Ingrounds are one of the most common tools in a lighting designer’s toolbox. They have been used since a long time in numerous lighting applications and produce astounding lighting effects when used creatively.
Although the use of ingrounds have been much frowned by the dark sky movement supporters as they direct a considerable portion of visible light into sky, yet they have been and are being used almost freely in most of the projects.
Almost all the users at some point of time have faced issues with the inground irrespective of the make/manufacturer.
Water entering the fixture from the ground below is the most common problem with the ingrounds. The most logical explanation comes from physics that materials expand as they heat up which even includes the air inside the luminaire.The heat can be due to the light source, or heat dissipated by LEDs during their functioning or even heating during the daytime(solar gain).
The actual problem begins when it starts to cool down – the fixture starts to pull in air to balance the pressure, which results in water being sucked along with air from any kind of entry point if, available.
The most common area where faults occur is cable connections. These are most of the time in the hands of unprofessional, untrained, novice technicians who just twist and turn the cables apply a tape and are done with it. This is actually from where water gets sucked into the luminaire causing it to fail.
IP68 cable glands supplied with the fixture is recommended to be used at the time of installation instead of a common plastic connector or manual tapeing which will prevent the water to get sucked in. BUT this is just – as they say “ treating the symptoms” !
The real problem lies in the water being accumulated around the inground fixture. Some ingrounds have even been found to be submerged in pots of water for long durations and fail.
Best practices of in-ground installation suggest that preparation of installation is the most important step than the installation itself. Water retention will depend on the topology of the soil in most of the cases. While some soil types may absorb most of the water but clay, for example will act as a reservoir.
The best remedy to stop water from getting in from below is to prepare the installation site that most of the water gets drained off immediately. Use of gravel at the bottom of the pit of considerable depth and layering the pit with coarse sand will ensure fast drainage of water.
Also, the use of IP68 T junctions filled with resin / gel is recommended for connections, since in most of the cases there will be a line of in-grounds connected to the main supply cable.
To sum up :
- Site preparation with layering with gravel/sand is critical for draining water
- Use of supplied IP68 cable glands only
- Use of IP68 “T” junctions and IP68 connection boxes is a must
The best practice is to install these correctly in the first time itself to avoid any problems later.