|
Posted to uk.d-i-y
|
|
|
Electrifying the summer house... gosh!
wrote:
On 19 Sep, 22:04, "Dave Liquorice"
wrote:
On Fri, 19 Sep 2008 19:38:48 +0100, John Rumm wrote:
won't the requirements for RCDs significantly increase base-load power
consumption? All the RCDs I've come across dissipate a few watts.
Can't say I have ever noticed a RCD getting warm, but then again I have
never measured their power consumption.
There is a difference between "dissipate" and "consume". The key is does
and RCD get warm when it is not passing any load? I don't think they do so
they don't "consume" any power in their own right. They simply "dissipate"
a bit when carrying a load, just like the cables do as well. No increase
in base load.
--
Cheers
Dave.
..."does and [sic] RCD get warm when it is not passing any load?" -
Yes! - At least every single one I have used has done so. They get
even warmer when passing load. My _guess_ is that all the ones I have
come across use a solenoid to keep the contact closed, and some power
is used in the solenoid. It isn't much - somewhere between 0.5 and 5
watts is my estimate when not under load, but multiply that up by the
number of RCDs across the country and it is a lot of power being used.
I have no idea why they warm up under load. I hope its not ohmic
heating across the contacts!
NO, they use the solenoid to break the trip.
IIRC they wind live and neutral together round a solenoid, the idea
being the currents cancel..any imbalance causes a net magnetic field and
trips the switch. You need a fair number of turns to get the
sensitivity, so there is an inevitable resistance, especially at high
load currents.
Cheers,
Sid
|