Am I being led up the garden path???

[--tom]

This is excellent stuff for learning.
Q1 Given that its a taped joint then what kind of junction box would you use?
Q2 What is the purpose of the 2no "Henley blocks"?
Q3 How would you go about rearranging the CU to take an RCD and say two extra breakers
Q4 Am i right in thinking that there are 7no modules present?

 

[plugwash]

if thae cable isn't twin and earth especially considering how short those stubs are i would run a new cable to the first accessory on the cuircuit

i don't personally think there is enoguh slack to do a decent join there especially if the existing cable is something unusual

those henly blocks don't seem to be serving much of a perpose atm they are used for splitting tails but atm you only have one CU connected

that CU is a bit small. if it has two neutral bars you could fit a split load kit but that would leave you with no space at all

given the narrow space i would keep the existing CU for non-rcd cuircuits and fit a seperate rcd CU below the fuseboard

here is the method for doing that (though many would say this was not a diy job and pulling the service fuse does require care)

turn off the CU main switch to stop current flow
pull the service fuse taking care to only touch plastic parts
remove the existing outgoing tails from the henly blocks

rewire with fresh 25mm tails from the henly bloacks to the existing CU and to a new RCD only CU

disconnect the existing earth running to the CU

fit an 8 terminal main earth terminal to the fuseboard and take a 16mm earth from the clamp on the service cable to it

take 16mm earths from the main earth terminal to both CUs
take 10mm earths from the main earth terminal to the gas and water pipes where they enter the house

 

[--tom]

plugwash, thanks for your detailed reply and patience.

If you had to make a re- connection at the taped cable position, how would you do it?

 

[plugwash]

it all depends on a copuple of things

1: what type of cable it is (it sure as hell doesn't look like twin and earth to me is it flex or something)
2: how much slack there is

personally i think those runs probablly need to be replaced because there probablly isn't enough slack to do adenent joint and if they are flex then it shouldn't be being used in fixed wiring anyway

if it is pyro then you will have to replace it because you won't have the tools or experiance to terminate pyro

 

[ban-all-sheds]

Cheers guys for your thoughts, just a few questions / clarifications...

Cant see any bonding cables leaving the board....

What are these?

The incoming service pipes (gas, water), assuming they are metal, should have a connection to earth. The earth cable that comes from direct from your incoming supply (BTW - is that clamp an approved method of connection?) should go to a main earth terminal (MET). The MET should then be connected to the service pipes and to the earth block in the CU.

No RCD for the sockets....

What are the benefits and why should these been in place as opposed to what is there already?

An MCB provides protection against overload, either simply drawing too much current, or a short circuit.

However, there is another type of fault that an MCB will not protect against. If a person touches something live, e.g. a damaged cable or a faulty appliance and completes a circuit to earth, then the amount of current that will flow through them is more than enough to kill, but nowhere near enough to trip even the smallest MCB to cut off the supply.

An RCD monitors the currents flowing in the live and neutral conductors, so if somewhere in the circuit some current is leaking to earth, e.g. through a person, it will detect that there is a difference between the current flowing out on one conductor and back on the other, and it will trip.

The idea is that the level, and speed, with which it trips are such that injury is prevented. The normal RCD rating, as found in CUs and individual RCD sockets is 30mA, and an RCD is supposed to trip at that level of imbalance in 300ms, although typically the time is around 100ms.

In a CU, the RCD will protect a number of circuits - either some or all depending on whether the board is a split-load or not.

You can get devices which combine the functions of both an RCD and an MCB, i.e. provide overload and fault protection to a single circuit - they are used in place of an MCB, and are called RCBOs (Residual Current Breaker with Overload).

Sockets which can reasonably be expected to supply equipment outdoors should have RCD protection - that's generally interpreted to mean those on the ground floor, and, obviously, any actually outside, or in garages, sheds etc. However, it is also generally accepted that it's a useful safety measure to have all sockets with RCD protection.

The reason for not having everything on an RCD is that there are some circuits where the risk of contact is very low (e.g. lighting) and the inconvenience of losing the circuit due to an earth fault somewhere else is high (e.g. lighting) or dangerous (e.g. fire & smoke alarms).

In an ideal world your CU wouldn't have an RCD in it - you'd use RCBOs for each individual circuit that you wanted protected, but that gets expensive...

http://www.westernautomation.com/pages/demystify.htm
http://www.simonstutorials.com/downloads/rcdpresentation.pdf
http://www.memonline.com/guide06.html

those taped up joints look like they may be to pyro although it is hard to tell does the outer of those short stubs of cable appear to be copper?

What do u mean by this?

Pyro is sparky-speak for MICC - Mineral Insulated Copper Clad cable (sometimes called MICS - copper sheathed). It has copper inner conductors that are insulated with a mineral compound. The cable has an outer sheath of copper and can be further protected against the atmosphere by a outer plastic sheath.

1 - LSF oversheath
2 - copper sheath
3 - magnesium oxide insulation
4 - copper conductors

It's expensive to purchase and specialist skills are needed to install it. However, it is long lived, is smaller that an equivalent SWA cable and importantly is fire proof. Hence it can be used to serve emergency services where the cable is required to remain in use during fire conditions, and hence the nickname "pyro".

http://www.micable.com/mic05.html


PS - what's with the bundle of cables running down on the right, that have not come from the CU, and what are all the brown ones?

 

[Adam_151]

what are all the brown ones?

Look like tv aerial cables to me

 

[ban-all-sheds]

Yo - that's what they look like to me too...

 

[IR8Matt]

Thanks for the feedback.

Yep the brown cables are co-ax for the TV, nothing to worry about there (I hope).

Haven't really looked at what type of cables those are going into the taped joins, not really that keen to untape them either and find out. Might try and take a closer look this evening.