On 21/08/2016 14:13, Graham. wrote:
On Sat, 20 Aug 2016 18:40:50 +0100, John Rumm
wrote:

On 20/08/2016 14:46, Lee wrote:
Other than the physical size and cost*, is there any other reason to
choose between a unit with a main switch +RCBOs and a unit with main
switch +RCD +MCBs?

Need to fit a consumer unit in a small space and very restricted on the
length (though depth and height not a problem).
*Only needs to have 1*6A, 1*32A and 1*40A, so the cost issue of RCBOs vs
MCBs isn't important.


All RCBO solutions are usually "best" in most circumstances. The only
exception being if you specifically wanted a circuit without RCD
protection - but in that case you could simply drop an RCBO for a MCB.

In a normal domestic installation, what would a circuit have to supply
to make that a sensible option?

Typically things like:

Sub-mains - feeding other CUs (so you can maintain discrimination
between circuits in the slave CU)

Circuits where you want a very low trip risk (Boiler, frost protection,
or freezer supply etc)

High reliability circuits - fire protection, medical equipment, some
lifting gear etc.

Circuits that tend to have high leakage currents combined with very low
shock risks like mineral insulated heating elements in damp environments
(immersion heaters, cookers etc)



--
Cheers,

John.

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