A situation that I can't found an answer to ... There is a DP isolator before the main CU (which has an isolator). This CU will be fitted with a 50A MCB feeding a 20m sub-main to a second CU elsewhere in the house. There are therefore 3 ways to isolate the sub-main. Is there a requirement for the second CU (at the end of the sub-main) to have an integral isolator switch?
I've no idea about the regulatory position, but I'd certainly fit an isolating switch unless there was an important reason (such has not having the extra 2" where I wanted to put the CU) not to. If just for convenience.
It will have an integral main switch.
If it doesn't have a main switch it's not a consumer unit, it's a distribution board.
Owain
Fair point, but this will be a custom confing of RCBOs, rather than being a standard, pre-configured, box.
If its a CU and not a distribution board, then you will need a main switch. There are two main reasons that spring to mind:
1) Expectation - from a user's PoV they expect there to be a main switch present. A guest / future owner etc will not have the background knowledge to know its a sub CU fed from another, and might be looking for a way of killing the power in an emergency. 2) Practical, you need some way to terminate the live of your incoming sub main on the the live bus bar(s) of the CU. The live bus bar has no terminals of its own, and relies on those of the main switch to connect the incoming feed to the bus bar.
Squidging the wire under the busbar in one of the MCB terminals would be really rough wouldn't it...
Owain
I had been wondering the same question. And, now that you mention it, your point 2) is pretty conclusive. It would be a shame for an amateur such as myself to discover one had insufficient ways to fit a main switch and and no other way of putting the thing together *after* ordering the parts!
I thought that, in a domestic situation, the terms "distribution board" and "CU" were interchangeable ...
It's quite a large house and the main DP isolator (after the meter) will be both more easily accessed than this sub-board and will isolate the whole electrical system, rather than just the one segment.
I'd planned to terminate the cable in crimped tags, bolted onto the busbar.
It's only a question of spec'ing a slightly larger CU (12 way rather than 10 way) so I'll keep an isolator. Thanks, as always, for taking the time.
The next question is which manufacturer: Hager, MK, BG, Wylex ... ? At the moment I'm leaning towards Hager or MK because of space for RCBOs and ease of getting parts. Are there any good deals out there?
I'm imagining someone discovering the cable is too thick to do that & splitting the strands over 3 MCBs :)
NT
You have never fitted a Schneider Easy 9 CU then.
You have to step back a bit and think things through.
You fit the DB and depart the area.
Bonzo comes along later and wants another breaker, feed whatever.
Bonzo is too bone idle to find the power source, or just forgets after perusing the breakers for something looking like a power switch.
Bonzo live connects a cable and fries himself.
You then have to ask yourself the following:-
Did I do everything reasonable to ensure Bonzo's and other users safety.
Have I a lot of money to defend the decision.
Will I sleep soundly even if my work is found to be legal and "safe".
DB's are normally supplied with switches. I have come across "isolate Elsewhere" units in industry, but they are a rarity and tight lockoff controls are employed.
As far as I'm concerned it's a no brainer.
AB
If you want cheaper then CPC do ProElec RCBOs for about £18 and a main switch CU with 19 spare ways for £50.
I have fitted ProElec and was happy with it.
And the mainswitch need not be part of the board. Although personally it would IMHO be silly not to buy one without a main switch.
Any views pl. on the Contactum range which I saw from TLC's email last week they are doing for £16 incl VAT?
I would say avoid.
Now I had forgotten about TLC when looking for prices.
TLC are doing the BG reduced height RCBOs for £15.72
I have never had a problem with BG CUs.
Sweet...
ta
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