# 230V Single Phase Doesn't Take Neutral?



## Techy

Typical '230' Volt items are most often used on 120/240 service


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## swimmer

Techy said:


> Typical '230' Volt items are most often used on 120/240 service


House 240V is more like figure 2, with 2 hots and no N.


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## Techy

I've never seen a '230v' connection that wasn't 2 hots and no neutral, so i'll step aside.


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## swimmer

Techy said:


> I've never seen a '230v' connection that wasn't 2 hots and no neutral, so i'll step aside.



Thanks. That's good information


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## fanelle

All the single phase xfmrs I have ever done that are 480p and 120/240x are two phases of your 480v on the primary and it will give you either 120, 240, or 120/240 depending on if you center tap your xfrmed windings. So more like the second diagram but I don`t recall ever seeing 133v to ground on the xfrmed phase. Typically its around 120v or so.


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## swimmer

fanelle said:


> I don`t recall ever seeing 133v to ground on the xfrmed phase. Typically its around 120v or so.


I used to work on systems that had the Figure 2 arrangement but I never measured. I just assumed the 277V to GND on the primary side would translate to 133V to GND on the secondary side. I'll do the figure 2 installation since it seems to be the standard and I'll make the measurement and post in this thread.

I sure would have liked to install a 35 lb unit rather than a 135 lb unit.


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## JRaef

It's going to depend on the type of load. Technically, either one will work. But if the equipment on the load side is sensitive to ground noise, it may not like the ground reference neutral in Figure 1, and if it CREATES noise on the line, that Fig. 1 circuit, not being an isolation transformer, gives that noise a direct path to everything else on the same ground plane. 

If however the 230V is just for an AC single phase motor AND NOTHING ELSE, it would not make a difference. 230V single phase in all other parts of the world except North America is derived from 400V phase to earthed neutral (nominal votlage levels expressed here for simplicity). It's not the same as what you show in Fig. 1 because they don't need the Buck Xfmr, but effectively, it's the same.


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## RePhase277

If all you need is two wires with 230 V between them, then go with the buck-boost. Figure two isn't legal as a utilization source because an isolation transformer will leave the secondary ungrounded. 

One wire of your 2-wire system should be grounded, and the BB does it. Most equipment doesn't know and doesn't care whether the current comes from two hot wires or one hot and one neutral. It can't tell.


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## Big John

swimmer said:


> ...The critical point here is that 230V single phase means:
> Two hot wires, each 133V from ground
> and not
> One hot wire, 230V from ground, and a neutral wire....


 I'm having trouble with this. Are you saying that the equipment cannot tolerate a voltage higher than 133V to ground?

Otherwise, I would install a buck-boost with a 230V hot and a neutral in a heart-beat.

-John


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## frenchelectrican

swimmer said:


> I need to install a 230V, 30A, Single Phase, pressure washer.
> My available power is 480V / 277V.
> I thought I'd be able to do it as per figure 1 of the attachment, which is phase 1 and N into a buck-boost.
> 
> The transformer representative told me I'd have to do it as per figure 2. which is phase 1 and phase 2 to into an isolation transformer.
> 
> The critical point here is that 230V single phase means:
> Two hot wires, each 133V from ground
> and not
> One hot wire, 230V from ground, and a neutral wire.
> 
> Is the transformer rep correct?
> 
> Just want to make sure I have it straight before proceeding.
> Thanks.


 
Swimmer.,

If you used the convental transfomer as you posted on second photo the secondary voltage which you will have 240 volts ( there is a good chance you may have centre tap there ) the line to ground will read 120 volts. Note I say not the line to netural s.v.p.


Big John., I will useally use the B/B in heartbeat majorty of the time if the load do not requried netural aka 120 volts but if they do then I will use the convental transfomer. ( avce centre tapped core ) 

Merci,
Marc


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## swimmer

Big John said:


> I'm having trouble with this. Are you saying that the equipment cannot tolerate a voltage higher than 133V to ground?
> -John


No, I'm not saying that.
What I'm saying is this:
Primary: Phase to ground = 0.577 * 480V = 277V
Secondary: Phase to ground = 0.577 * 230V = 133V

But I've never done this and it looks like I'm missing something based on other posts


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## Techy

You're getting hung up on the '230' part. Unless this is european equipment, i would hook it up to 120/240 just like your house,(2 hots, no neutral) and call it a day.

A standard 240v motor is rated 230v, 208 motors are rated 200v, 480v rated for 460v etc


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## 480sparky

Why would you hooking up 230v equipment to run between a hot and ground?


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## nolabama

480sparky said:


> Why would you hooking up 230v equipment to run between a hot and ground?


Why does it matter? A difference in potential is a difference in potential. I guess I am getting a little confused.


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## 480sparky

nolabama said:


> Why does it matter? A difference in potential is a difference in potential. I guess I am getting a little confused.



Um, using a grounding conductor as a return path?:blink:


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## nolabama

I am confused - I thought he wanted to use one leg of the hot and a noodle for the hook up. Im sure their is prolly code against that too.


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## Big John

swimmer said:


> No, I'm not saying that.
> What I'm saying is this:
> Primary: Phase to ground = 0.577 * 480V = 277V
> Secondary: Phase to ground = 0.577 * 230V = 133V


 I gotcha. Even though you're using two phases of 3 phase system you treat it like single phase. There's no 0.577 involved.


480sparky said:


> Um, using a grounding conductor as a return path?:blink:


 Based on his diagrams, he's not doing that. 

The question here just seems to be whether voltage-to-ground matters in this installation. I don't think it does.

-John


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