Would a SPD within a CU at the origin of an installation cover other CU at the origin from surges too?

Depends how they were connected - the benefit of an SPD will decline with longer connecting leads (i.e. away from the direct path from surge source to equipment to be protected) - usually 0.5m total is recommended, so if the total (of both L & N) from the SPD to the point where the other CU is connected (e.g. > 200mm to the Henley blocks) I'd say probably not adequately.

   - Andy.

Thanks Andy. Is that in the scenario where the SPD is in the CU further away than the CU without an SPD? If the SPD is in a CU nearest the origin and installed correctly less than 0.5m then this SPD will redirect the surge before it gets to the CU further away?

Thanks Andy. Is that in the scenario where the SPD is in the CU further away than the CU without an SPD? If the SPD is in a CU nearest the origin and installed correctly less than 0.5m then this SPD will redirect the surge before it gets to the CU further away?