saveing money

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Jeff Rae

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haveing a dicussion on saveings on airconditionars 120v. vs. 240v. when you multiply volts times amps you get the same watts and watts are what we pay for??? How would 208v. play into this. Whats your thoughts??!!
 
As you point out we pay by the kWh.

Regardless of the voltage watts will be more or less the same for a certain amount of cooling.

The only real savings with all other things being equal will be smaller conductors used to supply higher voltage equipment.
 
I agree with Bob. Higher voltages allow for smaller conductors and smaller assoicated equipment and materials. This is one reason why Europe supplies higher voltages to buildings and structures.
 
hockeyoligist2 said:
Does that mean that when I changed my well pump to 240v it still costs me the same to operate it? Geez all that trouble for nothing! :)
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Yeah....sorry, better put the plans on the purchase of a private jet on hold. ;) :D
 
I suspect the higher voltage machines have a higher level of efficiency (i.e., more work done for less input energy). But I have no way of quantifying it, or telling whether upgrading to the 240 volt A/C will pay for itself over a given period of time.
 
The principal advantages of using higher voltages in buildings are:
1. Smaller conductors
2. Lower voltage drop
3. Fewer or smaller circuits
4. Lower I2R losses (thus, more energy efficient)

Overall, save energy, save material, save money.


David
 
dahualin said:
The principal advantages of using higher voltages in buildings are:
1. Smaller conductors
2. Lower voltage drop
3. Fewer or smaller circuits
4. Lower I2R losses (thus, more energy efficient)

Overall, save energy, save material, save money.


David
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And we have done it that way for years! That's the way it was and we liked it!

I just learned this myself. Man, everyone has been lying to me :(
 
dahualin said:
The principal advantages of using higher voltages in buildings are:
1. Smaller conductors
2. Lower voltage drop
3. Fewer or smaller circuits
4. Lower I2R losses (thus, more energy efficient)

Overall, save energy, save material, save money.


David
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Edit: I realize this thread is relative to a 120V vs. a 240V air conditioner, but I've heard what's quoted above for entire building installations, and since I'm on the engineering side I'd like to comment on "high" voltage vs. "low" voltage in general. Relative to the quote: (end edit)

Maybe so, maybe not. Yes, conductors can be smaller, but if the conductors are properly sized you may or may not have lower voltage drop and you may or may not have lower I2R losses. Depending on the building (and the engineer) you may or may not have fewer circuits. What you do have at 480/277Y plus 208/120Y compared to 208/120Y only is panels at two voltages (which may or may not mean more panels) and step-down transformers (which take up space and generate heat).

If you take all the factors into account, including total materials cost, total installation cost, equipment efficiency (compare the 430.250 loads for a 20HP motor at 460V and at 208V -- the 208V motor VA is less), added losses in the step-down transformer(s), and added cooling loads because of transformer heat, I think you'll find that the results will vary as to which is cheaper to install and will vary as to which is cheaper to operate. There is no "one size fits all" answer to whether 480/277Y plus 208/120Y or 208/120 only is more cost effective, either first cost or operating cost, especially for small to moderate sized buildings.

Martin
 
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Maybe so, maybe not. Yes, conductors can be smaller, but if the conductors are properly sized you may or may not have lower voltage drop and you may or may not have lower I2R losses. Depending on the building (and the engineer) you may or may not have fewer circuits. What you do have at 480/277Y plus 208/120Y compared to 208/120Y only is panels at two voltages (which may or may not mean more panels) and step-down transformers (which take up space and generate heat).
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But back to the OP, an AC operating at 240 volts would have only half of the percentage of voltage drop of the same AC operating at 120 volts, so I2R losses would be less with the 240 volt operation.
 
I believe that United States has two voltage system (480/277 volt and 208/120 volt) for commercial building is because of the advantages of using higher voltages in buildings I mentioned in previous post. Otherwise, it is meaningless to use different voltage system. How to choose the service voltage is really depends. If the major loads are large motors and fluorescent lighting loads, and the feeder is long, it will tend to make the higher voltages, such as 480/277 Volt, more economical. Otherwise, low voltage (208/120 volts) makes more sense because the owner doesn't have to pay for the step-down transformer.


David
 
infinity said:
But back to the OP, an AC operating at 240 volts would have only half of the percentage of voltage drop of the same AC operating at 120 volts, so I2R losses would be less with the 240 volt operation.
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Trevor I don't understand that.

Wouldn't the I2R losses would be a factor of wire size as well so if the conductors where sized with this in mind it should be no different or could even be the other way around.
 
In my opinion this post by Martin sums this issue up very well.

As always there is no right or wrong answer, each application is different and many factors must be taken into consideration.

hmspe said:
Yes, conductors can be smaller, but if the conductors are properly sized you may or may not have lower voltage drop and you may or may not have lower I2R losses. Depending on the building (and the engineer) you may or may not have fewer circuits. What you do have at 480/277Y plus 208/120Y compared to 208/120Y only is panels at two voltages (which may or may not mean more panels) and step-down transformers (which take up space and generate heat).

If you take all the factors into account, including total materials cost, total installation cost, equipment efficiency (compare the 430.250 loads for a 20HP motor at 460V and at 208V -- the 208V motor VA is less), added losses in the step-down transformer(s), and added cooling loads because of transformer heat, I think you'll find that the results will vary as to which is cheaper to install and will vary as to which is cheaper to operate. There is no "one size fits all" answer to whether 480/277Y plus 208/120Y or 208/120 only is more cost effective, either first cost or operating cost, especially for small to moderate sized buildings.

Martin
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To really save money on copper, small conductor sizes, and negligable I2R losses, find a way to run equipment and devices directly on 4160 volts.

Once you matched the right mineral type to sustain a glowing filament out of rocks, at that voltage, the next trick would be cord connected appliances.

Since nothing could be bonded or grounded, without the building turning into a Tesla lighting-bolt experiment, in the absence of EGC's code would require cord-connected loads applliances be marked "Double insulated."

This might also require some exotic insulation and large surge arrestors on each termination, but I'm sure thats no problem for the talented engineers around here.
 
Why stop at 4160? 12KV has some real advantages!

Seriously, We are seeing more and more buildings go 480V now, in order to save on copper. You pay more for distribution transformers, but often you can make it up with smaller feeders, esp if there are long runs. Those 208V feeders add up fast if there is a long run of them.

IN a window air conditioner, they usually go to 240V when they get above 1500 watts or so, because a 120V 20A breaker can't handle any higher currents. So it is not really a matter of efficiency. If I was buying a new one, for the same size AC I'd probably go with 240V.
 
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