Three Phase Board 230V

[Dizzy_Maskell]

Just after people's opinions seen this a few times and although not incorrect still makes me think:
Three phase board 8-12 ways usually linked out to run on a single 230V supply.
Seen second hand boards converted using bus bar to make in affect a 36 way single phase board.
Always have been properly done e.g labelled and all circuits ok but just wondered how common it is as I am coming across it in a few places now and seems a practical way of having loads of circuits in a single DB.
PS everything done safely correct circuit protection, earth loop etc

 

[ChrisElectrical88]

I quite often fit a 3 phase board when I only have a single phase supply as I find them nice to work with and a 4 way 3 phase board has much more room than a standard 16way board. Nothing wrong with doing it this way so long as you fit a manufacturers phasing kit and label correctly.

 

[SirKit Breaker]

The only thing i dont like about it, is the cost of the bloody RCBO's to put in the thing.

Cheers..............Howard

 

[Dizzy_Maskell]

Yeah I really can see advantages

 

[ChrisElectrical88]

Obviously I don't go fitting them in domestic properties. But this way of doing it is great in small industrial units etc. We have a client that prefers this way also so it's win win really.

 

[Knobhead]

I’ll break my silence on this.

Bear in mind the neutral conductor in a three phase board is rated according to this calculation.

In = √((Ia²+Ib²+Ic²)-((Ia*Ib)+(Ia*Ic)+(Ib*Ic)))

The combined line conductors in your bodged up board will be three times the size of the neutral.

It’s OK so long as your total cumulative load over the three paralleled phases doesn’t exceed the normal rated current of one phase in normal use.

Don’t they teach electrical theory any more?

 

[Dizzy_Maskell]

I’ll break my silence on this.

Bear in mind the neutral conductor in a three phase board is rated according to this calculation.

In = √((Ia²+Ib²+Ic²)-((Ia*Ib)+(Ia*Ic)+(Ib*Ic)))

The combined line conductors in your bodged up board will be three times the size of the neutral.

It’s OK so long as your total cumulative load over the three paralleled phases doesn’t exceed the normal rated current of one phase in normal use.

Don’t they teach electrical theory any more?

I can not imagine in many circumstances where this is used this would happen,

Good point well made though, id better start taking out all the boards where i used the 10 63 Amp breakers

 

[cobrauk]

most would only be fused at 100amps wouldn't they ? so it wont apply

 

[mark ju]

I’ll break my silence on this.

Bear in mind the neutral conductor in a three phase board is rated according to this calculation.

In = √((Ia²+Ib²+Ic²)-((Ia*Ib)+(Ia*Ic)+(Ib*Ic)))

The combined line conductors in your bodged up board will be three times the size of the neutral.

It’s OK so long as your total cumulative load over the three paralleled phases doesn’t exceed the normal rated current of one phase in normal use.

Don’t they teach electrical theory any more?

But surely, if for instance you had a three phase board with a manufacturers link fitted to turn it into a single phase board and then said board was fed with say a set of 25mm tails, the above equatition doesn't come into play at all.

 

[Knobhead]

As I said the concern is the neutral current. A 24 way board used as single phase has the potential to become grossly overloaded.

 

[netblindpaul]

Tony,
I suggested this somewhere & I was ridiculed for it...

 

[Marvo]

I vaguely remember it was a thread about using a 3-phase supply to power 3 separate single phase circuits.

 

[netblindpaul]

Similar, IIRC, there is also the issue of harmonics, you should have seen the current waveforms I got off a power analyser last week, a 3yr old could have drawn a better sine wave than they looked like!!!

These problems & issues are real & out there NOW.

Remember & I can't at this time of night, but Triplen & 5th harmonics add to the current in the N?
Can someone else confirm.
Probably the best statement in the world (NOT) IYKWIM!

 

[Silly Sausage]

I think it's your multiples of 3 harmonics that sum, but they rapidly reduce beyond the 3rd.
Likewise Paul, no way am I looking that up now.
Think I'll watch the latest Star Trek film.

 

[netblindpaul]

Archy,
There is something with 5th harmonics too, but, that could just be with a specific type of kit I used to work with, I'll try to check one day!

That avatar is definitely not Star Trek!

 

[Marvo]

Yep, triplens add up to load a shared neutral.

View attachment Schneider Harmonics and Transformers.pdf

This was the best I could find after a long day and at short notice.

 

[Silly Sausage]

That's a picture of the wife.
















Unfortunately, not mine!

 

[High Tower]

Double edges sword, it's no different to loading a TPN board with lots of single phase circuits across the phases! Your still going to have high neutral current.

I think you have to do a assessment of the environment in which it is to be used. I have single phased a TPN board before in the branch of an estate agents, however I'd never do it in say a factory or workshop!

 

[mark ju]

Sorry but fail to see where there is any confusion here. The op said about using a three phase board fed from a SINGLE phase supply. With the correct linking kit fitted this board becomes a single phase board. It's just as possible to overload a purpose made single phase board as a "converted" board. And as its fed from a single phase supply the load on the neutral conductor will be the same as the live.

 

[Knobhead]

Double edges sword, it's no different to loading a TPN board with lots of single phase circuits across the phases! Your still going to have high neutral current.

I think you have to do a assessment of the environment in which it is to be used. I have single phased a TPN board before in the branch of an estate agents, however I'd never do it in say a factory or workshop!

Sorry HT but not so, Using the calculation for resistive load the maximum neutral current could match the highest loaded phase.
So:
R = 20A
Y = 0A
B = 0A
N = 20A

Change the loading to say:
R = 20A
Y = 10A
B = 5A
N = 13.2A
But now we have the natural triplen at 150Hz in the wave form.

I tried to do a wave form drawing of the neutral current, all I managed to do was send myself cross-eyed.