Date   : Wed, 02 Sep 2009 16:13:54 +0100
From   : rs423@... (Mick Champion)
Subject: Leccy @ Acorn World '09

Andrew Hancock wrote:
>> The power used by the device is a fraction of the peak demand when it is
>> initially powered (inrush current). For a (fully loaded) Beeb the current
>> pulse is 1.8A for 120ms dropping to 0.15A and for my Beeb Sony CRT monitor
>> it's around 5A for 850ms dropping to 1A. I think we will need to avoid a
>> situation where a lot of stuff gets turned on at the same time and if
>>     
> we're
>   
>> looking at RCDs that people don't try and reset the trip with everything
>> still switched on, otherwise the current rush could trip the main breaker
>> for the room. I doubt if we'd be popular ;)
>>     
>
>   
>> Dave
>>     
>  
> Thanks for answering an issue I have with my electric on my sockets
> ring-main, which is 32A, after a power-cut, it always trips out!
>
> and I have to go round the house turning stuff off, to get it back on again,
> I suspect it's inrush current exceeding 32A!
>
> Umm! Maybe I need to get an up-rated one! 

If I remember correctly (for I can't find a definitive answer on t'web), 
2.5 mm twin and earth cable (commonly used in ring main circuits) is 
rated at between 19 and 23 amps. A 32 amp breaker  is only permissible 
because each socket  has two cables feeding it from either side of the 
ring effectively doubling up the rating. (Say 38 amps to be on the safe 
side). Any MCB higher than 32 Amps would be asking for trouble.


All the best,

Mick







> Andrew
>
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