Can you take 2 phases to a consumer unit?

Gigsy · May 15, 2018

Hi,

I am training to become and electrician, I have passed my C&G level 2 exams. I am working as an electrical improver.

I came across a consumer unit today, which has two main switches and two phases L2 and L3 supplying it.

Does this board comply with regs?

Can you take 2 phases to a consumer unit?

Risteard · May 15, 2018

Is it rated for 400V and 25kA?

PEG · May 15, 2018

Hi,is there a "handy" single point of isolation?

Gigsy · May 15, 2018

PEG said:
Hi,is there a "handy" single point of isolation?

There is a single point of isolation at the main DB.

Gigsy · May 15, 2018

Risteard said:
Is it rated for 400V and 25kA?

It is just a consumer unit. A metal box cant be rated for 400v.
The switches are rated correctly for the voltage and current they are being used for.
There is a 400v warning sticker on it.

The Ghost · May 15, 2018

Oh actually I can just about see it now. I mean the phase colours.

Gavin John Hyde · May 15, 2018

The cable dressing police will be along in a moment to comment on the untidy cables....

Gigsy · May 15, 2018

Vortigern said:
Oh actually I can just about see it now.

The right switch they are using a black conductor L2, the left switch they are using a grey conductor L3. Both conductors are identified as line conductors , by brown tape?

Octopus · May 15, 2018

Gigsy said:
There is a single point of isolation at the main DB.

Which is where?

Risteard · May 15, 2018

Gigsy said:
It is just a consumer unit. A metal box cant be rated for 400v.

An enclosure and assembly absolutely can be rated for 400V or not as the case may be.

The Ghost · May 15, 2018

Ok well I am thinking why are there three neutrals on the first block on the right does this mean the neutral will be switched off with the first main switch, it is a bit hard to follow where the three neutrals go.

Risteard · May 15, 2018

Also I notice that 6kA rated devices have been used.

Gigsy · May 15, 2018

Murdoch said:
Which is where?

At the front of the building

buzzlightyear · May 15, 2018

that is not what I call coacher ,wrong board their boy .

westward10 · May 15, 2018

Dual tariff board?

Gigsy · May 15, 2018

T

Risteard said:
An enclosure and assembly absolutely can be rated for 400V or not as the case may be.

There is nothing on the metal box which identifies it as being rated for anything, The switches are rated for 400v. But they are only subject to 230v each?
It is a normal domestic consumer unit?

Gigsy · May 15, 2018

T

Risteard said:
An enclosure and assembly absolutely can be rated for 400V or not as the case may be.

There is nothing on the metal box which identifies it as being rated for anything, The switches are rated for 400v. But they are only subject to 230v each?
It is a normal domestic consumer unit?

Octopus · May 15, 2018

Gigsy said:
At the front of the building

Hum .......

Gigsy · May 15, 2018

Risteard said:
An enclosure and assembly absolutely can be rated for 400V or not as the case may be.

The switches are rated 230v/400v

Gigsy · May 15, 2018

Vortigern said:
Ok well I am thinking why are there three neutrals on the first block on the right does this mean the neutral will be switched off with the first main switch, it is a bit hard to follow where the three neutrals go.

Incoming neutral goes to 1st neutral bar.
Then linked from there to each switch

Gigsy · May 15, 2018

westward10 said:
Dual tariff board?

Not dual tariff

davesparks · May 15, 2018

Gigsy said:
T

There is nothing on the metal box which identifies it as being rated for anything, The switches are rated for 400v. But they are only subject to 230v each?
It is a normal domestic consumer unit?

That’s unusual, those contactum boards always used to have a label on the lid identifying the BS-EN standard they are built to, this standard will give the voltage and PSCC they are rated to. Maybe the sticker has fallen off?

The Ghost · May 15, 2018

Gigsy said:
Incoming neutral

Ah ok can see that now it makes sense.

Gigsy · May 15, 2018

davesparks said:
That’s unusual, those contactum boards always used to have a label on the lid identifying the BS-EN standard they are built to, this standard will give the voltage and PSCC they are rated to. Maybe the sticker has fallen off?

I will take a look on the lid tomorrow, thank you.

Gigsy · May 15, 2018

davesparks said:
That’s unusual, those contactum boards always used to have a label on the lid identifying the BS-EN standard they are built to, this standard will give the voltage and PSCC they are rated to. Maybe the sticker has fallen off?

I don't really understand this statement.

The metal box is just a metal box. The accessories inside the box ie. the switch, the RCD's and the MCB's are all marked with BS-EN numbers and breaking capacity numbers. Each accessory is only at a potential difference of 230v. I can do a PFC and PSCC test on the installation, but I know for a fact the tests will not exceed 6kA. Why do the accessories need to be rated at 25kA?

Midwest · May 15, 2018

I thought if you were going to use more than one phase, you used three to balance the load? So why would you use a domestic CU designed for a typical single phase domestic property, when you could use a properly designed three phase board, intended for that use?

PEG · May 15, 2018

Gigsy said:
I don't really understand this statement.

The metal box is just a metal box. The accessories inside the box ie. the switch, the RCD's and the MCB's are all marked with BS-EN numbers and breaking capacity numbers. Each accessory is only at a potential difference of 230v. I can do a PFC and PSCC test on the installation, but I know for a fact the tests will not exceed 6kA. Why do the accessories need to be rated at 25kA?

Not strictly true,as someone has had to assess,test,approve and certify that "box".

A test of this,is how many DB's with the equipment listed,have you seen,with a home made enclosure?

Spoon · May 15, 2018

Gigsy said:
I came across a consumer unit today,

I don't think he has wired this CU.

Gigsy · May 16, 2018

Midwest said:
I thought if you were going to use more than one phase, you used three to balance the load? So why would you use a domestic CU designed for a typical single phase domestic property, when you could use a properly designed three phase board, intended for that use?

The 3rd phase (L1) goes to a consumer unit downstairs. I think they have balanced the load.

Gigsy · May 16, 2018

PEG said:
Not strictly true,as someone has had to assess,test,approve and certify that "box".

A test of this,is how many DB's with the equipment listed,have you seen,with a home made enclosure?

It is not a home made enclosure, It is made by contactum.
The box has a 400v sticker on it, so anybody who wishes to service it knows the potential voltage.

Pete999 · May 16, 2018

Gigsy said:
Hi,

I am training to become and electrician, I have passed my C&G level 2 exams. I am working as an electrical improver.

I came across a consumer unit today, which has two main switches and two phases L2 and L3 supplying it.
I can see where you are coming from Gigsy, might seem a daft question but have you actually confirmed that the voltage between L2 and L3 is 4oo volts, I only ask because it seems an odd installation to me, probably barking up the wrong tree, but I thought I would ask just to be sure.

Does this board comply with regs?

Can you take 2 phases to a consumer unit?

View attachment 42245

Wilko · May 16, 2018

Hi Gigsy, been keeping busy I see !
These boards are intended by manufacturers to be used for single phase. For more than one phase a 3 phase board should be used, in my humble opinion. I would drop an email to manufacturer's tech dept for their view.

Octopus · May 16, 2018

Spoon said:
I don't think he has wired this CU.

Are you SO sure?

He seems to be defending its use rather than learning the reasons its not really suitable.

I would have said that this "box" needs a 3P isolator, in it, or at the very least adjacent to it.

telectrix · May 16, 2018

not sure about regs. but I'd not be comfortable with it.(even if the wiring was not a rat's nest).

Pete999 · May 16, 2018

Gigsy said:
Hi,

I am training to become and electrician, I have passed my C&G level 2 exams. I am working as an electrical improver.

I came across a consumer unit today, which has two main switches and two phases L2 and L3 supplying it.
I can see where you are coming from Gigsy, might seem a daft question but have you actually confirmed that the voltage between L2 and L3 is 4oo volts, I only ask because it seems an odd installation to me, probably barking up the wrong tree, but I thought I would ask just to be sure.

Does this board comply with regs?

Can you take 2 phases to a consumer unit?

View attachment 42245

Spoon · May 16, 2018

Murdoch said:
Are you SO sure?
He seems to be defending its use rather than learning the reasons its not really suitable.

No mate, I'm not sure. Just quoted what the OP stated in his first post. Lest ask...

Gigsy said:
I came across a consumer unit today

@Gigsy . Did you wire up this CU or do any changes to it?

Pete999 · May 16, 2018

Don't know if my last post went anywhere Gigsy, may seem a daft question, and I'm only asking because I'm not sure what I'm looking at, but have you canfirmedthat there are 2 phases present, by testing the Voltage between L2 and L3

Midwest · May 16, 2018

Gigsy said:
The 3rd phase (L1) goes to a consumer unit downstairs. I think they have balanced the load.

Long time since I did any 3 phase stuff, but that doesn't appear to be a very good design. Either of those two DB's could be altered over time, and without in depth knowledge of the installation, one could be significantly altered in preference to the other. Unlikely to happen in a single dedicated 3P DB, IMO.

Corbs · May 16, 2018

Anyone else notice the screws arnt done up (top left and right) someone could lift it up and pull it off the wall

westward10 · May 16, 2018

Corbs said:
Anyone else notice the screws arnt done up (top left and right) someone could lift it up and pull it off the wall

Its a flexible board

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