Single phase board use with 2 phases

[Danny124]

Hello guys new in this forum.

In my 19 years as an electrician I've never seen this. Looking for any thoughts on this.

Been asked to install a few new circuits In a domestic garage. There is a granny annex on top of this garage also.

Supply is 3 phase in to a 3 phase isolator. From there phase L1 supplies 1 CU for the granny annex.

Phases L2 & L3 go to a standard single phase wylex 18 way board.
It seems that it's been a split RCD adapted in a dual phase board. 1 side of this CU is L2 into a 100 Main switch then incorporates RCBOs for the circuits.
The other side of the CU has another main switch taking L3 phase with RCBOs too.
Each phase and N enters board at each side, L2 and N on bottom left and L3 and N on right side.

There is no certificate for this from previous owner, but looks to be a very neat job. But have my suspicions.

Inside the house is the same. 3 phase incoming to 3 phase isolator but has 3 single phase split load RCD CUs supplied by each phase.

My question is, has anyone seen anything like this before.
Search through the web, asked other electricians ask the wholesalers, and searched the regs.

Keep scratching my head at this one and it's making me bald.

Advice grately appriciated.

Regards

 

[westward10]

A pic would be helpful. You may have an adapted dual rcd consumer unit which has been altered or it is a dual tariff consumer unit which isn't being used for dual tariffs. Dual tariff is a single unit which incorporates peak and off peak in a single enclosure.

 

[Danny124]

Hi Westward.

Unfortunately unable to provide photos as my camera on phone is broken.

As far I can see, and investigated as far as I can by just looking and asking questions, the CU looks to be a Split load RCD converted into a 2 phase board with 2 main 100A switches. There is no dual tariff etc.

What i'm seeing looks good, but my mind is saying 'Hell No' and tell my potential client at best need to install another board to take that extra phase out of there, or just walk away and not bother pricing the job.

 

[davesparks]

Other than maybe putting a label on it to warn people of the 2 phases being in there I can't see much wrong with it.

Maybe check that the PFC isn't too high for the assembly.

 

[James]

Although it is an unusual setup, I can’t see a problem.

Although as said above, some warning labels would be a good idea.

If you had 2 boards next to each other from different phases, it would be fine.
Think of the arrangement as 2 separate boards, contained in the same box.
DB2-L and DB2-R

 

[dmxtothemax]

you are an electrician and you very quickly worked it out ?
So I don't see any big problems,
unusual for a domestic set up but not dangerous.
if it bothers you mark the panel as "multi phase supply"
or something along those lines.

 

[westward10]

Hi Westward.

Unfortunately unable to provide photos as my camera on phone is broken.

As far I can see, and investigated as far as I can by just looking and asking questions, the CU looks to be a Split load RCD converted into a 2 phase board with 2 main 100A switches. There is no dual tariff etc.

What i'm seeing looks good, but my mind is saying 'Hell No' and tell my potential client at best need to install another board to take that extra phase out of there, or just walk away and not bother pricing the job.

There may not be dual tariff but a consumer unit intended for dual tariff may have been utilised.

 

[snowhead]

Neat solution.
The other option of using a small 3 phase DB either with 1 phase not used or 2 of the 3 linked would have seemed just as odd, but still O.K.

 

[Andrew Hunter]

Sounds to me to be a creative solution to what may have been a problem at the time or could have been a solution to a lack of fluid finances at the time but as mentioned if labeled/identified correctly and as also mentioned if materials are suitable for the PFC and all exposed conductive parts are bonded to the same potential then there should not be any issues.
Curiosly is there enough room to fit a three phase board? Tirminating the current circuits to the correct phases as they are now? Incidently i have come accross this type of installation before wher at some point a three phase board fed on a 4 core armored cable has been replaced by 3 seperate CUs. This was in an office unit that at some point been segregated into seperate units for a spell then back again to one unit.
I did convert back to a three phase board but the only reason for this was the fact one of the phases was overloading another was mid way and one was hardly loaded at all.
The lighting was still wired in three phase with shared neutals and the socket outlets from the seperate 3 phases apperred to have just been linked together to create very lage area ring mains. (A very bad job done appaulingly) so there was lots of work to sort these issues starting by converting back to 3ph.

 

[Lucien Nunes]

At last... a valid reason to put a 400V warning label on a DB!

 

[FarmersFriend]

So is there a main switch on the DB that disconnects all the line conductors from both phases?

 

[Wilko]

Probably just me, but I would not adapt a single phase board in this way as I’m not using it in the way the manufacture designed it, presumably.

Is there a single switch in the board that isolates both phases and N?

 

[snowhead]

Probably just me, but I would not adapt a single phase board in this way as I’m not using it in the way the manufacture designed it, presumably.

Is there a single switch in the board that isolates both phases and N?

Probably not but then there isn't in a standard Dual Tariff board.

 

[Danny124]

Hi Guys, Sorry been on holiday.

The client is willing to either have a 3 phase DB installed, as he wants to tidy up that area, or separate the dual DB with 3 separate DB's (1 for each phase).

Either way I like that better than having 1 incorporating 2 phase, just doesn't sit right with me.

Just waiting for feedback on my quote

Thanks for all your comments.