"Greg R." wrote in message
news
I recently bought a house that has low-voltage outdoor Malibu lighting
(by Intermatic). Currently it has a 200w power supply to power 10 tier
lights and 5 20w flood lights. The setup is as follows, power supply -
3 spot lights - 10 tier lights - 2 spot lights. The strange thing is the
first 3 spot lights in the circuit are much brighter than the last two
spotlights (in relation to the the power supply). All the tier lights
seem the same brightness. My question is, why are the last two spotlights
so dim? I would assume that if the power supply was not strong enough,
all the lights would be dim. Do halogen bulbs dim as they are burning
out? Could they be different bulbs that the brighter flood lights (the
fixtures appear identical). Any suggestions?


You probably have voltage drop.

The last two spot lights at the end of the line arent' getting 12 volts
because of the power draw from the other lamps on the circuit and because
the maximum resistance of the wire is between them and the power supply.
You can check this by measuring the voltage at the power supply and then
measuring the voltage on each lamp down the line. The voltage available to
each lamp down the line will be lower.

Your system is designed to operate on 12 volts for several reasons including
safety. But by going to a low voltage the current in the wires has to go up
to supply the same power to a light bulb. For example, a 20watt floodlight
draws only 0.2amps. on 120 volts; but a 20watt 12 volt bulb would have to
draw 1.2 amps for the same light output.

A simple solution would be to get a length of liine equal to what you have
now. Connect one end to the power supply, then run it along the existing
line to the end and connect the ends together. Be sure to connect like
wires to each other or, in other words, observe polarity. This is called a
"ring" or "loop" circuit. It probably won't bring your last two flood
lights to full brightness; but again check the voltage at the lamps. The
extra wire should raise the voltage available to the lamps at the end of the
line considerably.

Halogen bulbs do not dim as they burn out; in fact, halogen bulbs keep their
brightness better than conventional incandescent bulbs over time.

It's certainly possible that different wattage bulbs were put into different
sockets along the line as bulbs burned out; but that's easy to check. The
wattage is marked on the bulb -- usually on the back in the case of a flood
light bulb.

TKM