Let's face it the only real situation where a domestic 32A socket circuit is likely to be fully loaded is the kitchen with washing machine, dishwasher, tumble drier, kettle etc and the possibility there is for a potential load of 40A or so, which is unlikely to trip a 32A MCB but a 2.5mm² T&E will be overloaded by 50%. Before anyone says it's unlikely, Mrs Sunray will typically put all of those and the toaster or microwave on first thing in the morning. I've measured the kitchen ring peaking >50A in normal useage albeit much of it is wired in 7/0.029" and full ring with no spurs.
Adding two spur sockets to Ring Final
- Thread starter Sard
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Not impossible, albeit those peak currents would only be likely to flow for pretty short periods of time.
However, what you describe is really 'no big deal'. You may think that "overloaded by 50%" sounds fairly dramatic, but don't forget that any cable (including 2.5mm² T+E) is deemed to be able to tolerate an "overload" of 45% for an hour without any problems (and greater degrees of 'overload' than that for shorter periods) for an hour without any problems.
Kind Regards, John
All agreed.
Glad you agree. It might interest you to look back to some data I presented in (this thread) , relating to the total demand of my entire installation over a period of about 2.5 years at the time (about 1,350,000 minutes). The most pertinent bits were the table below which shows that, of those ~1,350,000 minutes, there were only 6 minutes (0.0004%) when the total demand in my installation exceeded 40A, and only just over 0.1% of minutes during which the total demand was >30A
Kind Regards, John
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That's not unexpected in many abodes, I find that Mrs Sunray will habitually run through the sequence of washing machine, tumble drier (to soften previous days wash), dishwasher, toaster or microwave and kettle first thing. This could easily include the use of electric cooker or be at the same time as me using electric shower. I have never checked but I reckon we could easily be approaching our limit (believed to be 60A fuse as looped supply). I am concious of the limit so try to limit peak load by running dishwasher in the evening and time the shower etc.
I've just put the clamp meter on main tail; 0.32A, adding 18W of hall light so I can see meter better; 0.39A
As I've suggested, it's really a question of how long loads are very high- going beyond the CCC of cables or In of OPDs (even the cutout fuse) for relatively short periods is of little consequence.
Toasters, kettles, microwaves and even showers are not usually on for appreciable periods of time. Even washing machines and dishwashers only use 'high power' for pretty short periods, and cookers are usually very much 'up and down' with their thermostatic control. Tumble driers (and, of course, any sort of 'electric heater') are about the only common appliance which draws high current for relatively 'long periods'. As a consequence of all that, very high total loads which persist for appreciable periods (say, more than 15-30 mins) is probably pretty rare in domestic environments.
Kind Regards, John
Regarding the outdoor spur socket, would a 20A DP switch be adequate for isolating the new spur?
Yes it would for one socket. ( maximum current limited to 13 amps by the fuse in the one plug )
Yes.
yes perfect for one socket
Sorry confused by the mention of one socket. I am planning to put a double socket in the following order:
1) 2.5mm2 cable from original socket to 20A DP Switch
2) 2.5mm2 cable from 20A DP Switch to waterproof outdoor double socket
Then, strictly speaking, 20A is not enough as you could plug in 26A - although this is extremely unlikely.
Go for 32A or 45A if you want to.
Go for 32A or 45A if you want to.
Some people would say that a 20 amp switch would not be suitable for a supply to a double socket which could in theory need 26 amps ( 2 x 13 ) but is practice very unlikely
So yes the 20 amp switch would be OK for a double socket.
So yes the 20 amp switch would be OK for a double socket.
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