XLT XD-9006A (GAS Oven Version – C, AVI Hood Version – B) - Manual (Page 15)

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HOOD THEORY OF OPERATION
CS - The Current Sensor is a device that detects electrical current in a wire, and then generates a
signal proportional to it. It drives an LED indicator lamp (L3) to indicate that the VFD is drawing
current and operating. A minimum of 1.5 AAC is required.
L1 & L2 - These are standard incandescent light bulbs, and should illuminate when the contacts of
S1 are closed.
L3 – This is a green LED indicator that is driven by the CS to indicate that the VFD is drawing
current and operating.
M1 – The Exhaust Fan Motor is a 3-phase, direct drive motor. In normal operation, it is powered
by the VFD through R6, and it’s RPM will vary as the frequency from the VFD varies. In Manual
Mode, it is powered with line voltage and frequency by R7 and R5, and will run full speed. There
are no user serviceable parts in the motor, and the bearings are permanently lubricated.
PLUG 1, 2, & 3 – These are circular electrical plugs on one end of the Switch Relocation Cord
(SRC). The Plugs connect to Receptacles 1, 2, & 3 on the bottom of the Hood Control Box. The
other end of the SRC plugs into the oven wire harness, and eliminates the operator switch supplied
in the oven. Conversely, when the operator switch on the hood is turned off, the corresponding
oven is turned off as well.
R1, R2, & R3 – These are SPDT relays, which are electrically operated switches. They use an
electromagnet to operate a switching mechanism. When the contacts of S2, S3, or S4 are closed,
current flows through a coil in the relays, causing the contacts in the relay to close. This will com-
plete a circuit in the Dampers in the Roof Top Units (RTU).
R4 - This is a SPDT relay, which is an electrically operated switch. They use an electromagnet to
operate a switching mechanism. R4 is activated by fire alarm switch located in fire suppression
cabinet. When this NO switch is activated, voltage from P24 of VFD connects to terminal 4 of
VFD. This signals the VFD to advance the exhaust fan to full speed (60 HZ)
R5, R6, & R7 – These are 3PDT relays, which are electrically operated switches. They use an
electromagnet to operate a switching mechanism. R7 is used all of the time, regardless of whether
the unit is in normal operating mode or in manual mode. R5 & R6 are only used in manual mode.
R8 - This is a 3PDT relay (Standard Ovens) It is also a DPDT for (World Ovens), which is an
electrically operated switch. They use an electromagnet to operate a switching mechanism. R8 is
activated by fire alarm switch located in fire suppression cabinet. When this NO switch is acti-
vated, it then opens R8 disrupting the voltage to REC1-REC3.
REC 4, 5, & 6 - These are circular electrical receptacles mounted on the bottom of the Hood Con-
trol Box. They connect to the SRC and also to S2, S3, & S4. See PLUG 1, 2, & 3.