XLT XD-9007A (ELEC Oven Version – D, AVI Hood Version – C) - Manual (Page 14)

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14 HOOD THEORY OF OPERATION (STD w/FS)
R4, R5, & R6 - These are SPDT relays, which are electrically operated switches. They use an
electromagnet to operate a switching mechanism. When S2, S3, or S4 are activated line voltage is
supplied to the coil of corresponding relay switching it from NC to NO. This completes a circuit
for a damper that could be wired into 17,19, or 21 on TS 2. If only one damper is used install a
jumper between 17,19, and 21 to activate damper no matter which oven is on.
REC 1, 2, & 3– These are circular electrical receptacles mounted on the bottom of the Hood Junc-
tion Box. The switch relocation cord (SRC) connects into these and to main switch in the corre-
sponding oven. This deactivates the switch on the oven and relocates the operation of it onto the
front of the hood.
S1 - This SPST (NO) switch is located on the front of the hood and controls the lights.
S2, 3, & 4 - These DPST (NO) switches are located on the front of the hood and control the ov-
ens, as well as initiating and sequencing the operation of the VFD and damper circuits.
Line voltage is continuously applied to pin 1 of REC 4, 5, & 6, which is connected by a
wire to a contact in S2, 3, & 4. This is shown on the schematic as the lower RH connection point
of S2, 3, & 4. When the switch contacts are closed, shown on the upper LH connection point on
the schematic, power is applied to pin 2 of the receptacles, as well as terminal B of R1, 2, & 3.
Wires also connect terminal B and pin 4 of the receptacles. In essence, S2, 3, & 4 replace the
switches on the ovens, and also energize the coils of R4, 5, & 6, which closes the relay contacts
and sends a control signal to dampers or Make-up Air System.
The other set of contacts, shown as the upper set on the schematic, connect terminal 24 of
the VFD and terminals 4, 3, & 2 respectively. The VFD generates it’s own 24 VDC signal volt-
age, and the switches serve as inputs to the VFD. The VFD outputs user-selected frequencies de-
pending upon the combination of switches that are closed.
TS 1, 2, &3- These are terminal strips, which serves as a connection point for wires.
VFD - The Variable Frequency Drive (VFD) converts the AC supply voltage to DC and then con-
verts the DC to a suitable three-phase frequency source for M1. Incoming power connects to ter-
minals L1, L2, & L3. M1 connects to terminals T1, T2, & T3 through TS1. The VFD generates
it’s own 24 VDC control voltage on terminal P24. S2, S3, & S4 serve as user-controlled inputs
and connect terminals 1, 2, & 3 to terminal P24. User inputs include a <RUN> and <STOP/
RESET> buttons, as well as <UP> and <DOWN> arrow buttons. A complete manual can be
found at
www.xltovens.com .