Troubleshooting the Solid State High Limit

multimeter

Overview

Below outlines the function of the solid state high limit system and the troubleshooting methodology.

System Function

The solid state high limit system functions similarly to a normally open solid state relay controlled by a comparator circuit. The relay holds the 24VAC safety circuit closed, while the comparator circuit monitors the millivolt (mVDC) output of the thermocouple(s).

During Operation:

  1. AC line voltage is supplied to the module forcing the relay closed.

  2. A 24VAC loop is monitored by the control board across NO and COM.

    • When line voltage is present and the module is not in a tripped state, the circuit remains closed, allowing normal fryer operation.

    • If line voltage is removed or the module enters a tripped state, the relay opens, breaking the 24VAC loop and causing the control to display an E-10 High Limit error.

  3. The module continuously monitors the thermocouple milivolt (mV) DC output for unacceptable ranges. Depending on conditions, an output of 9.5–10 mVDC or greater will cause the module to open the relay, break the 24VAC circuit, and trigger an E-10 error.

    Thermocouples operate on DC voltage and are polarity-specific:

    • White wires are positive.
    • Red wires are negative.

    On dual thermocouple modules, if one thermocouple is wired with reversed polarity while the other is correct, the module will trip due to sensing a temperature difference of 70°F or greater.

Reset Operation

When the module trips, the oil must cool for 15 minutes or longer before pressing the reset switch.

  • Single thermocouple modules: A normally open switch is pressed, closing a circuit and sending a reset command to the module.
  • Dual thermocouple modules: A normally closed switch is wired in line with L1/L2. Pressing the switch temporarily removes line voltage, forcing the module to reset.

Troubleshooting:

The order of operations for troubleshooting should be:

  1. Check to see if your module is powered with line voltage on L1 and L2.

  2. If power is present, determine whether the module is tripped:

    • Dual high limit modules: Look for a blinking red LED.

    • Single high limit modules: Check continuity between NO and COM:

      • Open circuit = module is tripped

      • Closed circuit = module is operating correctly

    If the module is not tripped, proceed to Step 3.

  3. Measure 24VAC on the back of the control board.

    • 24VAC on both pins to ground, or no voltage on either pin to ground: The fault is in the control board. Attempt to reinitialize the control. If unsuccessful, replace the board.

    • 24VAC on only one pin to ground: There is a break in the wiring harness.

  4. If the module is in a tripped state, check the thermocouple. Please diagnose the thermocouple as follows:

    1. Take a DC millivolt reading of the thermocouple.

    2. Use the millivolt chart to determine the corresponding temperature (record this value).

    3. Measure the temperature at the thermocouple connection point to the control (record this value).

    4. Add the temperatures from steps b and c to obtain the actual thermocouple temperature.

    If the thermocouple checks out correctly, the module should be considered defective.

Thermoelectric voltage as a function of temperature (°F); reference junctions at 32 °F.

Thermoelectric Voltage in Millivolts
F 0 1 2 3 4 5 6 7 8 9 10
50 0.507 0.535 0.563 0.592 0.620 0.649 0.677 0.705 0.734 0.762 0.791
60 0.791 0.819 0.848 0.876 0.905 0.933 0.962 0.991 1.019 1.048 1.076
70 1.076 1.105 1.134 1.162 1.191 1.220 1.249 1.277 1.306 1.335 1.364
80 1.364 1.364 1.392 1.421 1.450 1.479 1.508 1.566 1.594 1.623 1.652
90 1.652 1.681 1.710 1.739 1.768 1.797 1.826 1.855 1.884 1.913 1.942
100 1.942 1.972 2.001 2.030 2.059 2.088 2.117 2.146 2.175 2.205 2.234
110 2.234 2.263 2.292 2.322 2.351 2.380 2.409 2.439 2.468 2.497 2.527
120 2.527 2.556 2.585 2.615

2.644

 2.673 2.703 2.732 2.762 2.791 2.821
130 2.821 2.850 2.880 2.909 2.938 2.968 2.997 3.027 3.057 3.086 3.116
140 3.116 3.145 3.175 3.204 3.234 3.264 3.293 3.323 3.353 3.382 3.412
150 3.412 3.442 3.471 3.501 3.531 3.560 3.590 3.620 3.650 3.679 3.709
160 3.709 3.739 3.769 3.798 3.828 3.858 3.888 3.918 3.948 3.977 4.007
170 4.007 4.037 4.067 4.097 4.127 4.157 4.187 4.217 4.246 4.276 4.306
180 4.306 4.336 4.366 4.396 4.426 4.456 4.486 4.516 4.546 4.576 4.606
190 4.606 4.636 4.666 4.696 4.726 4.757 4.787 4.817 4.847 4.877 4.907
200 4.907 4.937 4.967 4.997 5.028 5.058 5.088 5.118 5.148 5.178 5.209
210 5.209 5.239 5.269 5.299 5.329 5.360 5.390 5.420 5.450 5.480 5.511
220 5.511 5.571 5.571 5.602 5.632 5.662 5.692 5.723 5.753 5.783 5.814
230 5.814 5.874 5.874 5.905 5.935 5.965 5.996 6.026 6.056 6.087 6.117
240 6.117 6.178 6.178 6.208 6.239 6.269 6.299 6.330 6.360 6.391 6.421
250 6.421 6.452 6.482 6.512 6.543 6.573 6.604 6.634 6.665 6.695 6.726
260 6.726 6.756 6.787 6.817 6.848 6.878 6.909 6.939 6.970 7.000 7.031
270 7.031 7.061 7.092 7.122 7.153 7.184 7.214 7.245 7.275 7.306 7.336
280 7.336 7.367 7.398 7.428 7.459 7.489 7.520 7.550 7.581 7.612 7.642
290 7.642 7.673 7.704 7.734 7.765 7.795 7.826 7.857 7.887 7.918 7.949
300 7.949 7.979 8.010 8.041 8.071 8.102 8.133 8.163 8.194 8.225 8.255
310 8.255 8.286 8.317 8.347 8.378 8.409 8.439 8.470 8.501 8.532 8.562
320 8.562 8.593 8.624 8.654 8.685 8.716 8.747 8.777 8.808 8.839 8.869
330 8.869 8.900 8.931 8.962 8.992 9.023 9.054 9.085 9.115 9.146 9.177
340 9.177 9.208 9.238 9.269 9.300 9.331 9.362 9.392 9.423 9.454 9.485
350 9.485 9.515 9.546 9.577 9.608 9.639 9.669 9.700 9.731 9.762 9.793
360 9.793 9.823 9.854 9.885 9.916 9.947 9.977 10.008 10.039 10.070 10.101
370 10.101 10.131 10.162 10.193 10.224 10.255 10.285 10.316 10.647 10.378 10.409
380 10.409 10.440 10.470 10.501 10.532 10.563 10.594 10.625 10.655 10.686 10.717
390 10.717 10.748 10.779 10.810 10.840 10.871 10.902 10.933 10.964 10.995 11.025
400 11.025 11.056 11.087 11.118 11.149 11.180 11.211 11.241 11.272 11.303 11.334
410 11.334 11.365 11.396 11.426 11.457 11.488 11.519 11.550 11.581 11.612 11.642
420 11.642 11.673 11.704 11.735 11.766 11.797 11.828 11.858 11.889 11.920 11.951
430 11.951 11.982 12.013 12.044 12.074 12.105 12.136 12.167 12.198 12.229 12.260
440 12.260 12.290 12.321 12.352 12.383 12.414 12.445 12.476 12.506 12.537 12.568
450 12.568 12.599 12.630 12.661 12.691 12.722 12.753 12.784 12.815 12.846 12.877
460 12.877 12.907 12.938 12.969 13.000 13.031 13.062 13.093 13.123 13.154 13.185
470 13.185 13.216 13.247 13.278 13.308 13.339 13.370 13.401 13.432 13.463 13.494
480 13.494 13.524 13.555 13.586 13.617 13.648 13.679 13.709 13.740 13.771 13.802
490 13.802 13.833 13.864 13.894 13.925 13.956 13.987 14.018 14.049 14.079 14.110
500 14.110 14.141 14.172 14.203 14.233 14.264 14.295 14.326 14.357 14.388 14.418
510 14.418 14.449 14.480 14.511 14.542 14.573 14.603 14.634 14.665 14.696 14.727
520 14.727 14.757 14.788 14.819 14.850 14.881 14.911 14.942 14.973 15.004 15.035
530 15.035 15.065 15.096 15.127 15.158 15.189 15.219 15.250 15.281 15.312 15.343
540 15.343 15.373 15.404 15.435 15.466 15.496 15.527 15.558 15.589 15.620 15.650
550 15.650 15.681 15.712 15.743 15.773 15.804 15.835 15.866 15.897 15.927 15.958
560 15.958 15.989 16.020 16.050 16.081 16.112 16.143 16.173 16.204 16.235 16.266
570 16.266 16.296 16.327 16.358 16.389 16.419 16.450 16.481 16.512 16.542 16.573
580 16.573 16.604 16.635 16.665 16.696 16.727 16.758 16.788 16.819 16.850 16.881
590 16.881 16.911 16.942 16.973 17.003 17.034 17.065 17.096 17.126 17.157 17.188

Related Content

Replacing the Momentary Switch

Replacing the Primary Contactor

Replacing the Heat Contactor

Replacing the Heating Element Assembly

Replacing the Temperature Level Probe

Replacing High Limit Thermocouples

Temperature Probe Gauge Instructions

Reference

Error Codes

Warnings

Physical Dimensions

CFE 415 Fryer Wiring Diagrams

CFE 415 Fryer Annual Planned Maintenance

CFE 415 Plumbing Diagram