W. P. Law, Incorporated - Fluid Handling Professionals
W. P. Law, Inc. has developed an in-depth low voltage lighting installation manual to provide you with a precise step-by-step method of designing and installing low voltage landscape lighting.  The complete manual is available in PDF format by clicking on the link below.  A low voltage lighting calculator is also available in Excel format for transformer load calculations.  Please click on the link below to download this useful tool.

pdf icon   Download & Print the Lighting Technical Guide by Clicking here.
pdf icon   Download the Lighting Calculator by clicking here.

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The purpose of this manual is to provide you with a precise, step-by-step method of designing and installing low voltage landscape lighting.  This manual will take you through fixture choice, bulb selection, wire sizing, fixture installation using the hub method, transformer selection, and a reference section.

When a landscape is designed, attention is focused on highlighting the architecture, dividing public areas from the private ones, creating unity, flow, safety, and harmony between the different elements used whether it's plants or hard-scape.  Landscape lighting serves to do the same thing.

Beginning the design process starts with the focal point of the landscape, the home.  Look at the architecture, the texture of the building materials, and landscape materials in the foundation plantings.  Think about using fixtures that wash the walls or cast light into dark corners and to highlight doorways and trim.  Moving away from the home investigates illuminating shrubs, especially those plants or plantings that direct a visitor to the entrance or those plants that are accents to the architecture.  Still moving further from the foundation plantings are hard-scapes such as walks and drives.  These are one of the most difficult areas to illuminate.  This lighting should be done in such a way that the "landing strip" appearance is avoided.  If possible, wash the surface of a walk with a level ground directional light.  This will cast light horizontally across the walk and is far better than lining up a number of path lights.  With a little planning ambient light spilling from the foundation plantings and the home may be enough to create a glow to gently light a walk and provide safety.  Drives can be lit in the same manner or in combination with down lighting being used from nearby trees to light the way.  The last items to light are the lawn areas, front and back.  First frame the home by up lighting large trees in the front, back, and sides.  Next provide light in excessively dark areas of the lawn.  Next use accent lighting, either up lighting, area, or directional lighting to highlight points of interest.  

Below is a list of fixtures and a short description of what each one does.  Please note that this is a general description and a product catalog should be consulted to pick out the proper size, color, material, and bulb for the job.

Well Lights

Well lights are among the most versatile fixtures.  They are used in 80% of all landscape lighting applications.  Lenses and grates can be easily installed on these fixtures for many custom lighting applications.  Well lights are used mainly in areas where up lighting is required to illuminate the entire object or wash the object with light. 

well light


Path Lights

Path or area lights are best used to give down lighting on pathways, sidewalks, breezeways, driveways, or beds with seasonal color. 

path lights


Directional Lights

Directional lights are used when a concentrated beam of light is needed on statuaries, columns, signage, and water features.

directional lights


Underwater Lights

These lights are directional and require complete submergence to remain cool.  These are used to up light waterfalls, statuaries, and provide diffuse lighting of the feature.  Optional colored lenses are available.

underwater lights


Specialty Lights

Specialty lights are lights that serve a specific purpose.  These lights are usually low wattage and only produce a small amount of illumination.  Dock and step lights are just a few samples of this type of lighting. 


These devices step down the normal 120v household current to voltage that can be used in the lighting system.  They are available in wattages from 300 up to 1500 watts.  The transformers have multiple voltage taps of 12 to 22 volts which enables the user to run smaller gauge wire longer distances.  Transformers can be installed indoors or out and can be equipped with a timer and photo cell. They must be installed at least 12” above grade.


The next step involves the location of the transformers.  First you’ll want to guesstimate how many transformers might be needed for the job.  At this point simply add up all the wattages of all the fixtures used.  It is sometimes easier to use more than one transformer in different locations.  This will keep your wire runs to a minimum and allow for easier zoning of the lights.  Zoning the transformers this way will allow you to run areas independently.  This will save money in the operation of the system.  If, for example, both the back yard and front yard including the side yards yield 800 total watts used, two transformers of some wattage will be needed.  [The calculations for the absolute wattage required for the transformers will be shown shortly.]  Designate an area for each transformer, preferably as close to the center of each system as possible.


In the past, when low voltage tungsten bulbs were used, the fixtures where daisy- chained* with no real attention paid to bulb brightness, color or longevity because tungsten bulbs can burn for years on very little voltage.  The newer halogen bulbs on the other hand, produce a white light giving a truer color but operate in a narrower voltage range of 10.8 to 12 volts.  Therefore, to help the bulbs last for their full life rating, the fixtures are arranged in a “spider” or “hub”** configuration.  The fixtures used come from the factory with 25’ leads instead of the 18” leads in the past.  The fixtures are arranged so that the leads can be tied together to a trunk wire leading back to the transformer.  This trunk wire is referred to as a “homerun wire”.  How many lights tied together at a hub will depend on the total wattage of the hub.  A rule-of-thumb is a maximum of 4-5, 20 or 35 watt fixtures per hub. 

Of course some fixtures use smaller bulbs of 10 watts or less, so more of these lights may be tied together.   Sometimes the full 25 foot lead is not used.  If this occurs bury the extra at the base of the fixture or when using well low voltage garden lights, wrap the extra lead around the fixture. Never cut the leads to shorten them.  The reason is that the voltage drop in the lead has been accounted for and cutting the leads will result in differing voltages for each fixture. The voltage reading at the hub must reflect the same reading for all lights in the group.

hub method


The lighting transformer may be turned on or off by wiring it into a separate circuit using a wall switch or the lighting may be controlled remotely by attaching a timer, photocell or both to the transformer.  The timer used may be either analog or digital.  For simple lighting projects where the operation time is not varied during the week an analog timer is all that is required.  This is a motorized timer with pins that can be placed around a dial to turn on or shut down the lighting at a prescribed time.  This timer is limited to two start times per day.   It also features a manual override on/off switch.

A digital timer may be used for more complex lighting systems where multiple start times are required including start times on different days of the week.  The digital timer has an LCD display and is programmable using push buttons.  This device has a battery back-up to preserve the memory in case of a power outage and also features a manual start cycle.  Both timers fit a 120 volt outlet located on the face of the transformer.  To install a timer simply remove the plug from the outlet, insert the timer into the outlet, then re-plug the transformer into the outlet on the side of the timer.

A photocell can be used in lieu of the timers
and will operate the transformer from dusk to dawn. In order to conserve power, it is recommended to use the photo cell in conjunction with a timer to turn the power off at a predetermined time in the evening.  Another advantage to using a timer/photocell combination is to avoid having to reset the timer when the yearly time changes occur.

The photocell is attached to the side of the transformer through a knock-out on its side.
  The photocell leads are passed through the chassis of the transformer and plugged in where the wire loop is connected.  If the photocell is used, unplug the wire loop but do not discard it.  This loop is used in conjunction with an amp meter to check the amp draw on the primary (120 volt) side of the transformer, when trouble-shooting the system.  The photocell must receive direct sunlight in order to function properly.  Avoid placing the transformer in an area that will become shaded as the sun changes positions.  Because locations for transformer placement does not always provide for full sunlight, a photocell with a 25’ lead is available.

photocell


In the past, fixtures were attached at different locations along the main wire path using clunky two- piece wire piercing connectors or the line was cut and specialty gel filled wire nuts were used to make the splice.  The problem is that in order for low voltage cable to be flexible it is composed of stranded wire and with every connection made, some voltage loss occurs because a secure connection could not be obtained every time.  

The hub makes use of a brass set screw wire connector that will hold 4-5 wire leads plus the homerun wire securely.  In addition, a protective cap filled with a dielectric compound is screwed over the connector to protect the wire from corrosion.  The splice is then housed in an in ground junction box to facilitate ease of maintenance and location of the hub.

dielectric

sample design


When laying out low voltage lighting cable choose the shortest distance possible between the transformer and the hub.  It is not essential to run the cable in conduit unless it passes under sidewalks or drives.  Sleeving under these areas allows for ease of installation, maintenance or repairs.  If the transformer is located outdoors, it would be wise to enter the transformer with the appropriate sized conduit to protect exposed cable from gardening equipment such as string trimmers and provide a way to seal the transformer from insects.  Landscape lighting cable can be safely installed under mulch or in trenches when crossing lawns.


Besides having the basic hand tools for digging, we strongly recommend having a volt-ohm meter and an amp meter for trouble shooting purposes.  The volt-ohm meter is indispensable for checking the continuity of the system from the transformer to the low voltage garden lights and for checking voltage(s) at the hub(s) during installation or trouble-shooting.  The amp meter is used to ensure that the transformer is pulling the proper amperes during its operation.  “Over-amping” the transformer will void the manufactures warranty as it causes the device to fail prematurely.  Optional trouble-shooting tools are a wire locator and a fault locator.  All these tools can be used anywhere diagnostics are required of electrical components including irrigation systems.

Lighting Calculator and Low Voltage Lighting Installation Manual


Once the lighting system is installed, there are three checks you will want to make to ensure everything is functioning properly.

Check #1  lighting technical info
Check voltages at the hub with a volt/ohm meter.  The voltage at the hub should read between 11.5 to 12.5 volts.  If the voltage does not fall within this range, you will need to choose another tap at the transformer. 

Check #2  lighting technical info check box
Use an amp meter to check the amperage on the primary side (120V) of the transformer to ensure against possible overloads.  For this purpose, there is a loop of wire located under the cover of the transformer.  Plug it into the matching socket labeled "Photocell Plug" on the face of the transformer.  Clamp the amp meter to the wire loop to test for amperage.  Do not exceed 2.5 amps per 300 watts.

check box

Check #3  check box
Use an amp meter to check the amperage on the secondary side (12V) of the transformer for each wire run.  The amperage for each run should be equal to the wattage for the hub divided by 12.

check box

check box
pdf icon  Download & Print the Lighting Technical Guide by Clicking here.
excel icon  Download the Lighting Calculator by clicking here.

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