XLT TS Series Service Manual
5
Description
XLT Ovens consist of 3 basic subsystems: the Fan, Burner and Conveyor
subsystems. All of the ovens have 3 switches, which turn each of these on. The fan
switch supplies power to the burner and conveyor switches, so it must be turned on first.
Note that the 3270 ovens have an additional control box on the left side of the oven. This
oven can be controlled from either side, but the opposite side set of switches must be left
on. The Parts Manual shows part locations and exploded views.
The fan switch supplies power to the oven fan motor, the control box cooling fan,
the cool-down timer relay, the temperature control, the burner switch, and the conveyor
switches. The cool-down relay timer is connected to power when the oven is plugged in
and provides 30 minutes of power to the oven fan after the fan switch is turned off. The
oven fan has an internal centrifugal switch that completes the circuit to the burner blower
motor. The burner blower motor in turn has an internal centrifugal switch that completes
the circuit to the burner ignition control.
The burner switch applies power from the fan switch to the oven fan motor
centrifugal switch. The conveyor switch applies power from the fan switch to the
conveyor control. See the electrical schematics.
There are a few differences between the natural gas model ovens and the propane
(LP) gas models. Electrically they are the same. The burner orifice, modulating valve,
and combination gas valves are different for the two models. The propane models have
smaller burner orifices and higher gas pressure ranges. See the A4200 burner drawing in
the Parts Manual for orifice size information. The modulating valves have different
internal coils and are marked M420B for natural gas and M420BH for propane. The
combination gas valves are field convertible (Honeywell kit number 393691) and have
stainless steel pressure regulator springs for natural gas and red pressure regulator springs
for propane (LP).
Operation
1) When the Fan Switch is turned on:
a.
The main fan motor should run.
b.
The cooling fan on the side of the control box should run.
c.
The temperature control should display the actual temperature.
2)
When the Burner Switch is turned on;
a.
The combustion air motor should spin.
b.
The pilot gas valve should open and you should hear a “ticking”
noise. This is actually a high voltage spark arcing across tips.
c.
The main gas valve should open and the burner should light.
d.
The combustion should be audible and the actual temperature
should rise steadily.
e.
To verify burner ignition, remove the front panel, and you should
see a blue flame under the lower fingers near the back of the unit.
There is also a flame inspection window in the burner.
