is useful for determining whether light levels are adequate throughout the
garden, as well as for routinely checking if lights are operating to
specification (Fig 4.7).
Ensure the ballast and lamp are matched. For
example, lamps of different type (e.g. MH or HPS) or different size
(wattages), may require a specific ballast. If using an ‘electronic’
ballast ensure the lamp is compatible otherwise premature lamp failure or
blackening can occur.
Handling HID lamps
Lamps can explode if they are lit when cold,
or have fingerprints on the glass. Always wrap the lamp in clean paper or
a towel before handling. To clean the lamp glass use window cleaner or
rubbing alcohol, and allow to dry thoroughly before use. Lamps should not
be restarted immediately after being switched off. Before restarting, MH
lamps should generally be left off for at least 20 minutes; HPS for at
least 3 minutes.
Effective working life
The intensity of a lamp will diminish with
use, and may also use more power. Note that MH lamps have a shorter
effective working life than HPS. The capacitor in a magnetic ballast will
also deteriorate with use and consequently the light intensity will
diminish. Ask the manufacturer for the useful working life of these items.
Lamp directions will specify whether a lamp
can be orientated vertically or horizontally. Failure to comply can cause
poor lumen or color output, and shorten the life span of the lamp.
Note, HID lamps draw large amounts of electricity
therefore safety must be a priority.