Sanity Check Required - Do I really need 3 Phase Upgrade?

[bernardgreen]

Provided all the cables have been run to one single location where it was intended to have a 3 phase supply and distribution board ( or three consumer units ) then there should be no problem supplying them all from one phase, either one large consumer unit or a couple of smaller ones connected to the single incoming phase. ( a single point of supply disconnection such as a switch fuse between meter and consumer units may be needed if more than one consumer unit is used )

 

[JohnW2]

Looks like I will have to try once more to see if I can change my electrician's mind. It's a bit annoying as this only came to light after first fix was almost complete. It's not my choice of electrician - it's one of the people my "project manager" usually uses. Project manager in quotes as he seems to have no knowledge related to these technical things, just likes to do the design aspect! The cable runs have now been over-boarded so changing electrician at the stage could be painful.

Fair enough. As bernard has said, it's quite possible that most/all of the cable runs will still be suitable for a single-phase supply. As for the electrician, my personal concern would be uncertainty as to the extent that he could be trusted in relation to all aspects of the work, given the apparent lack of understanding that he seems to have exhibited.

Kind Regards, John

 

[philnixon]

Thanks John.

In terms of Part P certification, if I did get someone new in would they just be able to test the existing runs that have been put in, or do you think he'd want to see them exposed?

 

[OwainDIYer]

Looks like I will have to try once more to see if I can change my electrician's mind. It's a bit annoying as this only came to light after first fix was almost complete.

How can such a major, fundamental question arise after first fix if the electrician has properly designed the installation?

Ask for (demand) his distribution switchgear design and post it up here so we can have a good laugh. I mean WTF is a Cooker Ring anyway?

 

[philnixon]

I mean WTF is a Cooker Ring anyway?

To be fair to him that was my bad terminology! I haven't seen any design info from him - those were my groupings

 

[ban-all-sheds]

What is?

Having a dig at me by saying "Don't tell Ban that we're advising putting a 100A+ load onto a 100A fuse......" even though that would have been completely untrue, and all because I'd said one should not put a 26A load on a 20A breaker.

 

[ban-all-sheds]

As bernard has said, it's quite possible that most/all of the cable runs will still be suitable for a single-phase supply.

"Most" implies the possibility that not all of them will be.

I can't think why that might be.

 

[JohnW2]

As bernard has said, it's quite possible that most/all of the cable runs will still be suitable for a single-phase supply.

"Most" implies the possibility that not all of them will be. I can't think why that might be.

It really depend what this 'electrician' was planning. For all we know, he might have been intending to have three separate single-phase boards, in significantly different locations, in which case the wiring he has installed might not be suited (or, at least, ideally suited) for a single single-phase board - which is probably what the OP ought to have.

Kind Regards, John

 

[ban-all-sheds]

If it made sense for those boards to be dispersed with a 3P supply it would make just as much sense for them to be dispersed with a SP one.

He'd have had to have the feeders for those remote boards starting from switchfuses near the service head - no problems or changes needed for a SP supply except a couple of service connector blocks

 

[ban-all-sheds]

But sense does not seem to be amongst this "electrician"'s attributes.

 

[JohnW2]

If it made sense for those boards to be dispersed with a 3P supply it would make just as much sense for them to be dispersed with a SP one.

It would. However my hesitation to give a totally unqualified answer was based on uncertainty as to whether it necessarily did "make sense for those boards to be dispersed with a 3P supply" - given the other things which this 'electrician' has said. ... or are you confident that the design decisions of this 'electrician' will all "make sense"??

As you know, I personally do have extensively 'dispersed' CUs (and a 3-phase supply), but from what we've been told, I'm not at all certain that the OP's house, although fairly large, is necessarily large enough to warrant that.

Kind Regards, John

 

[ban-all-sheds]

Well, questioning the "making sense" is one thing, but saying that wiring suitable for 3P might be unsuitable for SP is another.

 

[JohnW2]

Well, questioning the "making sense" is one thing, but saying that wiring suitable for 3P might be unsuitable for SP is another.

I suppose it depends upon the extent to which one is prepared to compromise in one's definition of "suitable/unsuitable" in order to accommodate what has already been done by a seemingly less-than-fully-competent 'electrician'.

If a proper and appropriate design decision would have been to have a single single-phase CU in one location, then my inclination would be to insist on that, rather than to accept three 'scattered' CUs so as to fit in with what the 'electrician' had already done.

Kind Regards, John

 

[philnixon]

The plan initially was to have a single CU in a single place. When he then thought he needed a 3-phase, the plan remained to have the board in the single location. An 8 way TPN board has been specified in his updated quote.

 

[JohnW2]

The plan initially was to have a single CU in a single place. When he then thought he needed a 3-phase, the plan remained to have the board in the single location. An 8 way TPN board has been specified in his updated quote.

In that case, the installed cables should be as usable for a single single-phase CU as they would have been for a 3-Phase board in the same location.

Kind Regards, John