thin wires increase electricity consumption?

Resistance of the smaller wire causes wasted heat (I2R) and that increases the HVAC load so it is a double whammy. The voltage drop also affects the efficiency of the motors causing more waste heat. The NEC requirements are a minimum and may not reflect the most efficient operation. You can measue the voltage drop on your feeders and branch circuits to get an idea what you are dealing with.

You will only see the differences in very long runs or large installations. A home is not big enough to really make a difference unless you approach the max of the circuit. Example, your air compressor is in the garage and the electrical service is on the other side of the home. The compressor is fed off of a branch circuit for the garage you might see some voltage drop on start up. Running a separate circuit for it might be a good idea. If your compressor is airless, like most home owners buy. As long as you do not let it get hot from running hours on end you will get as much life out of it as possible. Oiless compressors do not last long if they get really hot. As for your computers, grounding is a lot more important than the size of the wire. Unless your overloading the circuit they are plugged into. 60 computers seems like a pretty heavy load to me. My math says @ 400 watts each, you looking at a load of 200 amps based on 120 volts. If your lucky enough to have them balanced on 2 phases you would have a load of 100 amps. Try here for a quick load verse wire size.

is wire length not the horizontal distance between the points.

| Is it true that if you use thinner electrical wires (less than | the requirements), the electrical consumption would increase?? | If not, what is the side effect? | | Pls. let me know other groups that can answer this because I | need to spend a lot if I have to replace all my wires with | thicker ones. I run a shop with 10 Horsepower aircon and over 60 | computers.

Are those 60 computers fed from 1 phase or 3 phase power?

| You will only see the differences in very long runs or large installations. | A home is not big enough to really make a difference unless you approach the | max of the circuit. Example, your air compressor is in the garage and the | electrical service is on the other side of the home. The compressor is fed | off of a branch circuit for the garage you might see some voltage drop on | start up. Running a separate circuit for it might be a good idea. If your | compressor is airless, like most home owners buy. As long as you do not let | it get hot from running hours on end you will get as much life out of it as | possible. Oiless compressors do not last long if they get really hot. | As for your computers, grounding is a lot more important than the size of | the wire. Unless your overloading the circuit they are plugged into. 60 | computers seems like a pretty heavy load to me. My math says @ 400 watts | each, you looking at a load of 200 amps based on 120 volts. If your lucky | enough to have them balanced on 2 phases you would have a load of 100 amps.

If a computer is pulling 400 watts, it better have a larger power supply. Usually people running a computer farm are not piling parts into each of those computers. OTOH, assuming the power supply capacity can be used as the very worst case. But someone with 60 computers all pushing their P/S units to capacity needs to be questioned.

And don't forget to calculate the heat they will be producing and the A/C capacity needed to remove that heat, and that subequent A/C load. A room with a 24,000 watt heater (what those computers all maxed out would be) is gonna be a very hot room.

| Try here for a quick load verse wire size. |

| Distance is wire length not the horizontal distance between the points.

Interesting page. Last updated date is: 8/2/100

| Try here for a quick load verse wire size. |

| Distance is wire length not the horizontal distance between the points.

Let's see here, copper, 18 AWG, 120 volt 1-phase, 200 amps, 10000 feet

30864.2 volts drop!!!! ouch!!! That could be very very dangerous :-)

On the size of wires - for the same load thinner wires get warmer and waste more energy. All wires waste some heat when they carry a load. This can be approximated by voltage drop. A voltage drop of no more than 5 percent is acceptable but a voltage drop of

2 percent is better. For 120 volts this would be 6 volts and 2.4 volts. To decrease voltage drop increase wire size. However, voltage drop alone is not enough to determine wire size. Conductors must also be selected so they do not exceed the maximum operating temperature of the insulation, usually 75 degrees C. For an interesting article on how much you may save by sizing wire up read: One Wire Size Up Means Big Savings by the Copper people at:

http://64.90.169.191/applications/electrical/energy/onesizeup.html

Well, there are some distracting assumptions built into the referenced chart. The chart assumes that electrical loads draw constant current, which they generally do NOT!

These calculations all assume that the load current is going to remain constant regardless of the conductor resistance. This assumption is approximately true for the case of the motor, as the motor will, to a first approximation, draw whatever current is necessary to supply its load. As the terminal voltage of an induction motor decreases, the motor will draw more proportionately more current to compensate, if we neglect the effects of increased power factor, increased slip and the consequent lower horsepower generally required by the load at the lower RPM.

However, in the case of lighting loads the situation is different. As you reduce the voltage of a lighting load the load draws less current and gives less light. The reduced current draw lessens the power consumption. For the chart to be correct it is necessary for you to remove load after installing the larger conductors to compensate for the increased current caused by the increased terminal voltage!

The chart is indeed correct if the circuit in question is carefully engineered and allowance is made for the effects of voltage drop on power consumption. But, if you take an existing installation feeding a room full of lights and replace #14 AWG with #12 AWG you will in all likelihood increase, rather than decrease, your power consumption. The conductor loss will in fact decrease, but the consumption of the fixtures will increase! The motor example will result in reals savings, however.

| The chart is indeed correct if the circuit in question is carefully | engineered and allowance is made for the effects of voltage drop on power | consumption. But, if you take an existing installation feeding a room full | of lights and replace #14 AWG with #12 AWG you will in all likelihood | increase, rather than decrease, your power consumption. The conductor loss | will in fact decrease, but the consumption of the fixtures will increase! | The motor example will result in reals savings, however.

With the larger wire size, you could also reduce the amount of light load you have. Using thinner wire is certainly the wrong way to cut your usage of electricity (you cut your benefit from it more than you cut what you draw).

Another way to reduce power loss in the wire is to increase the voltage so you can decrease the amperage. We all know about I^2*R. Yet we still use lighting circuits at 120 volts in most cases, in the US and Canada. Those in Europe have the advantage with 230 volts. US industry has 277 volts and Canadians can even do 347 volts. Too bad code limits the voltage to lights in most places (probably because of the risk of inserting bulbs of the wrong voltage ... but that's just a guess).

Cars in the US are switching to 36 volts DC, soon. Less copper to carry the high power for all the stuff we put in there these days equals less weight to haul around equals less fuel consumption ... maybe. Cheaper to manufacture more likely.

Since this guy specifically said a room full of computers, thinner wire will always increase consumption. Those switching power supplies are still going to pump out the required number of watts, only at a higher current, thus increasing the I2R loss. We are only arguing about how much.

Much easier on the battery power density requirement ~ 1/3 the draw for the same power, and the wire advantage you mention. I don't know how that translates - do they use physically smaller/lighter

12V batteries in series, or build 36 V batteries? My guess is a 36 V battery in the same footprint as a 12 V.

On Sat, 14 Feb 2004 00:54:34 GMT snipped-for-privacy@bellatlantic.net wrote: | | snipped-for-privacy@ipal.net wrote: |> |> Cars in the US are switching to 36 volts DC, soon. Less copper to carry the |> high power for all the stuff we put in there these days equals less weight to |> haul around equals less fuel consumption ... maybe. Cheaper to manufacture |> more likely. |> | | Much easier on the battery power density requirement | ~ 1/3 the draw for the same power, and the wire | advantage you mention. I don't know how that | translates - do they use physically smaller/lighter | 12V batteries in series, or build 36 V batteries? | My guess is a 36 V battery in the same footprint | as a 12 V.

My guess would also be a standard footprint 36 volt battery. I wonder if they will be changing some aspect of how it is connected to try to avoid mismatching bettery voltage, which is no doubt going to happen a lot unless they find a way to exclude it from being connectable. For example they could make all 36 volt batteries use a square bushing with a bolt hole, and the 36 volt cables be split "U" shape that mates over the bushing with a bolt through to hold it.

I bet there will be some cases of using 3 12 volt batteries in series. I wonder when the 36 volt DC input inverters and other equipment starts to show up on the market. You might find these in a truck stop store now as I believe many diesel trucking rigs use 36 volts already.

Actually, for totally resistive loads such as heating elements and incandescent lamp filaments, the total electrical energy consumption is SMALLER than it would be if larger wires were run. Wanta save a lot of money on electricity? Run infinitely small wires (infinitely high conductor resistances) to everything. Or better yet - just don't hook the wires onto the circuit breakers - same thing. Just kidding.

Anyway, your case involves motor loads which are a different story. You didn't give enough info (voltage, distance, size of existing wires, fla of the motor(s), etc) to be able to do any calculations but all you have to do is measure the voltage at your service panel and then measure it at the motor while it's running. Many people use a 3 - 5% voltage drop as a rule of thumb for when to decide about upping the wire size. It depends on the situation. Such voltage drop considerations are especially critical for motors. Running most AC induction motors on excessively low voltage causes overheating of the windings, decreasing the motor's life expectancy and maybe worse depending on the severity of the undervoltage. And yes, there is also a waste of energy due to the voltage drop - in resultant motor inefficiencies and heating and in the form of heating of the wiring. If you ran the wiring under the driveway in a ziz zag pattern and use it for snow melting in the winter then I'd keep it as is.

Perion

Interesting points. I wonder if the cars will use some sort of "dual system". 12 V for electronics - clock, radio, computers, etc. - and 36 V for the higher amperage stuff - starter, lights, power windows, seats etc. There's going to be a lot of money to be made - batteries,

36 V motors, lamps etc. for whoever can supply the auto manufacturers, and for whoever can supply the public with 36 V "accessories like the inverter you mentioned - anything that plugs into the cigarette lighter socket. How about a battery with 3 posts!