Incandescent Lamps

a. Standard Incandescent Lamps

Construction

• A typical construction of an incandescent lamp is shown in the figure below.
• An incandescent lamp produces light by using electric current to heat a metallic filament to a high temperature (above 5000° C/ 9000° F).
• A tungsten filament is used because of its high melting point and low rate of evaporation at high temperatures.
• The filament is coiled to shorten the overall length and to reduce thermal loss.
• The filament is enclosed in a glass bulb filled with inert gas at low pressure.
• The inert gas permits operation at higher temperatures, compared to vacuum, resulting in a smaller evaporation rate of the filament.
• The bulbs are often frosted on the inside to provide a diffused light instead of the glaring brightness of the unconcealed filament.

Shape Code

Lamp Designation

A lamp designation consists of a number to indicate the wattage, a shape code and a number to indicate the approximate major diameter.

Characteristics

More Information

• Refer to lamp manufacturers’ catalogues.

b. Tungsten Halogen Lamps

Construction

• The quartz tungsten halogen lamp is another type of incandescent lamp.
• The conventional incandescent lamp loses filament material by evaporation which is deposited on the bulb wall, leading to bulb blackening and reduced lamp efficacy during the life of the lamp.
• When a halogen element is added to the filling gas under certain design conditions, a chemical reaction occurs, as a result of which evaporated tungsten is redeposited on the filament, preventing any deposits on the bulb wall.
• The bulb of the tungsten halogen lamp is normally made of quartz glass to withstand the lamp’s high–temperature operating conditions.
• The fixture often incorporates a reflector for better heat dissipation and beam control.

Shape Code

Low Voltage Tungsten Halogen

• Operates at low voltage – mainly 12 V,
• Each fixture includes a transformer – supplying the low voltage to the lamp and are compact in size,
• These are more efficient than standard incandescent,
• These have longer life than standard incandescent,
• These are used mainly for display lighting.

c. Halogen PAR Lamps

General Description

• Halogen PAR lamps are lamps with a Parabolic Aluminum Reflector (PAR) which use a halogen capsule instead of a simple filament.
• The halogen capsule includes a tungsten filament and halogen gas.

PAR Lamp Families

• PAR lamps have evolved into four families, listed below, from lowest to highest efficiency:
• standard PAR lamps
• energy saving PAR lamps
• halogen PAR lamps
• Infra Red (IR) halogen PAR lamps.
• All PAR lamps have an aluminum or silver coating reflector on part of the bulb’s surface.
• PAR lamps are used for directional lighting, i.e., highlighting or spot lighting.
• Most common size is the PAR 38
• Other sizes include PAR 30, PAR 20 and PAR 16.
• Beam spreads are described as narrow spot (NS), spot (SP) and flood (FL).

Standard PAR Lamps (see also Section 7a, Incandescent Lamps)

• Use a tungsten filament but no halogen gas, i.e., no halogen capsule.
• Lamp watts: 75 W, 100 W, 150 W
• Life: 2,000 hours.

Halogen PAR Lamps

• Halogen PAR lamps use a halogen capsule instead of a tungsten filament.
• Lamp watts: 45 W, 65 W, 90 W.
• Life: 2,000 hours.

PAR 38 Lamp Replacement

Applications

Highlighting merchandise in stores and window displays:

• Downlights,
• Accent lighting,
• Outdoor lighting.

Advantages

Halogen PAR lamps have many advantages over standard and energy saving PAR lamps:

• energy savings in the order of 40% – 60%;
• whiter light;
• constant light output throughout lamp life without lamp darkening.

Limitations

Halogen PAR lamps are more expensive than standard and energy saving PAR.

Assessment

• Halogen PAR lamps provide energy savings which outweigh the lamp price difference in less than a year.
• Halogen PAR lamps provide better quality light.

d. Halogen PAR and MR IR (Infrared)Lamps

• Halogen PAR IR lamps use a halogen capsule with an infrared (IR) coating film on the capsule surface.
• The IR film is visually transparent and reflects heat back to the filament, making the lamp more efficient.
• These lamps are the most efficient incandescent PAR lamps.
• Lamp watts: 40 W, 50 W, 55 W, 60 W, 80 W, 100 W, and others.
• Life: 3,000 to 6,000 hours.
• These are an excellent replacement for conventional incandescent PAR lamps.

Standard incandescent PAR Lamp:
150PAR38fl, 2,000 hrs, 1,700 initial lumens, 11.3 lm/W

Halogen PAR Lamp:
120PAR38FL, 2,000 hrs, 1,900 initial lumens, 15.8 lm/W

Halogen HIR PAR Lamp:
90PAR38HIR/FL, 4,000 hrs, 2,030 initial lumens, 22.5 lm/W

e. Infrared Heat Lamps

General Description

Infrared heat lamps, also known as IR lamps, or simply heat lamps, are specially–designed incandescent lamps which produce mostly heat and little light.

Types

• There are two basic types:
• PAR type      – i.e., pparabolic aluminum reflector lamps.
• R type           – i.e., reflector type lamps.
   
• PAR type lamps are newer and more efficient. They include the following sizes:
• 175 W PAR 38,
• 100 W PAR 38.
   
• R type lamps are older and have been used more extensively. They include the following sizes:
• 250 W R40,
• 175 W R40,
• 150 W R40.
   
• The 250 W R40 lamp is presently the most widely–used heat lamp in the market.
   
• Most infrared heat lamps have a red front glass, but lamps with clear white glass are also available.

PAR Lamps Can Replace R Lamps

• PAR lamps are newer and more efficient than R lamps.
• PAR lamps can replace higher wattage R lamps with an equivalent heat output.
• Typical replacements:
• 175 W PAR can replace 250 W R lamp
• 100 W PAR can replace 175 W and 150 W R lamps
• The parameters used to compare the two types of lamps are listed below.

Technical Data

• Input wattage is the nominal lamp wattage.
• Heat output is the useful heat available from the front of the lamp i.e., the heat produced in a solid angle of 90° around the lamp axis in the front hemisphere.
• The heat output numbers included in the table above have been measured in a laboratory test.
• Heat lamp efficiency is defined as the ratio of the heat output over the nominal input wattage.
• Heat output in the 0° to 30° zone is the heat output near the centre axis of the lamp.

Lifetimes

Nominal lifetimes are listed below (manufacturers' data).

• Lamp life is defined statistically as the time in hours at which 50% of the lamps are still functioning (while 50% have failed).
• The expected lifetime of a single lamp is 5,000 hours, but by definition, the actual lifetime can be higher or lower.
• PAR lamps have a more rugged construction and use a tempered glass not easily broken by thermal shock or mechanical impact.
• In farm applications, typical conditions include high humidity,
  i.e., RH at least 75% and ammonia levels from 25 to 35 ppm, with an expected negative effect on lamp life.
• Fluctuations in voltage are common in farms and have a negative effect since higher voltages reduce the expected lifetime.
• Monitoring line voltage of a large number of lamps in a real farm setting and recording failure rates would provide a comparison of reliability and lamp life between PAR and R type lamps.

175 W PAR Lamps Can Replace 250 W R Lamps

• The technical data listed on the previous page indicates that the 175 W PAR lamp can be a more efficient replacement for the 250 W R lamp.
• Replacement results in savings of 75 W per lamp, i.e., 30% energy savings.
• Heat output is reduced by 29 W.
• Heat output in the 0° to 30° zone, i.e., heat output near the lamp axis zone, is almost the same for the old and the new lamp (only 3.5 W less).
• The heat lamp efficiency is improved.

100 W PAR Lamps Can Replace 175 W R Lamps

• The 100 W PAR lamp can be a more efficient replacement for the
  175 W R lamp.
• Replacement results in savings of 75 W per lamp, i.e., 43% energy savings.
• Heat output is reduced by 30 W.
• Heat output in the 0° to 30° zone, i.e., heat output near the lamp axis zone, is almost the same for the old and the new lamp (only 4 W less).
• The heat lamp efficiency is improved.

Applications

• Farm animal heating;
• In farm animal heating where lamps are on continuously;
• Restaurants also use them for keeping food warm.

Assessment

• PAR heat lamps offer a more efficient and overall better alternative to R type of heat lamps.