OK.. So today I have moved around some loads, tried to balance them as best as possible.. Lowered the 80A fuses to 50A including the fuse on the neutral. When all running at full load.. Neutral current is around 9A.. Certainly nothing that will blow the 50A or melt the wire.. So now it's a wait and see If there is a problem

 

I have yet to see a fuse in a grounded neutral?
Max.

 

I have yet to see a fuse in a grounded neutral?
Max.

Perhaps Bazzo will supply a photo.

 

OK.. So today I have moved around some loads, tried to balance them as best as possible.. Lowered the 80A fuses to 50A including the fuse on the neutral. When all running at full load.. Neutral current is around 9A.. Certainly nothing that will blow the 50A or melt the wire.. So now it's a wait and see If there is a problem

Given that there should not be a fuse in the neutral, I’d have left it at 80A – or better still, wired it out of circuit.

 

Once the intermittent fault returns, which should now cause one of the phase fuses to operate – you will then be left scratching your head, trying to understand why a lower rated equipment fuse failed to operate (rather than the 50A consumer unit fuse).

Permanently connected equipment might not be provided with internal fusing; with the installation instructions specifying external fusing protection that is required. If this was not taken into consideration and the equipment is relying on the consumer unit fuse for protection; this could be the cause of your problem.

 

I know nothing of the requirements in Spain and I am not sure if anything has changed in the UK since I practiced there, but when I did, the neutral was grounded at the distribution transformer star point and never at the customer service entry like it is here in N.A..
The service supplier would refuse to connect if the neutral was connected to the earth conductor at entry or anywhere in the installation.
Max.

I've never seen installations with fuses in the neutral conductor, and I can only see security problems in an interrupted neutral.

Max's description fits very well with the current rules for newer Danish installations, and since Denmark, Spain and the UK are currently members of the European Union, the rules must be similar.