California utilities are considering saving energy by reducing the voltage from 120 to 117.
According to them, this can be done without harm to appliances and a not-noticeable change in lighting, etc.
It can also save lots of juice and help avoid blackouts.
General questions:
Is this a good idea, what do you know that might be relevant to whether this should or should not be done?
They did the same thing in New York many years ago, IIRC. The voltage difference isn’t significant enough to harm anything (when you consider that voltages vary accross the US between 110 and 120 volts, in some places even more or less) and the energy savings, though slight, can add up.
I just heard this reported on NPR. I have zero expertise in this field so what I am about to relate is strictly based on what I heard on the radio (basically, take it with a grain of salt).
The purpose behind all of this is to save energy. They claim that if the drop to 117 is made it would save enough energy to avoid building 1 power plant.
They said if you were watching closely at the moment the voltage dropped to 117 you’d notice your incandescent light bulb get just a bit dimmer but if you weren’t watching you’d probably never know the difference. On the upside, they said the bulb would now last 20% longer.
They claim that many manufacturers and maybe electricians claim the voltage drop would harm things like electric motors. The idea being that the motor would now draw more amperage and overheat. In experiments so far, however, this doesn’t bear out. In fact some appliances, such as air conditioners, seem to run more efficiently.
The biggest concern I heard raised was that voltage drops the further you get from the transmission source. As a result, if you are at the end of a transmission line, your voltage may drop far below even 117. There is a limit to just how far down this ladder you can go so this may be a real concern for those people.
Lower line voltage will cause appliances to burn out faster. When I was about ten years old, we lived out beyond the ass end of nowhere in a house in the country. We had our own well and septic tank. The house was all electric. The well pump burned out twice in two years, we had to replace the heating rods in the oven, the clothes dryer, and the hot water heater. My father complained to the electric company several times - every time another appliance crapped out, actually. The company didn’t believe him when he told them that the lower voltage was burning out our appliances. They didn’t believe him, that is, until that memorable night in the middle of the hottest, most miserable part of a south Louisana summer when the low voltage burned out the electric meter and left us with out power. It really sucked, going from air conditioned bliss to high humidity heat and miserableness. I will never forget the fire works as my father put jumpers across the meter to get the A.C. going again. The next day, he called the electric company and this time they believed him. They not only replaced the meter, they also (finally) did something to the transformer by the house that boosted the voltage back up where it belonged.
The heating rods were burning out because they never got up to their proper operating temperature. The hotter the rod, the higher its resistance, the less current it draws. If it doesn’t get hot enough, the resistance stays down, and it draws more current. The connectors on the rods are laid out for a certain continuous current flow. When too much current flows, the connector gets hot instead of the rod, and the connector on the rod fails.
The motors quit because they couldn’t get up to speed quickly enough. The current draw (if the load on the motor is the same) depends on the RPM of the motor. If the motor doesn’t get enough power, it takes longer to get up to its normal operating speed and thus draws more current for a longer time. This higher current draw causes the coils in the motor to overheat, and at some point the insulation at some point fails and you get a short circuit that burns the coil in two, or the overheating directly causes the open circuit. Either way, you are looking at getting a new motor or having the old one rewound.
Our low voltage problem was an extreme case. I expect we were down below one hundred volts, although I don’t recall what the readings were that my dad had made back then. 117 volts is not going to cause problems, though.
To sum it up:
Low voltage can hurt your appliances. 117 Volts is not low enough to worry about.
I am not going to talk about motors as these are a different case and can be damaged by low voltage, but there is no way in the world an element which is strictly resistive would be damaged by low voltage. Lower voltage means lower power dissipated, lower temperature, and longer life. A lightbulb will give off less light and last longer. No exceptions.
Also, almost (if not) all appliances sold for use in the US are designed to work properly on any voltage between 110 and 125. Last year I checked the voltage at my house and discovered we were only getting 117-118.
The resistance of a conductor changes with temperature. Some conductors change very little - like copper. Some have a much higher change in resistance for each degree of temperature change. There are even materials whose resistance reacts the opposite of normal materials - the resistance of these negative temperature coefficient (ntc) materials goes down as the temperature rises, and rises again as the temperature sinks. This is the reverse of the more normal positive temperature coefficient (ptc) materials. Heating elements have a relatively high ptc, and this together with the temperature change in going from room temperature to the red hot operating temperature can cause very large changes in resistance. A large change in resistance means a large change in the current flowing through the material. If the heating rod can’t get up to its normal temperature as quickly as it should because the low voltage isn’t pushing enough power through the element, then the current draw stays high for a much longer period of time. This is what does the damage.
Phrased another way:
The heating rods draw lots of current at power on, and this tapers off rather quickly to a constant, much lower flow. The connectors are designed to handle a short period of high current and long periods of low current flow.
If the voltage is low, then it takes longer for the element to heat up because the surge of high current at the beginning isn’t powerful enough to heat the rod quickly. You end up with a lower peak current flow than with normal voltage, but it goes on for so much longer that the connectors heat up much hotter than normal and eventually either break (from heat stress and vibration) or simply burn through.
The AC voltage in my apartment is always jumping around. I brought home a handheld oscilloscope from the lab one day to test it, and it varied between 107 and 125 VAC, with periods of constant AC voltage interrupted by sudden changes.
I can even see it in my incandescent lamps. Sometimes I can see it changing when I hear my neighbors start and stop power equipment.
I haven’t noticed any effect on the lifetime of equipment, except perhaps fan motors. I seem to go thru a fan per room per year, but maybe that’s because I leave them running constantly from April to October, and then put them in a closet for the winter.
Also (bonus tip!) I use Garage Door Opener bulbs in all my lamps. They last far, far longer than the average 60W lamp bulb, and they only cost twice as much! I get mine at the grocery store in single bubble packs next to the vanity bulbs.