What is a base-can arrangement?
The buried housing under a light: it carries the fixture, takes the cables in, shelters the transformer and keeps the whole assembly dry.
A base can is a cylindrical housing set in the ground or pavement. The fixture bolts to its top flange, with spacer rings setting the height. The primary cable enters and leaves through conduits at the side, the isolating transformer sits lower down, and a short secondary cable runs up to the light.
The arrangement changes with the light. A deep can often holds the transformer directly beneath the fixture, a shallow can carries only the fixture with the transformer in a nearby housing, and an elevated light sits on a frangible coupling above the can. In every case the bottom is kept free-draining, because water around the transformer and connectors damages insulation.
Transformer and connectors inside, directly under the light.
Fixture only. Transformer sits in a separate housing or pit nearby.
Frequently Asked Questions
Q1What is a base-can arrangement in airfield ground lighting?
The way the buried housing is laid out: a cylindrical housing set in the ground or pavement that carries the light fixture on its top flange and holds the cable entries, and in many designs the isolating transformer and connectors beneath it.
Q2What is the arrangement inside a base can?
The fixture bolts to the top flange, the primary cable enters and leaves through conduits at the side, the isolating transformer sits lower down, and a short secondary cable runs up to the fixture. The bottom is kept free-draining.
Q3Is the transformer always inside the base can?
No. A deep base can often holds the transformer directly under the light. Where a shallow can is used, for example for some inset lights, the transformer sits in a separate housing or pit nearby and a secondary cable runs to the can.
Q4Why are spacer rings used at the top of the can?
They set the fixture to the correct height relative to the surface, flush for an inset light or at the specified height for an elevated one. They also allow the height to be corrected after resurfacing.
Q5Why does a base can need drainage?
Water standing around the transformer and connectors can degrade insulation. A gravel layer or drain at the bottom of the can, and a cover or fixture that sheds water, help keep the inside dry.
Q6Where are the base-can requirements defined?
FAA AC 150/5345-42 covers light bases, transformer housings and junction boxes, and ICAO Aerodrome Design Manual Part 5 covers electrical systems. Always confirm against the current edition and the manufacturer's installation data.
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