# What does "120/208" volts mean?



## sixspeed (Apr 11, 2012)

Split voltage appliance.

Some appliances require the 120v for control or the lighting circuitry (here in North America), and the 220v for the heating elements.

Your receptacle will need to be wired properly per the instructions so that the two voltages are provided.


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## Billy_Bob (Sep 11, 2008)

208 is not 220 (240)...

http://www.ccontrolsys.com/w/Electrical_Service_Types_and_Voltages


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## HouseHelper (Mar 20, 2007)

That is a commercial coffee maker designed to run on 120/208V as would be available from a three phase service. This will NOT run on a 120/240 residential service.


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## Code05 (May 24, 2009)

HouseHelper said:


> That is a commercial coffee maker designed to run on 120/208V as would be available from a three phase service. This will NOT run on a 120/240 residential service.


Hate to tell you this, but many residences such as condos and apartments have 120/208V single phase services off a three phase supply. That is why most appliances run off 208V or 240V.


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## HouseHelper (Mar 20, 2007)

Code05 said:


> Hate to tell you this, but many residences such as condos and apartments have 120/208V single phase services off a three phase supply. That is why most appliances run off 208V or 240V.


Re-read my second sentence carefully.


> This will NOT run on a *120/240* residential service.


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## Code05 (May 24, 2009)

HouseHelper said:


> Re-read my second sentence carefully.


I did, my point is that many-if not most- split voltage appliances- will run off 120/208V 1P or 120/240V 1P.

Go look at the nameplate on your dryer, stove, or HVAC unit.

The OP may have a 120/208V appliance only, but that is rare in the USA.


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## sixspeed (Apr 11, 2012)

The spec sheet (follow the link in that ebay listing, or here: http://www.primebusinesssurplus.info/images/CBS-2032s.pdf) does give a range of electrical configurations, including 120/208, 120/220, and 120/240.


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## Code05 (May 24, 2009)

sixspeed said:


> The spec sheet (follow the link in that ebay listing, or here: http://www.primebusinesssurplus.info/images/CBS-2032s.pdf) does give a range of electrical configurations, including 120/208, 120/220, and 120/240.


That would be quite common.:thumbsup:


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## AllanJ (Nov 24, 2007)

Appliances and equipment rated for 120/240 volts may be used on a system that measures 110/220 volts.

Appliances and equipment rated for 120/208 volts but not 120/240 volts may generally not be used on a 120/240 volt system or on a system that measures 110/220 volts. (Some analysis would need to be done to see if a particular item would work.)


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## HouseHelper (Mar 20, 2007)

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.


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## ShaneM (Jun 20, 2011)

This is a single phase unit yes. It also doesn't require any special wiring, as i have tested it just by plugging into a 208volt wall plug. 

What is confusing is why they would note the 120v. If you just plug it into a 208 socket like a typical 208 volt piece of equipment, why note it? 

Maybe i should have explained more: I actually sell equipment like this and am trying to understand electricity better. If this forum is not the place for questions like this, I apologize. 

When I sell it, I note exactly what it says on the infomation plate on the unit. The 120/208 confuses people, they think this unit could be run on just 110volts. 220 volts is so confusing. 208, 220, 240, 3 wire, 4 wire, single vs three phase. Sheesh.


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## sixspeed (Apr 11, 2012)

When the appliance lists two voltages (x/y), it usually means it requires BOTH voltages to operate, NOT EITHER one (x) or the other (higher) . 


It's like saying, you require cold AND hot water at your sink faucet, however you need only cold water to your toilet, and only hot water to your dishwasher...


A 208v socket may have just 208v and not 120v. What voltage(s) needed at the receptacle will determine the number of wires, and how they are hooked up in your premise.


Many appliances with electronic controls and lighting, in addition to the heating elements, require split voltage hookup. For example, your wall oven will typically have a light bulb inside the oven. If the oven were rated to run at 240v only, instead of 120/240v, you'd have to find a light bulb that is 240v rated when it came time to replace it. (How common in America is that?)

So if you plug your split voltage coffee maker into an improperly rated high voltage-only receptacle, not only will its controls and lower (120) voltage circuits not work, they may be completely damaged!


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## mpoulton (Jul 23, 2009)

zorn said:


> This is a single phase unit yes. It also doesn't require any special wiring, as i have tested it just by plugging into a 208volt wall plug.
> 
> What is confusing is why they would note the 120v. If you just plug it into a 208 socket like a typical 208 volt piece of equipment, why note it?


If it says 120/208, then it uses both 120 and 208V internally. This means it requires a 4-wire connection. If you are running it on a 3-wire connection, then the neutral and ground are improperly connected together and sharing one wire. This is not allowed by code and can result in the machine becoming electrified if the neutral/ground connection fails.


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## dmxtothemax (Oct 26, 2010)

zorn said:


> Some commercial equipment has power ratings that say "120/208", like this coffee brewer for example:
> 
> http://cgi.ebay.com/ws/eBayISAPI.dl...&ssPageName=ADME:X:AAQ:US:1123#ht_1060wt_1163
> 
> ...


Perhaps this appliance requires both 120v and 208v.
The control circuits probably run of the 120v,
And the big power guzzling heating element uses 208v.

Does this answer your question ?
Or have I mis interpretted ?


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## Stubbie (Jan 7, 2007)

HouseHelper said:


> 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.
​​​​​


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## Code05 (May 24, 2009)

stubie said:


> 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.


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## Stubbie (Jan 7, 2007)

Code05 said:


> 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.


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## kbsparky (Sep 11, 2008)

While this unit may be _availabl_e 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.


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## busman (Nov 7, 2008)

kbsparky said:


> 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


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## electures (Dec 22, 2009)

busman said:


> 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.


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## busman (Nov 7, 2008)

electures said:


> 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


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## electures (Dec 22, 2009)

busman said:


> 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.


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## busman (Nov 7, 2008)

electures said:


> 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


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## electures (Dec 22, 2009)

busman said:


> 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.


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## busman (Nov 7, 2008)

electures said:


> 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


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## AllanJ (Nov 24, 2007)

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.


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## mpoulton (Jul 23, 2009)

busman said:


> 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.


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## curiousB (Jan 16, 2012)

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)


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## electures (Dec 22, 2009)

busman said:


> 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.


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## electures (Dec 22, 2009)

curiousB said:


> I think the OP long left this debate.
> 
> Many devices are rated for multiple voltages. Particularly resistive heaters.
> 
> ...


Agreed. Why is it that almost everything posted here is turning into a d1ck measuring contest. When we try to explain something simple somebody has to come along and elevate it to engineering level. And I will admit I'm just as guilty of it as well.


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## AllanJ (Nov 24, 2007)

deleted


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## Stubbie (Jan 7, 2007)

electures said:


> Agreed. Why is it that almost everything posted here is turning into a d1ck measuring contest. When we try to explain something simple somebody has to come along and elevate it to engineering level. And I will admit I'm just as guilty of it as well.


Personally I don't have a problem with it. The original post mave have been answered but expanding on a topic is almost always a learning experience. What I don't care for is when stones start getting thrown because someone gets impatient with another members alternate explanation. We are all going to be somewhat 'incomplete' on this subject of 3 phase vs single phase. I would hate to see how many pages the 'complete' explanation encompasses ....


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## Code05 (May 24, 2009)

stubie said:


> We are all going to be somewhat 'incomplete' on this subject of 3 phase vs single phase. I would hate to see how many pages the 'complete' explanation encompasses ....


2500+ posts on one thread at my regular forum and we still never agreed.


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## busman (Nov 7, 2008)

electures said:


> 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.


I don't understand the comment about 277V lighting. In order to answer any question about phase, we need to be clear about whether we are talking about loads or services/SDS's. You can place single phase loads (277V lighting) on a three phase 277/480V service or SDS. I really don't understand the comment about SDS. An SDS is no different than a service, except that it's supply is something other than the utility.

Mark


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