A. End of Lamp Life

At lamp’s end of life, the voltage requirements of the lamp exceeds the output ability of the ballast. The usual failure mode for mercury is low light output followed by failure to operate, and for Metal Halide low light levels, color shifts, and lamp operating instability (cycling). Replace end of life lamp as dictated by lamp testing procedure.

B. Incorrect Lamp

Lamp wattage, voltage, burning position, and type must be checked against the fixture label to be sure the proper lamp has been installed.

C. Open Capacitor

This is the usual result of electrical failure or mechanical damage. Very often the capacitor can will be bulged or distorted. Where the capacitor is used in series with the lamp, the lamp will not operate. See tests for capacitors or replace with a known good capacitor.

D. Defective Starter

The function of the starter is to provide a high voltage pulse to ignite the lamp. To test, replace with a known good lamp. (Also see Ignitor/Starter testing procedure)

E. Incorrect Supply Voltage

When investigating problems of low light output or cycling, voltage readings first must be taken at the fixture to properly identify power distribution problems. In the case of multiple supply type ballasts, verification that the supply voltage is connected to the appropriate input lead is advised.

F. Photocontrol

Problems may result from electrical failure, incorrect wiring, or from an incorrect amount of light reaching the cell. First cover the eye of the cell with electrical tape to verify fixture and cell operation. If the fixture fails to operate, the cell must be bypassed electrically to identify the problem source. Problems of incorrect amount of light usually can be resolved by repositioning the fixture or by using cell caps to regulate the light level.

G. New Lamp Replacement

New lamps, when installed, go through a period of burn-in or seasoning which may extend for a period of 100 hours or more. The usual result is noticeable color variation between lamps. While metal-halide lamps are noted for this, the system will stabilize as the burn-in period ends. It is important to understand that some variation in color may be noted between lamp manufacturers, or between old and new lamps.

H. Line Voltage Dips

When investigating voltage dips, it is important to identify distribution system loading. The usual cause is the starting of large motors or the use of electric welding equipment. Line voltage recorders will usually identify the problem. It is important to understand that mild dips will cause a color shift, while severe dips will cause the lamp to go out. Dip tolerance depends on lamp type, lamp age and ballast type.

I. Shorted Capacitor

This is the direct result of electrical failure or mechanical damage. The most common result of a shorted capacitor is ballast failure. In all cases of shorted capacitors, both capacitor and transformer should be replaced. See tests for capacitors or replace with a known good capacitor.

This is the usual result of fixture connection to incorrect supply voltage. Repeated failure often in conjunction with capacitor failure may indicate short duration high voltage spikes on the distribution system. The use of a scope along with power company assistance is generally required to identify these spikes. Equally important as a cause of failure is a shorted capacitor (See "I" above - Shorted Capacitor). See tests for ballasts on preceding page and replace if necessary.

This may be caused by a short circuit in the lamp circuit wiring or by mechanical failure in the lamp. Carefully inspect all lamp circuit wiring. See tests for ballasts on preceding page and replace it if necessary. In all cases, replace the lamp.

K. Incorrect Ballast

The requires checking only a new fixture or if a recurring problem is encountered. Carefully compare details on the transformer to the fixture label and lamp used in the circuit. Change components as required.

High Pressure Sodium Service Checklist
Identify problem and test for cause in numerical sequence.

A. End of Lamp Life

At a lamp’s end of life, the operating voltage requirements of the lamp exceed the output ability of the ballast. This results in the lamp cycling off and on. It is important to understand that in the early stages of failure, the lamp may operate for several hours before cycling off. As the lamp nears total failure, the on time will decrease until the lamp fails to ignite at all. Cycling lamps should immediately be replaced to avoid starting aid damage. See lamp tests or replace with known good lamp.

B. Incorrect Supply Voltage

When investigating problems of low light output, cycling, or failure to start, voltage readings must be taken at the fixture to properly identify distribution system problems. For multiple supply type ballasts, proper lead connection must be verified.

C. Incorrect Lamp

Lamp wattage, voltage, burning position, and type must be checked against fixture label to be sure the proper lamp has been installed in the fixture.

D. Shorted Capacitor

This is the direct result of electrical failure or mechanical damage. The most common result is low light output; cycling may also occur.

E. Photocontrol

Problems may result from electrical failure or from an incorrect amount of light reaching the cell. First cover the eye of the cell with electrical tape, to verify fixture and cell operation. If the fixture fails to operate, the cell must be bypassed electrically to identify the problem source. Problems of incorrect amount of light usually can be resolved by repositioning the fixture or by using cell caps to regulate the light level. Occasionally, the cell will see light from the fixture reflected off a nearby object and turn itself off. Repositioning the cell or reflecting object may be required.

F. Line Voltage Dip

When investigation voltage dips, it is important to identify distribution system loading. The usual cause is the starting of large motors or the use of electric welding equipment. Line voltage recorders will usually identify the problem. It is important to understand that lamps nearing end of life will be more susceptible to voltage dips than new lamps, and lamp operating on reactor ballasts are more sensitive to voltage dips than those on regulating ballasts.

G. Defective Lamp

This is normally the result of some mechanical failure in the lamp. This can often be determined by brown or silver coating on the lamp outer jacket, or by deposits at the base of the lamp. See lamp testing procedures or replace with a known good lamp.

H. Defective Starter

The function of the starter is to provide a high voltage pulse to ignite the lamp. Failure to operate generally results from electrical failure in the starter. See tests for starters or replace with a known good starter.

I. Open Capacitor

This generally results from electrical failure or

mechanical damage. Very often the capacitor can will be bulged or distorted. When the capacitor is used in the secondary (lamp) circuit, the fixture will not operate. See tests for capacitors or replace with a known good capacitor.

J. Burned Ballast Windings

This is often the result of fixture being connected to incorrect supply voltage. Repeated primary winding failures often in conjunction with capacitor failures may indicate short duration high voltage spikes on the distribution system. The use of a scope in conjunction with power company assistance is generally required to identify these spikes. See tests for ballasts and replace if necessary.

Light Output Service Checklist
( Investigate In numerical sequence )

A. Voltage

Measurements must be checked a) at the fixture b) at the end of the distribution line. Confirm correct ballast voltage tap connection to supply voltage.

B. Socket Position

If adjustable, check fixture instructions and confirm correct position has been selected.

C. Lamps

Check for (a) correct wattage (b) correct burn position (c) high output vs. standard (d) does color appear to be correct. (after burn in)

D. Reflector

Has the correct reflector been installed? If adjustable, has the proper mounting position been selected? Verify whether reflector should be open or enclosed.

E. Reflectance

Recheck original calculations and confirm correct reflectance was used for walls, ceiling and floor. Ratio of incident light to reflected light is a measure of reflectance.

F. Obstructions

Note obstructions in the air and at the floor level that would restrict normal light distribution. In the air this would include piping, heating, crane rails, steel structure, fog, or other airborne contaminants. At floor level work in progress, racks, cabinets, machinery and partitions. In addition consideration must be given to guards, visors and other fixtures.

G. Light Meters

Use a second meter to confirm out of spec readings. Be sure the meter is not shadowed, not receiving reflected light, and held in the correct plane, and calibrated.

H. Dirt

Be sure the reflector lamp and lens (if involved) are clean and free of construction dust.

I. Current/Wave Form

Check for hot panels, conduit and feeder wiring indicating harmonics and overloading.

J. Spacing & Mounting Height

Confirm the installation is per the original design for fixture spacing mounting height and aiming (if involved). Check for pole spacing, pole heights, and setbacks.