Hood theory of operation – XLT XD-9007A (ELEC Oven Version – B1, AVI Hood Version – B) User Manual

Page 12

background image


Technical Support US: 888-443-2751

Technical Support INTL: 316-943-2751


The first part of the Theory of Operation explains how electrical power is delivered to the

hood and initial sequences when the main operator switch is turned on. The remainder of the The-
ory of Operation section explains the function of components in alphabetical order. These compo-
nents are also listed on the schematic.

When any one of, or all of, the Hood Operator Switches (S2, S3, & S4) are turned on;

1. The Exhaust Fan Motor (M1) located on the roof will run.
2. The Variable Frequency Drive (VFD) will display a set value. The values are preset from the

factory and can be referenced in the I&O manual.

3. The ovens associated with the corresponding switches will turn on.

Line voltage for Standard Hoods is assumed to be 208/240 VAC, 60 Hz. (1) Phase

Line voltage for World & Australian Hoods is assumed to be 230 VAC, 50 Hz. (1) Phase

Power for the hood originates at building’s electrical service panel. Two (2) circuits are

required; 1) is a three phase circuit for VFD/Fan circuit, and 2) is a single phase circuit for lights
and relays. The single phase circuit consist of a line and a neutral, and connects to the Terminal
Strip (TS). A wire connects the TS to Switch 1 (S1-SPST-NO), which operates the lighting cir-
cuit, and also to Switch 5 (S5-SPST-NC), which is used to manually override the Variable Fre-
quency Drive (VFD) in case of failure. The three phase circuit also connects to the TS, and wires
connect the VFD through Relay 7 (R7-3PDT) and a Circuit Breaker (CB). The single phase and
three phase circuits just described should have power at all times. The green run indicator directly
above the programming indicator is illuminated when the controller is in the run mode. The con-
troller is put in run mode by pressing the green run button.

Power for ovens are routed through the hood to Switches 2, 3, & 4 (S2, S3, S4, all DPDT-

NO) via a Switch Relocation Cord (SRC). When XLT Ovens are installed with an AVI Hood, the
SRC effectively eliminates the Main Switch located on the oven and transfers control to the DPDT
switches on the hood.

When the contacts of S1 are closed, single phase voltage will be carried thru the switch to

the light bulbs.

When the contacts of S2, S3, or S4 are closed, the 1st set of contacts perform the exact

same function as S1 does on the oven. In addition, they allow current to flow through coils located
in Relay 1, 2, or 3 (R1, R2, R3, all SPST NO) which closes the Relay contacts to provide a signal
out to Make Up Air (MUA) dampers located in Roof Top Units (RTU).

The 2nd set of contacts will connect terminal P24 of the VFD to either terminal 1, 2, or 3,

which will initiate operation of the VFD.