Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-20-2012, 11:32 PM   #16
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,042
Rewards Points: 2,054
Default

What does "120/208" volts mean?


Quote:
Originally Posted by HouseHelper View Post
Looking at the catalog entry for the particular appliance in question, the entry for electrical says:

Electrical: Available in 120/208 single phase, 120/220 single phase, or 120/240 single phase. Require 3 wires + ground

I take that to mean you have to select the voltage, NOT that it can be used on any of them.
IMO that would be the only way to look at it. The NEC requires the Appliance to be connected to the voltage source it is rated for... ( I'll provide the code section(s) for those interested). I'm not to familar with any appliances that list multiple connectibility to a variety of voltage sources. At any rate technically a 120/208 applaince (nameplate) cannot be connected to 120/240 1ph as this would be a listing violation and a violation of the NEC.


110.4 Voltages.
Throughout this Code, the voltage considered
shall be that at which the circuit operates. The voltage
rating of electrical equipment shall not be less than the
nominal voltage of a circuit to which it is connected.

V. Marking
422.60 Nameplate.
(A) Nameplate Marking.


Each electrical appliance shall
be provided with a nameplate giving the identifying name
and the rating in volts and amperes, or in volts and watts. If
the appliance is to be used on a specific frequency or frequencies,
it shall be so marked.
Where motor overload protection external to the appliance
is required, the appliance shall be so marked.
FPN: See 422.11 for overcurrent protection requirements.
(B) To Be Visible.


Marking shall be located so as to be
visible or easily accessible after installation.
422.61 Marking of Heating Elements.


All heating elements
that are rated over one ampere, replaceable in the
field, and a part of an appliance shall be legibly marked
with the ratings in volts and amperes, or in volts and watts,
or with the manufacturer’s part number.



Last edited by Stubbie; 06-20-2012 at 11:41 PM.
Stubbie is offline   Reply With Quote
Old 06-21-2012, 12:02 AM   #17
Member
 
Code05's Avatar
 
Join Date: May 2009
Location: Easton MD
Posts: 1,841
Rewards Points: 1,000
Default

What does "120/208" volts mean?


Quote:
Originally Posted by stubie View Post
IMO that would be the only way to look at it. The NEC requires the Appliance to be connected to the voltage source it is rated for... ( I'll provide the code section(s) for those interested). I'm not to familar with any appliances that list multiple connectibility to a variety of voltage sources. At any rate technically a 120/208 applaince (nameplate) cannot be connected to 120/240 1ph as this would be a listing violation and a violation of the NEC.
Okay, this coffee maker may be 120/208 only, but most major appliances- ranges, dryers, WH, and HVAC- and many small ones are rated at 120/208-230.
Code05 is offline   Reply With Quote
Old 06-21-2012, 01:40 AM   #18
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,042
Rewards Points: 2,054
Default

What does "120/208" volts mean?


Quote:
Originally Posted by Code05 View Post
Okay, this coffee maker may be 120/208 only, but most major appliances- ranges, dryers, WH, and HVAC- and many small ones are rated at 120/208-230.
Yes, I stand corrected though I think it would be 240 volts on the high end for resistive loads. As I remember kitchen ranges will be listed on the nameplates as 120/208 then a wattage range and 120/240 and the related wattage. A/C would be as you show.
Stubbie is offline   Reply With Quote
Old 06-21-2012, 06:15 AM   #19
Electrical Contractor
 
kbsparky's Avatar
 
Join Date: Sep 2008
Location: Delmarva
Posts: 3,368
Rewards Points: 2,000
Default

What does "120/208" volts mean?


While this unit may be available in 120/208 or 120/240 volt models, etc....

IF this particular unit has a nameplate stating 120/208 volts. This means the element is specifically designed to be fed from a single phase circuit originating from a 3-phase 208Y/120 Volt service.

Commonly found in restaurants, convenience stores, etc.

Commonly not found in most single-family dwelling units.

Although there are exceptions, in the case of multi-family, hi-rise, and specialty applications.

Bottom line? Do NOT connect this machine to a 120/240volt supply, as you may certainly burn up the heating element prematurely. It might even work for a short period of time, but should not last long.
__________________
-KB

Life is uncertain -- eat dessert first!!
kbsparky is offline   Reply With Quote
Old 06-21-2012, 10:10 AM   #20
Master Electrician
 
Join Date: Nov 2008
Location: Northern Virginia
Posts: 505
Rewards Points: 272
Default

What does "120/208" volts mean?


Quote:
Originally Posted by kbsparky View Post
This means the element is specifically designed to be fed from a single phase circuit originating from a 3-phase 208Y/120 Volt service.

I've seen this a few times in this thread. As far as I know, there is NO way to have a "single phase" of a three phase system provide both 120V and 208V. The only way to have "single phase" 120/208V would be to have a tap that's not centered on the transformer to provide these two voltages with the same phase or opposite (180 degrees) phase.

The common arrangement in apartment buildings is for the unit to be supplied with 2 phases of the 3 in the building and a neutral. In this case, the two phases are 120 degrees apart and not "single phase".

Mark
busman is online now   Reply With Quote
Old 06-21-2012, 10:14 AM   #21
Lic Electrical Inspector
 
electures's Avatar
 
Join Date: Dec 2009
Location: The Great Police State of New Jersey
Posts: 1,682
Rewards Points: 1,002
Default

What does "120/208" volts mean?


Quote:
Originally Posted by busman

I've seen this a few times in this thread. As far as I know, there is NO way to have a "single phase" of a three phase system provide both 120V and 208V. The only way to have "single phase" 120/208V would be to have a tap that's not centered on the transformer to provide these two voltages with the same phase or opposite (180 degrees) phase.

The common arrangement in apartment buildings is for the unit to be supplied with 2 phases of the 3 in the building and a neutral. In this case, the two phases are 120 degrees apart and not "single phase".

Mark
Single phase means any one of the individual phases to neutral. 208v is derived from any phase to any other phase. 120/208 3 phase is derived from a 277/480v 3 phase system. There also is the 208v leg of a hi leg service.
__________________
All responses based on the 2011 NEC.
If you live in New Jersey click here. All other states click here.
Please check with local, county and state officials as laws may vary.
Sizing motors here. Online motor calculator here. Online calculators here.

Last edited by electures; 06-21-2012 at 10:17 AM.
electures is offline   Reply With Quote
Old 06-21-2012, 11:00 AM   #22
Master Electrician
 
Join Date: Nov 2008
Location: Northern Virginia
Posts: 505
Rewards Points: 272
Default

What does "120/208" volts mean?


Quote:
Originally Posted by electures View Post
Single phase means any one of the individual phases to neutral. 208v is derived from any phase to any other phase. 120/208 3 phase is derived from a 277/480v 3 phase system. There also is the 208v leg of a hi leg service.
That's not correct. Your home A/C is running off of single phase 240V, but is connected to two hot wires (no neutral). Also, 120/208 frequently comes directly thru a transformer from the primary voltage. It doesn't always come from 277/480.

There are many things that operate off of a single phase and many that operate off three phase. There are some that can operate off two phases of a 3 phase system and a neutral (a 120/208 clothes dryer is one of these).

Mark
busman is online now   Reply With Quote
Old 06-21-2012, 11:49 AM   #23
Lic Electrical Inspector
 
electures's Avatar
 
Join Date: Dec 2009
Location: The Great Police State of New Jersey
Posts: 1,682
Rewards Points: 1,002
Default

What does "120/208" volts mean?


Quote:
Originally Posted by busman

That's not correct. Your home A/C is running off of single phase 240V, but is connected to two hot wires (no neutral). Also, 120/208 frequently comes directly thru a transformer from the primary voltage. It doesn't always come from 277/480.

There are many things that operate off of a single phase and many that operate off three phase. There are some that can operate off two phases of a 3 phase system and a neutral (a 120/208 clothes dryer is one of these).

Mark
How is my statement incorrect? I wasn't talking about 240v single phase and neither is the op. As for where 120/208v is derived from, it is most commonly found in large commercial occupancies. And yes it is supplied through a variety of primary voltages. So my statement is more incomplete then incorrect. Do we really need to go into all the possible combinations of transformer connections to derive 120/208v 3 phase? Not in a DIY forum.
__________________
All responses based on the 2011 NEC.
If you live in New Jersey click here. All other states click here.
Please check with local, county and state officials as laws may vary.
Sizing motors here. Online motor calculator here. Online calculators here.
electures is offline   Reply With Quote
Old 06-21-2012, 11:54 AM   #24
Master Electrician
 
Join Date: Nov 2008
Location: Northern Virginia
Posts: 505
Rewards Points: 272
Default

What does "120/208" volts mean?


Quote:
Originally Posted by electures View Post
Single phase means any one of the individual phases to neutral.
This is the part of the statement that is incorrect. There is no need to have a neutral (grounded conductor) to have single phase.

Mark
busman is online now   Reply With Quote
Old 06-21-2012, 11:58 AM   #25
Lic Electrical Inspector
 
electures's Avatar
 
Join Date: Dec 2009
Location: The Great Police State of New Jersey
Posts: 1,682
Rewards Points: 1,002
Default

What does "120/208" volts mean?


Quote:
Originally Posted by busman

This is the part of the statement that is incorrect. There is no need to have a neutral (grounded conductor) to have single phase.

Mark
So again it is incomplete not incorrect.
__________________
All responses based on the 2011 NEC.
If you live in New Jersey click here. All other states click here.
Please check with local, county and state officials as laws may vary.
Sizing motors here. Online motor calculator here. Online calculators here.
electures is offline   Reply With Quote
Old 06-21-2012, 12:04 PM   #26
Master Electrician
 
Join Date: Nov 2008
Location: Northern Virginia
Posts: 505
Rewards Points: 272
Default

What does "120/208" volts mean?


Quote:
Originally Posted by electures View Post
So again it is incomplete not incorrect.

You can call it incomplete. I call it incorrect. No matter what it's misleading.

The simplest way to define it is that if you have two conductors (A and B), you have single phase by definition (as long as the voltage is sinusoidal), because there is no reference to measure phase to. If you have more than two conductors (A, B and C), then you can define the voltage AB to be the phase reference and if the voltage AC is either in phase or 180 degress out of phase to AB and you still have single phase OR AC is not 0 or 180 phase to AB and you have something else. That something else could be part of standard 3-phase (120 degrees apart) or something else, such as the output of a polyphase converter system.

Mark

Last edited by busman; 06-21-2012 at 12:10 PM.
busman is online now   Reply With Quote
Old 06-21-2012, 12:51 PM   #27
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,965
Rewards Points: 2,026
Default

What does "120/208" volts mean?


Taken by itself, the 208 volts obtained between the phase A hot and the phase B hot is a single phase source.

But the 208 volts is not "in phase with" the A to neutral 120 volts nor with the B to neutral 120 volts. Some but not all internal circuitry of appliances and other 120/240 volt equipment does not care about this phase relationship.

You do not actually have three phase power at a given location unless you have all three hot legs A, B, and C there.
__________________
Forget super sized fries. The Washington Redskins could promote healthy eating with First Lady Obama by choosing a (red skinned) turnip for a mascot.

Last edited by AllanJ; 06-21-2012 at 12:56 PM.
AllanJ is offline   Reply With Quote
The Following User Says Thank You to AllanJ For This Useful Post:
Code05 (06-22-2012)
Old 06-21-2012, 01:13 PM   #28
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,557
Rewards Points: 2,010
Default

What does "120/208" volts mean?


Quote:
Originally Posted by busman View Post
You can call it incomplete. I call it incorrect. No matter what it's misleading.

The simplest way to define it is that if you have two conductors (A and B), you have single phase by definition (as long as the voltage is sinusoidal), because there is no reference to measure phase to. If you have more than two conductors (A, B and C), then you can define the voltage AB to be the phase reference and if the voltage AC is either in phase or 180 degress out of phase to AB and you still have single phase OR AC is not 0 or 180 phase to AB and you have something else. That something else could be part of standard 3-phase (120 degrees apart) or something else, such as the output of a polyphase converter system.
That's not how the terminology is used in the trade. Any circuit where less than 3 phases are provided is called single phase, even if there is a phase angle other than 180 degrees present. Two hots and a neutral is called single phase regardless of whether it comes from a split phase source (180 degrees) or a three phase source (120 degrees).

The reason for this is simple: you can't run a polyphase motor on two phases and a neutral (at least not properly) - it takes all three phases. Single phase loads don't care if the phase angle between hot and neutral is 180 degrees or 120, assuming the voltages are right. So service provided by a split-phase source is interchangeable with service provided by two phases of a 3-phase source. In either case, you throw a 2P breaker in the panel and call it good.

Last edited by mpoulton; 06-22-2012 at 01:31 AM.
mpoulton is offline   Reply With Quote
The Following 3 Users Say Thank You to mpoulton For This Useful Post:
Code05 (06-22-2012), electures (06-21-2012), HouseHelper (06-21-2012)
Old 06-21-2012, 02:54 PM   #29
Member
 
Join Date: Jan 2012
Location: IL
Posts: 737
Rewards Points: 618
Default

What does "120/208" volts mean?


I think the OP long left this debate.

Many devices are rated for multiple voltages. Particularly resistive heaters.

120/240 vac is most common in residential
120/208 is most common in commercial (due to 3 phases)
curiousB is offline   Reply With Quote
Old 06-21-2012, 03:23 PM   #30
Lic Electrical Inspector
 
electures's Avatar
 
Join Date: Dec 2009
Location: The Great Police State of New Jersey
Posts: 1,682
Rewards Points: 1,002
Default

What does "120/208" volts mean?


Quote:
Originally Posted by busman

You can call it incomplete. I call it incorrect. No matter what it's misleading.

The simplest way to define it is that if you have two conductors (A and B), you have single phase by definition (as long as the voltage is sinusoidal), because there is no reference to measure phase to. If you have more than two conductors (A, B and C), then you can define the voltage AB to be the phase reference and if the voltage AC is either in phase or 180 degress out of phase to AB and you still have single phase OR AC is not 0 or 180 phase to AB and you have something else. That something else could be part of standard 3-phase (120 degrees apart) or something else, such as the output of a polyphase converter system.

Mark
So does that mean that 277v lighting is not single phase. My intention was to explain in simple terms what 120/208v is to an armature. If you want to get into a discussion on separately derived systems this is not the place. I would be more then willing to continue this discussion at electrician talk.com.

__________________
All responses based on the 2011 NEC.
If you live in New Jersey click here. All other states click here.
Please check with local, county and state officials as laws may vary.
Sizing motors here. Online motor calculator here. Online calculators here.
electures is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tripping breakers,neutrals,120 volts and 240 volts OH My!!! Stubbie Electrical 17 06-11-2011 06:09 AM
Carrier weather maker 9200 furnace NO 24 volts mmtuxedo HVAC 1 09-25-2009 06:49 PM
Wire sizing to the condensor zootjeff HVAC 9 06-22-2009 08:02 AM
changing 250 volts into 115 volts hottlilmama Electrical 9 05-25-2009 09:33 AM
Does Home AC ever read 0 volts? step.gary Electrical 3 07-01-2006 03:57 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.