Other than the fact that 110v outdoor lighting installation is
typically more costly and complicated to install, what are the
advantages and disadvantages of low voltage vs. 110v outdoor lighting?
- Selection and variety of fixtures
- Energy efficiency
- Effectivenss/brightness of lights
- Cost of the fixtures themselves (not including installation costs)
- "Resale value"
Codes. Low voltage is easily installed and inherently safer than 120 volt
lighting. Any homeowner can do it and not kill himself or the paper boy
when he touches a fixture. Installing a 120 V system usually involves much
more labor, permits, more costly wiring, etc. Direct burial cable is needed
for 120 V, must be trenched at least 12" deep, have certain setups where it
comes up to the fixture. I'd consider using 120 for an end of driveway
lamp post, but any of the multiple garden lights and small walk lights, low
voltage just makes much more sense.
All of these are secondary to the 120V issue by itself.
What you say is all quite true.
Moreover, in smaller sizes, 12 volt lamps are more efficient and/or last
longer than a 120 volt bulb with the same watts.
The filament in a high voltage lamp has to be VERY thin to have sufficiently
high resistance to operate at high voltage.
different lamps have different jobs.
I have had a poll light for general front yard light plus some mini
accent lamps to light some steps and a mini flood shining on the
underside of a porch to iluminate the porch area.
I experimented one night with lamps and this was the most effective
combo for the job.
if you want area lighting some 300 or 600 watt halogen reflectors will
do the job for say cutting grass. run very long and your electric bill
will go sky high.
They now have a fixture that looks like a halogen with a CF lamp much
more enrergy efficent although not as brite.
Yeah but are any of those low voltage lights worth a damn? Seems like they
light enough to make themselves known but do little in the way of useful
lighting. Maybe someone ought to design a system using a LV version of
compact fluorescents. Then they could put out a decent amount of light
without drawing too much current to be practical which may be the problem
inherent in incandescent LV systems.
What you are proposing is extremly dangerous!! Before you go any
further on this ask yourself how you're going to feel if you child or
grandchild is killed by electrcution from that high voltage lighting
Invent something that will produce a brighter light, and pass safety
standards you set for you children or grandchildren, it will be
marketable and make you a weathy person.
If you use the proper cable and used proper grounding, there just isn't much
risk with running 120 wiring underground.
If you are "Belt & Suspenders" type, you can put a GFCI (ground fault
circuit interrupter) on the line going outside.
The GFCI provides better protection against personal injury than does
grounding. I have a GFCI protected circuits for some of my outside
lighting and I haven't had any tripping problems. There is the risk that
moisture can get inside fixtures and cause the GFCI to trip even when there
isn't a hard fault. But being a "belt & suspenders" type myself, my
outdoor fixtures are still grounded. In one case I have "underground"
cable protected by being placed in plastic conduit.
I have some 30w "flood" lights that are actually pretty decent considering
they are LV. There are also 50w ones. I use my LV lighting for effect more
then anything. They are adequate for lighting a walkway so you can find
your way, but you can't really see a lot of detail.
Problem I got with the LV stuff is the price. I've had 2 flood lights just
go bad on me, at $15 a pop. They rip you off almost 50% of the cost of an
entire unit just to get a replacemtn bulb. But, there's nothing else to
For pretty much all of your listed considerations there is no real
difference between 120V and 12V lighting.
Comparable selections are available in both 120V and 12V versions.
Little real difference in efficiency from a practical standpoint if you
are comparing incandescence or even halogen. Notable efficiency
differences appear when you consider fluorescent and HID fixtures which
are generally only available in 120V, with HID units only seen in true
commercial grade ($$$$) units.
Again comparable for quality fixtures i.e. cast metal fixtures, not
plastic. The low end garbage is just that.
Again comparable for most uses. For landscape, path and accent lighting
fixtures of both types are sufficiently bright. For full building facade
lighting units sufficiently bright are only commonly available in 120V
Again comparable. A cast metal fixture costs about the same to
manufacture, regardless of whether it is wired with a socket for a 120V
lamp or a 12V lamp.
Comparable given quality fixtures and good lighting design. An
installation with cheap plastic fixtures and/or poor lighting design
will have no resale value. A well designed installation with quality
metal fixtures will and value regardless of the system voltage.
The main difference between 120V and 12V systems is in the ease of
installation and the ease of changing the installation.
Low voltage systems require no permits, inspections or even much skill
to install. They lend themselves to "experimental" setups in the evening
while you develop the lighting plan. They are also easy to change if you
change your landscape layout.
120V Systems often require permits and inspections and require more
skill to install though it's not that difficult. Lighting plans
generally need to be worked out on paper from a landscape print and
fixture specifications which requires a fair amount of skill to get
correct. While it is possible to do temporary "experimental" setups with
120V fixtures it is much more tedious and difficult than with 12V
fixtures. Once 120V systems are installed they are comparatively
difficult to change if you change your landscaping.
Given the relative advantages and disadvantages of each type of system,
in larger installations the best option may be to use both types of
fixtures, preferably from the same manufacturer. Use the 12V fixtures
for most of the landscape and accent lighting where the landscape could
change. Use 120V fixtures for items that are both unlikely to change
such as lighting large trees, buildings or patio areas and which need
higher light levels than are available from common low voltage fixtures.
My two cents on low voltage vs 110v outdoor lighting says that 110v is
appropriate for lamps attached to the house, garage, or on a rugged
gate, pole lamp, etc, not for stringing into the bushes or for lighting
upon garden walkways, for reasons of safety and energy usage.
For 110v, a 2ft trench, PVC conduit, and periodic splice boxes are
required. I put a line out to an irrigation pump and A/C outlet on the
dock at the waterfront, and will do same for the entrance gate to my
property. At the time I that I trenched the 100 feet between the house
and watefront, I also buried PVC irrigation pipe, and 3/4" conduits for
low voltage wire and for the sprinkler valve system. I put period
junction boxes to ease the pulling of wire, and to provide places where
I could tap into for the low voltage and irrigation valve system. The
110v is there also should I want to simplify connections for a pool
pump or other such outdoor higher voltage needs.
My 900w low voltage system has a variety of lamps that no doubt
would increase the resale value of my home because it looks good having
accent lights on bushes, in trees, and along walkways, stairs down to
the waterfront, and on the dock itself. At Home Depot there are two
grades of lighting fixtures (I forget the brandname). The cheaper one
has a plastic like decorative finish over aluminum, which quickly wears
off in the sun and rain, and then the aluminum oxidizes, and so the
fixture looks horribly ugly and soon won't work. The top of the line
fixtures, which is all that I will buy now, are still being tested for
durability of finish, but so far they look pretty good. The top of the
line copper fixtures that the architect would recommend would be a
dream to have, and certainly would increase a home resale value, but
cost a fortune relative to the best at Home Depot.
I should also note that I've tried the solar low voltage route before
with rather disappointing results. The quality of units I used may be
the main problem, but I just didn't like the overly dim light cast by
the solar powered lamps. The large low voltage system I have in total
uses the equivalent of a couple outdoor flood lamps.
One more thing for DIY low voltage installers, when I examined the
little penetrating clips used to get power from the low voltage wire to
the lamp, I decided that over time, this connection could go bad, so I
dipped the connection in Scotchkote electrical coating, the same stuff
I used to waterproof my 110V splices, and then covered it in a piece of
the plastic packaging that comes with the low voltage lamp so that dirt
wouldn't stick to the connection. Instructions say that the wiring can
be strung along the ground, but since plastic degrades in sunlight and
dogs/children might like to play with the wiring, I dug tiny trenches
to cover over the wiring or stuffed it out of sight into the bushes.
The 24" trench and conduit are not required though they are good
NEC table 300.5 allows for 12" burial depth for type UF cable used on
residential branch circuits rated 120V or less with GFCI protection and
a maximum 20A overcurrent protection. Note 4 clarifies this.
The same table lists a requirement of 6" burial depth for the same type
UF cable used for low voltage lighting and irrigation control purposes
limited to 30V or less.
Not a lot of practical difference between direct burial cable at 6" or
12". Of course many low voltage lighting installations end up buried
under an inch of mulch at best.
I can believe the finish on the cheap ones failing in short order, but
they are so simple electrically that they will likely continue to
operate properly for a very long time.
Copper is certainly nice, but the epoxy painted or powder coated cast
aluminum fixtures of either voltage are quite durable.
None of the common solar powered units are worth a damn, plain and
simple. They simply do not have a sufficiently large PV panel to
generate a useful amount of power for any purpose other than simple
driveway edge marking.
This is not to say that solar landscape lighting is not viable, it just
isn't with the cheap individual fixtures. A "real" PV panel array rated
appropriately, coupled with a charge controller and deep cycle battery
could power a viable low voltage lighting system, however the cost would
be high and the pay back time based on electricity saved would likely
exceed the term of your mortgage.
A good idea for long term reliability. I think some of the better
fixtures have their IDC connections located up in the fixture where they
are protected vs. buried in the ground.
Interesting since that does not meet NEC table 300.5 requirements of 6"
cover for 0-30V on direct burial rated wire.
A much better way to do it and more consistent with NEC requirements.
On 20 Aug 2006 11:34:36 -0700, email@example.com wrote:
Right now it takes two cents to "make" a penny, This was an excellent
post. I live in the brightest city (place) on earth - Las Vegas. I
enjoy the low voltage lights. The guy next door has solar lights and I
often see several of them not burning at night. When they do, not much
I'm doing low voltage lights now in the landscape (remodel). Good
adive you had. Your property sounds like you got it going on.
solar lights are adversally effected by clouds and short winter days,
when you probably need them the most.
in pittsburgh its hopeless:(
too good a panel and someone will rip it off.........
main sales advantage of solar is no wiring, put a big panel on the roof
with a marine battery and the wiring advantage is lost
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