Linking Tails From Main Switch.

[Barx]

What's the low down on supplying a new consumer by linking from the tails on an existing consumer unit?

For some reason I have in my mind that it is a big No No, but I could well have created the myth when My brain was fried.

On the PV Installs I'm on at moment, I am stuck between a rock and a hard place. We have to install a new 2 way DB for the PV install; the contractor says to install in the meter box, which we all know we shouldn't do but the existing CU is just inside the front door (high level) with the tails concealed within the wall / cavity. There is another team doing these jobs too and sometimes they are installing the new CU adjacent the existing and linking the tails. Is this OK. If it is then I will do it as well were suits. It would definitely save time on some of them as the conduit runs are a nightmare do to porch / stone window sill and lintels plus the odd sky dish or scaffold bar to top it off. 

Thanks.

 

[Jono Pashley]

Long as both cables can be terminated securely, i wouldnt see any problem with it. Done it myself a couple of times where tails couldnt be split without major disruption.

 

[NozSpark]

IMHO I would doubt that the main switch terminals would be rated to take 2 x 25mm tails

 

[ProDave]

I assumed when he said "linking the tails" he meant with henley blocks, not two tails into one main switch?

 

[NozSpark]

I assumed when he said "linking the tails" he meant with henley blocks, not two tails into one main switch?

Oh, right... He mean't splitting the tails.... Done that plenty of times, but you should still have a single switch to isolate the entire installation (easily done with a REC4, no henly blocks needed )

 

[Barx]

No not splitting with henley blocks etc. I meant sticking 2 x tails in one main switch. They are 16mm btw.

The way we are currently doing it is with henley block in the meter cupboard but if doubling up in the main switch is seen as ok then would be easier. Not done it up to press as like I mentioned above, it seems wrong to me and if I'm not sure on something and cannot get a answer there and then, I play safe.

 

[Wilpickard]

Linking tails in the main switch would mean you wouldn't have 1 switch for the whole installation

 

[Nicky Tesla]

what amperage do those pvs produce.    would it be feeding back as a negative amperage or am i thinking under the wrong tree.?

 

[Jono Pashley]

Max of 16A on a normal domestic.

 

[Barx]

Linking tails in the main switch would mean you wouldn't have 1 switch for the whole installation

You wouldn't if you had 2 consumer units with tails connected with a henley block.

 

[Barx]

what amperage do those pvs produce.    would it be feeding back as a negative amperage or am i thinking under the wrong tree.?

Yes, Max. 16A and although they produce, I have read that the system is still classed as a load. Though the internet is not always right :innocent

 

[NozSpark]

You wouldn't if you had 2 consumer units with tails connected with a henley block.

But you should still have a single point of isolation

 

[Barx]

But you should still have a single point of isolation

Pull the bullet or kick the meter in the nuts. :slap

but in all seriousness, how would this be satisfied if  the DNO hasn't already fitted a DPI?

 

[Wilpickard]

I'm not involved with PV at all, but couldn't you run a short sub from the original board to a 2 way cu?

 

[Barx]

I'm not involved with PV at all, but couldn't you run a short sub from the original board to a 2 way cu?

Not really, the original CU's have a RCD main switch, also most of the existing cu's are small and full with a DIN mounted doorbell transformer taking up any spare room.

 

[Wilpickard]

I see, some one on here said you could use a REC4 without a Henley block but I'm still confused how you'd split the supply.

I know it's a 4 pole isolator but surely you'd have to link the feed terminals out?

 

[wozz]

In response to the OP, hav done it where no other option available, not unduly worried by it although decent labelling goes a long way.

as for single point of isolation how often do you see that on a E7 install?

 

[Wilpickard]

as for single point of isolation how often do you see that on a E7 install?

That's a very good point but regs are regs!

 

[NozSpark]

I see, some one on here said you could use a REC4 without a Henley block but I'm still confused how you'd split the supply.

I know it's a 4 pole isolator but surely you'd have to link the feed terminals out?

Yeh, link two poles together with bus bar!

In fact I just fitted one the other week on a 3ph job,, it even came with links, I obviously didn't use them

 

[Wilpickard]

Thanks nozspark, quite simple really! You actually join 2 pairs of poles out though I guess, so you'd have a pair for neutrals and a pair for lines