The discussion about hair-dryers & the possible overloading of circuits has prompted me to explain what I see as a problem here.
As most of you now know, the majority of homes here have 30A ring circuits feeding receptacles. The original IEE Regs. on these specified that a ring may serve any number of outlets within a floor area of 1000 sq. ft. The change to metric measurements altered this to 100 sq. meters, which is 1076 sq. ft.
The average home is smaller here than in the U.S., so in many cases a single ring was used. In larger homes (or smaller ones built to a better spec.) it has been the norm to install two such 30A rings.
The IEE Regs. specify that the designer should ensure that the "anticipated load is distributed evenly, as far as is reasonably practicable, between the circuits." As with many IEE rules, the wording is somewhat vague, but I think the intended aim is fairly obvious.
So the designer/installer isn't a mind-reader and can't allow for the unusual use of general-purpose outlets, but he should be able to make intelligent guesses as to what types of loads are likely to be used.
When two rings are installed in a two-story house, the most common arrangement seems to be one ring for each floor. The result is that the downstairs ring feeds all the heavy kitchen/utility appliances, while the upstairs ring often has no greater load than a couple of clocks and bedside lamps. In my mind, that's not ensuring the "reasonable" distribution of load.
"OK," I hear you say, "but 30A at 240V provides 7200W. Surely that's enough for serving kitchen/ground floor outlets?"
I agree that it would be, except for the fact that it's NOT usual to provide separate dedicated branches for washing machines, dryers, or dish-washers.
British washing machines & dish-washers usually incorporate a 3kW heating element. Start both at the same time (not uncommon) and there's 6kW already. That doesn't leave much spare for toasters, microwave ovens etc. running on the same ring. 99% of British kitchens have an electric kettle, rated between 2 & 3kW (Gotta make that tea!).
Add a clothes dryer as well, & the potential for overloads & trips is even greater. (Some large dryers are wired separately, but most are 3kW & plugged into a standard 13A outlet.)
When the ring was introduced here, washing machines were much less common than today, and dryers & dish-washers were practically non-existent in the average home.
Now, all three are common, yet we still have new homes wired so that all the heavy appliances end up on the same circuit.
The IEE Guidance Notes for the current edition acknowledge the increased loads in today's homes, but then seem to suggest a "solution" which is of little help. Their advice is to "consider the provision of a separate ring circuit to feed kitchen sockets."
As 90% of British homes have all the aforementioned appliances in the kitchen, and not a separate utility/laundry room, I don't understand the logic behind this. We'll still end up with an overloaded kitchen ring, only this time there'll be TWO 30A cicuits each running just table-lamps, TV's, etc., plus maybe an occasional heavier load from time to time.
Sure, there's a vaguely worded rule about ensuring sufficient number & capacity of circuits to allow for the expected load, but I don't see too many installations where this has been applied intelligently.
My preference is to follow American/Continental practice, and install a dedicated circuit for each of these major fixed loads.
Your thoughts on this? (With apologies for the lengthy explanation!)
