Mechanical (Kx) Thermostat Calibration - Vulcan-Hart VC4EC Service Manual

FULL SIZE ELECTRIC CONVECTION OVENS - SERVICE PROCEDURES AND ADJUSTMENTS
NOTE: Allow the oven to cycle at
least two times between
adjustments before performing
the calculation.
a)
C. If the above adjustment cannot be
obtained:
1) Turn the power switch OFF.
2) Replace the temperature control and
check calibration.
MECHANICAL (KX)
THERMOSTAT CALIBRATION
1. Place a thermocouple in the geometric center of
the oven cavity.
2. Set the power switch to ON.
3. Set the thermostat dial to 350 °F.
4. Allow the oven temperature to stabilize
(normally 3 cycles).
5. Record the temperature when the thermostat
cycles OFF and ON for at least three complete
cycles.
6. Calculate the differential by subtracting the
temperature indicated when heat lamp goes out
from temperature indicated when heat lamp
comes on.
A. The differential calculated should be less
than 30EF.
1) If the differential is 30 °F or less, the
thermostat is functioning properly.
a. Proceed to step 7.
2) If the differential is more than 30 EF,
the thermostat is malfunctioning.
a. Install a replacement thermostat
and check calibration.
F25105 (Rev. A, October 2007)
If the average temperature
still differs more than 10 °F
from the dial setting, adjust
the thermostat calibration
until the average
temperature is within
tolerance.
7. Calculate the average temperature by adding
the temperature indicated when the heat lamp
goes out to the temperature indicated when the
heat lamp comes on and dividing this answer by
2.
A. If the average temperature is 15 EF or less
from the dial setting, the thermostat is
properly calibrated.
B. If the average temperature is more than
15 EF of the dial setting, the thermostat
calibration must be adjusted.
1)
2)
8. Replace the knob and verify the setting is still at
350°F.
9. Repeat step 7 until the average temperature is
within tolerance.
NOTE: Allow the oven to cycle at least two times
between adjustments before performing the
calculation.
A. After the final adjustment is made and the
average temperature is within tolerance,
remove the knob and apply a non-
permanent type sealer around the head of
the set screw.
10. If the above adjustment cannot be obtained:
Page 18 of 60
Remove the thermostat knob.
Hold the thermostat shaft and turn the
inner set screw clockwise to decrease
temperature or counterclockwise to
increase temperature (¼ turn = 35EF).