Understanding voltage drop is the key to a successful low-voltage lighting design With the rising popularity of residential and commercial landscape lighting, end-users and homeowners have begun looking for systems and components that combine easy installation and adequate safety considerations in one package. Standard 120V systems are unable to meet these requirements, so the industry’s landscape lighting manufacturers have responded by adopting 12V low-voltage systems as the standard for outdoor applications.  Low-voltage systems use smaller light sources, are easy to modify to accommodate changes in landscape layout, and are safer to operate and maintain than their 120V counterparts. In standardizing the 12V low-voltage system, manufacturers have made available various sizes of step-down transformers to convert a standard 120V source to a 12V supply. The components of the system may be easier to work with, but voltage drop must be considered and understood to effectively service the customer’s landscape lighting needs. Depending on its size and length, the conductor serving the fixtures of a low-voltage lighting system acts as a resistor. As current runs through the conductor, a voltage drop occurs: the voltage at the end of the conductor is lower than at the source. Smaller wires and higher currents will increase the voltage drop by raising resistance and increasing the fixture load respectively. Why worry about it? Voltage drop on a lighting circuit in a 120V system isn’t considered a major issue. The branch circuit currents are relatively low—usually 20A or below—and the standard wire sizes are usually large enough to minimize resistance problems. When working with 12V systems, however, the line current for any given load increases by a factor of 10. For example, a 100W 120V incandescent lamp draws .83A, but an equivalent load of two 50W MR16 12V lamps draws 8.3A. If you use the same size and length wire in both systems, the voltage drop in the 12V system will be 10 times greater than in the 120V system. In this case, voltage drop becomes a significant consideration. When the actual voltage delivered to a given incandescent lamp is lower than the lamp’s rated voltage, the light output will be reduced. This relationship isn’t linear. When the voltage decreases to about 85% of its rated value, the visible light output is only about 50%. It continues to drop quickly from this point forward. How to minimize voltage drop. Once you’ve finalized the lighting layout, you can control voltage drop by selecting the most effective gauge wire. The smaller the gauge, the less the voltage drop.  A minimum light output of 50% for the last fixture on a given run is normally an acceptable limit.Table 1 shows the maximum wattage allowed at various distances from a 12V transformer for various wire sizes. You can use the information in Table 2 to identify the required wire size, length of straight run, and wattage load on a preselected value of light output at the end of any given cable. Many transformers have multiple taps on the low-voltage side of the unit that provide 12V, 13V, and 14V output. Using a higher voltage tap to offset the expected voltage drop helps maintain the desired light output by delivering a closer-to-rated voltage at the remote lamps. This technique is used primarily where the distance to the first fixture is a long way from the transformer. Take care to avoid providing an over-voltage situation to the first grouping of fixtures, as this would shorten the lamps’ life.  You can also minimize voltage drop by altering your cable layout design. There are several options you can use other than a straight run:
Locating several smaller transformers closer to the end of your cable runs can also help limit voltage drop. If at all possible, you should center the transformer in the run. If the light fixtures are located too far from the 120V source, consider running a 120V feed to a transformer located closer to the low-voltage lighting fixtures. If you’re only trying to serve a few limited fixtures, consider using direct burial, 12V transformers for each fixture, which can be fed with a 120V source. Another way to minimize voltage drop is to use lower voltage lamps in your design. For example, 18W lamps are the preferred choice for spread lights, but you can also use 12W lamps. If you do decide to use lower wattage lamps, however, recheck your photometric levels so you don’t wind up with an inferior lighting design. Troubleshooting. Low-voltage lighting installations require a great deal of care during installation due to the high currents in the system. Placing too many fixtures on the circuit or using the wrong wire size can lead to a system overload. Therefore, it’s important to troubleshoot the system after installation. The most common problems encountered in low-voltage landscape lighting installations are poor wire connections, too many fixtures on one transformer (overloading), and cables that are too small for the load. By understanding voltage drop, you can address these problems and implement a successful low-voltage lighting design. Low-voltage lighting will allow the end-user to change the landscape layout and ensure safe outdoor lighting. Liepold is a project management consultant for Progress Lighting in Spartanburg, S.C. |
Wednesday, June 29, 2011
The Fundamentals of a Successful Low-Voltage Lighting Design - EC&M Apr 29, 2003
Tuesday, June 28, 2011
Low Voltage Layout Guide
LENGTH OF RUN (FT.) / 7490
Example: a 100' run with 150 watts on it using 12 AWG wire will have: 150 w x 100 ft / 7490 cable constant = 2 voltage drop. Accordingly the run should be connected to the 13 or 14 volt tap so that after it loses 2 volts, the fixtures will still receive between 11-12 volts.
You can start by grouping fixtures into distance zones. \
- Group lighting fixtures with short distances of 0'-25' in the same zone,
- medium distance fixtures from 25'-50' in the same zone, and
- long distances 75'-100' in a zone
- A landscape lighting fixture that is 15 feet away from the transformer, and a fixture that is 100 feet away from the transformer should not be on the same run.
TIP #1
Lower loads per run means lower voltage drop. Break your layout up into multiple cable runs of ~ 100-150 watts per run. If you have more than 150 watts in an area -- break it up into 2 runs.
Break your layout into Distance Zones. For example put fixtures 15-30 ft away from the transformer on one run, fixtures 25-40 ft on another run, fixtures 30-50 ft on another run, and so on. The goal is have all the fixtures on a run be roughly the same distance from the transformer so they have similar amounts of voltage drop. That way when you adjust for voltage drop by increasing the voltage for that one run, the lights are not over-volted or under-volted.
Do not Daisy Chain the fixtures. In other words do not connect fixture after fixture in-line to the same cable. You can do a couple fixtures in series, but we don’t recommend exceeding more than 3 fixtures or 75 watts in series. Instead form T or spider splices so that there is never more than 2 fixtures between any one fixture and the transformer. Example you might have 6 fixtures on a run but the cable layout is like a T with 3 fixtures on the upper left part of the T and 3 fixtures on the upper right part of the T. Even the end fixture only has 2 fixtures between it and the transformer.
For each run, bring the wire from the transformer to the middle of that zone, and then branch off more cable from there to reach different areas. This can be done with a junction box/hub or by simply splicing in more cable to form a T layout. This T layout somewhat incorporates objectives we discussed above in TIPS 2 & 3, getting all fixtures with roughly the same length of cable to reach the transformer (TIP #2) and avoiding daisy chaining (TIP #3).
Layout Example:
- For example if you have 4 path lights along a driveway each 10 ft apart, run the cable from the transformer to the area between fixtures 2 & 3 (even if it means passing fixtures 1 & 2 without connecting them). Then splice in a T with cable going back to fixtures 1 and 2 and cable going out to fixtures 3 and 4, then connect the fixtures. This way electricity has to travel the same distance to reach the closest fixture (fixture #1) as it does to reach the farthest fixture (fixture #4). Additionally you only have 2 fixtures daisy chained in a row. If the farthest fixture is dim you can use a higher voltage tap on the transformer without over volting the closest fixture. All your lights in that distance zone/on that run have the same amount of cable to reach the transformer and accordingly will all have the same voltage and all be bright and even. It may seem odd to pass by a fixture with cable and then run more cable back to it, but what you are really doing is adding more cable distance to your close fixtures so that they equal the cable used in far fixtures.
Junction box/Hubs are an easy, efficient way to insure that you have done your layout properly. They virtually guarantee perfect results, bright even lighting, prevents over/under volting. Additionally all your connections are in one place (so they are easy to trouble shoot/service). Lastly, with VoltPro exclusive above ground Junction Box, all your connections are above ground in a dry, weather tight junction box, not in the ground exposed to constant moisture and harsh electrical conditions like traditional connections or even competing company's that sell "hub systems".
You do not have to hub every fixture. T-layouts are perfectly acceptable for a couple fixtures. A junction box is just more convenient if you have several fixtures all in a same area. Hubs can also make a great junction box for spider splicing several main cables together (10-2 or 12-2 cables). Many direct burial connectors cannot handle several thick gauge cables connecting together, hubs make for a convenient, dry, above ground place to make these connections. When doing more than a T connection but a spider splice with several cables in one place, junction boxes are great.
Monday, June 27, 2011
Panny Flat Screen Mounting Outfit
The mounting project through monoprice will cost $119 or as little as $60 depending on the level of refinement you demand. Let me place the order and do this.
The price you quoted for the mount and cables alone is ~$225 right? Any idiot can run the audio video cables because they are low voltage. PCR will probably charge you $300 for all the labor and materials. That's if you want a trade school dropout and not an electrician. . . .
A licensed electrician will raise the outlet for at least $75 plus materials.
Let me place the order and do this. Do you have paypal? If not, do so. You cant be half in and out of the 21st century. Go to their site and set one up. Email me what you want me to purchase (monoprice is 100% returnable). I'll tell you after the order is placed.
I'm Here to help to the extent you want.
Some useful info that supports my enthusiasm for tackling this job myself.
- Professional level install (better than PCRichards) costs more because you install fixed wall plates similar to power outlets that let you plug into them and likewise behind the mount.
- Going this route has other advantages related to the convenience of unplugging a highly accessible and visible cable should any components (the cable box and DVD player or TV need service).
Advantages:
- Convenience of unplugging a higlhy accessible plug
- Aesthetically less vulgar (black 3 ft cable connects tv to wall / white connects wall to DVD, etc).
- Should you ever leave it will retain value in a way to holes in wall
Disadvantage:
- Eventually the HDMI standard will evolve beyond the current version 1.4a. At that point you will need to buy 2 sets of short cables and two behind the wall (6 total) . Cost to upgrade 5 years is $20 vs $15.
- It does cost more and is more time consuming to install
The Product List is as follows (FYI):
- 10ft 24AWG CL2 High Speed HDMI Cable w/ Net Jacket - White
- 10FT Cat5e 350MHz UTP Ethernet Network Cable - Black
- 1-Gang Low Voltage Mounting Bracket 2-Gang Low Voltage Mounting Bracket
- 3ft 28AWG High Speed HDMI Cable w/Ferrite Cores - White
- Adjustable Tilting/Swiveling Wall Mount Bracket for LCD LED Plasma - Corner Friendly (Max 125Lbs, 32~52inch)
- Cat5E Punch Down Keystone Jack - White Recessed Low Voltage Cable Wall Plate WITH Recessed Power - White
- Two-Piece Inset Wall Plate with 4 Inch Built-in Flexible Extension Cables for High Speed HDMI w/ Ethernet - Dual Port (2P)
- Wall Plate for Keystone, 1 Hole - White
I can't say for sure but I'm pretty certain this does not rotate left and right 90 degrees. I can't picture it happening without the arm getting in the way. More info is scarce as the mount you bought doesn't ship to retailers until July 11th.
Pictured here is the Bell'O 7845 (Prior Year Model?)
The swivel on the one I picked is how they get around needing to rotate the TV flat against the extended arm:
Pictured here is the Bell'O 7845 (Prior Year Model?)
The swivel on the one I picked is how they get around needing to rotate the TV flat against the extended arm:
Wednesday, June 15, 2011
Tuesday, June 14, 2011
Lighting Fixtures
This will be a good place to consolidate the manufacturers' specification sheets for each of the new fixtures I am accumulating for the backyard berm and moonlighting project. New fixture information will be included for all new landscaping hardware and this section will be a comprehensive compendium of tech, beauty, and function.
Specifications
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Hadco Direct Links:
Before I introduce the Sportlights that I have selectoed to "audition" for this project I wqas ted to outline several fo the qualities I am looking for in an uplight so as to make the comparison here understandable as it is deleivered with respect to my own needs.
Requirements / Wish List:
- Multiple mounting options beyond the standard ground stake. It is necessary given my space restraints to mounts these fixtures with on the side of the house. Nearby trees.
- In a similar fashion - mounting oprtions should ideally include screw able extensions that boost the spots' height above intermediate obstacles.
- These type of accessories generally accompany products put forth by companies anticipating exacting standards from their clientele. This is a blessing and a curse because it carries with it a necessary premium for the base unit. The good part is illustrated next;
- Ideally any spot should be able accommodate a range of lenses and or mount configurations that allow it to be optimized in less ideal locations. (Think Louvers, Frosted glass, Deep Shrouds).
The first high-End Light I received was a
Kichler 15384.
Ipression out of the box was that this was a cut above. The adjustment necessary to enable the lamp to operate at various degrees had always been a plastic hand turned screw mounted. Generally my experience is that these lights have two parts: a base which scres into a stake or other mounting hardware, and a cylander that holds the fixture, lamp and glass.. The two parts meet each other with interlocking teeth. Untightened this gives the fixture a range of mobility. Once tightened interlocking teeth fill the gaps on opposing sides and lock the fioxture in the desired position.
As previously described those lights I have worked with in the past (Malibu, etc.) allow you to lock in the desired angle by turning a plastic wheel that tightens the screw connection. Great in the 30 minutes needed to achieved your desired look but don't revisit it after time has degraded the parts.
I've only had one fixture's ability to lock in an angle fail. More often though the knob separates from the screw making tightening futile. I digress.
The Kichler skipped this nonsense and included a beefy screw as the only piece holding the two together.
Without further ado..... The Tech Specs:
The Kichler Features the following:
Kichler:
MR-16 MINI WELL
This is also a Kichler though far longer in the market. The set I got was in horrendous shape but so cheap I couldn’t say no.
All housings were intact as were gaskets, lenses and Caps. The weakness was the degradation of the fixtures which I will need to replace for at least two.
All in all these retail for $108 apiece and I got five delivered for $25 total including lightbulbs (20% fail rate so far.
Smaller version of our popular standard well light to shed focused upwards illumination on special features in the landscape. Recommended for salt-air environments. Housing Durable high heat thermo-plastic composite resin. Heat resistant convex shaped glass lens. Fully sealed for watertight outdoor usage.
· Finish Black
· Light Source 12V Incandescent bi-pin, high temperature
· Porcelain socket
· Power Usage at 12V AC Input
· VA MAX: 50-W(VA)
Ordering Guide
· 15190 BK
· 15990 BK 6 Same as 15190 BK. Bulk packed in 6 (unbreakable master) with 25' of 16-gauge wire and Universal Connector for use with LV Junction.
The Deck
Deck Lighting:
Our Back Porch is bordered by two equi-length benches (backless). They were originally conceived as a substitute for a railing in a compromise with the inspector. The deck itself ironically was made two inches lower than it was designed to be. At the original height it would flow directly onto the covered concrete patio.
The inspector only agreed to sign off with no railings if we dropped the height two inches. We did and then his supervisor visited the site during the build and made it clear we would have to dismantle the entire deck if we didn't put a rail around it. We were able to negotiate for a bench in lieu of this. However the sad part is the deck is still two inches lower than it should be. The second consequence is that a third step had to be added making them narrow and shallower then one would normally wish for.
In any event the project here is to add recessed linear LEDs around the inside border under the bench. This will cast a glow onto the deck and offer a boundary or a point of perspective to delineate this area from the rest of the yard.
Previously I had installed 120 Volt Rope Light from home depot which looked damn fantastic. However powering it was a mess and the spacing of the lights were wide, such that the illusion of a single source of light was lost.
Points to consider:
Our Back Porch is bordered by two equi-length benches (backless). They were originally conceived as a substitute for a railing in a compromise with the inspector. The deck itself ironically was made two inches lower than it was designed to be. At the original height it would flow directly onto the covered concrete patio.
The inspector only agreed to sign off with no railings if we dropped the height two inches. We did and then his supervisor visited the site during the build and made it clear we would have to dismantle the entire deck if we didn't put a rail around it. We were able to negotiate for a bench in lieu of this. However the sad part is the deck is still two inches lower than it should be. The second consequence is that a third step had to be added making them narrow and shallower then one would normally wish for.
In any event the project here is to add recessed linear LEDs around the inside border under the bench. This will cast a glow onto the deck and offer a boundary or a point of perspective to delineate this area from the rest of the yard.
Previously I had installed 120 Volt Rope Light from home depot which looked damn fantastic. However powering it was a mess and the spacing of the lights were wide, such that the illusion of a single source of light was lost.
Points to consider:
- I do not want this light to spill off the deck and onto the plantings which surround the deck.
- Some effort will need to go into trying to integrate the rounded Dwarf Boxwoods which Flank the Benches.
- My dream would be to uplight these with a brilliant source of linear light but I haven't found a product that can offer the light necessary and still fit.
Inspirational Work:
Thursday, June 9, 2011
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