12.51 14.05 15.59
86°F 3.37 4.88 6.41 7.17 7.94 9.49 10.26 11.03 12.57 14.11 15.65
84°F 3.43 4.94 6.47 7.23 8.00 9.54 10.31 11.09 12.63 14.19 15.71
82°F 3.49 5.00 6.53 7.29 8.06 9.60 10.37 11.14 12.69 14.23 15.76
80°F 3.55 5.06 6.59 7.35 8.12 9.66 10.43 11.20 12.74 14.28 15.82
78°F 3.60 5.11 6.64 7.40 8.17 9.72 10.49 11.26 12.80 14.34 15.86
76°F 3.66 5.17 6.70 7.46 8.23 9.77 10.55 11.32 12.86 14.40 15.94
75°F 3.69 5.20 6.73 7.49 5.26 9.80 10.57 11.35 12.89 14.43 15.97
74°F 3.72 5.23 6.76 7.52 8.29 9.83 10.60 11.37 12.92 14.46 15.99
72°F 3.78 5.29 6.82 7.58 8.35 9.89 10.66 11.43 12.97 14.51 16.05
70°F 3.83 5.34 6.87 7.63 8.40 9.95 10.72 11.49 13.03 14.57 16.11
68°F 3.89 5.40 6.93 7.69 8.46 10.00 10.78 11.55 13.09 14.63 16.17
66°F 3.95 5.46 6.99 7.75 8.52 10.06 10.83 11.61 13.15 14.69 16.23
64°F 4.01 5.52 7.05 7.81 8.58 10.12 10.89 11.66 13.20 14.74 16.28
62°F 4.06 5.57 7.10 7.86 8.63 10.18 10.95 11.72 13.26 14.80 16.34
J U N C T I O N T E M P E R A T U R E
60°F 4.12 5.63 7.16 7.92 8.69 10.24 11.01 11.78 13.32 14.86 16.40