Wiring Regs - utility room

Discussion in 'Electricians' Talk' started by ChrisWoo, Oct 20, 2021.

  1. ChrisWoo

    ChrisWoo New Member

    Advice please. About 30 years ago I had an extension built including a utility room. The electrician fed this with a spur in 2.5mmT&E from the ground floor ring to a single 13A double-socket and a 5A fused outlet for the lighting. This was fine for the then washer-drier.

    Over the years this has been extended (by me) by fixed wiring to sockets supplying separate washing machine, tumble dryer and freezer. Total load about 5kW (22A). As all the wiring is consistent with Reference C, this is well within the capacity of 2.5T&E (27A). But someone could plug-in a 3kW kettle with everything else running, which would overload the wiring (35A), although this should trip the 32A ring main breaker on the consumer unit.

    The number of sockets means it definitely does not comply with wiring regulations but rewiring would be a nightmare. The spur runs through the cupboard under the stairs before entering the utility room. Could I make it compliant by terminating the spur in a 13A double socket with two 13A plugs feeding a junction box connecting them to the cable to the utility room?

    This would protect the circuit from overload and not infringe wiring regs because I understand that everything downstream of a 13A socket is outside the scope of the regulations. Am I right?
     
  2. Bazza-spark

    Bazza-spark Screwfix Select

    If this is a spur from the ring on a 32a breaker, none of it complies with BS7671 and is potentially a fire hazard as the 32A breaker will not protect your 2.5mm cable properly. There should be an up front FCU with a 13a fuse to limit the spur to a maximum of 13A. Only 1 socket is allowed on an unfused spur.
     
    bright_Spark likes this.
  3. AnotherTopJob

    AnotherTopJob Screwfix Select

    As you are aware, to comply you'd only be able to spur one socket or multiple sockets from a 13a FCU.
    With your existing wiring I don't see any alternative that will meet regs.
    Double sockets are only designed to handle 20A short term between the 2 outlets - and feeding a junction box from a plug sounds like a worse setup than you already have.
    (I'm not an electrician so others will suggest the best way forward).
     
  4. Jimbo

    Jimbo Screwfix Select

    It would be at least better if the first thing on the spur was a 13A FCU and everything else behind that. Getting a heat-pump tumble drier might be cheaper than rewiring it all to keep the load down (they need only about 700W) and save you a few quid on electric if it's used a lot.
     
    ChrisWoo and Starslikedust like this.
  5. Tony Goddard

    Tony Goddard Screwfix Select

    Absolutely not compliant in any way, only one socket (double or single) or FCU can be run off a spur - the FCU can be fused at 13A and then a chain of sockets and other spurs be put on the load side.

    The easy fix is to insert a 13A unswitched FCU as the first fitting on your spur with everything else on the load side of that.
     
  6. Bazza-spark

    Bazza-spark Screwfix Select

    If you look at the time/current curve for a 32A B type 60898 MCB you will see that it will carry 35A indefinitely.

    Your installation is dangerous, please get it sorted properly.


    upload_2021-10-20_18-40-25.png
     
  7. Bazza-spark

    Bazza-spark Screwfix Select

    If you mean to put the 2 lives, 2 neiutral and 2 earths together in terminal blocks to make a common conection that is every bit as dangerous.

    You need a pro to look at it and either advise or sort it.
     
  8. MGW

    MGW Screwfix Select

    This did not comply, never mind what you have added. An unfused spur can only feed one BS1363 device, be it a single socket, double socket, or fused connection unit, it can only feed one device.
     
  9. ChrisWoo

    ChrisWoo New Member

    Thank you to all who have replied to my post - your advice has been very helpful. I have done some more digging and came across this post from an electrician on an IET forum, which applies to my situation:

    "A 25 amp breaker is a 'standard, if not common' rating, which is within the rating of 2.5mm cable for at least some installation methods. I have used this to get out of a similar jam in the past (a DIYer had used a single spur point from a ring final to add a 'multiplicity of accessories'). The customer just wanted it to be safe and compliant. Turned out there was a B25 breaker for his model of board, and the load made the 7 amp reduction in available current acceptable."

    The electrician protected the 2.5mm spur by down-rating the ring-main breaker in the consumer unit to 25A and considered this to be compliant, even though it was not in accordance with BS7671. He was justified in this because BS7671 is guidance and not law. The law is the Building Regulations 2010. Section P of these regulations refers to electrical work. The preamble to this states: “Note that there may be other ways to comply with the requirements – there is no obligation to adopt any particular solutions contained in an approved document. (Their italics).

    Section P is an approved document and it states that installation work and modifications should comply with BS7671. But this is not compulsory if there are "other ways to comply with the requirements". The requirement in this case is to protect the spur from overload and the electrician considered this to be met by down-rating the breaker to 25A,

    I have no intention of going anywhere near my consumer unit. But it is a simple job to install a stand-alone 25A MCB in the cupboard under the stairs, which will protect the 2.5mm spur cable as it can take 27A.
     
  10. sparky steve

    sparky steve Screwfix Select

    Really:rolleyes:? You’ve asked on here for advice. You have been given good advice! and have chosen to ignore it. Crack ono_O
     
    robertpstubbs likes this.
  11. Bazza-spark

    Bazza-spark Screwfix Select

    Don't forget to tell your insurance company so they can either load your premiums or cancel the policy.
     
  12. Jimbo

    Jimbo Screwfix Select

    If doing so the Zs on the last socket should be less than 1.39 Ohms, assuming it's a B25.
     
    ChrisWoo likes this.
  13. bright_Spark

    bright_Spark Screwfix Select

    If you were to run a radial circuit for sockets the maximum breaker you would want to put on would be 20A anyway. I wouldnt mess about with this circuit yourself to be honest as you are not really in a position to make the correct decision most suitable for the safety of you or your family. It really is a job for an experienced electrician to take a look at and do it correctly.
     
  14. Comlec

    Comlec Screwfix Select

    Don't forget to ignore Appendix 15 of the current wiring regs too!
    Pay no attention to the handy diagram the IET provide.

    upload_2021-10-21_15-2-34.png
     
  15. ChrisWoo

    ChrisWoo New Member

    Thank you, Jimbo, for your advice on a heat pump dryer and the Zs value. Much appreciated.

    As to the others, I don't know why you are getting into such a hissy-fit because I prefer the IET electrician's advice to yours. All I wanted was a clever solution to making the supply to my utility room compliant without having to rewire everything. He provided that advice, you didn't.

    There is no safety issue whatsoever. The existing set-up has been running without incident for over 20 years. The maximum current draw (22A) will only occur when the heaters on the washing machine and tumble dryer are on at the same time and this will be of short duration until the thermostat on one or the other cuts-out. Even if 22A were to be continuous, that is well within the 27A permitted for the 2.5T&E, especially as it is a very short run of less than 3 metres.

    Having said that, I do appreciate the way you challenged by initial 2 x 13A plug idea, which has led to a better solution. Thank you once again.
     
  16. Bazza-spark

    Bazza-spark Screwfix Select

    Many of us here are also IET members and past members. I was a full member for many years.

    The information he gave applied to that particular situation, it does not necessarily mean it applies to yours!

    Do you have the test equipment and knowledge to ensure your trip times etc are within acceptable limits? Can you complete the necessary paperwork?

    With your attitude why did you bother asking here? My condolences for when you kill your family with your attitude and incompetence.
     
    bright_Spark likes this.
  17. bright_Spark

    bright_Spark Screwfix Select

    I am all for people wanting to save some money and have a go themselves providing that the nature of the work is well within a DIY scope of works. Everyone has different skill levels but a decent DIYer knows where to draw the line. This little project is not very trying for an electrician and the money that you will save by doing it yourself is not worth the risk. Things may well have ran fine for the last 20 years but now you are altering and adding to it and things may not quite work out too well this time around. You are quoting theoretical loads and current draw which on paper may seem ok. I would advise you to tread carefully with this and not to go down the path you are embarking on. Your wife would do well to give you a clip around the ear and stop you doing this if you havent got the sense to stop yourself.
     
  18. Tony Goddard

    Tony Goddard Screwfix Select

    OP, there is a huge difference between what you are suggesting and what the IET commentator was talking about. You can down rate a ring and make it into a radial by using a 20A breaker, I have done this myself where a section of a ring is damaged and the customer doesn't want the upheaval of putting new cabling in, you disconnect/remove the offending section and effectively form a two branch radial. So long as the reduction in current capability is acceptable all is well.

    The IET commentator suggests a 25A MCB, this might be acceptable for the above scenario if the cable fixing method / cable length still gave an acceptable safety margin, it would be a departure, but so long as it could be justified, as presumably the IET commentator could, fair enough.

    What you are suggesting is using a 25A breaker in place of a 13A cartridge fuse (as specified in the regs) to protect a ring circuit spur - the trouble here is, with other appliances in the ring, you could easily overload the ring itself.

    You could technically down rate the ring circuit to 16 or 20A and have the whole thing as a convoluted radial , which is what the IET poster is discussing.

    As to ring circuits, Comlec's poting of the diagram, which has been in the regs through various editions, shows all the possible permutations of a ring circuit, so as you will see at 9.00 or 3.00 on the circle, any more than one fitting must be fused with a 13A cartridge fuse, no question, no deviation.

    Us electricians love a good argument about many a point of order or interpretation of the regs, but ask as many (non cowboy) sparks as you like about spurs from rings and you will only get one answer, it is one area of the regs that is very clear, not open to interpretation or departure and unchanged more or less since the late 1940's - the queen came to the throne, the Beatles came and went, we won a world cup, and lost many more, all since this was put together - so I would argue that it's beyond the scope of any individual DIYer or pro spark to muck about with it, any future change would be made by the IET committee given much scrutiny and testing.

    Worth bearing in mind the Ring circuit itself was designed in a post war cost cutting excercise, it's a bit of an oddity, a peculiarly British thing, pushing the limits on the capacity of a cable technically undersized in order to save copper, hence its not a good idea to mess about with a long established normal.
     
    ChrisWoo and Mr Rusty like this.
  19. ChrisWoo

    ChrisWoo New Member

    Thank you for your further replies. On careful consideration I have decided to leave things as they are - if it ain't broke don't fix it. There is no safety risk as the total load on the spur is well within the 27A capacity of the 2.5mm T&E. The only appliances on the ring itself are the TV, hi-fi and a few table lamps; less than 5A max with everything switched on. So neither the spur to the utility room nor the ring are overloaded even with everything running at the same time, which would never happen in practice.

    The IET diagram shows that an electrician could wire a utility room in 2.5mmT&E with 2 double-sockets and a 13A FCU - which would comply with the regs.

    The client could then reasonably install a tumble drier, washing machine and freezer. This could draw 22A. This would not blow the 13A fuse. It may, however, cause the fuse and FCU to overheat and, in time, degrade the insulation. This is a real risk.

    With my set-up, there is no risk. This may be a case where slavish adherence to the regulations, as opposed to a proper risk-assessment, is detrimental to safety.
     
  20. Comlec

    Comlec Screwfix Select

    I have given the best advice I can but maybe we have to leave this one to Darwin or Karma to sort out.
     

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