XLT XD-9006A (GAS Oven Version – C, AVI Hood Version – C) - Manual (Page 11)

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GAS OVEN THEORY OF OPERATION
M3 - The Flow Path Pressure Generating (FPPG) fan supplies combustion air for the Burner. It is
wired in parallel with M1 and will continue to operate for 30 minutes after S1 is turned off. A fil-
ter is provided to ensure clean air.
PS - The Power Supply rectifies line voltage to 24 VDC, and supplies power to the Conveyor Con-
trol (CC). A 4 amp fuse is used to provide over current protection, which is mounted on the PS
itself. There are no other fuses used anywhere else.
PU - The Pick-Up is physically mounted within the Conveyor Motor (M2) and utilizes hall effect
technology integral to the M2 to monitor the rotation speed. The hall effect signal is transmitted to
the CC, which converts it into linear travel speed of the conveyor.
R1 - R1 is a 30-minute off delay relay which functions as a cool down timer. Applying power to
T6 activates the relay, which sends a voltage signal out from T9. When power is removed from
T6, voltage continues from T9 for 30 minutes. T9 supplies voltage to the Main Fan Motor (M1)
through a Circuit Breaker (CB2), and also supplies voltage to the FPPG (M3) Fan. M1 and M3 are
the only components that will continue to operate for 30 minutes after S1 is turned off. The off
delay relay is a safety feature to allow the oven to cool down to room temperature, and to eliminate
heat stress on the components of the oven.
RP – The Rectifier Plug has an integrated full-wave bridge rectifier circuit. It converts 24 VAC
from the Ignition Control (IC) into 22 VDC that is sent to the Multi-Valve (V1-V2).
S1 - The Main Switch is a SPST normally open switch, mounted on the front of the Control Box.
Activating this switch applies voltage to Terminal T6 of the Cool-Down Timer (R1) and to the pri-
mary side of the Transformer (XFMR). When used with the optional AVI Hood System, a remote
switch mounted in the front of the AVI Hood replaces it.
S2 - This Switch is a SPDT centrifugal switch physically mounted inside the Main Motor (M1).
When M1 comes up to full speed, S2 closes and sends a 24 VAC signal to the Temperature Con-
trol (TC) and the Signal Conditioner (SC). It functions as a safety feature to prevent burner opera-
tion if the M1 fails to rotate.
S3 - High Limit Switch (World). This is a bi-metal, NC, SPST switch physically mounted in the
side panel of the Bake Chamber. It’s purpose is to provide fail safe operation. If the temperature
of S3 exceeds 600°F, it opens and interrupts line voltage to all components except the Main Motor
(M1).
SC - The Signal Conditioner is powered by 24 VAC from the Transformer (XFMR) via the Main
Motor Centrifugal Switch (S2) and the Temperature Control (TC) on terminals 1 & 2. Incoming
power will be interrupted by the Temperature Control (TC) when the actual temperature rises
above the Maximum Operating Temperature (see Specification Sheet). The function of the SC is to
convert a 4-20 mA signal from the TC to a 45-250 mA signal and then applies that signal to the
multi valve (V3). This in turn modulates the valve to allow an appropriate amount of fuel to con-
trol temperature.