Multiple 1PH Supplies into 3PH board

[JackGetBack]

Hi everyone,

I'm a Carpenter managing a shop conversion and am wondering if it is possible, legal and sensible to utilise the existing 2Phases plus bring in a third 1PH supply (assuring they come from different phases at street level). It will be potentially cheaper and easier than bringing in a new 3PH supply.

Currently, there are 2Phases (treated as two separate supplies) into the shop. One feeds the shop, the other feeds the flat upstairs.
The meter for the flat is in the shop and Northern Powergrid suggests that they will pay for relocation of flat's meter and supply of separate connection to flat.
This leaves 2Phases in shop. Our idea is to just bring an additional single phase in (ensuring it is from the third phase).

If this happens, will there be metering complications/expense and can they all be fed into a 3PH DB and life procede normally? Will we end up with one 3PH meter? Northern Powergrid lads are awaiting news from 'upstairs' about our idea, and feedback from sparkies... I just wanted to do my own research.

In case it worries anyone, I'm not doing the work, I just don't have an electrician to ask yet.

Cheers, and please forgive my ignorance on a professional forum,
Jack

 

[telectrix]

i'd consider it bad practice to bring 2 supplies into 1 3 phase board. best get a 3 phase supply into the main board, then split as required from there.

 

[JackGetBack]

Further info: The proposed, two 1PH supplies can come from the same joint in the street, further reducing the cost and hassle to my customer and the flat resident. It's a rented property and a new business so money is a bit tight.

i'd consider it bad practice to bring 2 supplies into 1 3 phase board. best get a 3 phase supply into the main board, then split as required from there.

Thanks for your reply, @telectrix. Given that yours is the expensive option (it includes resiting DB, not just replacing), what are the specific reasons? If Powergrid guys terminate each off as 3 separate phases, then what difference does it make? I know it will be less neat than one SWA from one joint in the street, but is there a reason or regs restriction? I'm wondering if it's just a debate between my autistic and environmental preferences.

 

[Pete999]

i'd consider it bad practice to bring 2 supplies into 1 3 phase board. best get a 3 phase supply into the main board, then split as required from there.

Agree

 

[westward10]

Are you sure there are two phases in the shop and not two supplies off the same phase.

 

[JackGetBack]

Are you sure there are two phases in the shop and not two supplies off the same phase.

Yes, I'm certain. Confirmed with Northern Powergrid.

 

[The Ghost]

What do Northern Powergrid say about your proposals. As they are the ones doing the work surely they should be consulted as to what is and what is not feasible?

 

[JackGetBack]

What do Northern Powergrid say about your proposals. As they are the ones doing the work surely they should be consulted as to what is and what is not feasible?

They helped develop the idea and were happy; when I said that they were waiting for news from upstairs, I meant their office (planners), not the flat above the shop. They didn't so much know the internal commercial/domestic regs but rather their own external rules and specs.

 

[Richard Burns]

Effectively you are wanting to use a 3 phase supply that comes into the property in two different cables rather than one cable and also has two service heads and three meters rather than the usual one.
The usual statement from the DNOs is that a property should not have more than one incoming supply, however if they have agreed to have two incoming supplies then that is up to them.

If you fit a 4 pole isolator to receive all the supplies then from your point of view you have a standard 3 phase incomer to connect to your board. Not too sure about the neutral but since each one would be derived from the same supply cable they should be just parallel cables (might need more information on that one).

I just cannot see how it is cheaper, but you are there and so must be aware of why and how.

 

[NDG Elecs]

Why do you require a three phase supply? Is it for certain equipment? If it is, there is a bit of kit called a power converter or similiar, which changes single phase to three phrase. Obviously there may be issues with your maximum demand though.

Others on here will know about these things much better than I do, just thought it was worth a mention..

Re Richard's post above; NEDL (OP's area) were not happy about two different supplies entering one property that I dealt with recently, and insisted on completely removing one of these supplies.

 

[JackGetBack]

Been doing my homework, but still looking for answers. We may have saved money significantly elsewhere and be able to go for dedicated 3Phase install...

Power converter isn't an option as it is for high draw electric ovens, and bakery mixers. Too much draw for the single phase incomer and the two phases are not a complete polyphase setup; merely two of three (unless they are split phase which we doubt).

Thanks for the news that Northern Powergrid (once-upon-a-colourchange-ago called NEDL & YEDL) didn't like it previously. That might be a good guide; I'm having difficulty getting an update after our site visit.