FLUORESCENT BALLAST INSTALLATION
Electronic Fluorescent Ballast Lead “Bundling”
Compatibility with Power Line Carrier (PLC) Systems
Lamp Sockets and Wiring
ELECTRONIC FLUORESCENT BALLAST LEAD “BUNDLING”
Electronic ballasts operate lamps at a high frequency (greater than 40 kHz), which increases the likelihood of capacitive coupling between ballast output leads. The distance between output leads, operative frequency, and the total bundled area are all directly proportionate to the amount of potential coupling. High coupling can negatively affect ballast performance, potentially causing incorrect lamp starting, hard starting, or even failure to start.
Coupling problems will not occur when lead wires are routed next to each other. The potential for capacitive coupling can occur when leads are bundled or tightly twisted. This could negatively impact lamp ignition in both single and multiple ballast fixture applications. Although problems due to lead bundling are rare, they can still occur as some ballasts are more prone to these problems than others. Problems due to bundling or twisting will typically show up immediately.
To reduce the potential of improper operation, it is strongly recommended to not bundle or tightly twist leads. Bending leads should not cause problems. Avoid using plastic wires to tightly hold leads together.
COMPATIBILITY WITH POWER LINE CARRIER (PLC) SYSTEMS
PLC systems use electronic wiring devices to send information through high frequency signals over the 120 V or 227 V electrical power distribution system of a construction. A generator is used to impose a 1 V to 4 V high frequency signal on top of the existing voltage sine wave (60 Hz), which is generally in the 2 500 to 9 500 Hz range. Older systems operate at 19 500 Hz or higher.
STANDARD ballasts will not interfere with the electrical power distribution systems.
When many fixtures are on a single circuit, individual fusing is often used in order to immediately isolate a fixture which has failed. When troubleshooting, fusing will help circumvent complete circuit outage. Should you use a fuse, they should be of the slow-blow type. The inrush current and abnormal starting cycle should always be accommodated by the fuse.
Grounding is when a connection between an electrical circuit and the earth is established. The symbol for earth ground is:
With A/C wiring, grounds are wires which are electrically connected to the earth creating another conduit for electric current, thus avoiding the potential for electrical shock.
Ground wires can be directly or indirectly connected to one or several earth electrodes. They are also commonly connected to the neutral wire.
Ground wires are typically bonded to pipework, so that in case of a fault, the potential is kept the same as the electrical ground. Metal water supply pipes are commonly used as ground electrodes. All groundings should be made in accordance with applicable federal, provincial, and local codes and regulations.
Safety is the number one reason for grounding ballasts. A properly grounded ballast and electrical system are essential for personnel safety as they offer a low resistance path to the earth, meaning current will avoid workers’ bodies.
Ballasts, namely electronic ballasts, produce Electromagnetic Interference (EMI) which is limited to a maximum amount by the Federal Communications Commission (FCC). In light of this, all electronic ballasts have an internal EMI filter, which requires a proper ground in order to be effective and control electrical noise.
Without a proper ballast ground, FCC EMI limits cannot be respected. Ungrounded ballasts will generate much higher EMI emissions, and can be expected to interfere with other electrical equipment.
Grounding ballasts and luminaires is also important to ensure the proper starting of the fluorescent lamp, especially when working with magnetic ballasts. A metal reflector creates a capacitive path to ground through the wall of the fluorescent tube, which aids in ionizing the tube’s gases and triggers conduction. Once the tube has started, the supplementary capacitance becomes obsolete because the impedance in the ballast circuit is actually lower than this capacitive path.
The most common way to ground ballast is by mounting it to a grounded metal luminaire. If the ballast enclosure material is not made of metal, a separate grounding wire is required.
Switching off fluorescent lamps whenever a room is unoccupied saves energy. Frequent switching of lamps, however, may shorten their operating life. In order to achieve the desired energy savings while maintaining acceptable lamp life, it becomes important to select the ballast type as a function of lamp switching rate.
NEMA recommends that the minimum lighting “on time” be no less than 15 minutes. This allows for energy savings when people are out of the room for extended periods of time, but does not shorten lamp life by cycling lamps every time someone steps out of the room momentarily.
A product survey performed by the Lighting Research Center found that the vast majority of sensors would permit a minimum “on time” setting of 15 minutes and that many were adjustable to 20 and even 30 minutes. In the event that a given sensor is limited to less than 15 minutes, NEMA recommends setting the sensor to the longest time possible. If lamp life results at the 15-minute setting are unacceptable, then the time should be increased for those sensors with such flexibility. For the complete product survey, see “Specifier Reports—Occupancy Sensors: Motion-Sensing Devices for Lighting Controls,” National Lighting Product Information Program, Vol. 5, No. 1, October 1998.
Each of the three main types of ballasts has their own starting characteristic that can affect lamp life:
•Instant start ballasts are the most efficient and the most popular electronic ballast available today. They are recommended for applications with switching frequencies of less than five cycles per day or where energy savings is considered more important than lamp life. Instant starting can make a ballast very efficient, but it causes the electrodes of the lamp to degrade a little every time the lamp ignites compared with programmed start ballasts.
•Rapid start ballasts are not as efficient as instant start ballasts due to additional filament heating power supplied to the lamp, although this additional filament heating can produce longer lamp life in applications where lamp starting occurs less often than every three hours. Like the instant start ballast, they are recommended for applications with switching frequencies of less than five cycles per day. Rapid starting of lamps causes the electrodes of the lamp to degrade a little every time the lamp lights compared with programmed start ballasts.
•Programmed start ballasts provide the best lamp ignition and longest lamp life. In a programmed start ballast, electrodes are preheated prior to ignition, resulting in almost no electrode degradation. This allows frequent starts without a significant loss of lamp life. Programmed start ballasts are recommended in applications with frequent starts where extended lamp life is a primary concern.
•Use the longest practical minimum “ON” time setting for the occupancy sensor and other automatic cycling (15 minutes is recommended).
•Only use ballasts that meet ANSI requirements for lamp ignition.
•Use programmed start ballasts in areas that will result in a high number of switching cycles per day and where lamp life is a primary concern.
Polarity refers to the appropriate connection of ballast lead wires to power lines. To ensure proper installation of ballasts, the lead wires are colour coded for easy recognition. The WHITE coloured lead wire needs to be connected to the neutral (grounded). The BLACK coloured lead wire must be connected to the live wire. With certain ballasts, a change in polarity may decrease voltage from the lead to the ground and may interfere with the starting feature of the ballast.
Ballasts should be installed and operated in compliance with the Canadian Electrical Code (CEC), Canadian Underwriters Laboratories Inc. (cUL), Canadian Standards Association (CSA) requirements, and all applicable local codes and regulations to ensure proper operation. All installations, inspections and maintenance of fluorescent lighting fixtures should be carried out with the power to the fixture turned off. Only qualified persons should execute ballast installations since there may be exposure to potentially hazardous voltages.
Dedicated vs. Multiple Voltage and Frequency
Ballasts can either be dedicated to one voltage, or multiple voltages. Multi-volt ballasts offer input and frequency flexibility, as well as reduce inventory. It is critical to connect a ballast to the input voltage as indicated on the ballast label. To do contrary will be certain to cause damage to the ballast. Often, the utilities which supply the voltage experience voltage variations, and when these occur, it can cause light output to vary. The table below illustrates the recommended limits for electronic and magnetic ballasts:
Fluorescent ballasts should be installed to respect case temperatures in order to avoid a reduction in the life of the ballast due to heat generation during normal operation. For ballasts that have no case temperature indication on the product label, contact your respective customer service department prior to installation.
When several ballasts are installed in the same closed fixture, it is imperative that the ballasts be positioned with enough distance between them to allow for adequate heat dissipation. For proper ventilation of fixture, consult the fixture manufacturer.
LAMP SOCKETS AND WIRING
Improper wiring may cause field problems related to the installation of instant start ballasts. Installers should always familiarize themselves with the wiring and other requirements issued by the lamp, ballast, and socket manufacturers. The following document illustrates some of the principal requirements that contribute to the safe operation and optimum performance of T8 and PLL lamps when used with instant start ballasts.
Instant start electronic ballasts are quickly replacing rapid start magnetic ballasts. Rapid start ballasts are typically wired in series, while most instant start ballasts are wired in parallel. If a ballast is wired in series, this means that if one lamp fails or is intentionally removed, all lamps in the circuit will not be lit. Contrary, in a parallel circuit, should one lamp fail or intentionally be removed, all other lamps will remain lit and the ballast will continue to operate efficiently. Because of these wiring differences, different sockets are required for these different ballast types.
Fixtures containing rapid start ballasts are equipped with conventional sockets (Figure A) that are connected from the ballast by two wires per socket. Instant start ballasts on the other hand, require the use of a shunted socket (Figure B).
A shunted socket serves essentially the same function as installing a jumper (Figure C) from one side of the socket to the other, just internally. By doing this, the two pins at one end of the lamp have been connected together, protecting the lamp cathode and ensuring longer lamp life.
Should a shunted socket or a short jumper not be used, the cathodes will sputter, emitting excessive amounts of tungsten, resulting in blackening of the lamp ends and ultimately reduce lamp life.
Diagram 2 illustrates the proper way to wire (jumper) lamps when shunted sockets are not being used.
When installing bipin based T8 lamps (up to 5 feet in length and including U-shaped), the two wires from each socket must be connected together prior to connecting them to the appropriate single lead of an instant start ballast, as shown in Figure D. This connection should also be made within 4 inches of the sockets, and any jumpers between sockets used in any prior rapid start systems should be reconfigured as shown in Figure D.
When installing eight foot T8 lamps with high frequency electronic instant start ballasts in retrofit situations, existing single-pin sockets should be checked for signs of arcing and pitting; replace sockets if needed.
The spacing between existing or new sockets should also conform to the socket and lamp manufacturer’s requirements. Please keep in mind that a high frequency ballast will sustain an arc more easily in adverse conditions than the 60 Hz magnetic ballast it replaces.
When installing PLL lamps, the wiring should be as shown in Figure E. The socket contacts must be connected in pairs prior to connecting them to the appropriate single lead of the instant start ballast, as shown in Figure E.
The common connections should be within 4 inches of the sockets.
Note: For all installations, check that all existing socket leads are securely connected to the socket and all socket contacts should be in good condition and show no signs of arcing or pitting; replace sockets, if needed. Spacing between existing or new sockets must conform to both the socket and lamp manufacturer’s requirements.
Failure to perform either of the above functions may result in an arc being sustained between the single lamp pin and the socket, damaging the socket over time which may cause the lamp to fall out.
The following 2 diagrams illustrate the incorrect way to wire T8 and PLL lamps. These types of wiring or any derivative of them should be avoided as they are not acceptable. In each case, the lamp denoted by “the letter “C” is carrying the current of the other lamp(s) in the circuit and will overheat. Incorrect application of sockets voids the lamp and ballast warranties because they result in shortened lamp and ballast life.