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20
HOOD THEORY OF OPERATION (STD W/FS)
The first part of the Theory of Operation explains how electrical power is delivered to the
hood and initial sequences when the HUI is turned on. The remainder of the Theory of Operation
section explains the function of components in alphabetical order. These components are also
listed on the schematic.
Part 1:
Power for the hood originates at the building’s electrical service panel. A total of four (4)
circuits are required; one (1) is a single phase high voltage circuit for Variable Frequency Drive
(VFD)/Fan circuit that connects to TS-1 and TS-2, and the remaining three (3) circuits are single
phase low voltage minimum 20A circuits for each oven that connects at the Hood Machine Control
(HMC) P3-1, P3-5, and P3-9 for line side, and neutral will connect at P3-3, P3-7, and P3-11.
Lights piggyback off the top oven power P3-9 on HMC.
The HUI mounted on the hood controls the lighting, VFD activation, Make Up Air (MUA)
activation and oven function. When the HUI Light button is touched a relay is closed and voltage
goes to the lights. When ovens are installed with a hood, the Switch Relocation Cord (SRC)
effectively eliminates the main power button located on the oven and transfers control to HUI
buttons on the hood. When HUI controls are touched a communication signal is sent to the VFD
via ModBus signaling it to turn on to a set frequency. At the same time a relay will allow line
voltage to be carried through the SRC to the oven activating it. When the HUI is activated the
MUA will turn on. The VFD has a built in power supply that is wired to TS1-1L. This puts the
VFD in run mode so whenever a power loss is sensed the VFD will start back up in run mode once
power is restored. The NO switch in the fire alarm system in the building needs to be connected to
TS1-R9 and TS1-R10. When the alarm is activated 24 VDC from TS1-R9 will return from the fire
alarm system to TS1-R10 then to HMC P8 to turn off lights, cooling fans, HUI, MUA, shut down
ovens and making both relays R1 & R2 switch from NC to NO, causing the VFD to run at 60 Hz.
When any one of the three oven buttons on the Hood User Interface (HUI) are touched
(capacitive touch);
1.
The Exhaust Fan Motor (M1) located on the roof will run.
2.
The ovens associated with the corresponding buttons will turn on.
Legend from electrical schematics:
CB
Circuit Breaker
HMC
Hood Machine Control
HUI
Hood User Interface
LT
Lamp
M1
Motor, Exhaust Fan
M2
Motor, Cooling Fan
M3
Motor, Cooling Fan
PS
Power Supply
R1
Fire Suppression Relay
R2
Fire Suppression Time Delay
Relay
REC
Receptacle
S
Switch
SRC
Switch Relocation Cord
TS
Terminal Strip
VFD
Variable Frequency Drive
