Fire Protection Systems Flashcards
Class A Fires
Ordinary Combustibles, Wood, Paper, and Cloth.
Class B Fires
Flammable Liquids, Grease, Oil, Pain, and Solvents.
Class C Fires
Live electrical equipment, Electrical panel, Motor, and Wiring.
Class D Fires
Combustible Metal, Magnesium and Aluminum
Thermal switch
Bi-metallic thermal switch
How are thermal switches arranged?
In parallel to one another, in series with the indicator light.
Will a thermal switch still indicate a fire if the wire breaks?
Yes, because of the loop arrangement
How does a thermocouple function?
If all thermocouples increase in temperature at the same rate there is no voltage difference between them, and no indication is made.
How are thermocouples arranged?
In series with each other and the warning indicator.
What are three continuous loop systems?
Fenwal
Kidde
Pressure-type
How do Fenwal systems work?
Ceramic beads keep a wire in the center of the tube. Resistance decreases when the elements get hot. Element will indicate heat anywhere along the loop. Is a single conductor continuous loop.
How does a Kidde system work?
Two conductor continuous loop system. Material in the tube creates a certain amount of resistance between the wires. Overheat=less resistance. Fire=even less resistance.
How can a Kidde system be tested?
By sending power through the loop to see if there is a break or short.
How does a pressure type system work?
Held closed by sealed in helium gas pressure. Opens on loss of gas pressure.
How does a light refraction detector work?
Its a photoelectric cell with a light source, light gets reflected from the smoke into a photocell.
