Voltage Ratings: 110/115/120, 220/230/240 or 440/460/480

Mike01

Mike01

Senior Member
Location
MidWest
Thanks for posting this, something that was drilled into my head some time ago by someone [an old timer] I worked with. Now when I call things out this way or go to show someone why its not 120/208 [for a three phase four wire system] they give me funny looks like why dose it matter, for the next one can we dissect transformer vector group notation ex. Dyn1 I still get hung up on these need a good cheat sheet. Thanks all, great stuff!!
 
busman

busman

Senior Member
Location
Northern Virginia
Occupation
Master Electrician / Electrical Engineer
Working on a lot of ships in the past, one of their standard voltages seems to be 460V generation, 450V utilization.

Mark
 
FionaZuppa

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
When a local or country has 1 2 3 4 5, or whatever phases in the util distro system, calling out phase should be the standard. This way it does not matter how you write the #'s, having the phase designation removes any Port vs Starboard, Bow vs Stern, Forward vs Aft issue. ;)

"120/240 1ph" = "240/120 1ph"
"120/240 1ph" != "120/240 3ph"

And if you see just "240/120", then it begs the question, how many phases and why was it not labeled correctly/fully?

But that's just me.
 
D

dkarst

Senior Member
Location
Minnesota
Jraef said:
This subject comes up a LOT in this and other forums, so I thought it would be a good idea to make it a "Sticky" that can be found and referred to easily when it comes up.

There are two "standards" for voltage in North America depending on which END of the wire you are looking at; "Distribution Voltage" (also called "Service Voltage") and "Utilization Voltage", both set forth in ANSI (American National Standards Institute) Standard number C84.1, backed up by IEEE (Institute of Electrical and Electronics Engineers).

The official Distribution Voltage standard for single phase is 120 and 240V, for 3 phase it is 208, 240, 480 and 600. It has been this way since the 1930s after the REA (Rural Electrification Act) during the Great Depression went to bring electricity to farms and rural areas, because the Utilities all did what they wanted to and they didn't see enough profit in it. But because each utility was different at the time, (i.e. 110, 115, 117, 120, 125, etc. etc.), and the REA didn't want to have their service trucks carry around multiple voltage ratings, they picked a "middle ground" of 120/240V and called that the standard. It has been that way since. Later on, standards for the Utility industry came along and added that no matter what they give you, it has to be within +-5%. So for a 120V system, that is between 114V and 126V; for 240V it is 228 to 252V, etc. etc. However many of the older systems still deliver what they used to deliver, regardless of what it is officially called, so yes, there are still pockets of 110V, 220V and 440V out there.

For that reason, industry organizations for manufacturers, such as NEMA (National Electrical Manufacturers Assoc.) developed their OWN standards for the devices that use electricity, and their standard was +-10%, but based on a LOWER voltage, because there is an expected voltage drop from the Service Entrance to where the device connects. So for 120V Distribution, the Utilization voltage is 115V; for 240V it is 230V, for 208V it is 200V, for 480V it is 460V and for 600V it is 575V.

So how that works out is that a MOTOR for example will be built for 230V, +-10%, so it can accept anything from 207 to 253, and because the Distribution Voltage is 228 to 252V, it fits right in. But also if the Utility was still putting out 220V instead of 240V, the LOW end of their range would be 220-5%, so 209V, still within the acceptable range of the Utilization standard.

People however are not swift on the change though, so LOTS of people still refer to residential as being 110/220, or 115/230 or 120/240 (inset joke from the movie "The Money Pit" where Michel Keaton says "220/221.whatever it takes..."). But OFFICIALLY, it is supposed to be 120/240V.

While we are on the subject of "officialdom"; When describing distribution systems that have more than one voltage available, there is a "convention" in the description that should be used to help avoid confusion.
  • If the subject is SINGLE PHASE, the LOWER voltage is listed first, followed by the higher . So a residential single phase system is described as "120/240V".
  • If the subject is THREE PHASE, the HIGHER voltage is listed first, followed by the lower. So 480/277V would be correct, 277/480V would not. This is especially important because we have 240/120V 3 phase 4 wire systems available. So by calling it 240/120V you are differentiating it as three phase, compared to 120/240V being single phase.
Click to expand...

Excellent post with great information ... My only thing to add is I believe the Keaton quote "220/221 whatever it takes.." is from "Mr. Mom" not "The Money Pit" :)
 
FionaZuppa

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
The demand to standardize nomenclature in ink is the best way.
The use of "# ph" or "# phase" should be the std on labels and such.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
dkarst said:
Excellent post with great information ... My only thing to add is I believe the Keaton quote "220/221 whatever it takes.." is from "Mr. Mom" not "The Money Pit" :)
Click to expand...
Damn, you are correct! My memory of important things like old movies is starting to fade… I knew it was Keaton that said the line, but was not even in The Money Pit, that was Tom Hanks.
 
G

garbo

Senior Member
Jraef said:
This subject comes up a LOT in this and other forums, so I thought it would be a good idea to make it a "Sticky" that can be found and referred to easily when it comes up.

There are two "standards" for voltage in North America depending on which END of the wire you are looking at; "Distribution Voltage" (also called "Service Voltage") and "Utilization Voltage", both set forth in ANSI (American National Standards Institute) Standard number C84.1, backed up by IEEE (Institute of Electrical and Electronics Engineers).

The official Distribution Voltage standard for single phase is 120 and 240V, for 3 phase it is 208, 240, 480 and 600. It has been this way since the 1930s after the REA (Rural Electrification Act) during the Great Depression went to bring electricity to farms and rural areas, because the Utilities all did what they wanted to and they didn't see enough profit in it. But because each utility was different at the time, (i.e. 110, 115, 117, 120, 125, etc. etc.), and the REA didn't want to have their service trucks carry around multiple voltage ratings, they picked a "middle ground" of 120/240V and called that the standard. It has been that way since. Later on, standards for the Utility industry came along and added that no matter what they give you, it has to be within +-5%. So for a 120V system, that is between 114V and 126V; for 240V it is 228 to 252V, etc. etc. However many of the older systems still deliver what they used to deliver, regardless of what it is officially called, so yes, there are still pockets of 110V, 220V and 440V out there.

For that reason, industry organizations for manufacturers, such as NEMA (National Electrical Manufacturers Assoc.) developed their OWN standards for the devices that use electricity, and their standard was +-10%, but based on a LOWER voltage, because there is an expected voltage drop from the Service Entrance to where the device connects. So for 120V Distribution, the Utilization voltage is 115V; for 240V it is 230V, for 208V it is 200V, for 480V it is 460V and for 600V it is 575V.

So how that works out is that a MOTOR for example will be built for 230V, +-10%, so it can accept anything from 207 to 253, and because the Distribution Voltage is 228 to 252V, it fits right in. But also if the Utility was still putting out 220V instead of 240V, the LOW end of their range would be 220-5%, so 209V, still within the acceptable range of the Utilization standard.

People however are not swift on the change though, so LOTS of people still refer to residential as being 110/220, or 115/230 or 120/240 (inset joke from the movie "The Money Pit" where Michel Keaton says "220/221.whatever it takes..."). But OFFICIALLY, it is supposed to be 120/240V.

While we are on the subject of "officialdom"; When describing distribution systems that have more than one voltage available, there is a "convention" in the description that should be used to help avoid confusion.
  • If the subject is SINGLE PHASE, the LOWER voltage is listed first, followed by the higher . So a residential single phase system is described as "120/240V".
  • If the subject is THREE PHASE, the HIGHER voltage is listed first, followed by the lower. So 480/277V would be correct, 277/480V would not. This is especially important because we have 240/120V 3 phase 4 wire systems available. So by calling it 240/120V you are differentiating it as three phase, compared to 120/240V being single phase.
Click to expand...
Back in the 1960's around my area called it 110& 220 volts for residental & 220.& 440 volts for industrial sites. For a short time called residental 110 & 230 volts then for last 40.years 120 & 240 volts.
 
Besoeker3

Besoeker3

Senior Member
Location
UK
Occupation
Retired Electrical Engineer
tortuga said:
What about 400V three phase?
And I thought there was some 110V for construction sites?
Click to expand...
Yes, industrial units do use 110Vac but that is fed locally from a local 110V control transformer. These transformers are typically 500VA, sometines 1.0kVA. The 400V is industrial and commercial. Residences all use 230V.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
garbo said:
Back in the 1960's around my area called it 110& 220 volts for residental & 220.& 440 volts for industrial sites. For a short time called residental 110 & 230 volts then for last 40.years 120 & 240 volts.
Click to expand...
And the high leg was 190 volts.
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
ggunn said:
I don't see how there could be 240/120V three phase delta.
Click to expand...

240/120V three phase delta is another name for 'high leg' delta. This is a 240V delta with the mid point of one phase coil tapped and grounded to provide 120V line to 'neutral'. But you only get 2 of the 3 phases giving 120V to the grounded conductor; the other phase gives 208V to the grounded conductor. The 208V is simply not used.

The grounded conductor is 'neutral' to the two 120V phases, but not 'neutral' to the complete 3 phase set.

You of course cannot have all three phases at 120V to the grounded conductor in a nice symmetric three phase arrangement while at the same time getting 240V phase to phase.

There are variations on this form of service, eg. and 'open delta' which is used with mostly 120/240V single phase loads, with a 'stinger' to provide the 3rd phase for a small amount of 3 phase loading. Another version is a symmetric 240V three phase system tapped for grounding and to provide for a small amount of 120V loading.

-Jon
 
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