Group Relamping

Do you wait to change your spark plugs until your car won't start at an intersection? When you do change your spark plugs, do you tell the shop to change just one or two of them? We hope you answered no to both questions above. Unfortunately, only a small percentage of buildings run lighting maintenance programs where all lamps in an area are replaced on a regular basis--before the lamps fail. This process is referred to in the industry as 'group relamping.' The alternative, which is to replace lamps on an as required basis, is referred to a 'spot relamping.'

Maintaining Light Levels

The primary advantage of group relamping over spot relamping is that group relamping ensures that lighting levels are maintained at higher levels.
As time progresses, lamps will deteriorate and dirt will accumulate. Lamp failures will start to climb and dirt will continue to accumulate. The combination of failures, reduced lumen output and dirt accumulation result in a reduction of light level by as much as 30% of initial output after only two years.
With spot relamping, the lenses and luminaire surfaces are rarely adequately cleaned.

Occupant Satisfaction

Group relamping improves occupant satisfaction because work areas are better lit, which improves visual comfort.

Cost Savings

The cost to replace a lamp is mostly labour. It takes 20 minutes on average for a random lamp replacement. On the other hand, group relamping averages two to three minutes per lamp. Thus, planned lighting maintenance reduces labour costs.

What Happens After a Lighting Retrofit?

If you have retrofitted your lighting system, you need to maintain it. A group relamping strategy should be considered for the same reasons mentioned above. Typically, group relamping should be completed after four years but this will depend on the operating hours of the facility.
In many instances, it is even MORE important to maintain your lighting system after a retrofit than before.
Taking into account all the factors in a retrofit, including improved lamp lumen depreciation for T-8 lamps, reduced heat from the ballast, and improved optics of the luminaire, when you convert a four lamp 2' x 4' luminaires to two T-8 lamps and a specular reflector, the lighting levels are approximately 80% of the original system. In most cases this is fine: many buildings that were built over the last 20 years were designed for over 70 foot-candles and a reduction is acceptable. However, because the "waste" has been eliminated, it becomes important to pay greater attention to maintaining the lighting system.

Other Rewards

Group relamping offers a number of other benefits:

  • greater control of costs - planned yearly maintenance can improve the accuracy of annual budget costs for lamps, maintenance and labour.
  • lower labour costs - reduced time to perform work reduces cost.
  • greater productivity - higher lighting levels result in better and safer working conditions. We have simplified the issue here for space reasons. As more buildings are now operating with retrofitted lighting systems with lower lighting levels, closer attention must be paid to ensure the safety and productivity of the occupants.


If your building does not have a scheduled lighting maintenance program, contact our office and we would be glad to help you out in this area.