Selection of MCB for SPD protection

[Julien Leblanc]

Hello,
I need to install a type 1+2 SPD into the main panel of a small business building, which needs lightning protection.
The main breaker in the main panel is a 4 poles 40A MCB.
I was looking for a SPD and I found this: Schneider A9L16634.
In the technical specification sheet it says "Associated circuit breaker NG125N 80A curve C - Icu 15 kA".
I was wondering why the associated breaker needs to have such a high current (80A)? It seems i cannot ensure the selectivity of the breakers.
Could anyone explain what can happen if i use a smaller breaker, for example a 32A one for the protection of the SPD?

Thank you.

 

[DefyG]

If it is a Type 1 it is probably designed to be at the source (intake).
If your board is protected by a 40A MCB it sounds like a secondary dist board, where just a type2 might do?
Generally follow manufacturers advice.
Perhaps the board you are using doesn't have 32A breakers with sufficiently high short circuit breakage capacity (kA)?
If a breaker is used with insufficient capacity it may be damaged in the event of a surge and not disconnect properly resulting in damage to equipment you are trying to protect?

 

[Timbo]

You could try Surge Devices
I found them very helpful with a job.