chapter 5

• Lamp


  • Wide variety of forms, shapes and sizes
  • Base is also made of various types and designs
• Lamps are critically dependent on the wattage supply that even for a small fluctuation of the current voltage, its life, output, and efficiency is materially affected
• Effects of 10% undervoltage on incandescent lamp

  • 15% less light output (lumens)
  • 7% lower power consumption (watts)
  • 8% lower efficacy (lumens per watt)
  • 72% more life (burning hours)
• Effects of 10% overvoltage on incandescent lamp

  • 16% more light (lumens)
  • 6% more power consumption (watts)
  • 8% higher efficacy (lumens per watt)
  • 42% less life (burning hours)
• Incandescent lamp is very sensitive to voltage change, and voltage change materially affects its life span
• At an average 10% lower voltage supply, incandescent lamp life span is increased by 25% and reduces by 15% with 10% over voltage supply
• On average, less than 10% of the wattage is utilized to produce light and the rest produces heat
• Incandescent lamp is considered a poor choice for energy conservation because it produces poor and low level of lighting
• Advantages of incandescent lamp

  • Instant start and re-start
  • Simple inexpensive dimming
  • Simple and compact installation requiring no accessories
  • High power factor
  • It can be focused
  • Its life is independent of the number of start
  • It has good color
• Disadvantages of incandescent lamp

  • Low efficiency
  • Shorter life
  • Sensitive and critical to voltage changes or fluctuations
  • High maintenance cost
  • More heat is produced than light
• Applications of incandescent lamp

  • Infrequent or short duration use
  • Where low cost dimming is necessary
  • In focusing fixtures
  • Where minimum initial cost is required
• Fluorescent lamp


  Cylindrical glass tube sealed at both ends, containing a mixture of an inert gas generally argon, and low pressure mercury vapor. At each end, is a cathode that supplies the electrons to start and maintain the mercury arc or gaseous discharge. The short wave ultra-violet light produced by the mercury arc is absorbed by the phosphors coating inside the tube and is re-radiated in the visible light range.
• Fluorescent lamp requires ballast in its circuit. The ballast is basically made of coil to limit the current in the circuit in which, if not controlled, will open the fuse or circuit breaker.
• Fluorescent lamp


  • Efficacy is much higher than the incandescent lamp
  • About 200% of its input energy becomes light, 80% is converted to heat including the ballast heat energy loss
• Efficiency


  Refers to the amount of energy converted to visible light
• Efficacy


  Measure of the lumens per watt produced by the lamp
• Fluorescent lamp has longer life span compared with the incandescent lamp
• Fluorescent lamp life span is materially affected by the number of times the lamp is switched on and switched off
• Continuous burning of fluorescent lamp would last about 30,000 hours. With an average of 3 hours burning per start, fluorescent lamp could last for about 12,000 hours only
• Pre-heat fluorescent lamp


  When the lamp circuit is closed, the starter energizes the cathode. After 2 to 5 seconds delay, it initiates a high voltage arc across the lamp causing it to start
• Rapid start fluorescent lamp


  Eliminates the delay inherent in preheat circuit by constantly keeping the cathodes heated or preheated
• Rapid start fluorescent lamp specifications

  • F40 T12 WW VS
  • F48 T12/CW/VHO
  • F72 T12/CW/HO
• Instant start fluorescent lamp


  Has only one pin at each end acting as a switch to break the ballast circuit when the tube is removed. Operates at various current such as 200 and 425 milli-amperes
• Instant start fluorescent lamp specifications

  • F42 T6 CW Slim line
• For instant start lamp, the number following the letter F indicates the length of the tube, not the wattage
• r 6/8 in. diameter tube

  Tube diameter
• Cool White, Instant start

  Lamp type
• For Instant Start Lamp, the number following the letter F indicates the length of the tube, not the wattage. This is applicable to all lamps that operate at other than 425 milli-amperes which is the normal current.
• Fluorescent Lamp Data


  • Lamp Code
  • Lamp Initial Watts
  • Current milli-amp
  • Ballast Watts
  • Total Watts
  • Lumens
  • Actual Watts
  • Actual Lumens
  • Efficacy Lumens/Watt
• Preheat Lamps have a lower efficacy compared to Rapid Start, High Output, and Very High Output lamps
• Instant Start (Slimline) Lamps have a lower efficacy compared to other fluorescent lamp types
• Cold Cathode Tube is another type of lamp that offers a very long life service compared with the hot cathode lamp. It is not affected by the number of starting or switching of the lamp and has a lower overall efficacy compared to the hot cathode lamp.
• Fluorescent Lamp


  • Life span depends on the burning hours per start
  • Lumen output decreases rapidly during the first 100 hours of burning and thereafter much more slowly
  • Efficacy depends on the operating current and the phosphors utilized. Warm white lamp is more efficient than white, cool white, daylight and colored lamps.
• Mercury lamp is a combination of the arc discharge characteristics of a fluorescent lamp and the compact focusable shape of an incandescent lamp. This combination effect is responsible for its efficiency and long life in various uses.
• American Standard Institute code for mercury lamps

  • H - Mercury lamp
  • 38 - Ballast number
  • MP - Lamp Physical characteristics
  • 100 - Lamp wattage
  • DX - Indicates phosphors, glass coating or coloring
• Mercury Lamp


  • Available in wide variety of shape, size and color with rating from 50 to 150 watts
  • Requires ballast that could be mounted away from the lamp
  • High efficiency makes it a good replacement for incandescent lamp
  • Dimming is possible with a dimming ballast
• The lamp life of a mercury lamp is extremely long with an average of 24,000 hours based on 10 burning hours per start. It is not suitable for installation which is subject to constant switching.
• Factors affecting mercury lamp life

  • Ambient temperature
  • Line voltage
  • Ballast design
• Clear mercury lamp has the best lumen maintenance, followed by the color improved and phosphors coated units.
• Types of Ballast


  • Reactor Ballast
  • Auto transformer Ballast
  • High Power Factor Auto transformer Ballast
  • Constant Wattage Auto transformer Ballast (Lead Circuit Ballast)