split phase supply

[nobelz66]

Hi guys ive just joined this forum so im hopeing for some help please
Ive just been asked to estimate a job basically to supply power to 15 new log cabins each requireing a 32a sp supply ,the existing park is supplied by a 3 wire split phase supply rated at 400A split also there is an existing 100a 3 phase board not fully loaded been run on a 4c 50mm2 swa and a 95mm2 cpc via a 200A panel board at mains position the L1 and L2 is supplied from one side of the split phase the other L3 connected to the other my question is as follows:

1 # do i calculate the new cable run as a 3 phase cable ie 4 c 120mm2 or calculate as a single phase which would make the cable 180mm2 min
2 # do i allow diversity on the log cabbins called niceic they said yes

any help would be very gratefull

 

[Engineer54]

First off, It's not a split phase supply, it's simply 2 phases and neutral. (Unless that supply is derived from a single phase 3 wire transformer, which i very much doubt!! lol!!!) Though why the park is being supplied with such a 2 Ph +N arrangement, only the original installer would know!!!

1/ ...Yes, as a multi phase supply.

2/ ...yes.

 

[mechelec]

Why can it not be split phase eng ? Measure between phases if 0V single phase if 480V split phase or am I missing something. The rest I agree with.

 

[somersetsparks]

Split phase is fairly common round here engineer! Usually gives you nearing 500v Phase to phase.

 

[Knobhead]

As usual it's all guess work without some readings from the OP.

View attachment 13770

 

[Guest123]

I cant see how traditional 3P can be derived from a split phase supply???

 

[Knobhead]

From how I read the OP there is a smaller 3Ph available.
I’m totally confused as to why the DNO would make the 2[SUP]nd[/SUP] supply either 2 or split phase.

 

[Silly Sausage]

I cant see how traditional 3P can be derived from a split phase supply???

Not my field, so possible nonsense alert.
I can't see how you can without the use of 'technology'.
Is a split phase supply derived from a centre tapped winding, like a tool tranny, phases 180[SUP]o[/SUP] apart?

 

[Edd]

Would be greatfull if someone could explain the split phase setup, compared to the 3 phase that im used to.. thx

 

[Guest123]

Not my field, so possible nonsense alert.
I can't see how you can without the use of 'technology'.
Is a split phase supply derived from a centre tapped winding, like a tool tranny, phases 180[SUP]o[/SUP] apart?

Essentially, yes.

The Tx will have a single phase primary with the secondary centre tapped to provide 2 x single phases 180 apart with a shared neutral.

Measured at the building incommer between the two and you would read typically 480V.

 

[Edd]

my delete button dont work

 

[Knobhead]

Would be greatfull if someone could explain the split phase setup, compared to the 3 phase that im used to.. thx

Here you go.
The centre leg would be earthed.
View attachment 13771
It also shows the two legs are not at 180