3 phase in domestic CU?

[virgilns]

Hi - I have 3 phase cabling run into my house but just SP meter feeding the current (old) CU.

I need or get 3phase to the garage and run two CUs in the house (one for ground floor and one for 1st and 2nd floors)

The question is (as I'm limited to under cupboard space) can I use TP isolator and MCBs in a domestic CU then feed the two 'house' CUs and armoured cable for the garage from this?

Wylex NH metal clad domestic CU's are the perfect size and a 4pole 415v isolator fits exactly as a 2pole does. I'd need a TP MCB for the garage and two SP MCBs for the house sub mains.

I'd have to wire the MCBs directly from the switched isolator (max two 16mm cables) as there's no phase bus bars...

Is this allowed or do I HAVE to use a TP dist board? or is there another way (minimal space used)

thanks,

Virgil

 

[malcolmsanford]

Welcome to the forum

Unfortunately before you do anything you need to contact your supplier to install a 3 phase meter for you. If you don't then your in danger of stealing electricity because your plan use of the other 2 phases would not be metered.

Can I ask though what your going to have running off these 2 extra phases ?

 

[cobrauk]

you will have to install a meter and a 3 phase distribution board 4 x 3phase ways being the minimum size you can get (that's 12 single phase ways)

 

[malcolmsanford]

Cobra why can't the OP use a 3 way Ryefield board and then take his single phases to his CUs.

In fact if he wanted he could go into 3 x single phase switch fuses and then go to his CUs, he doesn't have to get a 12 way board

 

[cobrauk]

He said he needed 3 phase at the garage ?

he could also leave the 2 c/units as they are and just have a 3 phase switch fuse if he wanted ?

 

[virgilns]

I've got the supplier coming in to swap the meter for a three phase one on the 18th...cables are already run in and have three 100amp fuses on the board...don't worry - no nicking of power here!

i don't need three phase in the house, but makes license to use it when its there. Especially as I want two house boards anyway.

i NEED three phase in the garage to run a three phase lathe...its currently running on an inverter which isn't good enough. And i'll run the third phase as the single phase in the garage for sockets.

The main question is can i use a domestic board (wylex nh metal clad) for the three phase isolator and MCBs?
Does the Ryefield 3 way board allow the MCBs to be mounted? looks just like the 100amp fuses to me??

Thanks for the input so far

 

[cobrauk]

The Ryefield 3 is a 3 Way Ryefield Board 100A | RY3100 | Sparks Direct is just a 3phase switch fuse, it is not a distribution board that why I said to fit a 3 phase distribution board, if you already have 2 single phase con units installed then it will do the job,

 

[virgilns]

...which makes sense. It's the 3 phase dist board that's giving me the headache...they're all BIG...i know they're designed to be for industry, but frustrating that I can't find a physically small TP board...

 

[cobrauk]

No they do not make anything small, the smallest is the MGBN4 Merlin Gerin that's a 4 TP way that gives you 12 sp ways and thats 484 high x 470 wide , but like I said you don't need to have that if you already have two con/units you just need to have 3 mains blocks to connect to the meter then a TP switch fuse to feed your garage.

 

[Deleted member 26818]

Do you have room for a couple of DP Henly blocks?
Take the three phases and neutral to the two Henly blocks, then feed whatever you need from them.
TP&N to the garage, single phase to the existing CU, and another single phase to the new CU.

 

[Engineer54]

No they do not make anything small, the smallest is the MGBN4 Merlin Gerin that's a 4 TP way that gives you 12 sp ways and thats 484 high x 470 wide , but like I said you don't need to have that if you already have two con/units you just need to have 3 mains blocks to connect to the meter then a TP switch fuse to feed your garage.

That's not completely correct!!

You can use a pretty much standard domestic Schneider Consumer unit and use a 3 pole isolator(main switch) and a compact insulated 3 phase bus-bar. (every way is on a different phase)
If you look and study the Schneider catalogue, you will see there many configurations you can make up with the various components available!!

 

[virgilns]

Thanks engineer54. Unfortunately by the time I saw your reply I'd bought a couple of 3phase wylex boards. 4way for the house and 6 way for the garage. All installed and working now