Domestic Power Wiring - Upstairs & Downstairs

I have surveyed a house and have observed a domestic ring circuit which is serves a floor area exceeding 100m2, including upstairs, downstairs and utility containing (washing machine and tumble dryer) (kitchen ring is separate). I am ok with this circuit contravening the 100m2 guidance, and not being respective to the load of the whitegoods, but I understand there is guidance on a domestic ring only covering a single level.

Can somebody point me towards this guidance either in published Guidance Notes or the Regulations.

Thanks

Slight smile

  • The limit of 100 square metres is only a guideline and not a requirement and the installation might be fine, unless unusually heavy loading is expected. As kitchen ring circuits tend to be heavily loaded, one circuit for the kitchen and one for the rest of the home can be a good approach.

  • Not aware of any guidance that says single level in the regs or the OSG - it is of course useful if there is more than one power circuit to divide it in a way that does not lead to the wrong circuit being isolated in an emergency.

    The regs requirement is that there is enough information that it is clear what the breaker or fuse is serving. It is much easier if that is 'sockets up' /'sockets down' or 'kitchen' /'non- kitchen' which are the two most common configurations around here but it is quite possible with the use of labels and a felt tip to cover almost any case.
    I have been known in the past to leave a 'map' in an envelope beside the CU in complex cases.


    Certainly nothing big to worry about unless it is showing signs of overload.


    Mike.

  • Thanks for your comments mapj1. I am aware of it being only guidance :) There are things happening in the house that have caused the investigation, so we do have signs of significant overloading. I do believe that if common guidance were used the end user would not have any issue and I am seeking to repair this circuit in line with common guidance.

    The reason I ask about upstairs/downstairs is that the wiring is not your typical all of downstairs and then all up upstairs. Is up/down/up/down/up/down ie the nearest socket irrespective of whether it's up or down. Don't know it that came across clear. 

    If I recommend that the circuit is wired as 2 rings Upstairs and Downstairs, we are looking at a full rewire of that full circuit, not good for the occupier nor the developer. If upstairs/downstairs is not in any published guidance I will recommend that the utility only is rewired. This reducing load and bringing the circuit below 100m2.

  •  Is there enough slack capacity in the kitchen ring to to allow a 'kitchen and utility ring'  and a 'non kitchen and utility' ?

    Without seeing the layout of course it is hard to say but perhaps a new small lasoo in the utility and maybe blank off or unthread the sockets in that zone that are on the overloaded ring may be a suitable compromise.

    Unless the rest of the wiring is actually damaged, so long is it buzzes out OK, no real need to redo the lot, just redo the troubled sections.
    But  do make the circuit labelling clear or leave a map ;-)  the next guy in will really appreciate it.

    Mike.

  • The reason I ask about upstairs/downstairs is that the wiring is not your typical all of downstairs and then all up upstairs.

    I think that this is potentially dangerous because the labelling has to be pretty clear so that people do not make assumptions about the normal layout.  It may arise because of the history or layout of the house, particularly if two parts (with separate supplies at one time) have been joined.

    I take very little notice of the 100 m² rule - perimeter would make more sense, and you could squash several high-load appliances in a small place.

  • What possible relevance can a blanket 100 square meters have?

    Are the areas 10 x 10 (40 all the way around) or 25 x 4 (58 all the way around) or 10 x 5 (30) with one 50 sq.m. on top of another? 

  • It used to be considered good practice to split the layout vertically rather than horizontally, so that two ring circuits both supplied upstairs and downstairs, so if a circuit MCB tripped half the sockets remained working on both floors.

  • A conventional house with solid floor downstairs and floorboard’s upstairs is best like lounge with bedrooms above, kitchen with bedrooms above etc. Saves on cable and circuit lengths. If floor boards up and down better to split downstairs/upstairs but basically it’s cable length and load that matters.

  • What possible relevance can a blanket 100 square meters have?
    Buried in the mists of time, and back then it was actually 1000 square feet, but given the roughness of the calculation, who cares ;  it was considered the area in which the use of more than 2 lots of 3kW of electric heating at once was unlikely - based on the kind of glow bar portable electric fires of the period, and how many fireplaces a normal house of that sort of size might have.

    Nowadays you will struggle to find a 3 bar fire, and folk do not use the building as if there is just a fireplace in the  sitting room and the parlour  and the rest is unheated unless someone is ill.

    The utilitarian Belling 213 for the living room My grandparents had the later coal effect model where a little disk span above the red light bulb to give 'flame effect'


    The grander Adam 916 for those wanting to entertain impressionabe  guests ;-) Mind that finger guard, it is quite possible to touch the spring elements

    In mitigation reducing the ring load, most houses now have double glazing and no longer have doors that fit so badly a limbo dancer is a likely hazard, these effects have more or less compensated, and in any case fixed heaters are likely not on the ring, if indeed it is not gas.

    Looked at it a more modern  way whatever the appliance is (except perhaps an air con unit or an extractor fan..) all the energy that is drawn via the plug eventually heats up the building and how much heat do you sensibly want in a given space before it gets overheated.

    Now there will always be odd cases, like large kitchens where the heat is needed but then pumped outside, but for a lot of simple cases a constant power per area assumption is a good start of no other info is available and usually is not too far off.

    But it is not sensible for example if the circuit serves a garden, or some really draughty space. And certainly if there is real data about intended fixed loads,  say workshops or kitchens, then really data that should be used instead.

    Mike.

  • Looked at it a more modern  way whatever the appliance is (except perhaps an air con unit or an extractor fan..) all the energy that is drawn via the plug eventually heats up the building and how much heat do you sensibly want in a given space before it gets overheated.

    Yes, but ...

    Washing machine heats up the water (but may be only to 30º C, which isn't going to kill off any microbes) and later dumps it down the drain. Tumble drier, if vented, blows all the hot air out of the building.

    That said, an unvented standard tumble drier can make a kitchenette in Army accommodation staggeringly hot.