Garage electrics improvement

[Flinstone]

Current setup:
House CU contains all re-wirable fuses. No RCD fitted.

Approx. 8mtrs of 2.5mm T&E cable from house (kitchen) to detached garage, clipped at the top of a 2.5m high wall built between house and garage. The cable is believed to be from a spur on the kitchen circuit and also without an FCU (both these points to be confirmed).

Inside the garage the T&E terminates inside a switched FCU located close to the incoming cable entry which controls one ceiling lamp. Within the FCU too is connected a length of 2.5mm T&E that runs along the garage walls to 2x 2-gang power sockets.

Requirements:
1. Add a new switched FCU to the supply cable spurred inside the kitchen (for protection & limited to 13A).
2. Replace the garage lighting FCU (old, plastic) with a metal version.
3. Disconnect the 2.5mm cable between the FCU and the 2x sockets and discard ALL of it (bc old components, messy wiring, wrong sockets location).
4. Add a new metal 2G socket closer to and below the switched FCU (this will be the ONLY socket in garage).

In summary I would like to keep the same single light, update the switched lighting FCU, and add a new 2G socket to allow for the charging of two mobility scooters simultaneously. There is no intention to have any more sockets.

The house CU (all fuse wire) is at the front of the property and the garage cable's spur point is in the kitchen at the opp end of the property so I prefer not to disturb this arrangement due to a lot of work to gain access under floor, walls, etc.

My primary question is what is the appropriate form of (currently non-existent) RCD protection I should add? Should I :
1. Put in a 2G socket with built in RCD such as this: (£16.29) ?
2. Install a garage CU such as this fitted with this. (£33.55) ?

On the one hand a garage CU is double the cost and several forum comments suggest overkill for simple installation power requirements.

But on the other hand might it be useful to have separate MCBs/isolation within the garage?
It seems good to know too that an RCD would protect everything from the point of entry instead of just at the power socket; assuming RCD protection is advantageous to protect the user with the lighting circuit e.g., if a problem arose in a potentially damp garage with condensation??

Also would a garage CU be appropriate to use in conjunction with a 13A FCU spur in the kitchen?

Hope this makes at least some sense!
Cheers

 

[ericmark]

To comply with regulations RCD FCU or RCD sockets will not comply, wrong BS EN numbers, however not a clue why they are not permitted.

So there is a massive jump between complying with regulations and simply making it safe. Regulations are not law, and the only real problem is with rented property where the law requires an EICR so one is at the whim of the inspector.

I swapped my fuse box for an all RCBO consumer unit, but if you want to penny pinch I would fit a RCD FCU in the main house.

Then whole of garage is protected. But since nothing short of a new CU will comply, if using a scheme member electrician to do the work you may have no option.

 

[Flinstone]

Is that a fact? How do they get sold I wonder?

Not wishing to penny pinch between the two I suggested, just want to know what is reasonable to do under the circumstances

Coincidentally i looked at that same RCD FCU but got put off when I read an answer in the SF Q&A section..

Can this be used to protect a shed and garden socket ? 2.5mm2 armoured cable has been used for supply . Using garden tools and DIY etc
There is no RCD protection in the house . The Fused Spur is from the downstairs ring main.

Manufacturer's Response (Lucecco Technical Team aka British General):
As long as you don't presume that the RCD will protect against every possible fault/accident then yes, you could use this FCU to feed your shed with 13A (3120W / 3.12kW) of power for use by any device(s) in there.
The 13A fuse in it will protect against massive overloads and the RCD against power leaking out of the circuit instead of returning through the Neutral side (potentially because it is exiting through a person), but other faults or accidents may not cause either of these protective measures to cut the power being supplied.

 

[SUNRAY]

Is that a fact? How do they get sold I wonder?

Not wishing to penny pinch between the two I suggested, just want to know what is reasonable to do under the circumstances

Coincidentally i looked at that same RCD FCU but got put off when I read an answer in the SF Q&A section..

Can this be used to protect a shed and garden socket ? 2.5mm2 armoured cable has been used for supply . Using garden tools and DIY etc
There is no RCD protection in the house . The Fused Spur is from the downstairs ring main.

So your objectives are shown in red:

Manufacturer's Response (Lucecco Technical Team aka British General):
As long as you don't presume that the RCD will protect against every possible fault/accident then yes, you could use this FCU to feed your shed with 13A (3120W / 3.12kW) of power for use by any device(s) in there.
The 13A fuse in it will protect against massive overloads and the RCD against power leaking out of the circuit instead of returning through the Neutral side (potentially because it is exiting through a person), but other faults or accidents may not cause either of these protective measures to cut the power being supplied.

Is there anything else you wish to achieve?

If you were to fit a new circuit back to your fuse box and install a 16A RCBO for the shed(yes I understand you can't but bear with the explanation), the 16A RCBO will protect against massive overloads and the RCD against power leaking out of the circuit (potentially because it is exiting through a person).

My personal view is the RCD FCU as the interface between ring circuit and your 2.5mm² T&E is a good solution in the circumstances.

Ideally the T&E should be replaced with a better cable (better UV protection) or protected with conduit or trunking.

 

[Flinstone]

Thanks for the reassurance and point taken.

I did originally think this was the function of a fuse and RCD - until I read the "but..." bit and it came across as (unhelpfully to my mind) too negative, translated to me as "You can use the known X if you absolutely insist, but you do know it it won't help you with unknown Y don't you?". For curiosity could you give me a meaningful accident example?

"My personal view is the RCD FCU as the interface between ring circuit and your 2.5mm² T&E is a good solution in the circumstances."
- my only reservation is that the cable enters the house under the kitchen worktops. An RCD located under there could be accessible if the cupboard is emptied to gain access in future. Nothing in the regs against putting out of sight is there?

"Ideally the T&E should be replaced with a better cable (better UV protection) or protected with conduit or trunking."
- Agreed I was planning on replacing with HO7 shortly, have some available for that

Thanks again for going to the trouble to reply, it's appreciated.

 

[Flinstone]

BTW should I use a switched RCD FCU in my application (spur from kitchen) or does pressing the test button suffice as isolated (doubt it's allowed is it)?

 

[ericmark]

To isolate both line and neutral should be switched. However with a TN supply there is in the regulations where it is permitted to only switch line.

With a CU with RCD protection any borrowed neutral will trip the RCD. However with no RCD protection a borrowed neutral can cause the neutral to become line voltage.

I draw fuse but treat as if working on a live circuit, which since neutral is classed as a live wire it is.

 

[JohnW2]

To isolate both line and neutral should be switched. However with a TN supply there is in the regulations where it is permitted to only switch line.

Whilst that is true, there are very few situations in which the regulations actually require true 'isolation' (as defined in regs). When people talk about 'isolators', they are often/usually referring to devices for 'emergency switching' (or even, sometimes, functional switching), not 'isolation' in the regulatory sense.

Kind Regards, John

 

[ericmark]

Whilst that is true, there are very few situations in which the regulations actually require true 'isolation' (as defined in regs). When people talk about 'isolators', they are often/usually referring to devices for 'emergency switching' (or even, sometimes, functional switching), not 'isolation' in the regulatory sense.

Kind Regards, John

I would agree with you, however aware there is no RCD fitted, however today we are seeing a move to even isolating the earth with some EV chargers.

 

[JohnW2]

I would agree with you, however aware there is no RCD fitted, however today we are seeing a move to even isolating the earth with some EV chargers.

Maybe, but it remains the case that the regs currently require true 'isolation' (in the sense that the regs use that term) in very few situations.

In particular (given the questions/discussions we so often see), there is no requirement for 'isolators' for cooking (or any other 'kitchen'/utility room) appliances, and certainly not for bathroom fans

Kind Regards, John

 

[flameport]

RCD sockets and FCUs are not presently permitted for reasons covered extensively in other threads.

Adding a consumer unit in the garage makes it notifiable work, and is not necessary for a light and a socket.
Supplying a consumer unit from a 13A FCU is entirely pointless.

House CU contains all re-wirable fuses. No RCD fitted.

Decades overdue for replacement, and money would be far better spent on a new consumer unit for the house rather than attempting to make mostly irrelevant alterations to a socket and light in a garage.

 

[JohnW2]

Adding a consumer unit in the garage makes it notifiable work, ...

If one wants to be pedantic, in terms of what the word of the law 'actually says' (which some people around here seem to want to do), whereas "replacing a consumer unit" is, indeed, notifiable, it says nothing to indicate that "adding" a consumer unit (where none was previously present) is notifiable!

... and is not necessary for a light and a socket. Supplying a consumer unit from a 13A FCU is entirely pointless.

All very true.

Kind Regards, John

 

[ericmark]

it says nothing to indicate that "adding" a consumer unit (where none was previously present) is notifiable!

Oh I like it, also it uses the phrase "consumer unit" which means it only applies if the distribution unit has only items installed authorised by the manufacturer, add a bell transformer from another manufacturer and the distribution unit loses its type testing label, so no longer a consumer unit.

One wonders if this was an accident or intentional, maybe the get out was intended?

 

[JohnD]

Oh I like it, also it uses the phrase "consumer unit" which means it only applies if the distribution unit has only items installed authorised by the manufacturer, add a bell transformer from another manufacturer and the distribution unit loses its type testing label, so no longer a consumer unit.

One wonders if this was an accident or intentional, maybe the get out was intended?

Which are the words you are looking at?

 

[JohnW2]

Oh I like it, also it uses the phrase "consumer unit" which means it only applies if the distribution unit has only items installed authorised by the manufacturer, add a bell transformer from another manufacturer and the distribution unit loses its type testing label, so no longer a consumer unit. ... One wonders if this was an accident or intentional, maybe the get out was intended?

All surely 'accidental'?

It is surely fairly 'obvious' that the actual 'intent' will have been to require notification of any 'installation' of a any sort of DB in domestic premises, whether as a 'replacement' or an 'additional' one, and regardless of whether or not the DB qualified as a 'consumer unit' - but the person(s) who drafted the rules did a very bad job of turning that 'intent' into written law!

Kind Regards, John