Extending Cooker Feed - Notifiable?

[JohnW2]

As I understand this, you suggest he runs a 10mm SWA cable directly to a socket, with an FCU somewhere along the run to feed the light. How do you connect the FCU and socket to the SWA?

You understand incorrectly. For that option, we were talking about 4mm² SWA (with a 32A MCB in house) terminated in a JB in garage, hence via 4mm² T+E to socket, and with the FCU fed from either JB or socket.

Kind Regards, John

 

[JohnW2]

The wiggle room about notifying is one thing. There is no wiggle room when it comes to the design. Spurring to run a 12 metre length of SWA and then connecting directly to the sockets and FCU would be poor design.

Spurring what from what - have you read this thread? We're talking about extending an unused old cooker circuit (the clue is in the title of the thread ) - give or take a JB (and, possibly, the need to notify!), the same as running the garage circuit all the way back to its dedicated MCB in the CU.

Kind Regards, John

 

[JohnW2]

You wouldn't run the feed to sub-main in 10mm cable and then carry this on the individual circuits.

Indeed one wouldn't. No-one is suggesting that one would, and this was not was being discussed. I was merely responding to a side question as to whether itv would be acceptable to have a ring final circuit (presumably in 2.5mm² cable) fed from the CU by 4mm² cable. I was saying that I could see no electrical reason (or regulatory reason, provided it was protected by a 32A MCB) why this could not be done - pointing out that it would not be conceptually different from an RFC fed from a CU run from a sub-main. In any event, I added that I don't think Daniel really needs a ring final, anyway!

Kind Regards, John

 

[JohnW2]

Not everybody asking for advice here would have the background knowledge to deternine whether it was safe to ignore the requirement to notify. I also think it's a silly law, but wouldn't print here that I'd ignore it (as this could be read as advice). It's a grey area, but the arbiter is the LABC (some would say it needs notifying and others would say not). My point is that, assuming a job is notifiable there is no justification for ignoring it.

I don't really disagree with any of that, but I'm not sure that you fully understand my position. If the law intends that an otherwise non-notifiable job becomes notifiable if it involves a JB which happens to be in a kitchen then, yes, I would regard that as very silly - but if the law were explicit in saying that then 'that would be the law' - so (regardless of how I might choose to act myself) I would never suggest, imply or 'advise' that anyone should break that law. However, what is actually silly is the poor way in which the law is written, leaving far too many uncertainties. That is the reason why I would personally be happy to proceed in the belief that the law intends such work to be non-notifiable - as I said, in the face of unclear law (and also invoking common sense), I think I would have a strong argument/defence for that view. Despite what you say, it is the Courts, not the LABC who are the ultimate arbiter of interpretation of the law, and I strongly suspect that most LABCs would back down rather than trying to argue this particular point in court!

If you want an even 'greyer' (and potentially even more silly!) thing to think about, what if there were no JB in the kitchen, but the (intact) cable forming part of some (otherwise non-notifiable) work happened to pass through a kitchen?!

Of course,, for a self-certifying electrician, these discussions are all essentially irrelevant. If there is the slightest doubt about notifiability, they can simply self-certify, at minimal effort or cost.

Time for bed ... you've kept me up too late

Kind Regards, John

 

[scousespark]

Exactly. That's the usual 'simple' supply to a garage.

You may have seen this, but it is not common for a detached garage. It's a poor design.

I obviously cannot argue with your experience, but I've seen it a lot. It's also what one commonly sees being advised here, with OPs often being quizzed as to why they feel they need a CU in a garage (rather than just a socket or two and an FCU for the lighting).

Kind Regards, John

I have seen this too, but it's not the best design. We cannot guess at what the sockets will be used for, but the garage CU would offer a better chance of reducing the effect of a fault in the garage.

 

[scousespark]

There is no justification for a DIYER not working to the same standards as a professioinal.

No argument with that.

Where have you seen it stated that you can ignore discrimination if you are only supplying a couple of sockets?

Discrimination between what and what? Are you referring to the undesirability of having both power and lighting on the same OPD (which is not really 'discrimination') - as in the 'no CU in garage' approach? With that approach, there is obviously no discrimination issue. The (prbably 3A or5A) FCU fuse will (probably!) discrimate from the (32A) MCB in the house CU, and the garage sockets have no discrimination issue at all, since their only OPD is in the house.

Kind Regards, John

I was referring to the case where a garage CU is fitted and the discrimination between that and the house. If this was your house, what would you do? Would you do as little as you could get away with, or try to minimise the effects of faults in the garage?

 

[JohnW2]

Discrimination between what and what? Are you referring to the undesirability of having both power and lighting on the same OPD (which is not really 'discrimination') - as in the 'no CU in garage' approach? With that approach, there is obviously no discrimination issue. The (prbably 3A or5A) FCU fuse will (probably!) discrimate from the (32A) MCB in the house CU, and the garage sockets have no discrimination issue at all, since their only OPD is in the house.

I was referring to the case where a garage CU is fitted and the discrimination between that and the house. If this was your house, what would you do? Would you do as little as you could get away with, or try to minimise the effects of faults in the garage?

You seem to be grabbing at bits of this thread and commenting on them out of context, without taking the totality of the discussion into account. We (including the OP) have agreed that if there is a CU (and hence OPD) in the garage, then the proper approach is to try to achieve discrimination - e.g. by a 60A fuse in the house and a 32A MCB in the garage (which may provide discrimination). However, the discussion you were commenting on related to the situation in which there is no CU in the garage, hence no discriminatiuon issue.

Kind Regards, John

 

[JohnW2]

I obviously cannot argue with your experience, but I've seen it a lot. It's also what one commonly sees being advised here, with OPs often being quizzed as to why they feel they need a CU in a garage (rather than just a socket or two and an FCU for the lighting).

I have seen this too, but it's not the best design. We cannot guess at what the sockets will be used for, but the garage CU would offer a better chance of reducing the effect of a fault in the garage.

As I said, I've personally seen it a lot, have seen it being advocated a lot (in this and other forums) and I've seen many cases of it being done like this by electricians.

Perhaps more to the point, it is the only approach discussed in the good (and very often cited) article on electricity supplies to garages and outbuildings in the Autumn 2005 edition of IET's "Wiring Matters". They discuss and describe two options, one where the supply has it's own supply from a dedicated MCB in the house CU and the other in which the garage is spurred off a house ring - but neither involve a garage CU. I don't pretend that the IET is divine or omniscient, but would they really publish a lengthy article describing something that was uncommon and 'bad design'?

As you say, it obviously depends a lot on anticipated usage and load - but for the great majority of garages, which require just a light and a socket for occasional use for, say, a lawn mower or battery charger, I personally think (as, seemingly, so do the IET and many others) that it is a perfectly reasonable design.

Kind Regards, John

 

[scousespark]

I obviously cannot argue with your experience, but I've seen it a lot. It's also what one commonly sees being advised here, with OPs often being quizzed as to why they feel they need a CU in a garage (rather than just a socket or two and an FCU for the lighting).

I have seen this too, but it's not the best design. We cannot guess at what the sockets will be used for, but the garage CU would offer a better chance of reducing the effect of a fault in the garage.

As I said, I've personally seen it a lot, have seen it being advocated a lot (in this and other forums) and I've seen many cases of it being done like this by electricians.

Perhaps more to the point, it is the only approach discussed in the good (and very often cited) article on electricity supplies to garages and outbuildings in the Autumn 2005 edition of IET's "Wiring Matters". They discuss and describe two options, one where the supply has it's own supply from a dedicated MCB in the house CU and the other in which the garage is spurred off a house ring - but neither involve a garage CU. I don't pretend that the IET is divine or omniscient, but would they really publish a lengthy article describing something that was uncommon and 'bad design'?

As you say, it obviously depends a lot on anticipated usage and load - but for the great majority of garages, which require just a light and a socket for occasional use for, say, a lawn mower or battery charger, I personally think (as, seemingly, so do the IET and many others) that it is a perfectly reasonable design.

Kind Regards, John

I have read the thread and it sort of meanders. The original question asked if an outside socket is notifiable. The next option discussed was to install circuits in the detached garage. The remainder of the thread seems aimed at getting away from notification.

An electrician will design a circuit based on the expected load. I am not psychic, so I don't know what the OP is feeding. The cable length only appeared in page 3, in answer to your suggestion to use 6 oir 10 mill SWA.

I suggest you read the article again John. The preferred option is to feed from the house CU with a 2-way garage CU to feed the sockets and lights.The OP has a spare way and the only reason to take option 2 is to remove the need to notify.

 

[JohnW2]

Perhaps more to the point, it is the only approach discussed in the good (and very often cited) article on electricity supplies to garages and outbuildings in the Autumn 2005 edition of IET's "Wiring Matters". They discuss and describe two options, one where the supply has it's own supply from a dedicated MCB in the house CU and the other in which the garage is spurred off a house ring - but neither involve a garage CU. I don't pretend that the IET is divine or omniscient, but would they really publish a lengthy article describing something that was uncommon and 'bad design'?

I suggest you read the article again John. The preferred option is to feed from the house CU with a 2-way garage CU to feed the sockets and lights.

Sorry - yes, you're right. It's a long time since I read the article in full. However ...

• (a) the second option they discuss in detail (even if not their 'preferred' option) is the the sort of design we've been talking about, without a garage CU and ...
  (b) going back to your comments about discrimination, their 'preferred' option does not really allow for more than a 16A socket circuit (plus 6A lighting - 22A total) which will give discrimination against the largest MCB that one is likely to get for a domestic CU (even 22A vs 45/50A would not give much certainty of discrimination). Also, of course, that would mean using at least 10mm² cable to supply a 22A load, just to satisfy a desire for discrimination.

The real 'preferred' ('best design') option is surely neither of the IETs but, rather (as discussed in this thread) to forget the house CU and feed a garage CU from a switch-fuse, allowing potential for discrimination against higher-rated OPDs in the garage - but, again, one would be using a much fatter cable than necessary for the load, purely so as to achieve discrimination. The more pragmatic amongst us may well ask whether, in situations such as we are discussing, discrimination is really all that crucial.

The OP has a spare way and the only reason to take option 2 is to remove the need to notify.

Yes, I suppose that is largely true. In fact, he essentially has two spare ways in the CU, since the cooker circuit we're talking about is 'spare'. But you're right - if he ran a new cable back to that very same MCB that is currently protecting the (unused) cooker circuit cable, he would have to notify, whereas (as being discussed in this thread) it would appear that by merely 'extending' the cooker circuit to provide additional sockets and lighting, the job would become non-notifiable [avoiding a CU in the garage is, of course, another thing which would be essential if he wanted to avoid the need for notification].

I realise that notifiability is of virtually no importance to you, so you can concentrate fully on achieving an ideal design. However, the system has created a situation in which, for a DIYer, the difference between extending an existing cable and running a new cable back to the same MCB can mean a few hundred pounds difference. Whilst we are agreed that DIYers should ideally work to the same standards (including design ones) as professionals, the DIYers are faced with these financial pressures (potentially conflicting with ideal design) which the professionals don't have to take into consideration.

Kind Regards, John

 

[scousespark]

I don't think the article is definitive. It describes 2 specific methods (spur from ring, or dedicated circuit from house CU).
The load available in the garage is limited to 13A by the FCU, whereas the dedicated circuit offers some flexibility.
The CU limits the risk of a fault on the lighting circuit taking out the suply to the garage.
Pure discrimination is impossible to achieve, as the MCBS don;t always behave as predicted. Howwver, the design should aim to discriminate as much as possible.
I would say the switchfuse option would be a bit of overkill, from a practical point of view.

Option 1 is the sensible (practical option).

I totally understand the issue of the cost of notification as, in cases such this one, the cost is out of proportion to the job.
I am not ignoring this cost. However, the design should aim to be as safe as possible and minimise the impact of a fault.

dhutch seems to have got bored with his pidldling littel garage and is now wiring up the lights in a boat shed. See post entitled Lighting a large fabrication shed.

 

[JohnW2]

I don't think the article is definitive. It describes 2 specific methods (spur from ring, or dedicated circuit from house CU). The load available in the garage is limited to 13A by the FCU, whereas the dedicated circuit offers some flexibility. The CU limits the risk of a fault on the lighting circuit taking out the suply to the garage.
Pure discrimination is impossible to achieve, as the MCBS don;t always behave as predicted. Howwver, the design should aim to discriminate as much as possible.

Yes, I agree with all of that. Have you not got your statement about lighting faults the wrong way around? - if one didn't have a CU in the garage, the 3A (or 5A) fuse in the FCU would stand a very good chance of discriminating against the 32A MCB in the house in the case of a garage lighting circuit fault, leaving the sockets citcuit unaffected. It would be a fault on the garage sockets circuit that would cause the problem - since it would cause the house MCB to operate, hence taking out the garage lights as well.

I would say the switchfuse option would be a bit of overkill, from a practical point of view.

Yes, so would I - but it obviously is, in design terms, the way to "to discriminate as much as possible", which you've said above is what you feel you should strive to achieve.

Option 1 is the sensible (practical option).

It is certainly, in my opinion (FWIW!), a reasonable option, but only really if (in the OP's case) one accepts the cost (including notification fees), and increased work, of installing higher CSA cable, all the way back to the CU, facilitating a higher rated house MCB and hence optimise the chance of discrimination. If he wanted to stick with extension of the existing 4mm² 'cooker circuit' cable (possibly avoiding notification), hence limiting him to a 32A MCB in the house, I wouldn't say that it was a very good option. At best, he would have to limit the garage sockets circuit to 16A and, even then, may well not get discrimination from the 32A MCB in the house.

I totally understand the issue of the cost of notification as, in cases such this one, the cost is out of proportion to the job. I am not ignoring this cost. However, the design should aim to be as safe as possible and minimise the impact of a fault.

Agreed - but, apart from the fact that a garage sockets fault would take out the garage lighting, do you feel that there is anything else 'wrong' (even applying the most exacting of standards) with a design run in 4mm² all the way from a house 32A MCB to socket(s) and an FCU for lighting in the garage?

dhutch seems to have got bored with his pidldling littel garage and is now wiring up the lights in a boat shed. See post entitled Lighting a large fabrication shed.

Yes, I noticed that

Kind Regards, John

 

[scousespark]

The current set up has a radial, which can be extended, without rewiring.
The ONLY reason the garage CU is being discounted is cost.

Even in the dumbed down world of electrical training, design takes safety and convenience into account. The additional cost of notification is not a design consideration.

In December 2004 the garage CU was the preferred option and it still is.

 

[ban-all-sheds]

Installing a CU in the garage may not be notifiable - depends how large the garage is, what it's made of, etc.

 

[JohnW2]

The current set up has a radial, which can be extended, without rewiring. The ONLY reason the garage CU is being discounted is cost.

Hmmm. If I understand what you're saying, extending the (4mm²) cable without rewiring (and having a garage CU) would limit the house-end MCB to 32A, which, as I've discussed, will seriously frustrate attempts to get discrimination from an MCB in a garage CU - which appears to be one of the major issues you've been raising. On the other hand, if you mean that the only reason a garage CU is being discounted is because of the cost (including notification) of running a higher CSA cable all the way back to the CU, so as to improve prospects of discrimination, then I would partially agree.

Only 'partially agree', because another reason (for not having a garage CU) would be if it wasn't considered necessary. As I asked before, do you believe that there is any problem with not having a garage CU, other than that a fault on the garage sockets circuit would take out the garage lights?

Even in the dumbed down world of electrical training, design takes safety and convenience into account. The additional cost of notification is not a design consideration.

Agreed. Do you see any safety problems with the design without a garage CU - and, as above, is the only convenience issue you can think of the fact that a garage sockets fault would take out the garage lighting?

Kind Regards, John