An exterior luminaire, or fixture, must be constructed to withstand its intended use and operate in harsh ambient conditions, such as a corrosive chemical environment or in an area where vibration, dirt, and possible physical abuse come into play. Additionally, if the luminaire will be in an excessively hot or cold environment, its internal components, such as the ballast or capacitor, should be rated for the expected temperature. But how do you know what type of system will work best in certain environments? Where do you turn when you're not sure how best to install a fixture for long-term service life? One source of information is NECA/IESNA-501, Recommended Practice for Installing Exterior Lighting Systems (ANSI).
The material presented in this document is intended to comply with the most current edition of the National Electrical Code in effect at the time of its publication. It's not intended to duplicate NEC requirements or to establish any new regulatory requirements for electrical construction, but instead provide a solid reference for making a quality installation. The lighting systems and equipment covered in this document include, but are not limited to, pole-mounted luminaires and bollards, wall-mounted and in-ground fixtures and equipment, along with canopy and soffit lighting.
To better understand how to properly install different types of outdoor pole-mounted systems and components, let's look at a few of the key issues discussed in this standard.
General prep work. Since a building architect, a civil engineer, or a landscape architect may have design responsibility at the site, determine the specific party responsible for the design and coordination of work in the area. Secure proper clearances and approvals from this person prior to beginning any work.
Determine if systems like HVAC, plumbing, lawn irrigation, storm sewer, sanitary sewer, water supply, and gas lines are sufficiently complete to allow installation of lighting systems. Be sure that final grading is completed and that appropriate site landscaping is finished. An important concurrent factor for lawn irrigation systems is determining the exact type and location of irrigation heads.
Since exterior luminaires generally require watertight integrity, check all of the sealing needs for the luminaires and the related electrical components, such as in-ground junction boxes or transformers. Inspect gaskets, O-rings, and other water sealing components and replace any defective items. Use only the potting or sealing compound recommended by the manufacturer — don't make substitutions. Avoid direct contact of dissimilar metals. Try to avoid the use of steel components and other materials subject to corrosion unless specifically directed by the fixture manufacturer or engineer.
Ensure that the poles and associated lighting fixtures you're getting ready to install can withstand the local weather conditions. Consult a map that shows the annual extreme wind conditions over a 50-year mean recurrence level interval. Review local codes since they may have more stringent requirements than what's listed in the wind chart.
Since pole-mounted electrical equipment is stored outdoors, the material should be left in the original packaging until the actual time of installation. If necessary, set up a clear path for moving assembled luminaires from the staging area to the installation site. For any large equipment, such as poles and mast arms, determine if the manufacturer recommends special measures to prevent damage prior to installation.
Preparing the pole properly can eliminate many potential problems. In the case of standard steel poles, they must be painted to prevent destructive rusting. These poles usually have either a factory-applied finished coat or a prime-coat, in which case on-site finishing is required. If it's necessary to finish the coating in the field, do it as soon as possible to avoid unnecessary weathering of the pole surface. If poles are to be painted outdoors, the temperature should be above 50∞F, and any blemishes on the prime coat should be repaired before applying the finish coat.
Foundation prep work. With regard to pole foundations, install conduits, ground wires, and other indicated electrical work during form preparations. Provide adequate sweeps of conduit and extensions. And be sure that conduit sizes correspond to the manufacturer's recommendation.
Anchor bolts must be installed in concrete, and adequate time must be allowed for the concrete to cure (harden) before erecting the pole. Only anchor bolts and nuts supplied by the pole manufacturer should be used, although a qualified engineer may approve other types of hardware on certain occasions. You can further improve corrosion protection by purchasing anchor bolts with a plated or galvanized finish either on the entire bolt or only on the threads. Extreme environments and sites where the bolt tops will be exposed to the weather are examples of where a galvanized finish is preferred. Normally the pole manufacturer provides a paper template used to make a plywood or steel mounting aid that holds the bolts in place during a concrete pour. Make sure that the bolts remain in a plumb orientation while the concrete is poured and vibrated.
If the electrical distribution system is already installed, make certain that the location of junction boxes and branch circuit home runs are properly located. Inspect local or supplementary grounding to confirm that things like ground rods and cables are installed and ready for final connection. Coordinate with other trades and with the appropriate professional designer responsible for overseeing the installation, such as a civil engineer or a landscape architect.
Occasionally, pole locations may need to be shifted from their original location. If this is the case, then make sure you check with other trades for possible interference before starting work in a new area. Additionally, it's important to locate any existing buried lines that might be present in the area where trenching will be done. In most areas, toll-free, one-call services handle the arrangements for locating existing buried utility lines. Allow sufficient time for the utility to mark the site.
Even after the utilities have marked their facilities you should still make a sweep of the area with an electronic locator before starting any underground work. Since it's possible for a line to be incorrectly marked, double-checking the location and depth of any possible underground hazards is very important.
Installing the pole. The manufacturer's recommended installation procedures and the use of allied materials should be carefully followed. Since a pole-mounted luminaire — whether it's installed alone or in a cluster — is a heavy component, proper and secure mounting is extremely important. For example, safety supports provided with luminaire components may be attached to the luminaire, but the addition of components like chains that aren't supplied with the luminaire may violate the product listing.
When securing the pole to the anchor bolts, follow the manufacturer's bolt pattern since, in some cases, orientation of the bolt pattern is critical to not damaging the mounting plate. Leveling nuts help to ensure the pole remains properly plumb. Flat washers and lock washers go on before installing the top nuts. Minor adjustment to the leveling nuts may be done before tightening the top nuts to the torque level recommended by the pole manufacturer.
As a last step, place a non-shrinking or expanding type concrete grout in the void between the base of the pole and concrete foundation. Puddle the grout around the edge of the pole base and firmly pack the space between the pole and the foundation. Use a short piece of small-diameter pipe to make a drain hole through the grout to the pole interior.
Most poles have an electrical grounding nut attached to the pole interior near the hand hole for installing a ground connector and a bare ground wire. Don't wrap any ground wire around an anchor bolt or just below the anchor bolt nut. When working direct burial or nonmetallic-conduit circuits to supply equipment mounted on metal standards or poles, the use of an equipment-grounding conductor is necessary. This conductor provides a low-impedance path for ground-fault current return and ensures fast, effective operation of the circuit protective device in the event of a fault.
As part of a final inspection, carefully look at the fasteners, welds, anchor bolts, and nuts, as well as the concrete foundation for any loose nuts or for cracking or spalling of the concrete grout.
Wiring connections. Check to make sure the supply wires conform to the temperature rating on the luminaire label. If necessary, use tap conductors of the appropriate gauge and temperature from the fixture terminal connection to the branch-circuit wiring. Be sure that the conductor insulation characteristics correspond to the ambient conditions, such as a wet or damp location, or a situation where resistance to UV radiation is important.
Wire connectors should have proper capacity, and where applicable, the connectors should have a below-grade rating. In other words, they must provide a barrier against moisture. If vibration will be encountered, the use of twist-on wire connectors is recommended and should be followed by wrapping the connection with insulating tape.
Determine if branch-circuit conductors will run through raceways, junction boxes, or outlet boxes that are part of the luminaire. If that's the case, be sure the luminaire is listed for this application. Refer to the luminaire label for the maximum size and number of conductors allowed for through wiring.
Apply circuit identification to luminaires for safety and maintenance purposes. If label size and location isn't specified in the project documents, consult with the owner. In addition, observe if special wiring requirements for control circuits or emergency power must be satisfied.
Lamping and accessories. Protected type lamps should be used in luminaires with open bottoms when required by the manufacturer. Because the MH lamp arc tube operates at a high internal pressure, the potential exists for arc tube rupture, especially at the end of lamp life. Over time crystallization can occur, creating stresses in the glass of the tube. Thus the arc tube can rupture with enough force to fracture the outer bulb.
For that reason, the American National Standards Institute divides MH lamps into three classifications: E-type lamps for use in enclosed fixtures; S-type lamps (350W to 1,000W) used in open fixtures in which the lamp is operated vertically; and O-type lamps that have a protective glass sleeve over the quartz arc tube to contain any glass parts following a rupture.
Final adjustment and testing. Aiming and adjustment of light distribution and lighting control is handled after installation. Reduction in light pollution and light trespass are both important concerns today. Street and area lighting systems should be designed to minimize or eliminate light emission above the horizontal plane. Many municipalities have ordinances that restrict light pollution to adjacent properties. Be aware of these ordinances. Shields and baffles may be required to provide proper cutoff of the light distribution.
Sidebar: PV Systems
Although outdoor photovoltaic lighting isn't covered in the recommended practice of NECA/IESNA-501, it's gaining increasing importance. Outdoor photovoltaic (PV) lighting uses PV panels, or modules, to convert sunlight to DC power, which in turn is stored in batteries for nighttime consumption. Compared to installing line voltage power conductors, the PV system can be cost-effective for relatively small lighting loads. Examples where PV can be practical are municipal park lighting, street lighting, and campground recreation area entrance signs. Nickel cadmium, sealed lead acid and lead acid batteries are commonly used for this application.
Sidebar: Understanding Floodlighting/Area Fixtures
A pole-mounted outdoor area luminaire generally distributes light in only very specific directions: to the flat surface of a playing field or a parking area. So this type of equipment uses what's called a floodlight data sheet. Floodlight beam spreads and their projection distances, classified by joint IES/NEMA designation, are shown in this type of data sheet.
Generally, narrow projection beams (Type 1, 2, 3, and 4) used for a long throw to light specific objects, such as a monument or statue, or for wall washing up the side of a tall building, have a symmetrical beam shape. The beam-spread angles are identical in both the vertical and horizontal axes.
However, floodlights used to project their light at medium or close distances will use Type 5, 6, and 7 beam spreads. But for this “close up” use, the luminaire often has a different beam pattern for the vertical and horizontal axes. For example, a sports lighting luminaire (also called a cutoff luminaire) will have a Type 4 beam spread in the vertical axis and Type 7 beam spread in the horizontal axis, so it's called a 4×7 beam shape.