On 26/08/2019 14:36, dennis@home wrote:
snip
The company fuse should protect those.
Typically its 100A, mine is only 80A though.
Obviously if the SPD you buy specifies less then you need something
extra to protect it.


1.Â*Â*Â* You may be happy to risk a faulty SPD taking out the "company
fuse". Others wouldn't.

2.Â*Â*Â* Some SPDs specify maximum overcurrent protection of less than
80A - including the one in photo (63A).


Then they are the wrong ones to use in that CU, unless you don't mind
your supply being reduced to 63A and you fit another fuse/breaker.


You have misunderstood how SPDs work.Â* They are in /parallel/ with the
circuits they protect. So an SPD which needs a max 32A MCB can happily
sit in a CU and protect 100A loads.Â* See the BEAMA guide - link in one
of my earlier posts.

It can but MCBs and RCDs have coils in them so don't expect the same
surge protection if the surge current has to traverse breakers.
To work well, they need a low impedance at a higher frequency than mains
so even small coils will have an effect.

If you are worried about that then use a fuse rather than an MCB, or use
an SPD with integral overcurrent protection so it's all taken into
account in the specs.


--
Robin
reply-to address is (intended to be) valid