Split phase on new building

[marc8]

Hi All

I have read the previous thread on this but just wanted some help with a project we are about to complete.

we are set up already for 3 phase we have a panel board 3 phase with metering to 6 outgoing circuits, we have 5 3 phase boards in the mains room, 2 3 phase panels fed from 2 distribution boards, 1 3 phase going to another building fed from the panel board.

all circuits are now terminated & ready for testing & inspection & have been for some time, we have had the TBS supply jointed & power over to the new building ready to go, 3 phase head installed on the TBS & on the new building but turns out we only have split phase, this did not matter on the TBS as we only needed single phase.

so it has come to light now, our paperwork completed & information fro UKPN was that we were having 3 phase but now only found out they only have split phase at & around the site, I am not involved in the paperwork side but I can guess what is happening that we are being asked to probably pay for the upgrade.

we only have a few things that are going to be 3 phase so could use convertors that's not what I am looking at it is the distribution system we have built for 400v 3 phase & ripping it out & converting to split phase.

anyone recommend or used split phase equipment as in PB & DB's if so where did you get the equipment or is there a way we could convert what we have ? any help would be appreciated

 

[Silly Sausage]

No answers so far ...
Split phase as in "Split phase - http://www.electriciansforums.co.uk/threads/split-phase.98791/#post-1055747"

Oh dear, sounds like someone's screwed up big time.
I'd be spending my time finding out who's responsible and pointing remedial costs in their direction ASAP!

Good luck!

edit: Oh aye, admit nothing until the truth is out!

 

[Richard Burns]

If you have paperwork from UKPN stating they will supply three phase then they need to supply three phase, they have given you a price and it is then up to them to supply the promised service for that price.

 

[Lucien Nunes]

To avoid the problem of 460V being present in every board (which might not be rated for it) you might look at converting all the sub DBs to SP+N, if they and the submains are rated highly enough. The maximum load on each would be less than on TP+N, even with the pairs of cores in the submains paralleled, but if the spec was generous to start with it might save a lot of work. You will have to confirm whether the main DB is OK for one line on each of two phases and whether you can fit large enough OCPD for the higher rated SP+N submains.

 

[marc8]

Hi Richard

there will be small print I would imagine mentioning if the equipment ect ect ect

 

[marc8]

Lucien

yes good idea I could single phase out the DB's then at panel board support either 1st or 2nd phase for that board, I could then change the CT coil to single phase & wire the outgoing meter to single phase yes that would work.
V good idea, thanks I understand & that would work certainly, therefore just the panel board at 460V

 

[marc8]

another thought as I would be increasing the load on the single phase on the two DB's feeding the sub boards I could double up the cores as I would have had 3 phase & N anyway as I ran separate earth with each submain

 

[Lucien Nunes]

Yes I was assuming you would do that, so that you can have approaching 2/3 of the original total capacity. E.g. a 3ph 4-wire 100A circuit converts to something less than 200A on 1ph 2-wire because the cable rating per core with all 4 cores loaded is less than the rating for 3ph 4-wire, where (harmonics aside) only three cores can be fully loaded at once.

 

[Leyland30]

If your going to combine cores to increase capacity at SPN, Are we effectively talking about reduced size neutrals? Have you Considered the implications of this in regards bs7671 requirements and the associated electrical loads. I've had 'issues' with DNOs in the past but nothing like this. Best of luck, let us know how you get on.

 

[Leyland30]

Is there an option to approach an alternative supplier for your connection.

 

[marc8]

N&P will be both same size CSA as they panels were 3 phase N, doubling up cause single phase will result in them being the same on single phase.
It is network that is the issue as being only split phase. I think Luicen is correct should be okay implications of alterations not as bad as upgrade costs me thinks, just have to balance DB'S over the 2 phase so load on each phase is as balanced as I can get it.
Network operator is happy for us to have the split phase as is our draw was never that high anyway our biggest load is probably the 6 single phase air on units of which were across 3 phases, now will be on one of the phases.

 

[marc8]

Quick update for anyone who is Intrested,
As we had used a 400A panel due to the outgoing metering requirements we are using CNX compact breakers & these have 36KA breaking capacity at 400V if we intend to use split phase then we have to dearte them to 25KA breaking capacity.
Now just speak with the designer about the incoming N side of things & what we can load up.

 

[Mark42]

I had one of those horrible 460V (that's RMS - actual metered peak was around 485V) split-phase supplies on my own sprawling ex-farm site, and asked a question on here years ago about using 'standard' three-phase distribution boards, but run at the increased interphase voltage. No one would commit either way, including the manufacturers.
What I did in the end was to wire (as you have done) a 'standard' three-phase install using Hager TP boards, then paralleled L2 and L3 at source, awaiting an upgrade to three-phase in the future. At which point I needed only to remove one link, with no further work needed apart from swapping around a few final circuits for load balancing.
I reckon there's enough tolerance in modern kit to allow the slight voltage increase between phases. What is perhaps significant is that the DNO install a standard three-phase meter for split-phase supplies, ignoring the '3x230V/400V' printed on the meter!