13
Service Manual for
RCO Speed Oven
Voltage
Relay
Location of Voltage Relay
Operation and Testing
The Voltage Relay is connected to the output of the DC
power supply. The power supply provides a 24 VDC
signal from the control board for the 208VAC supply
condition. For 240VAC, the mechanical relay is not
triggered. After plugging the unit into a rated power
source, the control board determines if the supply
source holds a voltage of either above or below 220VAC.
Voltages above 220VAC are considered the default
condition (no relay switching occurs). The 240VAC tap
wire remains active on the high voltage transformer.
Voltages below 220V cause the mechanical relay to
switch to the tap wire to 208VAC on the high voltage
transformer tap.
To test, disconnect the oven from power. It must be
disconnected each time it is tested so the Voltage
Relay returns to its default state. When connected to
a 240VAC supply, the Voltage Relay should remain in
the default state. When tested with a 208VAC supply
the Voltage Relay should switch to the 208VAC within
three seconds of the oven being turned on.
1. Remove the unit from its power source and follow
the proper Lockout/Tagout procedures.
2. Remove the top panel.
3. Tag and disconnect the Voltage Relay wires.
4. Remove the faulty relay.
5. Install the replacement relay.
6. Temporarily power up unit and ensure relay is
working as designed.
7. Remove unit from its power source and reattach
all panels and covers.
8. Restore unit to its power source.
LINE FUSE
Before performing any service that
involves electrical connection or disconnection
and/or exposure to electrical components, always
follow the Electrical LOCKOUT/TAGOUT Procedure.
Disconnect all circuits. Failure to comply can
cause property damage, injury or death.
The line fuse is a component of the supply circuit for
all components, including all of the cooling fans. It is
located in the fuse clip on the upper right side of the
electrical component panel.
A fuse trip is a function of an over voltage / current
condition or a Monitor circuit activation. The Monitor
circuit protects against hazardous microwave leakage
by disabling the oven if a fault exist in the microwave
system with the oven’s door open or ajar. The Monitor
circuit trips the internal 30A Fast Blow Fuse with a door
open / microwave fault state through the output contacts
of the Monitor Relay. The Monitor Relay coil is energized
by feedback from the Mag SSR output through the
normally closed contacts of the Monitor Door Switch.
Failure of the Mag SSR, failure of components in the
magnetron system, or a combination of failures of
the controller PCB, the Primary Door Switch, and the
Secondary Door Switch are sources of Monitor circuit
activation and the resultant fuse trip. The Monitor
Relay output contacts experience excessive current
loads when activated preventing future operation of
this safety circuit.
The Monitor Relay must be replaced if the 30A fuse
in the oven trips. Do not attempt to reuse a Monitor
Relay after a fuse trip event.
Line Fuse
Location of Line Fuse
Line Fuse Replacement
1. Remove the unit from its power source and follow
the proper Lockout/Tagout procedures.
2. Remove the top panel.
