On 24/09/2017 08:36, wrote:

Thanks John

I checked the consumer unit. There is a bank of MCBs and then a RCCB
then another bank and another RCCB.

That sounds like a typical 17th edition style split load CU, where you
have all circuits protected by RCDs, but they are spread out over a pair
of devices, so you maintain some discrimination. For example a layout like:

http://wiki.diyfaq.org.uk/index.php/...th5-5Fixed.JPG

I assume the RCCB protects the
bank of MCBs to the left of it. Is that correct?

Generally that seems to be the most common arrangement - although it
does depend on the brand of CU. Some place the main switch or RCD on the
left of the protected block of devices.

If so, the bank of
MCBs to the left are... 2xB6 2xB16 2xB32 1xB40

It sounds like that there are no non RCD protected circuits (as you
might find with a so called "high integrity" CU with provision for some
non protected circuits that can be fitted with MCBs or RCBOs:

http://wiki.diyfaq.org.uk/index.php/...hIntegrity.JPG

The implication of this is that you *do not* need any further RCD
protection for the spa pumps / heaters.

The RCCB is 80A 30mA. 80a seems a bit odd given the total of the MCBs
is much more. Unless it only protects the nearest 1 or 2 MCBs?

No it will protect all of them. Finding that the maximum load on all
circuits when summed is greater than the rating of some upstream device
is not uncommon, but allowances can be made for diversity in the loads.
More detail he

http://wiki.diyfaq.org.uk/index.php/Diversity


--
Cheers,

John.

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