In a similar way to George, how can a second CU be connected to the main one? Straight off the (load side) main 100A incomer, or from a MCB (appropriately rated of course)? Can the second CU be split load, with a 100A incomer and appropriate RCBO, even though it will never take that much current?
To divide the incoming supply to feed 2 x cu, take your meter tails and connect them into a 'Henley' Splitter block rated at 100A. Take 2 new supply pairs out of this and connect to your 2x CUs. Please yourself as to whether or not you choose split-load or whatever - your choice - your wallet.
Do you need 1 henley block for the phase and 1 for neutral and 1 for earth etc. or does one block provide the necessary terminals to split 0ne pair into two?
The most common is one Henley for L & another for N. There is a double-stacked L & N block. Not a Henley for the Earth. You shouldn't need another block for the earth, if you do then get a MEB, a bare-metal screw terminal block specially for earth connections.
I've seen the advice to use these Henley blocks before, but what is their real advantage over using a spare CB in the main CU.
hi dja Consumer Units (CU) main function is to provide a safe means of distributing the incoming power supply in to individual circuits around the house and provide a means of isolating these circuits from the supply. It is where all the circuits connected are final, that means they do not supply more circuits upstream. In this way individual circuits can be isolated without affecting anything else that might be fed from them and without having to isolate the entire power supply to all circuits. The main reason to split the supply tails is to provide a separate feed to a new CU which can then serve the function described above. If a sub-circuit is taken off the only CU using a spare way then it is not a final circuit but a sub-circuit. Also by doing this you are limiting that sub-circuit to a current rating that is not going to overload the board and you are also creating a dependence on the CU for the sub circuit. So main advantages of splitting tails are: 1. making the supply independent 2. avoiding potential overload of the CU 3. maximising capacity in both CU's Thats my views. Anyone else welcome to chip in RSS
I agree with unphased - and that's just what I did. I used a splitter block (DP) and put an isolator between it and the meter. Then new tails went to existing CU and additional CU elsewhere. I also upgraded the main earth from the meter cabinet, which was 10mm, maybe less! I put a new 16mm earth from the meter cabinet into an 8 way earth terminal block, then 16mm from that to both CUs, and 10mm bonding to pipework as required. Bonded bathroom to earth block with 10mm. Also, the 6 way Henley block has three spare 'ways', so if I really wanted I could fit another three CUs. Highly unlikely though. I used 25mm double insulated tails and 16mm earth throughout. The tails were difficult to bend but I got there eventually!
so am i right in saying that from the meter tails they go through a 100amp isolator onto the henley block then fee both cu with 25mm tails.any one recommend a good 100amp isolator????
I usually use an MK 100 amp main switch, fitted in to a 2 way mounting box. These are nice and small and just big enough to get meter tails into....
I usually use an MK 100 amp main switch, fitted in to a 2 way mounting box. These are nice and small and just big enough to get meter tails into.... I rarely ever see these Isolators, are they specific to particular DNO's or areas?
If you look in the red book, under isolation 537.1.4 It states that a main switch should be provided as near as possible to the origin of the installation, and that it must be double pole. In a normal installation, the switch in the consumer does this, as soon as you fit a second unit, you are effectively removing this switch as the main isolator. So when fitting a second consumer unit, you should always put in a double pole isolator before the henley block. On my last NICEIC visit, i took the inspector to a job where i had fitted a second consumer unit. He mentioned that it is something they are clamping down on now. The other option is to supply the second consumer unit from the first one, which is sometimes possible, depending on the make of the unit.
cannot belive people even read posts which are 5 years old in the first place They need to get a life.
Hello Syholl. It isn't so much a single point of isolation as a failure to recognise that an individual property may have two or more 'installations' - each requiring their own main switch. The actual 'Regulation' that has caused this rift over the years, does not call for a single point of isolation. It merely requires that an installation should have a main switch. The meaning behind this is, to prevent the use of a Dis-Board, having no main switch, being used as a first-line control. This is an industrial issue essentially - but somehow, someway, a domestic wallah became infected with it and the rumour spread like wildwire....
surely the main incoming fuse should be enough protection or is it the matter of fact of isolating the boards without removing this fuse? from a protection point of view the main isolators in the cu's is enough isn't it
Forums
Facebook
Twitter
You Tube
Instagram
Shop