Vulcan-Hart ML-126743 Service Manual page 21

VC4E & VC6E Series Full Size Electric Convection Ovens - SERVICE PROCEDURES AND ADJUSTMENTS
Fig. 36
c. Replace knob and re-tighten set
screw.
d. Rotate knob to lowest
temperature setting then back to
350°F.
e. Repeat average temperature
calculation in Step 7.
NOTE: Allow oven to cycle at least two times between
adjustments before performing calculation.
a)
C. If above adjustment cannot be obtained,
replace temperature control and check
calibration.
UNITS AFTER JUNE 2013
1. Place a thermocouple in geometric center of
oven cavity.
2. Set ON-OFF-COOL DOWN switch to ON.
3. Set temperature control dial to 350°F.
4. Allow oven temperature to stabilize (normally 3
cycles).
5. Record temperature at which Heat lamp goes
OFF and comes ON for at least two complete
heating cycles.
If average temperature still
differs more than 10°F from
dial setting, adjust
thermostat calibration until
average temperature is
within tolerance.
6. Calculate differential by subtracting temperature
indicated when lamp goes out from temperature
indicated when lamp comes on.
Differential = Heat lamp OFF - Heat lamp ON
Example: 360° (lamp off) - 340° (lamp on) =
20°
A. Calculated differential should be less than
20°F.
1)
2)
7. Calculate average temperature by adding
temperature indicated when lamp goes out to
temperature indicated when lamp comes on and
dividing this answer by 2.
[Temp. (lamp off) + Temp. (lamp on)] ÷ 2 =
Average Temp. Example: (360° + 340°) ÷ 2 =
350°
A. If average temperature is less than 10°F
from dial setting, thermostat is properly
calibrated.
B. If average temperature is more than 10°F
from dial setting, thermostat calibration
must be adjusted.
1)
2)
NOTE: If no access hole exists in overlay, you may
carefully create one.
Page 21 of 64
If differential is less than 20°F,
temperature control circuit is
functioning properly.
a. Proceed to Step 7.
If differential is more than 20°F:
a. Check temperature probe as
outlined under TEMPERATURE
PROBE TEST (SOLID STATE
CONTROL).
b. If probe is functioning properly
then temperature control is
malfunctioning.
a) Install a replacement
temperature control and
check calibration.
Loosen temperature control knob set
screw and remove knob from stem.
Access adjustment potentiometer
located at 3 o'clock position (Fig. 37).
F25105 Rev. B (0217)