110/220 Volt Electrical Question

John B. · Sep 27, 2014

It's always said if you can run an electric device on 220v it's cheaper or you're better off doing so than running on 110v.

How is this because when using the electrical formula the watts still come out to be the same?
When you double the voltage the amperage is cut in half. I just thru these numbers out there in the formula as an example.

Volts x Amps = Watts
110 x 14 = 1540
220 x 7 = 1540

What am I over looking?

Paul Janke · Sep 27, 2014

As near as I know, the only difference is the reduced losses in the wire with higher voltages. The loss is amperage squared times resistance of the wire. Doubling the voltage cuts the amperage in half and therefore cuts the line loss to one quarter.

MarkB_MI · Sep 27, 2014

Less voltage drop is better.

With typical resistive loads, the advantage is simply the elimination of loss in the building wiring. But with motors, it gets more complicated: A motor will draw as much current as it needs to do the job, up until it stalls. The more current it draws, the greater the voltage drop. Less voltage means it has to draw even more current (to maintain constant power), which means even more voltage drop, and so on. So it's really important to minimize voltage drop in motor circuits. And the simplest way to minimize voltage drop is to wire the motor use the highest available line voltage.

teddy52food · Sep 27, 2014

Magnetic field comes from the atoms of a conductor excited by the voltage. Higher voltage makes a stronger field. Amps produce heat which does nothing to turn the shaft. A motor on 110 runs warmer than on 220 doing the same work.

evilboweivel · Sep 27, 2014

It's always said if you can run an electric device on 220v it's cheaper or you're better off doing so than running on 110v.

CHEAPER NO
better off yes IF very far from panel OR high amperage as in above 10amps. really need to keep in mind voltage drop when figuring out which works best for you.
10amps 120vac long enough run will require 4/0 cable or 10amps 120 vac at a shorter run will require 14 gauge wire.
motors start better on the highest voltage they are rated at.
wired up a table saw 30 yrs ago 5hp 208vac less than 40 feet total wire run to panel. motor was lazy starting. after a year or so had the chance to wire it to 480 vac 100+ feet from panel. that motor snapped on, no more lazy starting. wire size was such that less than 80% amp load both times.
also been there with a 120 vac air compressor plugged directly into an outlet in a comercial building. hard starting would not start under load. finally traced the wire all the way back to the panel thru all the conduit runs. panel was approx 70' away line of sight over 230' away as the wire was routed. chnaged compressor over to 220vac used same wires just on 220vac and no more problems starting

Ron

John T · Sep 27, 2014

Here's the deal and why I was always taught and practiced to utilize higher (better yet 3 phase) motor voltages where possible.

Its true Watts still = Volts x Amps regardless if you operate at 120 or 240 and you cant create or destroy energy, only change its form. For one thing if you run higher voltage and therefore less amperage you waste less energy in the form of I Squared R Heat Losses in conductors. The R is the same so if I is less, I squared is wayyyyyyyyyy less. A part of the energy goes to heat versus to turn the motor which is the work you want to accomplish when you pay for the energy instead of it being lost as heat.

Motors are obviously NOT perfect devices, not all the energy in is = to the energy the rotating shaft can provide, some of is heat. Energy in must equal energy out, its just that the less you waste as heat in all the conductors the better off you are.

John T

Texasmark1 · Sep 27, 2014

+1............. Gets more important as the line run lengthens. The power to my shop comes off the same transformer that powers my house. It's about 200' just to the shop service entrance plus another up to 80' inside the building. Line drop matters to me.

Mark

buickanddeere · Sep 27, 2014

It's either cheaper to purchase smaller wire to run the same sized loads at higher voltages. Or it''s cheaper to run the same load, on the same sized cable as the I2R losses are lower.
Performance is particular the starting of compressors is particularly improved.
There were somebody around here recently that made me cringe by operating a 2HP compressor on 120V and a 20 amp breaker

fixerupper · Sep 27, 2014

My 1.5hp table saw really snapped to attention when I switched it from 110 to 220. It possibly has a little more power but what I noticed the most is how fast it came up to speed when I hit the switch and there is no more tripped breaker when I'm really loading it down. Jim

teddy52food · Sep 27, 2014

Thanks, you have just proved my point. If the magnetic field came from the current, then it should have way more power when the amps are higher. But it doesn't & the amps will turn to heat & burn out the windings. Magnetic field comes from the atoms of the conductor excited by the VOLTAGE.

Bruce SEKs · Sep 27, 2014

We have a pool pump that runs 24/7 in the summer. It costs us up to and over a $100/month. I changed it this year to a 220 Volt from the 110 Volt and ran it the same. Electric dropped down to $20/month

todd hamilton · Sep 27, 2014

All of these folks making this too complicated. Amperage or current draw is what makes your electric meter turn. More current is just like more water flow on a water meter. All of your current is measured on the 220 feed. So if at 220 volts you use 1/2 the current to produce same power (watts/actual energy) then your meter flows 1/2 as fast.

russ1 · Sep 27, 2014

The meter is a watt hour meter. It measures watts per hour and you get billed for watts per hour.

David G · Sep 27, 2014

I agree with John T

Ford and Gravely · Sep 27, 2014

Was an Electrical Engineer for 40 years. All who have mentioned I^2R losses are correct. Double the current by using 120 and you get to heat the air by 4 times as much. That's not strictly speaking though. The motor will also see less than the intended operating voltage due to V=IR. This makes the motor draw even more current which makes even more meter power go up in wasted heat.

MarkB_MI · Sep 27, 2014

> The meter is a watt hour meter. It measures watts per hour and you get billed for watts per hour.

"watts per hour" is not the same as a watt-hour.

A watt-hour is a unit of energy or work

A watt is a unit of power, which is the rate of doing work.

A watt per hour would be the rate of the rate of doing work. It is a unit seldom if ever used in engineering.

MarkB_MI · Sep 27, 2014

No Teddy, I didn't prove your point. I'm not even sure you had one. Just because you can make up your own definitions for terms like "magnetic field" doesn't mean they are correct, let alone accepted by scientists and engineers.

MarkB_MI · Sep 27, 2014

Magnetic flux is a function of current, not voltage. This is not just theory, it can be proven empirically with simple devices.

Ford and Gravely · Sep 27, 2014

There is a good reason why power companies run their transmission lines at 120 thousand volts.

dgasper · Sep 27, 2014

I am always amazed by some of the responses these electrical questions get. Most are well thought out and accurate. A few, not so much.

IH2444 · Sep 27, 2014

(quoted from post at 13:43:32 09/27/14) Thanks, you have just proved my point. If the magnetic field came from the current, then it should have way more power when the amps are higher. But it doesn't & the amps will turn to heat & burn out the windings. Magnetic field comes from the atoms of the conductor excited by the VOLTAGE.

Magnetic fields are from the current.
No current no magnetic field.

.

John T · Sep 27, 2014

EXACTLY, if an electrical or legal question is asked here, it draws everyone and their brother in law (especially Billy Bob and Bubba) out of the woodwork and all are experts. After all remember Billy and Bubba wired their garage while drinking a case of beer n by golly it all works. I to enjoy the topics and try my best to help.

John T Too long retired Electrical Engineer and rusty as an old nail

John T · Sep 27, 2014

WE must be about the same age, I got my BSEE at Purdue in the class of 69, we still studied vacuum tubes back then lol

John T BSEE, JD

Wile E · Sep 27, 2014

You are paying for watts....Not amps.

So, I do not think it matters, I am not taking into account the efficency of motors, voltage drops, etc. I have not read the other comments below.

IH2444 · Sep 27, 2014

(quoted from post at 20:55:56 09/27/14) You are paying for watts....Not amps.

So, I do not think it matters, I am not taking into account the efficency of motors, voltage drops, etc. I have not read the other comments below.

Watts is measured by multiplying voltage times amps. No amps no watts.

todd hamilton · Sep 27, 2014

6550s usually replaced in matched pairs. You have to measure the transconductance for balance. Then it is best to monitor the grid voltage about 1/2 hour to make tube is sealed and not "gassy." A 6550 is a pentode power output meaning five grids...input, plate (anode),cathode,suppressor and screen. I'm getting old too, all this from memory

JMOR · Sep 28, 2014

Lot of replies here! So, let us cut to the chase as they say. The reason you use less lectricity when you run your motor on 240 vs 120 is that it burns up in minute and thus no more Watts consumed. It was right in front of all of you all the time but no one saw it. :^)

110/220 Volt Electrical Question

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