3 Phase dist board

[Norn Iron]

Hi Guys need a bit of expert advice and guidance. I have been asked to do a bit of work at my friends new office premises. The office is located inside a warehouse and is Fed via a 16 Way 3 Phase Distribution board with a 35mm 4-Core SWA.

However the Dist board is almost full and even after stripping out some old supplies that are not required I will not have enough room for some of the new circuits that are required. This is where I require help, Is it possible for me to either

A. Run a set of tails from one of the 3 Phases in the Main switch with a Neutral and Earth and install a single phase Consumer unit..... or

B. Run a set of tails from all 3 phases with a Neutral and Earth and install another smaller 3 phase Dist board.

Bearing in mind the Mains powering the 16Way Dist board already installed comes from a load centre at the far end of the warehouse.

I hope this all makes sense and look forward to your guidance and advice, Thanks in advance.

 

[Paul.M]

What are the new circuit you need to supply and at what load?

 

[Norn Iron]

Hi Paul there is a Ring main for a Kitchen area complete with a fridge, washing machine, dishwasher, and waste disposal unit. There is also a Hob being installed was going to put it on its own supply, an undersink water heater, There are 2 more ring mains for 14 sockets for Computers etc, possibly 3 smal electric fan heaters (overdoor)and 2 handryers (optional)

 

[amlu]

install a single phase unit, move smaller loads (lights, alarm etc) in there, should give you more space on the 3 phase board.
do an estimate of the loads and split them between 3 available phases not to cause imbalance.

 

[Norn Iron]

Would I also be able to drop the tails to 25mm or would I have to get a cutting of 35mm SWA to piggyback off the chosen Phase?

 

[davesparks]

Unless that main switch has been designed to connect two conductors then you should not be connecting two conductors to it.

 

[Norn Iron]

What do you suggest I do then Dave?

 

[davesparks]

What do you suggest I do then Dave?

Without seeing the installation or knowing a lot more about the installation I can't really suggest much.
What is the submain fused at?
What is the existing average and maximum demand on this submain? Is this measured or calculated?
Does it have the capacity to feed your new circuits?
What would be the consequences of a fault on one of the new circuits taking out all of the new circuits?
Can the new circuits be spread over three phases or would they be better all on the same phase?
What impact will the new circuits have on the phase balance if they do go on one phase only?
Does the existing submain have a reduced csa neutral? Will your new circuits have an effect on this of it does?

 

[stevey1983]

Depending on the make you might be able to fit 100A terminal blocks on a free way and feed your new DB. Such as these http://www.cef.co.uk/catalogue/products/4080524-100a-1-pole-terminal-block

 

[edexlab]

Another option not mentioned depending on load/capacity etc is to move existing circuits into a new board as above (amlu) and use the new spare way freed up by this to feed the sub board from an appropriately rated Mcb

 

[Darkwood]

Another option not mentioned depending on load/capacity etc is to move existing circuits into a new board as above (amlu) and use the new spare way freed up by this to feed the sub board from an appropriately rated Mcb

This would be poor design, feeding a submain of an mcb would render little to no disrimination between the possible 40 - 63amp OCPD and the circuits in the new board a nightmare if you lose all your computers because of a faulty element in a kettle on a different circuit.

You should not feed submains mcb boards off a front end mcb, especially in the OP's set-up.

 

[edexlab]

Fair point !
I was just thinking really about a method of connection for tails , rather than doubling up at the main terminals.

 

[VoltzElectrical]

Would it be preferable to 'upgrade' the 16 way board to one that can handle the new capacity required (load requirements withstanding)? It may be better to do it this way rather than increase capacity by adding on in other ways (no pun intended)!