Harmonizing the 2nd lowest American utilization voltage.. 208 and 240v

[Electric-Light]

Devices that find use on 208v and 240v nominal lines are common enough that we experience performance and/or cost compromise from having to design them to accommodate both.


Resistive heating devices rated at 240v, but allows 208 and 240v use runs at 3/4 the power which is a performance compromise.

Motors: those meant for 208 and 240 service don't fully accommodate the +/- 6% plus expected drop as the usual min-max range is 196 to 254v. When operated at 196v service at service entry on 208v nom. service, the voltage at motor terminals can reasonably be 185v or so, which may not provide full starting torque, or draw excess current at full load or do not provide overload ability to what the name plate says.

When the service is 254v (240v + 6%), it will suffer higher losses no load or low load conditions.

They're usually rated 196-253v

In Europe and much of Asia, they're mostly using one system of 400Y/230 to do everything we do using
120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480

So, we got the funky 208v from a design centered around 120v, then they work their way down from 480v design and come up with 277v to let lighting and some misc loads piggy back from it.


Couldn't we just get rid of 240v single phase and just harmonize to 208y/120 and design motors optimized for 208v?

 

[Besoeker]

In Europe and much of Asia, they're mostly using one system of 400Y/230 to do everything we do using
120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480
Couldn't we just get rid of 240v single phase and just harmonize to 208y/120 and design motors optimized for 208v?

I asked a similar question about that previously on this forum.
For me, and I suppose others both here (UK) and elsewhere on the Eurozone, it seems inordinately complex, perhaps burdensome would be a better word.
Here, as you correctly note, everything is 400/230V. And we have no centre tapped 120-0-120 so the lost neutral that seems to be the bane of many residential problems.
It's simple - I like simple........

The answer given was that the system is historical and it would be too difficult to change it now.

 

[Sahib]

Resistive heating devices rated at 240v, but allows 208 and 240v use runs at 3/4 the power which is a performance compromise.

I do not believe resistor manufacturer recommends 240 V rated resistor to be used at 208V.

Motors: those meant for 208 and 240 service don't fully accommodate the +/- 6% plus expected drop as the usual min-max range is 196 to 254v. When operated at 196v service at service entry on 208v nom. service, the voltage at motor terminals can reasonably be 185v or so, which may not provide full starting torque, or draw excess current at full load or do not provide overload ability to what the name plate says.
When the service is 254v (240v + 6%), it will suffer higher losses no load or low load conditions.
They're usually rated 196-253v

If the motors are designed for operation for 208V and 240V operation, their expected operational voltage range is 196 to 254v with +/- 6%. I do not see any thing that could prevent a motor manufacturer to do that.

In Europe and much of Asia, they're mostly using one system of 400Y/230 to do everything

This may not prove so safe or economical in certain circumstances as using

120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480

Couldn't we just get rid of 240v single phase and just harmonize to 208y/120 and design motors optimized for 208v?

Using 240V is more economical than 120V in certain circumstances

 

[kingpb]

You might want to take a look at a list of voltages around the world, because there are at least as many that use 380/220V systems.

There are also other countries besides the US that use 208V, and then there is also 50 vs 60Hz as well.

 

[Besoeker]

If the motors are designed for operation for 208V and 240V operation, their expected operational voltage range is 196 to 254v with +/- 6%. I do not see any thing that could prevent a motor manufacturer to do that.

Don't you think that design comprises would required to accommodate that range of voltages?

This may not prove so safe or economical in certain circumstances as using
120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480

Or safer since it obviates the risk of connecting something an incorrect voltage.
Safety depends on awareness of the risks and good working procedures which are more tightly regulated in some countries than others.
And some countries using 220-250V 50Hz have far more fatal accidental electrocutions than countries in the EU using 230V

http://medind.nic.in/jal/t12/i1/jalt12i1p13.pdf

Using 240V is more economical than 120V in certain circumstances

Thinner wire for a start.....

 

[Sahib]

Don't you think that design comprises would required to accommodate that range of voltages?

Like?

the risk of connecting something an incorrect voltage.

Voltage range available to a residence is limited in US.

And some countries using 220-250V 50Hz have far more fatal accidental electrocutions than countries in the EU using 230V
http://medind.nic.in/jal/t12/i1/jalt12i1p13.pdf

It is not substantiated in the article that fatal accidental electrocutions are lesser in countries in the EU using 230V

 

[kwired]

Devices that find use on 208v and 240v nominal lines are common enough that we experience performance and/or cost compromise from having to design them to accommodate both.


Resistive heating devices rated at 240v, but allows 208 and 240v use runs at 3/4 the power which is a performance compromise.

Motors: those meant for 208 and 240 service don't fully accommodate the +/- 6% plus expected drop as the usual min-max range is 196 to 254v. When operated at 196v service at service entry on 208v nom. service, the voltage at motor terminals can reasonably be 185v or so, which may not provide full starting torque, or draw excess current at full load or do not provide overload ability to what the name plate says.

When the service is 254v (240v + 6%), it will suffer higher losses no load or low load conditions.

They're usually rated 196-253v

In Europe and much of Asia, they're mostly using one system of 400Y/230 to do everything we do using
120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480

So, we got the funky 208v from a design centered around 120v, then they work their way down from 480v design and come up with 277v to let lighting and some misc loads piggy back from it.


Couldn't we just get rid of 240v single phase and just harmonize to 208y/120 and design motors optimized for 208v?

It would have been much easier from the start to design differently. Now we have to deal with the fact there is a lot of existing equipment out there.

How do you propose to deal with single phase distribution in rural/remote areas where it would be pretty costly to make everything 208/120 wye systems? Where limited three phase is needed in these areas open delta is the cost effective way to go.

IMO electrical professionals are supposed to know the differences between these systems and how to apply them. Harmonizing it into one system fits all makes it more of a plug and play system - which may have some benefit, but I can also see much more hack work arising from it, as all the non professionals will think they are more of an engineer than they currently think they are.

 

[JoeStillman]

This is one of those great ideas, like switching to metric, that will never get any traction in north America.

There's too much installed infrastructure in the United States at 208V and 240V to eliminate either one. It would be as hard to accomplish as switching to 50 Hz.

 

[Besoeker]

Like?

If the motor is to produce rated output at the lowest voltage, the conductors will need to be rated accordingly and thus of greater capacity than at the top end of the voltage range.

Voltage range available to a residence is limited in US.

And?
The mention of 120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480 does not limit it to residential.
But if you want residential only, you have 120-0-120.
EU land has just 0-230V. You can't plug your table lamp into a socket that has the wrong voltage. Nor the washing machine, nor the toaster, nor the microwave, nor anything else.

It is not substantiated in the article that fatal accidental electrocutions are lesser in countries in the EU using 230V

Might I suggest that you read the abstract again?

 

[JoeStillman]

I do not believe resistor manufacturer recommends 240 V rated resistor to be used at 208V.

It is actually quite common for heating elements. This catalog gives the derated output wattage for some commonly used 208/240 rated heaters.

 

[kwired]

I do not believe resistor manufacturer recommends 240 V rated resistor to be used at 208V.

Why are they going to have a problem with undervoltage? A specific appliance may have performance issues with amount of heat produced if the tolerance of heat output was selected from a pretty tight range, but that wouldn't be much of a problem for the resistor itself and therefore not the resistor manufacturer either.

It is not substantiated in the article that fatal accidental electrocutions are lesser in countries in the EU using 230V

I think that statistic has more to do with some of the installation practices then it has to do with the fact the voltage is higher.

They are typically running from a 400/230 wye system. Many of us have seen what kind of arcing can be easily sustained from a 480/277 system as compared to a 208/120 or 120/240 system, their 400/230 is much closer to 480/277 then 120/240 is from that aspect. They are also running 50Hz in most cases - not sure what impact that may have on arcing issues.

 

[JoeStillman]

Multi-volt electronic ballasts help a lot. The problem of 200/208/230 volt motors is another matter though. It helps to evangelize your mechanical counterparts about the virtue of specifying the right voltage.

 

[JoeStillman]

I do not believe resistor manufacturer recommends 240 V rated resistor to be used at 208V....

Is there a need for much comfort heating in your part of India?

 

[Besoeker]

This is one of those great ideas, like switching to metric, that will never get any traction in north America.

There's too much installed infrastructure in the United States at 208V and 240V to eliminate either one. It would be as hard to accomplish as switching to 50 Hz.

I agree with your second point.
Not so sure about the first. Metric or SI units are being used on some things. I think there will be a shift to conform with the rest of the world for ease of trading.

 

[Sahib]

If the motor is to produce rated output at the lowest voltage, the conductors will need to be rated accordingly and thus of greater capacity than at the top end of the voltage range.

It is a design specification and not a design compromise.

And?
The mention of 120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480 does not limit it to residential.

NEC does it.

But if you want residential only, you have 120-0-120.
EU land has just 0-230V. You can't plug your table lamp into a socket that has the wrong voltage. Nor the washing machine, nor the toaster, nor the microwave, nor anything else.

230V single phase voltage presents a higher shock hazard than a 120V single phase voltage, even when you inserting your plug in the 'correct' socket.

Might I suggest that you read the abstract again?

230V is nowhere mentioned.

 

[Sahib]

It is actually quite common for heating elements. This catalog gives the derated output wattage for some commonly used 208/240 rated heaters.

It is dual rated. It is not that a resistor rated at particular voltage should not be operated at lower voltage; it will not give its rated heat output.

Is there a need for much comfort heating in your part of India?

There is a need for much comfort cooling here.

 

[Sahib]

I think that statistic has more to do with some of the installation practices then it has to do with the fact the voltage is higher.

The article did not mention about installation practices.

They are also running 50Hz in most cases - not sure what impact that may have on arcing issues.

With the same input and output voltages and same KVA, a 50Hz transformer is smaller than a 60Hz transformer and so the arc hazard is lesser.

 

[Besoeker]

It is a design specification and not a design compromise.

Silly me. I forgot that you're an expert in motor design.

NEC does it.

Does what? Mentions 120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480?
Not sure what point you were making.

230V single phase voltage presents a higher shock hazard than a 120V single phase voltage, even when you inserting your plug in the 'correct' socket.

And 120-0-120 presents an even greater one.

230V is nowhere mentioned.

Countries in the EU have 230V single phase as the nominal voltage.

 

[Besoeker]

With the same input and output voltages and same KVA, a 50Hz transformer is smaller than a 60Hz transformer and so the arc hazard is lesser.

That's just plain wrong. It isn't smaller.

 

[JDBrown]

...
But if you want residential only, you have 120-0-120.
EU land has just 0-230V. You can't plug your table lamp into a socket that has the wrong voltage. Nor the washing machine, nor the toaster, nor the microwave, nor anything else.
...

That's why we have different plug configurations for different voltages (and for different current ratings, for that matter). Perhaps not as simple as the UK/EU method, but still effective for preventing plugging things into the wrong voltage.

I've never heard of somebody even trying to plug their 240V range or dryer (pretty much the only cord-connected residential appliances to use 240V) into a 120V receptacle, let alone succeeding. If anyone has done this, they would have to have hacked off the cord and replaced it with a 120V cord--not something even your most boneheaded homeowner is likely to do (then again, maybe I just don't know the right kind of boneheads). The same is true of trying to plug a table lamp into the 240V range or dryer receptacle.

Of course, now that I've put this out there, somebody else will come along with a link to a news article about someone getting electrocuted or burning down their house when they somehow managed to plug a microwave into the range receptacle. :roll: