Having discussed identifying and buying the correct replacement lamp in a previous blog, it is necessary to discuss voltages and the effect they can play on the lifespan of bulbs. When a lamp is rated for 12 or 24 volts, this doesn’t mean it actually operates at that voltage. In fact most 12 volt lamps will last up to 50% longer if they are set at 10.5 to 11 volts. The opposite is true if you go over 12 volts at the lamp, then the lifespan of the bulb dramatically decreases. Lowering the voltage saves energy, money, and time spent replacing burnt out bulbs.
The transformer, the box supplying the electricity, has multiple taps at different voltages. As electricity is transmitted it loses strength over the distance of the wire. So when it reaches the fixture it may have decreased by 1 volt and the light is only at 11 volts. The number of fixtures on any individual run from transformer also effects the amount of voltage drop. The more fixtures, the more voltage drop that will occur. So from our previous example of the one voltage drop for one fixture. Now say we add three more lights to that wire, now the voltage may drop by 2.5 volts, so the voltage will read 9.5. This means the wire needs more electricity from the transformer so it is upped to 14 volts causing the light fixtures to fall into the 10.5 – 12 volt range we are trying to obtain.
This is where the trouble lies, many home built systems and even some contractor installed systems are not designed properly. Some contractors installs lighting fixtures on a daisy chain. Which means they lay wire down to the farthest away fixture and then install more fixtures on that line. The problem with this method is, if it isn’t done properly, the first fixture on the line has too high of voltage and the last fixture too little. This causes the bulbs to burn out at a much higher rate, blacken and die. The homeowner then becomes frustrated because it always seems that one fixture is never working or the lights are always burning out. This is further compounded by the fact that when one light on the chain burns out the rest of the lights instantly have a higher voltage because there is less stress on the system. When the voltage increases because of the burnt our lamp, it decreases the lifespan of the rest of the lamps because it now is receiving too high of voltage. This is why it is important to make sure when one light burns out to just replace the rest of the lights on that chain. If you do not replace all the lamps when the first lamp burns out it becomes a viscous cycle of constantly replacing burnt out lamps.
When performing service at an install that is not our own, this is one of the first things we check. If the voltages vary too much we cannot guarantee any lamp life for the system. If possible we will correct these deficiencies or give recommendations to the homeowner for possible solutions. When we design and install landscape lighting systems, we always ensure the voltage range is correct.