fmtjfw
Senior Member
- Location
- Fairmont, WV, USA
The following is the description I gave the contestants. Their first task was to design it. Anyone want to draw it or critique it? (control drawing ladder, power drawing schematic)
Kitchen Ventilation Project
The project is to design and build the motor control system for a commercial kitchen's ventilation system. The system runs two fan motors:
1. a hood vent fan which pulls fumes and heated air from the kitchen
2. an intake air fan which brings in outside air to cool the kitchen.
The fans are controlled by motor starters. The motor starter for the vent fan is controlled by a start-stop pushbutton set. The motor starter for the intake fan is controlled by an on-off rotating switch. Both motor starters are also controlled by fire alarm contacts.
The fire alarm contacts consist of a normally-opened (NO) and normally-closed (NC) contact. The contacts have three connections: NO, NC, and common (COM). The COM connection connects to the NO and NC contacts at one end. This is normally found in a kitchen extinguisher system cabinet in the form of a 3-wire Microswitch?. The NO contacts close on alarm and the NC contacts open on alarm.
The purpose of the fire alarm interconnect is to remove as much smoke as possible to reduce the danger to people and to stop any intake air from being blown in so as not to fan the flames.
The vent fan uses momentary pushbuttons to start and stop it. If the fire alarm indicates a fire, the vent fan is run, the operation of the start-stop pushbuttons is IGNORED.
The intake air is controlled by a rotary switch that is either on or off. If the fire alarm indicates a fire, the intake air fan will not be allowed to run, the position of the rotary switch is IGNORED.
The two motors are powered by motor starters each with three power contacts, a NO control contact, a NC overload contact, and a NO overload alarm contact. Under normal (other than fire alarm conditions) the motors are to be protected from overload by the overload contact of the motor starters.
If the fire alarm is tripped, the overload contact on the vent fan is ignored. This is known as ?run to destruction? which is used for items like fire pumps, smoke vent fans, and ammunition hoists on battleships. The reason is that the motor's continued (even short term) operation is more important to ?life safety? than its long-term survival.
Both motors are single-phase. The motor starters are three-phase. The instruction sheet for the motor starters states that if used for single-phase, all three power contacts and all three poles of the overload relay must have the motor current passed through them. You need to connect a single pole disconnect between the load side of each motor starter and motor.
You need to install a GFCI-protected receptacle near the motors.
All metal boxes and the DIN rail the motor starters are mounted on are to be grounded using the green wire from the power fuse box.
The MicroSwitch is simulated by a three-way wall switch. The disconnects are simulated by single-pole wall switches. The motors are simulated by light bulbs.
Kitchen Ventilation Project
The project is to design and build the motor control system for a commercial kitchen's ventilation system. The system runs two fan motors:
1. a hood vent fan which pulls fumes and heated air from the kitchen
2. an intake air fan which brings in outside air to cool the kitchen.
The fans are controlled by motor starters. The motor starter for the vent fan is controlled by a start-stop pushbutton set. The motor starter for the intake fan is controlled by an on-off rotating switch. Both motor starters are also controlled by fire alarm contacts.
The fire alarm contacts consist of a normally-opened (NO) and normally-closed (NC) contact. The contacts have three connections: NO, NC, and common (COM). The COM connection connects to the NO and NC contacts at one end. This is normally found in a kitchen extinguisher system cabinet in the form of a 3-wire Microswitch?. The NO contacts close on alarm and the NC contacts open on alarm.
The purpose of the fire alarm interconnect is to remove as much smoke as possible to reduce the danger to people and to stop any intake air from being blown in so as not to fan the flames.
The vent fan uses momentary pushbuttons to start and stop it. If the fire alarm indicates a fire, the vent fan is run, the operation of the start-stop pushbuttons is IGNORED.
The intake air is controlled by a rotary switch that is either on or off. If the fire alarm indicates a fire, the intake air fan will not be allowed to run, the position of the rotary switch is IGNORED.
The two motors are powered by motor starters each with three power contacts, a NO control contact, a NC overload contact, and a NO overload alarm contact. Under normal (other than fire alarm conditions) the motors are to be protected from overload by the overload contact of the motor starters.
If the fire alarm is tripped, the overload contact on the vent fan is ignored. This is known as ?run to destruction? which is used for items like fire pumps, smoke vent fans, and ammunition hoists on battleships. The reason is that the motor's continued (even short term) operation is more important to ?life safety? than its long-term survival.
Both motors are single-phase. The motor starters are three-phase. The instruction sheet for the motor starters states that if used for single-phase, all three power contacts and all three poles of the overload relay must have the motor current passed through them. You need to connect a single pole disconnect between the load side of each motor starter and motor.
You need to install a GFCI-protected receptacle near the motors.
All metal boxes and the DIN rail the motor starters are mounted on are to be grounded using the green wire from the power fuse box.
The MicroSwitch is simulated by a three-way wall switch. The disconnects are simulated by single-pole wall switches. The motors are simulated by light bulbs.