Pick Ya Brains

[Steve]

RF, what were the 3 phase circuits for again? i seem to remember you telling us before. and what sort of premises was this?

RCBOs are just an MCB and RCD combined. The tails go to neutral, and theres sometimes one for earth too.

 

[Spark123]

Theres also one of the old type RCBOs in there 3&4 modules up from the other four.

 

[JohnD]

RCBOs are a wonderful device provide the overcurrent/short-circuit protection of an MCB with the earth leakage protection of an RCD. as you see from the pic, the Merlin Gerin (and most other brands) latest version will fit into the same position as an MCB, although they are taller.

They can mostly be fitted into ordinary DBs or CUs and are much more convenient than a split-load configuration, since an earth fault on one circuit will not inconvenience users of other circuits.

they are however more expensive.

MEM has a particularly cunning design of a snap-on pod containing the RCD that can be fitted to any of their SP MCBs for Memera and Memshield 2 (except the AD range). Some of us know how to take these pods off and reassemble them on a different MCB when requirements change.

 

[RF Lighting]

Blimey, what a lot of questions.

The installation was in a bookbinding and printing factory.

The TP circuits fed overhead 63A busbar trunking, into which all the machines are connected.

I was installing the RCBOs, that is why the earth leads are not connected either (for the eagle eyed viewer)

The outgoing TP wires were only 16.0mm².
The MCBs were feeding RCDs in a seperate enclosure on the factory floor (for easy resetting should one trip), then onto the busbar trunking.

The incomming tails were 95.0mm², and bonding to water, gas and steel were all 70mm²

Here is the cutout and you can just see the CT meter lurking on the right of the picture.

 

[Spark123]

What I thought was quite good on the old ones was you could differentiate between the MCB tripping and the RCD tripping, with the old merlin, mk etc they had both a black and a white switch, iirc the black one only tripped for MCB and both black and white for RCD. On the old square D qoe range the switch would trip but not go all the way down for earth leakage, you had to push it down before resetting it. Nowadays they seem to like to go for the single module ones, although imo it is a backward step that it is no longer clear what has caused it to trip.

 

[DanTheMainsMAn]

is the big box on the left the db board and whats on the right what you canny see

 

[RF Lighting]

The big grey box on the left of the picture is the DNOs imcomming supply. The sandy coloured box on the right (a bit out of view) is the dist. board I posted front on nude.

 

[DanTheMainsMAn]

last thing if you use full load on 1 db board and if you add anymore main trip blows what do you do

 

[Steve]

The big grey box on the left of the picture is the DNOs imcomming supply. The sandy coloured box on the right (a bit out of view) is the dist. board I posted front on nude.

oooh matron.

OOI, and at risk of looking stupid, what is a CT meter?

and are you saying that those tails at the top of the picture are 95mm²? i have never seen such a beast, but i wouldnt say they were any bigger than 35mm², but then again, the equipment could be deceptively large . . .

 

[DanTheMainsMAn]

crafty if say you have 125A Supply and you are continuosly using it what do you do if you want more CU's

 

[RF Lighting]

The power is too large for a standard meter so each outgoing phase passes through a current transformer (CT). The power induced into the CT is then measured by the meter, working out how much power is used.

The tails are 95mm²

You can just see my radio sat on top of the cutout at the left hand side.

 

[DanTheMainsMAn]

how do you post PICs

 

[Steve]

crafty if say you have 125A Supply and you are continuosly using it what do you do if you want more CU's

most supplies are over-specced. Lets say you have a shop, like mine, with a 3 phase board (the original one i posted). the load on this board is not 300A. its actually less than 63A per phase (average i reckon is about 30A per phase). So it was ok to add the second DB to the left, since we have a 100A 3 phase supply. MOST supplies aren't fully loaded, this is why you see extra DBs tacked on over the years the supply in our shop is only 3 years old so it was specced for expansion. Before, it was a 63A single phase - before our company took over it was a dusty little backstreet shop.

if you have maxxed out the supply, you need an upgrade. 3 phase 300A is the largest commonly available i believe, before you need your own transformer.

post pics here: http://www.imageshack.us

 

[DanTheMainsMAn]

here are my CU's that i have done at my house and ive rewired using square

http://img257.imageshack.us/my.php?image=picture001vv1.jpg

 

[DanTheMainsMAn]

is it any good have i done a good job