12 NEBULA OPERATION
DIMMER INSTALLATION
The Nebula like all SCR dimmer packs is an inherent generator of EMI (electro-magnetic Interference) and requires careful
installation following good wiring and earthing practice. The potential for power problems with a dimmer installation increases
with the number of dimmers. Involving professional assistance with proven experience is highly recommended, as correcting
problems later can be very expensive. The following points should be considered in order to achieve reliable operation, and to
ensure minimum interference to other equipment such as audio and video equipment in Theatres and TV Studios:
SUPPLY TRANSFORMER
1. Locate the dimmers and the supply transformer as close together as possible.
2. Ensure the transformer is of the correct type and rating for the non-linear load of the dimmers you are
installing.
3. On larger installations consider using a dedicated transformer for the dimmer installation.
DIMMER SUPPLY CABLING
1. Keep the supply cabling between the transformer, switchboard and dimmers as short as possible.
2. Minimum inductance in the supply cabling is critical. Keep all phase and neutral cables tightly bunched
together. On smaller installations use of neutral screen or composite cables is recommended. On larger
installations ensure that all phase cables are bound close to the neutral cable(s). Avoid solid buss-bar riser
systems.
3. Use of a neutral conductor that is at least 1.5 times the area of any phase conductor is recommended. This
becomes more important in larger installations.
DIMMER LOAD CABLING
1. Install the dimmers as close to the lighting loads as possible.
2. Do not use common neutrals. Each dimmer must have its own phase and neutral conductor, preferably a
twisted pair.
3. The phase and neutral for each dimmer must be grouped together or be adjacent cores in a composite cable.
4. Dimmer load cables are a source of EMI interference. Keep dimmer load cables clear of all other power and
data cables. Run dimmer cables in earthed metal conduit or trunking if EMI interference may be an issue.
5. Ensure all equipment and exposed metal is correctly earthed.
Summary of Contents for NEBULA
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