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#72149 - 11/20/06 01:27 PM 208/230v can run off 240?
Trick440 Offline

Registered: 08/15/05
Posts: 248
Loc: Waterford, MI, USA
Just like the topic says can 208/230v run off 220v/240v?

We have a residential home that for some reason is 3 phase, 110/208v.

It is being changed to standard residential voltage of 220. The AC and other appliances are rated for 208/230. Will there be a problem with this?
Shake n Bake

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#72150 - 11/20/06 04:06 PM Re: 208/230v can run off 240?
livetoride Offline

Registered: 01/11/05
Posts: 109
Loc: san diego ca usa
Most of the time no problem. SOME electronic stuff can be a problem,(control voltage xformers). Check the taps on motor loads(fans,A/C)Household stuff should be fine. Rod

#72151 - 11/20/06 05:01 PM Re: 208/230v can run off 240?
electure Offline


Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
You seem to have your voltages all confused.
1) There is no such thing as 220/240.
2)There is no such thing as 3Ø 110/208
3) There is no 220 in the US.

Nominal system voltages are 120, 208, & 240.
120/208 or 120/240.

230 volt motors are designed to run on 240.
460 volt motors are designed to run on 480
208/230 volt motors are designed for use with 208 or 240 volt supplies.

[This message has been edited by electure (edited 11-20-2006).]

#72152 - 11/20/06 06:07 PM Re: 208/230v can run off 240?
skipr Offline

Registered: 01/03/05
Posts: 41
Loc: Huntington Beach, Ca.
If a motor is three phase 208 there is no way your going to get it to work on 240 single phase.I believe this is the only problem you would encounter..motors. If they are 3 phase they can't be used at all on a 120/240 system, unless u have a phase converter. But it would be cheaper to buy a motor.

#72153 - 11/20/06 07:11 PM Re: 208/230v can run off 240?
Trick440 Offline

Registered: 08/15/05
Posts: 248
Loc: Waterford, MI, USA
Yup I did have my voltages messed up. Thanks for the correction. (I always hear 220 ovens, 220 ac, 220 breaker, etc. confused me i guess.) "220, 240.. whatever it takes."

Skip, there are no 3 phase motors. All are single phase. So that will work out. I have never seen residential 3 phase before. Kinda weird.

Thanks for the help.

[This message has been edited by Trick440 (edited 11-20-2006).]
Shake n Bake

#72154 - 11/23/06 07:08 AM Re: 208/230v can run off 240?
Almost Fried Offline

Registered: 09/04/06
Posts: 104
Loc: Madison County, Ark. USA
Electure, thanks for that clarification. I usually let it pass, the general population probably keep referring to it as 110/220, but in my experience, the only 110 I have encountered was in a tiny 7.2 KV:110 pot(1 kVA) feeding a control circuit operating a 12,470 capacitor bank.

Most of the time I run into high voltages i.e., 123-127 volts. I get to sell a lot of 130 volt bulbs

#72155 - 11/23/06 11:02 AM Re: 208/230v can run off 240?
renosteinke Offline
Cat Servant

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Let's not confuse what the PoCo provides with what is stamped on the nameplate.

I have seen all sorts of markings on equipment. Some of this is a creation of testing methods.

For example, NEMA standards expect motoes to work within 10% of the nameplate markings. So-
- a motor marked "240" would be tested at 216 volts as well as 264 volts;
- a motor markes "208" wuld be tested at 187 and 229 volts;
- a motor marked "208/240" would be tested over the entire range of 187 to 264 volts (with re-wiring as appropriate); and...

- a motor marked "220" would be tested at 198 and 242 volts.

I set the last one apart, because by having such a rating, a motor could be made to serve both 208 and 240 volt systems, without the need for multiple taps.

In short, the nameplate rating is completely separate from the nominal voltages of the power grid.

#72156 - 11/23/06 12:08 PM Re: 208/230v can run off 240?
SteveFehr Offline

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
120V at the service can easily become 110V at the equipment once its fully energized. It would still be called "120V" though.

In Europe you run into the same thing, with panels being marked 400V or 380V despite the two being essentially the same thing.

[This message has been edited by SteveFehr (edited 11-23-2006).]

#72157 - 11/24/06 10:20 AM Re: 208/230v can run off 240?
Texas_Ranger Offline

Registered: 12/17/01
Posts: 2332
Loc: Vienna, Austria
That's a slightly different thing, they raised the nominal grid voltage from 220/380V to 230/400V, each +/-10% tolerance.
Some people say old 380V motors tend to burn up if they're connected to a new transformer that provides a higher voltage.

#72158 - 11/24/06 11:04 AM Re: 208/230v can run off 240?
Lostazhell Offline

Registered: 02/21/04
Posts: 1248
Loc: Bakersfield, CA (Originally Or...
Almost all of the motors we hook up out where I work are 9 or 12 lead, 230/460V 3phase... Although unless it's way off in some corner of the lease, the 480V network tends to run about 492V phase to phase, ungrounded delta.We've never had a problem with motors biting the dust that I've seen. (Largest motor I've connected was 250 HP. @ 1400 rpm. The 800A MCC rattled louder than that motor on startup )
Controls and buildings feed from "PanelTrans" that output 120/240V single phase.. We usually put these a tap lower on the primary connection and get a nice 121/243V output.


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