What is fixture elevation?
How high the light sits — an inset fixture projecting only as far as the design allows, an elevated fixture at its design height with the frangible coupling at its break point, each measured from a datum before the area is handed back.
Fixture elevation is the height of the fixture relative to the pavement or ground around it. An inset fixture is set flush with the surface or to project only as far as the design allows. An elevated fixture is set at its design height above ground, with its frangible coupling at the designed break point. The height is set mainly by the level of the base can and checked as part of fixture installation.
A fixture that is too proud can be struck by tyres or snow-clearing equipment, and one that is too low collects water, dirt and snow and can have its optics covered. An elevated fixture that is too high becomes an obstruction and moves its frangible point away from the design. Use only the riser or spacer rings the manufacturer provides, never unapproved packing, and do not lengthen or modify a frangible coupling to gain height. Check elevation together with fixture alignment once the bolts are at final torque. Work only on a circuit that has been isolated, locked out and proved dead.
- Isolate. Switch off, lock out and prove the circuit dead before any work.
- Set the datum. Establish the pavement or ground level and the design height from the drawings.
- Set the base. Bring the base can, and any specified riser, to the correct level.
- Seat the fixture. Fit the fixture or mast the manufacturer specifies at the design height.
- Measure. Check an inset fixture with a straight edge and an elevated one with a rule or gauge from the datum.
- Lock and record. Torque as specified, re-check the height, clear all tools and log the result.
Frequently Asked Questions
Q1What is fixture elevation in AGL installation?
The height of the fixture relative to the pavement or ground around it. An inset fixture is set flush with the surface or to project only as far as the design allows. An elevated fixture is set at its design height above the ground, with its frangible coupling at the designed break point.
Q2Why does the height of an inset fixture above the pavement matter?
A fixture that stands too proud can be struck by tyres and snow-clearing equipment and can be damaged or cause damage. A fixture set too low collects water, dirt and snow, and its optics can be covered or shadowed. Both are faults, so the height is checked against the design limits.
Q3How is the height of an elevated fixture set?
Set the base can and any specified riser to the design level, fit the fixture or mast the manufacturer specifies, and measure the height from the ground or datum on the drawings. The frangible coupling must stay at its designed break point, so do not lengthen, strengthen or modify it to gain height.
Q4What is used to adjust fixture elevation?
The main adjustment is the level of the base can at installation. Where the manufacturer provides riser, spacer or adjusting rings, use only those, in the quantity the design allows. Do not stack unapproved packing under a fixture, and do not use one in place of a correctly set base can.
Q5Can fixture elevation change after installation?
Yes. Resurfacing raises the pavement, ground can settle, and soil or grass can build up around an elevated light. Any of these changes the height against the design. Check the height after resurfacing or earthworks and re-set it to the design where it has changed.
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