3 phase test readings help

[Bradley6969]

Hi have wierd dilemma, looks to be 3 phase - 4 wire system so testing am getting this
L1-L2 Nothing
L2-L3 450v
L1-L3 450v
L1-N 230v
L2-N 230v
L3-N 230v
Why no L1-L2?

 

[Strima]

They're on the same phase.

 

[Bobster]

Correct, it's not a true 3 phase supply.

L1 and L2 have the same phase angle.

 

[buzzlightyear]

They're on the same phase

DRAT STRIM ,BEAT ME TO IT .

 

[westward10]

Your line to line voltage indicates you may have a split phase supply and the fact there is 0v between L1 and L2 points to them being on the same phase.

 

[Bradley6969]

Yes got it guys thanks just realised haha

 

[buzzlightyear]

Yes got it guys thanks just realised

we have all been their Bradley scratching your head thinking now how do this three phase work ,lol.
back to school you need to go .

 

[Charlie_]

I was called out a few years ago to a faulty compressor..
Spoke to the sparky on site who confirmed all was ok, voltages checked, fuses ok, etc..
One of the fuses to the compressor had blown, L1 going through winding and back up onto L2 fuse..
said he had checked both sides of fuses and they were all live, he scratched his head for a while, drew him the circuit and the penny dropped...
I put it down to a faulty overload, saved him his blushes

 

[Bradley6969]

Thanks guys so I have some outgoing circuits to connect up, so I just balance the load between L1 and L3 it’s only temporary till they get supply sorted sorry only apprentice

 

[Bobster]

Balance the load across all 3, the DNO have provided this set up for a reason.

Also, if you are an apprentice, who is supervising you?

 

[Bradley6969]

Balance the load across all 3, the DNO have provided this set up for a reason.

Also, if you are an apprentice, who is supervising you?

But L1-L2 are on the same phase? And I’m with a couple of guys just thought I’d ask saves me looking stupid

 

[Charlie_]

At what position in the installation are you doing your tests?
It needs to be right at the incomer on the supply side with the load side isolated

 

[Bradley6969]

At what position in the installation are you doing your tests?
It needs to be right at the incomer on the supply side with the load side isolated

Done at the very point the supply’s income is connected all fuses disconnect

 

[Charlie_]

So to confirm; with everything isolated you had two common phases?

 

[Bobster]

Have you asked the experienced guys what they think, have they done or supervised any of this testing?

You should apply for the trainee part of the forum if you are an apprentice, that way answers are tailored better suited for someone who is learning. Will also get less grief for asking what would be a silly question for someone experienced.

 

[Bradley6969]

So to confirm; with everything isolated you had two common phases?

Yes correct and where transformer is on top of the pole there 2 fuses not sure what there called and then one cable tapped into the other what looks like

 

[Bradley6969]

You should apply for the trainee part of the forum if you are an apprentice, that way answers are tailored better suited for someone who is learning. Will also get less grief for asking what would be a silly question for someone experienced.[/QUOTE]
Well there on the same site but doing other bits so thought I’d ask so I kind of know what I’m talking about

 

[Charlie_]

What apprentice year are you?
Don’t ever hesitate asking questions, it’s the best way to learn and also it shows to your colleagues that you are interested and keen to learn

 

[Bradley6969]

Only 2nd year and I know just like to show I kind of know what I’m looking for and at
L1-L2 Nothing
L2-L3 450v
L1-L3 450v
L1-N 230v
L2-N 230v
L3-N 230v

So if I connect all sub circuits the same then there should be no issues?

 

[Bobster]

Have you any actual 3 phase or multi phase loads that need supplying?

 

[R-fur]

Bradly
There are two main possibilitys, If it is rural and fed off its own pole mounted transformer it could be a split phase supply where the transformer is HV to 500V with a center tap giving 250V between each end to the center neutral tap and 500V between the outers.
If it is in a town it may be fed off an old DC cable which has been converted to two phase and neutral.
A third option is that it is a cable fault with an open circuit/weld.

 

[Lucien Nunes]

The voltage measured between the lines (450V) suggests a split-phase 230-0-230 supply rather than two phases out of a 3-phase 400/230V system.

A look at the meter(s) will confirm as they will have the appropriate spec for the supply in use. Also, if the HV feeding the transformer is single-phase (with two lines only) then the LV service must be split-phase.

If you are only connecting single-phase loads, then you can follow normal practice. If this is the main DB with one outer shared between the L1 & L2 ways, the total load load on those should probably equal the load on the L3 ways.

 

[Bradley6969]

The voltage measured between the lines (450V) suggests a split-phase 230-0-230 supply rather than two phases out of a 3-phase 400/230V system.

A look at the meter(s) will confirm as they will have the appropriate spec for the supply in use. Also, if the HV feeding the transformer is single-phase (with two lines only) then the LV service must be split-phase.

If you are only connecting single-phase loads, then you can follow normal practice. If this is the main DB with one outer shared between the L1 & L2 ways, the total load load on those should probably equal the load on the L3 ways.

Hi thanks, I have some double pole switches and single pole so just connect as normal?

I also have a 3 phase pool to wire up so I’m not sure how that’s going to work yet

 

[Bradley6969]

Have you any actual 3 phase or multi phase loads that need supplying?

Hi I have double pole switches eg 2 lives from there and then just single pole MCBS

Have pool to do which is 3 phase but I’m not sure what needs to be done with thay

 

[Pete999]

Hi I have double pole switches eg 2 lives from there and then just single pole MCBS

Have pool to do which is 3 phase but I’m not sure what needs to be done with thay

Make sure you get the phase sequence the right way around Mate otherwise when you empty the pool the dain water will go in a different way than normal.

 

[Strima]

I also have a 3 phase pool to wire up so I’m not sure how that’s going to work yet

The pool will work fine, the pumps however are a different story.

You need to confirm if you have two or three phases otherwise it’s going to start getting expensive.

 

[Bradley6969]

Make sure you get the phase sequence the right way around Mate otherwise when you empty the pool the dain water will go in a different way than normal.[/QUO
Thanks so single phase circuits all good? Just the pool I’m sure there getting an extra phase so need to confirm

 

[Bradley6969]

The pool will work fine, the pumps however are a different story.

You need to confirm if you have two or three phases otherwise it’s going to start getting expensive.

Well I have split phase supply all my outgoing circuits are either single pole or the use of 2 phases eg black and brown from a 2 pole MCB so there all fine just the one pool

 

[Charlie_]

Are you not working to any plans or specifications?

 

[Bradley6969]

Are you not working to any plans or specifications?

Yes but contractor has quoted saying there’s 3 phase when there’s not

 

[Bradley6969]

So my single pole and double pole with all be ok?

 

[Bradley6969]

it’s only temporary till they sort supply out

 

[Charlie_]

Work to the plans and specifications and don’t deviate from it unless you have revisions..

 

[Pete999]

Yes but contractor has quoted saying there’s 3 phase when there’s not

Best put him right then Mate. Otherwise it could be your gonads being hung out to dry, when it all goes Mamery's up.

 

[davesparks]

I also have a 3 phase pool to wire up so I’m not sure how that’s going to work yet

It won't work, don't connect a three phase load to this supply, it won't work and may damage it.

 

[Strima]

Well I have split phase supply all my outgoing circuits are either single pole or the use of 2 phases eg black and brown from a 2 pole MCB so there all fine just the one pool

It sounds very much like you don't have a three phase supply so connecting three phase equipment is not advisable as it will not work correctly and worst case it could be damaged which will get expensive.