Advice required on domestic wiring to an outbuilding

[freedomrun]

I am looking at doing some work on a domestic install (TN-C-S, Fuses to BS3036) the property is a flat above a shop and it has an outbuilding in the back yard (10m from property) connected to the Flat's electrical installation. The ring main final is on a BS3036 30A fuse, 2.5 T&E - in the past somebody has taken a point on the ring (socket outlet) removed the accesssory and put this part of the ring in to another CU to act as a DP isolator with two further BS3036 fuses, a 5A for an outside security light & two internal lights + a 15A to supply a Radial cct comprising of a 30ma RCD unit to a JB then SWA to the outbulding then another isolator then off to a double 13A Socket outlet. I measured the Zs at this point and it is 1.93 Ohms, the RCD operation is compliant, but the way this has been put together can't be compliant work? Therfore - I'm gonna replace the CU at the meter head, i am thinking that i should remove this second CU acting as an isolator for the outbuilding and run a new circuit from the new CU that i intend to fit to the JB. Then i'm gonna put a Garage CU with 30ma RCD in the outbuilding to replace the isolator in there, then i can add lighting and S/O. Is my thinking on this correct or have i overlooked something, any advice would be much appreciated.

Two additional issues, the main protective bonding conductors to Gas & water are not connected to the MET in the Flat, also one lighting cct has no cpc - i have asked the question about these in an additional post - advice on this would be much appreciated also. Thanks.

 

[Deleted member 26818]

Whilst not conventional, the CU on the RFC is not IMHO a problem.
The combined rating of the two fuses are the same as the rating for BS1363 double sockets.
The Zs appears to be well within the limits for the 15A BS3036 fuse, and you say the RCD protecting the double 13A Socket outlet functions correctly.
What is it about the set up that you believe doesn't comply?

 

[freedomrun]

Could you let me know where i can find the combined rating for these BS3036 fuses being the same as the rating for BS1363 double sockets - where is the description or chart / table that describes this please? I'm looking at changing the CU at the meter head for a 17th ed compliant one, do you think i should change this set up supplying the outbuilding and some lighting from this isolator to a 'garage type' CU with incoporated RCD and MCB's or leave as is as it tests as safe, but just an odd way (obviously diy way) of going about it.

 

[Deleted member 26818]

What's the combined rating of the two BS3036 fuses?
What's the minimum rating for BS1363 double sockets?

 

[Deleted member 26818]

Apart from not being compliant with BS 7671.

Ring finals are only allowed to serve BS 1363 accessories - see 433.1.5.

Regulation 433.1.5 States: Accessories to BS 1363 may be supplied through a RFC.....
There is nothig in BS7671 that states RFCs must utilise BS 1363 accessories.

 

[freedomrun]

Thanks for this - exactly what i was looking for some clarification on. This CU used as a DP Isolator with BS3036 fuses off the Ring Main is really just a big Fused connection unit i suppose & if i treat this addition to the RFC as a FCU, then it would comply and my Zs is good at the end of the cct for the BS3036 fuse (fuses) used. Any other advice on this please.

 

[Deleted member 26818]

Thanks for this - exactly what i was looking for some clarification on. This CU used as a DP Isolator with BS3036 fuses off the Ring Main is really just a big Fused connection unit i suppose & if i treat this addition to the RFC as a FCU, then it would comply and my Zs is good at the end of the cct for the BS3036 fuse (fuses) used. Any other advice on this please.

Yes this would be my take on the situation, unconventional but otherwise well within the scope of the Regulations.
Obviously, that is only my opinion, others may well disagree.

 

[Des 56]

Sod the ring final,just give me the cash

 

[telectrix]

it also says in pubs " NO SMOKING ALLOWED ". does that mean you are allowed not to smoke, but you can smoke if you want to?

 

[Deleted member 26818]

100% AAF.

"Accessories to BS 1363 may be supplied..." means that they may also not be supplied by a ring final.

It does not mean that RFCs can be used to supply other things.

Some analogies:

"The winner of the competition may choose a cash prize" Does not mean that a cash prize could also be chosen by someone who is not a winner.

"If you have a full driving licence you may drive on motorways". Does not mean that someone without a full licence may also drive on motorways.

It's basic English...

I suggest you re-think your understanding of the phrase basic english.
Neither the definition of a RFC in Part 2, or Regulation 433.1.5 indicate that RFCs are only permitted to use accessories to BS1363.
Here is the definition from Part 2: "Ring final circuit. A final circuit arranged in the form of a ring and connected to a single point of supply."
If the definition instead stated: 'Ring final circuit. A final circuit utilising accessories to BS1363 arranged in the form of a ring and connected to a single point of supply.'
Or if Regulation 433.1.5 Stated: 'Only accessories to BS1363 may be supplied through a RFC.'
Then I would agree with you interpretation. However neither the definition, or Regulation 433.1.5 indicate that RFCs are only use accessories to BS1363, I disagree with your interpretation.

 

[Deleted member 26818]

I don't see that the use of a CU in this instance, would be any different to using two FCUs.
A double socket rated at 20A has been replaced with a CU that has fuses with a combined rating of 20A.
Other than your assertations that it doesn't comply with the Regulations, what problems do you believe exist?
Is there likely to be an overcurrent which will cause damage to either the accessories or the conductors in the event of a fault or in normal use?

 

[freedomrun]

I'm starting to wonder now if should do either of the following. 1, replace this CU conected to the RFC with combined rating of 20A with two 13A FCU (one for the outside secuirity light and the other for the outbuilding). 2, replace this second CU with a distribution circuit back to the new CU i'm gonna install in the property and put a gargage CU in the outbuilding. Any thoughts on this, of course the second option is more expensive - some may consider using FCU to supply a couple of sockets and a light in an outbuilding rough, but would comply and would be the cheaper option. Or i could leave as is as the opinion seems to be that the CU now in situ with combined rating of 20A on BS3036 fuses off a point on the RFC (protected by BS3036 30A fuse) also complies.