Temperature Probe Test (Solid State Control) - Vulcan-Hart ML-126743 Service Manual

VC4E & VC6E Series Full Size Electric Convection Ovens - SERVICE PROCEDURES AND ADJUSTMENTS
6. Check for proper voltage across terminals COM
AC to 120VAC or COM AC to 208-240VAC for
power to the control.
A. If correct, proceed to step 7.
B. If incorrect, problem is not with the
temperature control. See
TROUBLESHOOTING.
7. Check relay voltages on the board:
A. For 120VAC controls - check across
OUTPUT RELAY terminal (left side) to 120
VAC terminal for input to the internal relay.
Check across OUTPUT RELAY terminal
(right side) to 120 VAC for output from the
internal relay.
B. For 208-240VAC controls - check across
OUTPUT RELAY terminal (left side) to
208-240 VAC terminal for input to the
internal relay. Check across OUTPUT
RELAY terminal (right side) to 208-240 VAC
for output from the internal relay.
1) If input voltage to the internal relay is
correct, proceed to step 8. If input
voltage to the internal relay is not
present, problem is not with the
temperature control. See
TROUBLESHOOTING.
2) If output voltage from the internal relay
is correct proceed to step 8. If output
voltage from the internal relay is not
correct, check temperature probe as
outlined under TEMPERATURE
PROBE TEST (SOLID STATE
CONTROL).
8. Set the temperature control to the minimum
setting.
NOTE: Oven temperature must be above 300°F.
9. Check for zero (0) volts AC across terminals
OUTPUT RELAY terminal (right side) to 120 VAC
or OUTPUT RELAY terminal (right side) to
208-240 VAC for no output from the internal
relay.
A. If correct, temperature control is functioning
properly.
B. If incorrect, check temperature probe as
outlined under TEMPERTURE PROBE
TEST (SOLID STATE CONTROL).
1) If temperature probe is OK:
a. Turn the power switch OFF.
F25105 Rev. B (0217)
TEMPERATURE PROBE TEST
(SOLID STATE CONTROL)
NOTE: The temperature probe used in conjunction
with the Solid State Temperature control is an RTD
(resistance temperature detector) of the Thermistor
type. As temperature increases the resistance value
decreases.
1. Remove the right side panel as outlined under
COVERS AND PANELS in REMOVAL AND
REPLACEMENT OF PARTS.
NOTE: If right side panel is not accessible, this
component can be serviced by removing the control
panel as outlined underCOVERS AND PANELS.
2. Place a shielded thermocouple in the geometric
center of the oven cavity and determine the
temperature in the oven cavity.
3. Remove the probe lead wires from the solid state
temperature control.
4. Test the probe with an ohmmeter.
A. If the measured resistance values are inside
the given tolerance then the probe is
functioning properly.
B. If the measured resistance values are
outside the given tolerance then replace the
probe and retest.
1)
5. Reverse procedure to install.
TEMP (°F)
77
240
Page 24 of 64
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
b. Replace the temperature control
and check calibration as outlined
under SOLID STATE
TEMPERATURE CONTROL
CALIBRATION.
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
There may be multiple circuits. Be sure
all circuits are disconnected.
Check oven for proper operation.
OHMS * TEMP (°F)
90,000 360
4,077 380
OHMS *
822
656